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Monarch butterfly

January 30, 2023

The monarch butterfly or simply monarch (Danaus plexippus) is a milkweed butterfly (subfamily Danainae) in the family Nymphalidae.[5] Other common names, depending on region, include milkweed, common tiger, wanderer, and black-veined brown.[6] It is amongst the most familiar of North American butterflies and an iconic pollinator,[7] although it is not an especially effective pollinator of milkweeds.[8][9] Its wings feature an easily recognizable black, orange, and white pattern, with a wingspan of 8.9–10.2 cm (3.5–4.0 in).[10] A Müllerian mimic, the viceroy butterfly, is similar in color and pattern, but is markedly smaller and has an extra black stripe across each hindwing.

Monarch butterfly
Male
Female

Least Concern (IUCN 3.1)[1] (entire species)

Endangered (IUCN 3.1)[2] (migratory subspecies)
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Nymphalidae
Genus: Danaus
Species:
D. plexippus
Binomial name
Danaus plexippus
Synonyms
  • Papilio plexippus (Linnaeus, 1758)
  • Danaus archippus (Fabricius, 1793)[3]
  • Danaus menippe (Hübner, 1816)[4]
  • Anosia plexippus (Dyar, 1903)

The eastern North American monarch population is notable for its annual southward late-summer/autumn instinctive migration from the northern and central United States and southern Canada to Florida and Mexico.[5] During the fall migration, monarchs cover thousands of miles, with a corresponding multigenerational return north in spring. The western North American population of monarchs west of the Rocky Mountains often migrates to sites in southern California, but individuals have been found in overwintering Mexican sites, as well.[11][12] In 2009, monarchs were reared on the International Space Station, successfully emerging from pupae located in the station's Commercial Generic Bioprocessing Apparatus.[13]

Etymology

The name "monarch" is believed to have been given in honor of King William III of England, as the butterfly's main color is that of the king's secondary title, Prince of Orange.[14] The monarch was originally described by Carl Linnaeus in his Systema Naturae of 1758 and placed in the genus Papilio.[15] In 1780, Jan Krzysztof Kluk used the monarch as the type species for a new genus, Danaus.

Danaus (Ancient Greek Δαναός), a great-grandson of Zeus, was a mythical king in Egypt or Libya, who founded Argos; Plexippus (Πλήξιππος) was one of the 50 sons of Aegyptus, the twin brother of Danaus. In Homeric Greek, his name means "one who urges on horses", i.e., "rider" or "charioteer".[16] In the tenth edition of Systema Naturae, at the bottom of page 467,[17] Linnaeus wrote that the names of the Danai festivi, the division of the genus to which Papilio plexippus belonged, were derived from the sons of Aegyptus. Linnaeus divided his large genus Papilio, containing all known butterfly species, into what we would now call subgenera. The Danai festivi formed one of the "subgenera", containing colorful species, as opposed to the Danai candidi, containing species with bright white wings. Linnaeus wrote: "Danaorum Candidorum nomina a filiabus Danai Aegypti, Festivorum a filiis mutuatus sunt." (English: "The names of the Danai candidi have been derived from the daughters of Danaus, those of the Danai festivi from the sons of Aegyptus.").

Robert Michael Pyle suggested Danaus is a masculinized version of Danaë (Greek Δανάη), Danaus's great-great-granddaughter, to whom Zeus came as a shower of gold, which seemed to him a more appropriate source for the name of this butterfly.[18]

Taxonomy

 
White morph of the monarch in Hawaii called the white monarch

Monarchs belong in the subfamily Danainae of the family Nymphalidae. Danainae was formerly considered a separately family Danaidae.[19] The three species of monarch butterflies are:

  • D. plexippus, described by Linnaeus in 1758, is the species known most commonly as the monarch butterfly of North America. Its range actually extends worldwide, including Hawaii, Australia, New Zealand, Spain, and the Pacific Islands.
  • D. erippus, the southern monarch, was described by Pieter Cramer in 1775. This species is found in tropical and subtropical latitudes of South America, mainly in Brazil, Uruguay, Paraguay, Argentina, Bolivia, Chile, and southern Peru. The South American monarch and the North American monarch may have been one species at one time. Some researchers believe the southern monarch separated from the monarch's population some 2 million years ago, at the end of the Pliocene. Sea levels were higher, and the entire Amazonas lowland was a vast expanse of brackish swamp that offered limited butterfly habitat.[20]
  • D. cleophile, the Jamaican monarch, described by Jean-Baptiste Godart in 1819, ranges from Jamaica to Hispaniola.[2]

Six subspecies and two color morphs of D. plexippus have been identified:[6]

  • D. p. plexippus – nominate subspecies, described by Linnaeus in 1758, is the migratory subspecies known from most of North America.
    • D. p. p. "form nivosus", the white monarch commonly found on Oahu, Hawaii, and rarely in other locations.[21]
    • D. p. p. (as yet unnamed) – a color morph lacking some wing vein markings.[22]
  • D. p. nigrippus (Richard Haensch, 1909) – South America - as forma: Danais [sic] archippus f. nigrippus. Hay-Roe et al. in 2007 identified this taxon as a subspecies[23]
  • D. p. megalippe (Jacob Hübner, [1826]) – nonmigratory subspecies, and is found from Florida and Georgia southwards, throughout the Caribbean and Central America to the Amazon River.
  • D. p. leucogyne (Arthur G. Butler, 1884) − St. Thomas
  • D. p. portoricensis Austin Hobart Clark, 1941 − Puerto Rico
  • D. p. tobagi Austin Hobart Clark, 1941 − Tobago

The population level of the white morph in Oahu is nearing 10%. On other Hawaiian islands, the white morph occurs at a relatively low frequency. White monarchs (D. p. p. "form nivosus") have been found throughout the world, including Australia, New Zealand, Indonesia, and the United States.[21] However, some taxonomists disagree on these classifications.[20][23]

Genome

The monarch was the first butterfly to have its genome sequenced.[24]: 12  The 273-million-base pair draft sequence includes a set of 16,866 protein-coding genes. The genome provides researchers insights into migratory behavior, the circadian clock, juvenile hormone pathways, and microRNAs that are differentially expressed between summer and migratory monarchs.[25][26][27] More recently, the genetic basis of monarch migration and warning coloration has been described.[28]

No genetic differentiation exists between the migratory populations of eastern and western North America.[24]: 16  Recent research has identified the specific areas in the genome of the monarch that regulate migration. No genetic difference is seen between a migrating and nonmigrating monarch, but the gene is expressed in migrating monarchs, but not expressed in nonmigrating monarchs.[29]

A 2015 publication identified genes from wasp bracoviruses in the genome of the North American monarch[30] leading to articles about monarch butterflies being genetically modified organisms.[31][32]

Life cycle

 
The life cycle of the monarch butterfly

Metamorphosis

Like all Lepidoptera, monarchs undergo complete metamorphosis; their life cycle has four phases: egg, larva, pupa, and adult. Monarchs transition from eggs to adults during warm summer temperatures in as little as 25 days, extending to as many as seven weeks during cool spring conditions. During their development, both larvae and their milkweed hosts are vulnerable to weather extremes, predators, parasites, and diseases; commonly fewer than 10% of monarch eggs and caterpillars survive.[24]: 21–22 

Egg

 
Egg

The egg is derived from materials ingested as a larva and from the spermatophores received from males during mating.[33] Female monarchs lay eggs singly, most often on the underside of a young leaf of a milkweed plant during the spring and summer.[34] Females secrete a small amount of glue to attach their eggs directly to the plant. They typically lay 300 to 500 eggs over a two- to five-week period.[35]

Eggs are cream colored or light green, ovate to conical in shape, and about 1.2 mm × 0.9 mm (0.047 in × 0.035 in) in size. The eggs weigh less than 0.5 mg (0.0077 gr) each and have raised ridges that form longitudinally from the point to apex to the base. Although each egg is 1⁄1000 the mass of the female, she may lay up to her own mass in eggs. Females lay smaller eggs as they age. Larger females lay larger eggs.[33] The number of eggs laid by a female, which may mate several times, can reach 1,180.[36]

Eggs take three to eight days to develop and hatch into larvae or caterpillars.[24]: 21  The offspring's consumption of milkweed benefits health and helps defend them against predators.[37][38] Monarchs lay eggs along the southern migration route.[39]

Larva

 
Size comparison between an eastern black swallowtail caterpillar (top), a monarch caterpillar (middle), and a queen caterpillar (bottom) all on a human hand

The larva (caterpillar) has five stages (instars), molting at the end of each instar. Instars last about 3 to 5 days, depending on factors such as temperature and food availability.[5][40]

The first-instar caterpillar that emerges from the egg is pale green or grayish-white, shiny, and almost translucent, with a large, black head. It lacks banding coloration or tentacles. The larvae or caterpillar eats its egg case and begins to feed on milkweed with a circular motion, often leaving a characteristic, arc-shaped hole in the leaf. Older first-instar larvae have dark stripes on a greenish background and develop small bumps that later become front tentacles. The first instar is usually between 2 and 6 mm (0.079 and 0.236 in) long.[40]

The second-instar larva develops a characteristic pattern of white, yellow, and black transverse bands. The larva has a yellow triangle on the head and two sets of yellow bands around this central triangle. It is no longer translucent, and is covered in short setae. Pairs of black tentacles begin to grow, a larger pair on the thorax and a smaller pair on the abdomen. The second instar is usually between 6 mm (0.24 in) and 1 cm (0.39 in) long.[40]

The third-instar larva has more distinct bands and the two pairs of tentacles become longer. Legs on the thorax differentiate into a smaller pair near the head and larger pairs further back. Third-instar larvae usually feed using a cutting motion on leaf edges. The third instar is usually between 1 and 1.5 cm (0.39 and 0.59 in) long.[40]

The fourth-instar larva has a different banding pattern. It develops white spots on the prolegs near its back, and is usually between 1.5 and 2.5 cm (0.59 and 0.98 in) long.[40]

The fifth-instar larva has a more complex banding pattern and white dots on the prolegs, with front legs that are small and very close to the head. Fifth-instar larvae often chew a shallow notch in the petiole of the leaf they are eating, which causes the leaf to fall into a vertical position. Its length ranges from 2.5 to 4.5 cm (0.98 to 1.77 in).[5][40]

As the caterpillar completes its growth, it is 4.5 cm (1.8 in) long (large specimens can reach 5 cm (2.0 in)) and 7 to 8 mm (0.28 to 0.31 in) wide, and weighs about 1.5 g (0.053 oz), compared to the first instar, which is 2 to 6 mm (0.079 to 0.236 in) long and 0.5 to 1.5 mm (0.020 to 0.059 in) wide. Fifth-instar larvae greatly increase in size and weight. They then stop feeding and are often found far from milkweed plants as they seek a site for pupating.[40]

In a laboratory setting, the fourth- and fifth-instar stages of the caterpillar showed signs of aggressive behavior with lower food availability. Attacked caterpillars were found to be attacked when it was feeding on milkweed leaves, and the caterpillars attacked when foraging for milkweed.[41] This demonstrates the aggressive behavior of monarch caterpillars due to the availability of milkweed.

Pupa

 
Chrysalis

To prepare for the pupal or chrysalis stage, the caterpillar chooses a safe place for pupation, where it spins a silk pad on a downward-facing horizontal surface. At this point, it turns around and securely latches on with its last pair of hind legs and hangs upside down, in the form of the letter J. After "J-hanging" for about 12–16 hours, it soon straightens out its body and goes into peristalsis some seconds before its skin splits behind its head. It then sheds its skin over a period of a few minutes, revealing a green chrysalis. At first, the chrysalis is long, soft, and somewhat amorphous, but over a few hours, it compacts into its distinct shape – an opaque, pale-green chrysalis with small golden dots near the bottom, and a gold-and-black rim around the dorsal side near the top.[42] At first, its exoskeleton is soft and fragile, but it hardens and becomes more durable within about a day. At this point, it is about 2.5 cm (0.98 in) long and 10–12 mm (0.39–0.47 in) wide, weighing about 1.2 g (0.042 oz). At normal summer temperatures, it matures in 8–15 days (usually 11–12 days). During this pupal stage, the adult butterfly forms inside. A day or so before emerging, the exoskeleton first becomes translucent and the chrysalis more bluish. Finally, within 12 hours or so, it becomes transparent, revealing the black and orange colors of the butterfly inside before it ecloses (emerges).[43][44]

Adult

 
An emergent monarch clinging to its chrysalis shell

The adult emerges from its chrysalis after about two weeks of pupation. The emergent adult hangs upside down for several hours while it pumps fluids and air into its wings, which expand, dry, and stiffen. The butterfly then extends and retracts its wings. Once conditions allow, it flies and feeds on a variety of nectar plants. During the breeding season, adults reach sexual maturity in 4–5 days. However, the migrating generation does not reach maturity until overwintering is complete.[45]

The adult's wingspan ranges from 8.9 to 10.2 centimetres (3.5 to 4.0 in).[10] The upper sides of the wings are tawny orange, the veins and margins are black, and two series of small white spots occur in the margins. Monarch forewings also have a few orange spots near their tips. Wing undersides are similar, but the tips of forewings and hindwings are yellow brown instead of tawny orange and the white spots are larger.[46] The shape and color of the wings change at the beginning of the migration and appear redder and more elongated than later migrants.[47] Wings size and shape differ between migratory and nonmigratory monarchs. Monarchs from eastern North America have larger and more angular forewings than those in the western population.[24]

In eastern North American populations, overall wing size in the physical dimensions of wings varies. Males tend to have larger wings than females, and are typically heavier than females. Both males and females have similar thoracic dimensions. Female monarchs tended to have thicker wings, which is thought to convey greater tensile strength and reduce the likelihood of being damaged during migration. Additionally, females had lower wing loading than males, which would mean females require less energy to fly.[48]

Adults are sexually dimorphic. Males are slightly larger than females and have a black spot on a vein on each hindwing. The spots contain scales that produce pheromones that many Lepidoptera use during courtship. Females are often darker than males and have wider veins on their wings. The ends of the abdomens of males and females differ in shape.[46][49][24][50][51][52]

The adult's thorax has six legs, but as in all of the Nymphalidae, the forelegs are small and held against the body. The butterfly uses only its middle and hindlegs when walking and clinging.[53]

Adults typically live for 2–5 weeks during their breeding season.[24]: 22–23  Larvae growing in high densities are smaller, have lower survival, and weigh less as adults compared with those growing in lower densities.[54]

Vision

Physiological experiments suggest that monarch butterflies view the world through a tetrachromatic system.[55] Like humans, their retina contain three types of opsin proteins, expressed in distinct photoreceptor cells, each of which absorbs light at a different wavelength. Unlike humans, one of those types of photoreceptor cells corresponds to a wavelength in the ultraviolet range; the other two correspond to blue and green.[56]

In addition to these three photoreceptors cells in the main retina, monarch butterfly eyes contain orange filtering pigments that filter the light reaching some green-absorbing opsins, thereby making a fourth photoreceptor cell sensitive to longer-wavelength light.[55] The combination of filtered and unfiltered green opsins permits the butterflies to distinguish yellow from orange colors.[55] The ultraviolet opsin protein has also been detected in the dorsal rim region of monarch eyes. One study suggests that this allows the butterflies the ability to detect ultraviolet polarized skylight to orient themselves with the sun for their long migratory flight.[57]

These butterflies are capable of distinguishing colors based on their wavelength only, and not based on intensity; this phenomenon is termed "true color vision". This is important for many butterfly behaviors, including seeking nectar for nourishment, choosing a mate, and finding milkweed on which to lay eggs. One study found that floral color is more easily recognized at a distance by butterflies searching for nectar than floral shape. This may be because flowers have highly contrasting colors to the green background of a vegetative landscape.[58] On the other hand, leaf shape is important for oviposition so that the butterflies can ensure their eggs are being laid on milkweed.

Beyond the perception of color, the ability to remember certain colors is essential in the life of monarch butterflies. These insects can easily learn to associate color, and to a lesser extent, shape, with sugary food rewards. When searching for nectar, color is the first cue that draws the insect's attention toward a potential food source, and shape is a secondary characteristic that promotes the process. When searching for a place to lay its eggs, the roles of color and shape are switched. Also, a difference may exist between male and female butterflies from other species in terms of the ability to learn certain colors; however, no differences is noted between the sexes for monarch butterflies.[58]

Courtship and mating

Monarch butterfly mating (video)

Monarch courtship occurs in two phases. During the aerial phase, a male pursues and often forces a female to the ground. During the ground phase, the butterflies copulate and remain attached for about 30 to 60 minutes.[59] Only 30% of mating attempts end in copulation, suggesting that females may be able to avoid mating, though some have more success than others.[60][61] During copulation, a male transfers his spermatophore to a female. Along with sperm, the spermatophore provides a female with nutrition, which aids her in laying eggs. An increase in spermatophore size increases the fecundity of female monarchs. Males that produce larger spermatophores also fertilize more females' eggs.[62]

Females and males typically mate more than once. Females that mate several times lay more eggs.[63] Mating for the overwintering populations occurs in the spring, prior to dispersion. Mating is less dependent on pheromones than in other species in its genus.[64] Male search and capture strategies may influence copulatory success, and human-induced changes to the habitat can influence monarch mating activity at overwintering sites.[65]

Distribution and habitat

 
String of monarchs wintering at California's Pismo State Beach Monarch Preserve (2015)
 
Monarch flying away from a sunflower in Mexico

The range of the western and eastern populations of D. p. plexippus expands and contracts depending upon the season. The range differs between breeding areas, migration routes, and winter roosts.[24]: 18  However, no genetic differences between the western and eastern monarch populations exist;[29] reproductive isolation has not led to subspeciation of these populations, as it has elsewhere within the species' range.[24]: 19 

In the Americas, the monarch ranges from southern Canada through northern South America.[5] It is also found in Bermuda, Cook Islands,[66] Hawaii,[67][68] Cuba,[69] and other Caribbean islands[24]: 18  the Solomons, New Caledonia, New Zealand,[70] Papua New Guinea,[71] Australia, the Azores, the Canary Islands, Madeira, continental Portugal, Gibraltar,[72] the Philippines, and Morocco.[73] It appears in the UK in some years as an accidental migrant.[74]

Overwintering populations of D. p. plexippus are found in Mexico, California, along the Gulf Coast of the United States, year-round in Florida, and in Arizona where the habitat has the specific conditions necessary for their survival.[75][76] On the East Coast of the United States, they have overwintered as far north as Lago Mar, Virginia Beach, Virginia.[77] Their wintering habitat typically provides access to streams, plenty of sunlight (enabling body temperatures that allow flight), and appropriate roosting vegetation, and is relatively free of predators.

Overwintering, roosting butterflies have been seen on basswoods, elms, sumacs, locusts, oaks, osage-oranges, mulberries, pecans, willows, cottonwoods, and mesquites.[78] While breeding, monarch habitats can be found in agricultural fields, pasture land, prairie remnants, urban and suburban residential areas, gardens, trees, and roadsides – anywhere where there is access to larval host plants.[79]

Larval host plants

 
Mating monarchs in captivity

The host plants used by the monarch caterpillar include:

 
Inflorescence of swamp milkweed, one of many species of Asclepias milkweeds that serve as hosts for monarch caterpillars
 
A second-instar monarch caterpillar feeding on Asclepias fascicularis
 
Monarch feeding from marigold flower

Asclepias curassavica, or tropical milkweed, is often planted as an ornamental in butterfly gardens. Year-round plantings in the USA are controversial and criticised, as they may be the cause of new overwintering sites along the U.S. Gulf Coast, leading to year-round breeding of monarchs.[98] This is thought to adversely affect migration patterns, and to cause a dramatic buildup of the dangerous parasite, Ophryocystis elektroscirrha.[99] New research also has shown that monarch larvae reared on tropical milkweed show reduced migratory development (reproductive diapause), and when migratory adults are exposed to tropical milkweed, it stimulates reproductive tissue growth.[100]

Adult food sources

 
Nectaring on purple coneflower (Echinacea purpurea)
 
An adult monarch sucking nectar from Salvia clevelandii

Although larvae eat only milkweed, adult monarchs feed on the nectar of many plants, including:[101]

Monarchs obtain moisture and minerals from damp soil and wet gravel, a behavior known as mud-puddling. The monarch has also been noticed puddling at an oil stain on pavement.[76]

Flight and migration

Further information: Monarch butterfly migration
 
Migrating monarchs resting on a pine tree in Fire Island National Seashore on Long Island, New York (September 2021)

In North America, monarchs migrate both north and south on an annual basis, in a long-distance journey that is fraught with risks.[5] This is a multi-generational migration, with individual monarchs only making part of the full journey.[102] The population east of the Rocky Mountains attempts to migrate to the sanctuaries of the Mariposa Monarca Biosphere Reserve in the Mexican state of Michoacán and parts of Florida. The western population tries to reach overwintering destinations in various coastal sites in central and southern California. The overwintered population of those east of the Rockies may reach as far north as Texas and Oklahoma during the spring migration. The second, third, and fourth generations return to their northern locations in the United States and Canada in the spring.[103]

Captive-raised monarchs appear capable of migrating to overwintering sites in Mexico,[104] though they have a much lower migratory success rate than do wild monarchs (see section on captive-rearing below).[105] Monarch overwintering sites have been discovered recently in Arizona.[106] Monarchs from the eastern US generally migrate longer distances than monarchs from the western US.[107]

Since the 1800s, monarchs have spread throughout the world, and there are now many non-migratory populations globally.[108]

Flight speeds of adults are around 9 km/h (6 mph).[109]

Interactions with predators

In both caterpillar and butterfly form, monarchs are aposematic, warding off predators with a bright display of contrasting colors to warn potential predators of their undesirable taste and poisonous characteristics. One monarch researcher emphasizes that predation on eggs, larvae or adults is natural, since monarchs are part of the food chain, thus people should not take steps to kill predators of monarchs.[110]

Larvae feed exclusively on milkweed and consume protective cardiac glycosides. Toxin levels in Asclepias species vary. Not all monarchs are unpalatable, but exhibit Batesian or automimics. Cardiac glycosides levels are higher in the abdomen and wings. Some predators can differentiate between these parts and consume the most palatable ones.[111]

Butterfly weed (A. tuberosa) lacks significant amounts of cardiac glycosides (cardenolides), but instead contains other types of toxic glycosides, including pregnanes.[112][113][114] This difference may reduce the toxicity of monarchs whose larvae feed on that milkweed species, as a naturalist and others have reported that monarch caterpillars do not favor the plant.[115] Some other milkweeds have similar characteristics.[116]

Types of predators

While monarchs have a wide range of natural predators, none of these is suspected of causing harm to the overall population, or are the cause of the long-term declines in winter colony sizes.

Several species of birds have acquired methods that allow them to ingest monarchs without experiencing the ill effects associated with the cardiac glycosides (cardenolides). The black-backed oriole is able to eat the monarch through an exaptation of its feeding behavior that gives it the ability to identify cardenolides by taste and reject them.[117] The black-headed grosbeak, though, has developed an insensitivity to secondary plant poisons that allows it to ingest monarchs without vomiting.[118] As a result, these orioles and grosbeaks periodically have high levels of cardenolides in their bodies, and they are forced to go on periods of reduced monarch consumption. This cycle effectively reduces potential predation of monarchs by 50% and indicates that monarch aposematism has a legitimate purpose.[117] The black-headed grosbeak has also evolved resistance mutations in the molecular target of the heart poisons, the sodium pump. The specific mutations that evolved in one of the grosbeak's four copies of the sodium pump gene are the same as those found in other milkweed butterflies like the common crow that also evolved to resist cardiac glycosides.[119] Other bird predators include brown thrashers, grackles, robins, cardinals, sparrows, scrub jays, and pinyon jays.[111]

The monarch's white morph appeared in Oahu after the 1965–1966 introduction of two bulbul bird species, Pycnonotus cafer and Pycnonotus jocosus. These are now the most common avian insectivores in Hawaii, and probably the only ones that eat insects as large as monarchs. Although Hawaiian monarchs have low cardiac glycoside levels, the birds may also be tolerant of that toxin. The two species hunt the larvae and some pupae from the branches and undersides of leaves in milkweed bushes. The bulbuls also eat resting and ovipositing adults, but rarely flying ones. Because of its color, the white morph has a higher survival rate than the orange one. This is either because of apostatic selection (i.e., the birds have learned the orange monarchs can be eaten), because of camouflage (the white morph matches the white pubescence of milkweed or the patches of light shining through foliage), or because the white morph does not fit the bird's search image of a typical monarch, so is thus avoided.[120]

Some mice, particularly the black-eared mouse (Peromyscus melanotis), are, like all rodents, able to tolerate large doses of cardenolides and are able to eat monarchs.[121] Overwintering adults become less toxic over time making them more vulnerable to predators. In Mexico, about 14% of the overwintering monarchs are eaten by birds and mice and black-eared mice can eat up to 40 monarchs per night.[75][121]

In North America, eggs and first-instar larvae of the monarch are eaten by larvae and adults of the introduced Asian lady beetle (Harmonia axyridis).[122] The Chinese mantis (Tenodera sinensis) will consume the larvae once the gut is removed thus avoiding cardenolides.[123] Predatory wasps commonly consume larvae,[124] though large larvae may avoid wasp predation by dropping from the plant or by jerking their bodies.[125]

Aposematism

 
Chemical structure of oleandrin, one of the cardiac glycosides

Monarchs are toxic and foul-tasting because of the presence of cardenolides in their bodies, which the caterpillars ingest as they feed on milkweed.[64] Monarchs and other cardenolide-resistant insects rely on a resistant form of the Na+/ K+-ATPase enzyme to tolerate significantly higher concentrations of cardenolides than nonresistant species.[126] By ingesting a large amount of plants in the genus Asclepias, primarily milkweed, monarch caterpillars are able to sequester cardiac glycosides, or more specifically cardenolides, which are steroids that act in heart-arresting ways similar to digitalis.[127] It has been found that monarchs are able to sequester cardenolides most effectively from plants of intermediate cardenolide content rather than those of high or low content.[128] Three mutations that evolved in the monarch's Na+/ K+-ATPase were found to be sufficient together to confer resistance to dietary cardiac glycosides.[126] This was tested by swapping these mutations into the same gene in the fruit fly Drosophila melanogaster using CRISPR-Cas9 genome editing. These fruit flies-turned monarch flies[129] were completely resistant to dietary ouabain, a cardiac glycoside found in Apocynaceae, and even sequestered some through metamorphosis, like the monarch.[126]

Different species of milkweed have different effects on growth, virulence, and transmission of parasites.[130] One species, Asclepias curassavica, appears to reduce the symptoms of Ophryocystis elektroscirrha (OE) infection. The two possible explanations for this include that it promotes overall monarch health to boost the monarch's immune system or that chemicals from the plant have a direct negative effect on the OE parasites.[130] A. curassavica does not cure or prevent the infection with OE; it merely allows infected monarchs to live longer, and this would allow infected monarchs to spread the OE spores for longer periods. For the average home butterfly garden, this scenario only adds more OE to the local population.[131]

After the caterpillar becomes a butterfly, the toxins shift to different parts of the body. Since many birds attack the wings of the butterfly, having three times the cardiac glycosides in the wings leaves predators with a very foul taste and may prevent them from ever ingesting the body of the butterfly.[127] To combat predators that remove the wings only to ingest the abdomen, monarchs keep the most potent cardiac glycosides in their abdomens.[132]

Mimicry

 
Monarch (left) and viceroy (right) butterflies exhibiting Müllerian mimicry

Monarchs share the defense of noxious taste with the similar-appearing viceroy butterfly in what is perhaps one of the most well-known examples of mimicry. Though long purported to be an example of Batesian mimicry, the viceroy is actually reportedly more unpalatable than the monarch, making this a case of Müllerian mimicry.[133]

Human interaction

The monarch is the state insect of Alabama,[134] Idaho,[135] Illinois,[136] Minnesota,[137] Texas,[138] Vermont,[139] and West Virginia.[140] Legislation was introduced to make it the national insect of the United States,[141] but this failed in 1989[142] and again in 1991.[143]

Homeowners are increasingly establishing butterfly gardens; monarchs can be attracted by cultivating a butterfly garden with specific milkweed species and nectar plants. Efforts are underway to establish these monarch waystations. [144]

An IMAX film, Flight of the Butterflies, describes the story of the Urquharts, Brugger, and Trail to document the then-unknown monarch migration to Mexican overwintering areas.[145]

Sanctuaries and reserves have been created at overwintering locations in Mexico and California to limit habitat destruction. These sites can generate significant tourism revenue.[146] However, with less tourism, monarch butterflies will have a higher survival rate because they show more protein content and a higher value of immune response and oxidative defense.[147]

Organizations and individuals participate in tagging programs. Tagging information is used to study migration patterns.[148]

The 2012 novel by Barbara Kingsolver, Flight Behavior, deals with the fictional appearance of a large population in the Appalachians.[149]

Captive rearing

Humans interact with monarchs when rearing them in captivity, which has become increasingly popular. However, risks occur in this controversial activity. On one hand, captive rearing has many positive aspects. Monarchs are bred in schools and used for butterfly releases at hospices, memorial events, and weddings.[150] Memorial services for the September 11 attacks include the release of captive-bred monarchs.[151][152][153] Monarchs are used in schools and nature centers for educational purposes.[154] Many homeowners raise monarchs in captivity as a hobby and for educational purposes.[155]

On the other hand, this practice becomes problematic when monarchs are "mass-reared". Stories in the Huffington Post in 2015 and Discover magazine in 2016 have summarized the controversy around this issue.[156][157]

The frequent media reports of monarch declines have encouraged many homeowners to attempt to rear as many monarchs as possible in their homes and then release them to the wild in an effort to "boost the monarch population". Some individuals, such as one in Linn County, Iowa, have reared thousands of monarchs at the same time.[158]

Some monarch scientists do not condone the practice of rearing "large" numbers of monarchs in captivity for release into the wild because of the risks of genetic issues and disease spread.[159] One of the biggest concerns of mass rearing is the potential for spreading the monarch parasite, Ophryocystis elektroscirrha, into the wild. This parasite can rapidly build up in captive monarchs, especially if they are housed together. The spores of the parasite also can quickly contaminate all housing equipment, so that all subsequent monarchs reared in the same containers then become infected. One researcher stated that rearing more than 100 monarchs constitutes "mass rearing" and should not be done.[160]

In addition to the disease risks, researchers believe these captive-reared monarchs are not as fit as wild ones, owing to the unnatural conditions in which they are raised. Homeowners often raise monarchs in plastic or glass containers in their kitchens, basements, porches, etc., and under artificial lighting and controlled temperatures. Such conditions would not mimic what the monarchs are used to in the wild, and may result in adults that are unsuited for the realities of their wild existence. In support of this, a recent study by a citizen scientist found that captive-reared monarchs have a lower migration success rate than wild monarchs do.[105]

A 2019 study shed light on the fitness of captive-reared monarchs, by testing reared and wild monarchs on a tethered flight apparatus that assessed navigational ability.[161] In that study, monarchs that were reared to adulthood in artificial conditions showed a reduction in navigational ability. This happened even with monarchs that were brought into captivity from the wild for a few days. A few captive-reared monarchs did show proper navigation. This study revealed the fragility of monarch development; if the conditions are not suitable, their ability to properly migrate could be impaired. The same study also examined the genetics of a collection of reared monarchs purchased from a butterfly breeder, and found they were dramatically different from wild monarchs, so much so that the lead author described them as "franken-monarchs".[162]

An unpublished study in 2019 compared behavior of captive-reared versus wild monarch larvae.[163] The study showed that reared larvae exhibited more defensive behavior than wild larvae. The reason for this is unknown, but it could relate to the fact that reared larvae are frequently handled and/or disturbed.

Threats

In February 2015, the U.S. Fish and Wildlife Service reported a study that showed that nearly a billion monarchs had vanished from the butterfly's overwintering sites since 1990. The agency attributed the monarch's decline in part to a loss of milkweed caused by herbicides that farmers and homeowners had used.[164]

Western monarch populations

See also: Threats to monarch butterfly in California
 
Western monarch populations from 1997 to 2013 (from Xerces Society data)

Based on a 2014 20-year comparison, the overwintering numbers west of the Rocky Mountains have dropped more than 50% since 1997 and the overwintering numbers east of the Rockies have declined by more than 90% since 1995. According to the Xerces Society, the monarch population in California decreased 86% in 2018, going from millions of butterflies to tens of thousands of butterflies.[165]

The society's annual 2020–2021 winter count showed a significant decline in the California population. One Pacific Grove site did not have a single monarch butterfly. A primary explanation for this was the destruction of the butterfly's milkweed habitats.[24][166] This particular population is believed to comprise less than 2000 individuals, as of 2022.[167]

Eastern and midwestern monarch populations

 
Area covered by monarchs (D. plexippus, eastern migratory population) in their overwintering areas in Mexico between 1993 and 2018

A 2016 publication attributed the previous decade's 90% decline in overwintering numbers of the eastern monarch population to the loss of breeding habitat and milkweed. The publication's authors stated that an 11%–57% probability existed that this population will go almost extinct over the next 20 years.[168]

Chip Taylor, the director of Monarch Watch at the University of Kansas, has stated that the Midwest milkweed habitat "is virtually gone" with 120–150 million acres lost.[169][170] To help fight this problem, Monarch Watch encourages the planting of "Monarch Waystations".[155]

Habitat loss due to herbicide use and genetically modified crops

Declines in milkweed abundance and monarch populations between 1999 and 2010 are correlated with the adoption of herbicide-tolerant genetically modified (GM) corn and soybeans, which now constitute 89% and 94% of these crops, respectively, in the U.S.[168] GM corn and soybeans are resistant to the effect of the herbicide glyphosate. Some conservationists attribute the disappearance of milkweed to agricultural practices in the Midwest, where GM seeds are bred to resist herbicides that farmers use to kill unwanted plants that grow near their rows of food crops.[171][172]

In 2015, the Natural Resources Defense Council filed a suit against the United States Environmental Protection Agency (EPA). The Council argued that the agency ignored warnings about the dangers of glyphosate usage for monarchs.[173] However, a 2018 study has suggested that the decline in milkweed predates the arrival of GM crops.[174]

Losses during migration

 
Monarch nectaring on a zinnia flower during its migration southward to Mexico, late September of 2022

Eastern and midwestern monarchs are apparently experiencing problems reaching Mexico. A number of monarch researchers have cited recent evidence obtained from long-term citizen science data that show that the number of breeding (adult) monarchs has not declined in the last two decades.[175][176][177]

The lack of long-term declines in the numbers of breeding and migratory monarchs, yet the clear declines in overwintering numbers, suggests a growing disconnect exists between these life stages. One researcher has suggested that mortality from car strikes constitutes an increasing threat to migrating monarchs.[178] A study of road mortality in northern Mexico, published in 2019, showed very high mortality from just two "hotspots" each year, amounting to 200,000 monarchs killed.[179]

Loss of overwintering habitat

The area of Mexican forest to which eastern and midwestern monarchs migrate reached its lowest level in two decades in 2013. The decline was expected to increase during the 2013–2014 season. Mexican environmental authorities continue to monitor illegal logging of the oyamel trees. The oyamel is a major species of evergreen on which the overwintering butterflies spend a significant time during their winter diapause, or suspended development.[180]

A 2014 study acknowledged that while "the protection of overwintering habitat has no doubt gone a long way towards conserving monarchs that breed throughout eastern North America", their research indicates that habitat loss on breeding grounds in the United States is the main cause of both recent and projected population declines.[181]

Parasites

 
Pteromalus cassotis on monarch chrysalis

Parasites include the tachinid flies Sturmia convergens[182] and Lespesia archippivora. Lesperia-parasitized butterfly larvae suspend, but die prior to pupation. The fly's maggot lowers itself to the ground, forms a brown puparium and then emerges as an adult.[183]

Pteromalid wasps, specifically Pteromalus cassotis, parasitize monarch pupae.[184] These wasps lay their eggs in the pupae while the chrysalis is still soft. Up to 400 adults emerge from the chrysalis after 14–20 days,[184] killing the monarch.

The bacterium Micrococcus flacidifex danai also infects larvae. Just before pupation, the larvae migrate to a horizontal surface and die a few hours later, attached only by one pair of prolegs, with the thorax and abdomen hanging limp. The body turns black shortly thereafter. The bacterium Pseudomonas aeruginosa has no invasive powers, but causes secondary infections in weakened insects. It is a common cause of death in laboratory-reared insects.[183]

Ophryocystis elektroscirrha is another parasite of the monarch. It infects the subcutaneous tissues and propagates by spores formed during the pupal stage. The spores are found over all of the body of infected butterflies, with the greatest number on the abdomen. These spores are passed, from female to caterpillar, when spores rub off during egg laying and are then ingested by caterpillars. Severely infected individuals are weak, unable to expand their wings, or unable to eclose, and have shortened lifespans, but parasite levels vary in populations. This is not the case in laboratory rearing, where after a few generations, all individuals can be infected.[185]

Infection with O. elektroscirrha creates an effect known as culling, whereby migrating monarchs that are infected are less likely to complete the migration. This results in overwintering populations with lower parasite loads.[186] Owners of commercial butterfly-breeding operations claim that they take steps to control this parasite in their practices,[187] although this claim is doubted by many scientists who study monarchs.[188]

Confusion of host plants

The black swallow-wort (Cynanchum louiseae) and pale swallow-wort (Cynanchum rossicum) plants are problematic for monarchs in North America. Monarchs lay their eggs on these relatives of native vining milkweed (Cynanchum laeve) because they produce stimuli similar to milkweed. Once the eggs hatch, the caterpillars are poisoned by the toxicity of this invasive plant from Europe.[189]

Climate

Climate variations during the fall and summer affect butterfly reproduction. Rainfall and freezing temperatures affect milkweed growth. Omar Vidal, director general of WWF-Mexico, said, "The monarch's lifecycle depends on the climatic conditions in the places where they breed. Eggs, larvae, and pupae develop more quickly in milder conditions. Temperatures above 35 °C (95 °F) can be lethal for larvae, and eggs dry out in hot, arid conditions, causing a drastic decrease in hatch rate."[190] If a monarch's body temperatures is below 30 °C (86 °F), a monarch cannot fly. To warm up, they sit in the sun or rapidly shiver their wings to warm themselves.[191]

Climate change may dramatically affect the monarch migration. A study from 2015 examined the impact of warming temperatures on the breeding range of the monarch, and showed that in the next 50 years the monarch host plant will expand its range further north into Canada, and that the monarchs will follow this.[192] While this will expand the breeding locations of the monarch, it will also have the effect of increasing the distance that monarchs must travel to reach their overwintering destination in Mexico, which could result in greater mortality during the migration.[193]

Milkweeds grown at increased temperatures have been shown to contain higher cardenolide concentrations, making the leaves too toxic for the monarch caterpillars. However, these increased concentrations are likely in response to increased insect herbivory, which is also caused by the increased temperatures. Whether increased temperatures make milkweed too toxic for monarch caterpillars when other factors are not present is unknown.[194] Additionally, milkweed grown at carbon dioxide levels of 760 parts per million was found to produce a different mix of the toxic cardenolides, one of which was less effective against monarch parasites.[195]

Conservation status

On July 20, 2022, the International Union for Conservation of Nature added the migratory monarch butterfly (the subspecies common in North America) to its red list of endangered species.[196][2]

The monarch butterfly is not currently listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora or protected specifically under U.S. domestic laws.[197]

On August 14, 2014, the Center for Biological Diversity and the Center for Food Safety filed a legal petition requesting Endangered Species Act protection for the monarch and its habitat,[24] based largely on the long-term trends observed at overwintering sites. The U.S. Fish and Wildlife Service (FWS) initiated a status review of the monarch butterfly under the Endangered Species Act with a due date for information submission of March 3, 2015, later extended to 2020. On December 15, 2020, the FWS ruled that adding the butterfly to the list of threatened and endangered species was "warranted-but-precluded" because it needed to devote its resources to 161 higher-priority species.[198]

The number of monarchs overwintering in Mexico has shown a long-term downward trend. Since 1995, coverage numbers have been as high as 18 hectares (44 acres) during the winter of 1996–1997, but on average about 6 hectares (15 acres). Coverage declined to its lowest point to date (0.67 hectares (1.66 acres)) during the winter of 2013–2014, but rebounded to 4.01 hectares (10 acres) in 2015–2016. The average population of monarchs in 2016 was estimated at 200 million. Historically, on average there are 300 million monarchs. The 2016 increase was attributed to favorable breeding conditions in the summer of 2015. However, coverage declined by 27% to 2.91 hectares (7.19 acres) during the winter of 2016–2017. Some believe this was because of a storm that had occurred during March 2016 in the monarchs' previous overwintering season,[199][200][201] though this seems unlikely since most current research shows that the overwintering colony sizes do not predict the size of the next summer breeding population.[202]

In Ontario, Canada, the monarch butterfly is listed as a species of special concern.[203] In fall 2016, the Committee on the Status of Endangered Wildlife in Canada proposed that the monarch be listed as endangered in Canada, as opposed to its current listing as a "species of concern" in that country. This move, once enacted, would protect critical monarch habitat in Canada, such as major fall accumulation areas in southern Ontario, but it would also have implications for citizen scientists who work with monarchs, and for classroom activities. If the monarch were federally protected in Canada, these activities could be limited, or require federal permits.[204]

In Nova Scotia, the monarch is listed as endangered at the provincial level, as of 2017. This decision (as well as the Ontario decision) apparently is based on a presumption that the overwintering colony declines in Mexico create declines in the breeding range in Canada.[205] Two recent studies have been conducted examining long-term trends in monarch abundance in Canada, using either butterfly atlas records[206] or citizen science butterfly surveys,[207] and neither shows evidence of a population decline in Canada.

Conservation efforts

See also: Monarch butterfly conservation in California

Although numbers of breeding monarchs in eastern North America have apparently not decreased, reports of declining numbers of overwintering butterflies have inspired efforts to conserve the species.[175][176][177]

Federal actions

On June 20, 2014, President Barack Obama issued a presidential memorandum entitled "Creating a Federal Strategy to Promote the Health of Honey Bees and Other Pollinators". The memorandum established a Pollinator Health Task Force, to be co-chaired by the Secretary of Agriculture and the Administrator of the Environmental Protection Agency, and stated:

The number of migrating Monarch butterflies sank to the lowest recorded population level in 2013–14, and there is an imminent risk of failed migration.[208]

In May 2015, the Pollinator Health Task Force issued a "National Strategy to Promote the Health of Honey Bees and Other Pollinators". The strategy laid out federal actions to achieve three goals, two of which were:

  • Monarch Butterflies: Increase the Eastern population of the monarch butterfly to 225 million butterflies occupying an area of approximately 15 acres (6 hectares) in the overwintering grounds in Mexico, through domestic/international actions and public-private partnerships, by 2020.
  • Pollinator Habitat Acreage: Restore or enhance 7 million acres of land for pollinators over the next 5 years through Federal actions and public/private partnerships.[209]

Many of the priority projects that the national strategy identified focused on the I-35 corridor, which extends for 1,500 miles (2,400 km) from Texas to Minnesota. The area through which that highway travels provides spring and summer breeding habitats in the United States' key monarch migration corridor.[209]

The U.S. General Services Administration (GSA) publishes sets of landscape performance requirements in its P100 documents, which mandate standards for the GSA's Public Buildings Service. Beginning in March 2015, those performance requirements and their updates have included four primary aspects for planting designs that are intended to provide adequate on-site foraging opportunities for targeted pollinators. The targeted pollinators include bees, butterflies, and other beneficial insects.[210][211][212]

On December 4, 2015, President Obama signed into law the Fixing America's Surface Transportation (FAST) Act (Pub. L. 114-94).[213] The FAST Act placed a new emphasis on efforts to support pollinators. To accomplish this, the FAST Act amended Title 23 (Highways) of the United States Code. The amendment directed the United States Secretary of Transportation, when carrying out programs under that title in conjunction with willing states, to:

  1. encourage integrated vegetation management practices on roadsides and other transportation rights-of-way, including reduced mowing; and
  2. encourage the development of habitat and forage for Monarch butterflies, other native pollinators, and honey bees through plantings of native forbs and grasses, including noninvasive, native milkweed species that can serve as migratory way stations for butterflies and facilitate migrations of other pollinators.[214]

The FAST Act also stated that activities to establish and improve pollinator habitat, forage, and migratory way stations may be eligible for Federal funding if related to transportation projects funded under Title 23.[214]

The United States Department of Agriculture's Farm Service Agency helps increase U.S. populations of monarch butterfly and other pollinators through its Conservation Reserve Program's State Acres for Wildlife Enhancement (SAFE) Initiative. The SAFE Initiative provides an annual rental payment to farmers who agree to remove environmentally sensitive land from agricultural production and who plant species that will improve environmental health and quality. Among other things, the initiative encourages landowners to establish wetlands, grasses, and trees to create habitats for species that the FWS has designated to be threatened or endangered.[215][216][217][218]

Other actions

Agriculture companies and other organizations are being asked to set aside areas that remain unsprayed to allow monarchs to breed. In addition, national and local initiatives are underway to help establish and maintain pollinator habitats along corridors containing power lines and roadways. The Federal Highway Administration, state governments, and local jurisdictions are encouraging highway departments and others to limit their use of herbicides, to reduce mowing, to help milkweed to grow and to encourage monarchs to reproduce within their right-of-ways.[172][219]

National Cooperative Highway Research Program report

In 2020, the National Cooperative Highway Research Program (NCRHP) of the Transportation Research Board issued a 208-page report that described a project that had examined the potential for roadway corridors to provide habitat for monarch butterflies. A part of the project developed tools for roadside managers to optimize potential habitat for monarch butterflies in their road rights-of-way.[220][221]

Such efforts are controversial because the risk of butterfly mortality near roads is high. Several studies have shown that motor vehicles kill millions of monarchs and other butterflies every year.[178] Also, some evidence indicates that monarch larvae living near roads experience physiological stress conditions, as evidenced by elevations in their heart rate.[222]

The NCRHP report acknowledged that, among other hazards, roads present a danger of traffic collisions for monarchs, stating that these effects appear to be more concentrated in particular funnel areas during migration.[223] Nevertheless, the report concluded:

In summary, threats along roadway corridors exist for monarchs and other pollinators, but in the context of the amount of habitat needed for recovery of sustainable populations, roadsides are of vital importance.[223]

Butterfly gardening

Further information: Butterfly gardening
 
A monarch waystation near the town of Berwyn Heights in Prince George's County, Maryland (June 2017)

While scientific studies on the subject have been reported, the practice of butterfly gardening and creating "monarch waystations" is commonly thought to increase the populations of butterflies.[224][225][226][227][228][229][230] Efforts to restore falling monarch populations by establishing butterfly gardens and monarch waystations require particular attention to the butterfly's food preferences and population cycles, as well to the conditions needed to propagate and maintain milkweed.[231][232]

For example, in the Washington, DC, area and elsewhere in the northeastern United States, monarchs prefer to reproduce on common milkweed (A. syriaca), especially when its foliage is soft and fresh. Because monarch reproduction in that area peaks in late summer when milkweed foliage is old and tough, A. syriaca needs to be mowed or cut back in June through August to assure that it will be regrowing rapidly when monarch reproduction reaches its peak. Similar conditions exist for showy milkweed (A. speciosa) in Michigan and for green antelopehorn milkweed (A. viridis), where it grows in the Southern Great Plains and the Western United States.[80][233][234][235][236][237] In addition, the seeds of A. syriaca and some other milkweeds need periods of cold treatment (cold stratification) before they will germinate.[238][239][240][241][242][243]

To protect seeds from washing away during heavy rains and from seed–eating birds, one can cover the seeds with a light fabric or with an 0.5-inch (13 mm) layer of straw mulch.[244][245] However, mulch acts as an insulator. Thicker layers of mulch can prevent seeds from germinating if they prevent soil temperatures from rising enough when winter ends. Further, few seedlings can push through a thick layer of mulch.[246]

Although monarch caterpillars will feed on butterfly weed (A. tuberosa) in butterfly gardens, the plant has rough leaves and is typically not a heavily used host plant for the species.[247] The plant's low levels of cardenolides may also make the plant unattractive to egg-laying monarchs.[115] While A. tuberosa's colorful flowers provide nectar for many adult butterflies, the plant may be less suitable for use in butterfly gardens and monarch waystations than are other milkweed species.[247]

Breeding monarchs prefer to lay eggs on swamp milkweed (A. incarnata).[248][249][250][251][252][253] However, A. incarnata is an early successional plant that usually grows at the margins of wetlands and in seasonally flooded areas. The plant is slow to spread via seeds, does not spread by runners and tends to disappear as vegetative densities increase and habitats dry out.[253][254] Although A. incarnata plants can survive for up to 20 years, most live only two-five years in gardens. The species is not shade-tolerant and is not a good vegetative competitor.[254]

See also

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  232. ^ Landis, Thomas D.; Dumroese, R. Kasten (2015). "Propagating Native Milkweeds for Restoring Monarch Butterfly Habitat" (PDF). International Plant Propagators' Society, Combined Proceedings (2014). 64: 299–307. (PDF) from the original on March 8, 2021. Retrieved July 11, 2021 – via United States Department of Agriculture: United States Forest Service.
  233. ^ Cariveau, Alison B.; Caldwell, Wendy; Lonsdorf, Eric; Nootenboom, Chris; Tuerk, Karen; Snell-Rood, Emilie; Anderson, Eric; Baum, Kristen A.; Hopwood, Jennifer; Oberhauser, Karen (2020). Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies. Washington, D.C.: National Academies Press. pp. 79–80. doi:10.17226/25693. ISBN 9780309481328. LCCN 2020935714. OCLC 1229163481. S2CID 218854539. National Cooperative Highway Research Program (NCRHP) Research Report 942. from the original on July 29, 2020. Retrieved July 8, 2021. Could roadside mowing stimulate milkweed growth and support monarch breeding? Limited research in eastern North America has shown that spring or summer mowing can promote new growth and extend the availability of milkweed plants for monarch breeding. Mowing may stimulate growth of some milkweed species, particularly those that spread through rhizomes like common milkweed (A. syriaca) and showy milkweed (A. speciosa). Summer (June or July) mowing in Michigan resulted in more monarch eggs on regenerated stems than unmowed stems. Summer (July) mowing and burning can increase green antelopehorn milkweed (A. viridis) availability in the late summer and early fall in the Southern Great Plains, whereas in areas without mowing, the milkweed has senesced by August. In the West, showy milkweed will regrow after summer mowing and continue to support monarch breeding (Stephanie McKnight, personal observation). However, more research is needed in other areas to determine the optimal timing and frequency of mowing that promotes not only milkweed but also nectar plants. It is also unknown if the benefit of additional milkweed availability in the fall outweighs the costs of the larval mortality caused by summer mowing. The benefits are likely greater in areas that primarily have breeding monarchs in the spring and fall and where the dominant species of milkweed spread by rhizomes. Sources: Alcock et al. 2016; Baum and Mueller, 2015; Bhowick 1994; Haan and Landis 2019; Fischer et al. 2015
  234. ^ {{cite news|first=Adrian|last=Higgins|url=http://www.washingtonpost.com/lifestyle/home/creating-a-rest-stop-for-the-monarch/2015/05/26/cd81a75c-ffcb-11e4-805c-c3f407e5a9e9_story.html%7Ctitle=A gardener's guide to saving the monarch|department=Home & Garden|newspaper=The Washington Post|access-date=October 17, 2020|date=May 27, 2015|archive-url= 31, 2015 |url-status=live|quote="The monarch doesn't care where the milkweed grows, and putting it in residential neighborhoods makes perfect sense," said Doug Tallamy, an entomologist at the University of Delaware, author and expert on wildlife habitat gardens. [...] The [[Smithsonian Gardens#Gardens and landscapes|Smithsonian Institution's Butterfly Habitat Garden [...] and the Ripley Garden [...] are both good places to see milkweed integrated into a garden setting. At the butterfly garden, you can see the common milkweed [...] now looking pretty good in fresh, unblemished clumps. By late summer, it looks tall, tired and tough. Tallamy says if you grow it, you should cut it back at least by half in June to produce soft foliage in late summer that will be more munchable for the caterpillars. If you do that, make sure there are no larvae on the plant before you chop it.}}
  235. ^ Abugattas, Alonzo (January 3, 2017). "Monarch Way Stations". Capital Naturalist. from the original on March 8, 2021. Retrieved July 5, 2021 – via Blogger. Virginia is blessed for instance with 13 native Asclepias species plus 4 climbing vines that Monarch caterpillars can feed on. For the best results, cut the some of the stems back in late summer after they've bloomed. Fall is the when we get the most Monarchs laying eggs on our milkweeds. Since the mother butterflies prefer young, more tender growth, you can provide this by timing your pruning so there are new leaves by September or so for the arriving Monarchs. Just make sure to leave a few to produce pods for seeds. The local monarch favorite is Common Milkweed (A. syriaca), .....
  236. ^ Gomez, Tony. "Asclepias syriaca: Common Milkweed for Monarch Caterpillars". Monarch Butterfly Garden. MonarchButterflyGarden.net. from the original on March 16, 2015. Retrieved October 17, 2010. Cut- At mid season after the blooms have faded, cut some common plants back by about a third. This promotes fresh plant growth and could get you an extra generation of monarchs on the fresh new leaves. Leave some plants uncut if you want to harvest milkweed seeds in fall.
  237. ^ Stevens, Michelle. "Plant guide for common milkweed (Asclepias syriaca)" (PDF). United States Department of Agriculture: Natural Resources Conservation Service: National Plant Data Center. (PDF) from the original on July 5, 2021. Retrieved July 5, 2021.
  238. ^ Borders, Brianna; Lee–Mäder, Eric (2014). "Milkweed Propagation and Seed Production: Stratification" (PDF). Milkweeds: A Conservation Practitioner's Guide: Plant Ecology, Seed Production Methods, and Habitat Restoration Opportunities. Portland, Oregon: The Xerces Society for Invertebrate Conservation. pp. 28–29. (PDF) from the original on July 4, 2021. Retrieved July 12, 2021.
  239. ^ Landis, Thomas D.; Dumroese, R. Kasten (2015). "Propagating Native Milkweeds for Restoring Monarch Butterfly Habitat" (PDF). International Plant Propagators' Society, Combined Proceedings (2014). 64: 302. (PDF) from the original on March 8, 2021. Retrieved July 11, 2021 – via United States Department of Agriculture: United States Forest Service. Many sources of milkweed seeds require stratification (cold, moist treatment) before sowing. In a review of stratification requirements for common milkweed, recommendations varied from as short as 7 days to as long as 11 months at 5°C (41°F) (Luna and Dumroese, 2013). Butterfly milkweed (A. tuberosa) germination increased from 29 to 48 to 62% as stratification duration increased from 0 to 30 to 60 days, respectively (Bir, 1986). Our informal natural stratification trial with showy (milkweed) and narrow leaf milkweed (A. fascicularis) in southern Oregon revealed that seeds began to germinate after 15 weeks in stratification (Fig. 3A).
  240. ^ Higgins, Adrian (May 27, 2015). "7 milkweed varieties and where to find them". Home & Garden. The Washington Post. from the original on September 26, 2020. Retrieved October 17, 2020. Seed may be stubborn to germinate and may need a period of cold treatment.
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  252. ^ Vogt, Benjamin (February 19, 2015). "Great Design Plant: Asclepias incarnata for a Butterfly Garden: Beautiful swamp milkweed makes it easy to help monarchs and other pollinators in eastern U.S. gardens". Palo Alto, California: Houzz. from the original on May 7, 2021. Retrieved July 5, 2021.
  253. ^ a b Abugattas, Alonzo (January 3, 2017). "Monarch Way Stations". Capital Naturalist. from the original on March 8, 2021. Retrieved July 5, 2021 – via Blogger. A better option for most gardeners might be Swamp Milkweed (A. incarnata) which, despite its name, does fine in regular garden soil and doesn't spread by runners.
  254. ^ a b "Asclepias incarnata". Bring Back The Monarchs. Monarch Watch. from the original on June 12, 2021. Retrieved July 5, 2021. Life span: In gardens most plants live two-five years but known to survive up to 20 years. [...] Propagation: Slow to spread via seeds. [...] 'Overhead Conditions: Not shade tolerant. An early successional plant that tends to grow at the margins of wetlands and in seasonally flooded areas. It is not a good vegetative competitor and tends to disappear as vegetative density increases and habitats dry out.

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January 30, 2023
monarch, butterfly, monarch, butterfly, simply, monarch, danaus, plexippus, milkweed, butterfly, subfamily, danainae, family, nymphalidae, other, common, names, depending, region, include, milkweed, common, tiger, wanderer, black, veined, brown, amongst, most,. The monarch butterfly or simply monarch Danaus plexippus is a milkweed butterfly subfamily Danainae in the family Nymphalidae 5 Other common names depending on region include milkweed common tiger wanderer and black veined brown 6 It is amongst the most familiar of North American butterflies and an iconic pollinator 7 although it is not an especially effective pollinator of milkweeds 8 9 Its wings feature an easily recognizable black orange and white pattern with a wingspan of 8 9 10 2 cm 3 5 4 0 in 10 A Mullerian mimic the viceroy butterfly is similar in color and pattern but is markedly smaller and has an extra black stripe across each hindwing Monarch butterflyMaleFemaleConservation statusLeast Concern IUCN 3 1 1 entire species Endangered IUCN 3 1 2 migratory subspecies Scientific classificationKingdom AnimaliaPhylum ArthropodaClass InsectaOrder LepidopteraFamily NymphalidaeGenus DanausSpecies D plexippusBinomial nameDanaus plexippus Linnaeus 1758 SynonymsPapilio plexippus Linnaeus 1758 Danaus archippus Fabricius 1793 3 Danaus menippe Hubner 1816 4 Anosia plexippus Dyar 1903 The eastern North American monarch population is notable for its annual southward late summer autumn instinctive migration from the northern and central United States and southern Canada to Florida and Mexico 5 During the fall migration monarchs cover thousands of miles with a corresponding multigenerational return north in spring The western North American population of monarchs west of the Rocky Mountains often migrates to sites in southern California but individuals have been found in overwintering Mexican sites as well 11 12 In 2009 monarchs were reared on the International Space Station successfully emerging from pupae located in the station s Commercial Generic Bioprocessing Apparatus 13 Contents 1 Etymology 2 Taxonomy 3 Genome 4 Life cycle 4 1 Metamorphosis 4 1 1 Egg 4 1 2 Larva 4 1 3 Pupa 4 1 4 Adult 5 Vision 6 Courtship and mating 7 Distribution and habitat 8 Larval host plants 9 Adult food sources 10 Flight and migration 11 Interactions with predators 11 1 Types of predators 11 2 Aposematism 11 3 Mimicry 12 Human interaction 12 1 Captive rearing 13 Threats 13 1 Western monarch populations 13 2 Eastern and midwestern monarch populations 13 2 1 Habitat loss due to herbicide use and genetically modified crops 13 2 2 Losses during migration 13 2 3 Loss of overwintering habitat 13 3 Parasites 13 4 Confusion of host plants 13 5 Climate 14 Conservation status 15 Conservation efforts 15 1 Federal actions 15 2 Other actions 15 2 1 National Cooperative Highway Research Program report 15 3 Butterfly gardening 16 See also 17 References 18 External linksEtymology EditThe name monarch is believed to have been given in honor of King William III of England as the butterfly s main color is that of the king s secondary title Prince of Orange 14 The monarch was originally described by Carl Linnaeus in his Systema Naturae of 1758 and placed in the genus Papilio 15 In 1780 Jan Krzysztof Kluk used the monarch as the type species for a new genus Danaus Danaus Ancient Greek Danaos a great grandson of Zeus was a mythical king in Egypt or Libya who founded Argos Plexippus Plh3ippos was one of the 50 sons of Aegyptus the twin brother of Danaus In Homeric Greek his name means one who urges on horses i e rider or charioteer 16 In the tenth edition of Systema Naturae at the bottom of page 467 17 Linnaeus wrote that the names of the Danai festivi the division of the genus to which Papilio plexippus belonged were derived from the sons of Aegyptus Linnaeus divided his large genus Papilio containing all known butterfly species into what we would now call subgenera The Danai festivi formed one of the subgenera containing colorful species as opposed to the Danai candidi containing species with bright white wings Linnaeus wrote Danaorum Candidorum nomina a filiabus Danai Aegypti Festivorum a filiis mutuatus sunt English The names of the Danai candidi have been derived from the daughters of Danaus those of the Danai festivi from the sons of Aegyptus Robert Michael Pyle suggested Danaus is a masculinized version of Danae Greek Danah Danaus s great great granddaughter to whom Zeus came as a shower of gold which seemed to him a more appropriate source for the name of this butterfly 18 Taxonomy Edit White morph of the monarch in Hawaii called the white monarch Monarchs belong in the subfamily Danainae of the family Nymphalidae Danainae was formerly considered a separately family Danaidae 19 The three species of monarch butterflies are D plexippus described by Linnaeus in 1758 is the species known most commonly as the monarch butterfly of North America Its range actually extends worldwide including Hawaii Australia New Zealand Spain and the Pacific Islands D erippus the southern monarch was described by Pieter Cramer in 1775 This species is found in tropical and subtropical latitudes of South America mainly in Brazil Uruguay Paraguay Argentina Bolivia Chile and southern Peru The South American monarch and the North American monarch may have been one species at one time Some researchers believe the southern monarch separated from the monarch s population some 2 million years ago at the end of the Pliocene Sea levels were higher and the entire Amazonas lowland was a vast expanse of brackish swamp that offered limited butterfly habitat 20 D cleophile the Jamaican monarch described by Jean Baptiste Godart in 1819 ranges from Jamaica to Hispaniola 2 Six subspecies and two color morphs of D plexippus have been identified 6 D p plexippus nominate subspecies described by Linnaeus in 1758 is the migratory subspecies known from most of North America D p p form nivosus the white monarch commonly found on Oahu Hawaii and rarely in other locations 21 D p p as yet unnamed a color morph lacking some wing vein markings 22 D p nigrippus Richard Haensch 1909 South America as forma Danais sic archippus f nigrippus Hay Roe et al in 2007 identified this taxon as a subspecies 23 D p megalippe Jacob Hubner 1826 nonmigratory subspecies and is found from Florida and Georgia southwards throughout the Caribbean and Central America to the Amazon River D p leucogyne Arthur G Butler 1884 St Thomas D p portoricensis Austin Hobart Clark 1941 Puerto Rico D p tobagi Austin Hobart Clark 1941 TobagoThe population level of the white morph in Oahu is nearing 10 On other Hawaiian islands the white morph occurs at a relatively low frequency White monarchs D p p form nivosus have been found throughout the world including Australia New Zealand Indonesia and the United States 21 However some taxonomists disagree on these classifications 20 23 Genome EditThe monarch was the first butterfly to have its genome sequenced 24 12 The 273 million base pair draft sequence includes a set of 16 866 protein coding genes The genome provides researchers insights into migratory behavior the circadian clock juvenile hormone pathways and microRNAs that are differentially expressed between summer and migratory monarchs 25 26 27 More recently the genetic basis of monarch migration and warning coloration has been described 28 No genetic differentiation exists between the migratory populations of eastern and western North America 24 16 Recent research has identified the specific areas in the genome of the monarch that regulate migration No genetic difference is seen between a migrating and nonmigrating monarch but the gene is expressed in migrating monarchs but not expressed in nonmigrating monarchs 29 A 2015 publication identified genes from wasp bracoviruses in the genome of the North American monarch 30 leading to articles about monarch butterflies being genetically modified organisms 31 32 Life cycle Edit The life cycle of the monarch butterfly Metamorphosis Edit Like all Lepidoptera monarchs undergo complete metamorphosis their life cycle has four phases egg larva pupa and adult Monarchs transition from eggs to adults during warm summer temperatures in as little as 25 days extending to as many as seven weeks during cool spring conditions During their development both larvae and their milkweed hosts are vulnerable to weather extremes predators parasites and diseases commonly fewer than 10 of monarch eggs and caterpillars survive 24 21 22 Egg Edit Egg The egg is derived from materials ingested as a larva and from the spermatophores received from males during mating 33 Female monarchs lay eggs singly most often on the underside of a young leaf of a milkweed plant during the spring and summer 34 Females secrete a small amount of glue to attach their eggs directly to the plant They typically lay 300 to 500 eggs over a two to five week period 35 Eggs are cream colored or light green ovate to conical in shape and about 1 2 mm 0 9 mm 0 047 in 0 035 in in size The eggs weigh less than 0 5 mg 0 0077 gr each and have raised ridges that form longitudinally from the point to apex to the base Although each egg is 1 1000 the mass of the female she may lay up to her own mass in eggs Females lay smaller eggs as they age Larger females lay larger eggs 33 The number of eggs laid by a female which may mate several times can reach 1 180 36 Eggs take three to eight days to develop and hatch into larvae or caterpillars 24 21 The offspring s consumption of milkweed benefits health and helps defend them against predators 37 38 Monarchs lay eggs along the southern migration route 39 Larva Edit Size comparison between an eastern black swallowtail caterpillar top a monarch caterpillar middle and a queen caterpillar bottom all on a human hand The larva caterpillar has five stages instars molting at the end of each instar Instars last about 3 to 5 days depending on factors such as temperature and food availability 5 40 The first instar caterpillar that emerges from the egg is pale green or grayish white shiny and almost translucent with a large black head It lacks banding coloration or tentacles The larvae or caterpillar eats its egg case and begins to feed on milkweed with a circular motion often leaving a characteristic arc shaped hole in the leaf Older first instar larvae have dark stripes on a greenish background and develop small bumps that later become front tentacles The first instar is usually between 2 and 6 mm 0 079 and 0 236 in long 40 The second instar larva develops a characteristic pattern of white yellow and black transverse bands The larva has a yellow triangle on the head and two sets of yellow bands around this central triangle It is no longer translucent and is covered in short setae Pairs of black tentacles begin to grow a larger pair on the thorax and a smaller pair on the abdomen The second instar is usually between 6 mm 0 24 in and 1 cm 0 39 in long 40 The third instar larva has more distinct bands and the two pairs of tentacles become longer Legs on the thorax differentiate into a smaller pair near the head and larger pairs further back Third instar larvae usually feed using a cutting motion on leaf edges The third instar is usually between 1 and 1 5 cm 0 39 and 0 59 in long 40 The fourth instar larva has a different banding pattern It develops white spots on the prolegs near its back and is usually between 1 5 and 2 5 cm 0 59 and 0 98 in long 40 The fifth instar larva has a more complex banding pattern and white dots on the prolegs with front legs that are small and very close to the head Fifth instar larvae often chew a shallow notch in the petiole of the leaf they are eating which causes the leaf to fall into a vertical position Its length ranges from 2 5 to 4 5 cm 0 98 to 1 77 in 5 40 As the caterpillar completes its growth it is 4 5 cm 1 8 in long large specimens can reach 5 cm 2 0 in and 7 to 8 mm 0 28 to 0 31 in wide and weighs about 1 5 g 0 053 oz compared to the first instar which is 2 to 6 mm 0 079 to 0 236 in long and 0 5 to 1 5 mm 0 020 to 0 059 in wide Fifth instar larvae greatly increase in size and weight They then stop feeding and are often found far from milkweed plants as they seek a site for pupating 40 In a laboratory setting the fourth and fifth instar stages of the caterpillar showed signs of aggressive behavior with lower food availability Attacked caterpillars were found to be attacked when it was feeding on milkweed leaves and the caterpillars attacked when foraging for milkweed 41 This demonstrates the aggressive behavior of monarch caterpillars due to the availability of milkweed Pupa Edit This section needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed October 2021 Learn how and when to remove this template message Chrysalis To prepare for the pupal or chrysalis stage the caterpillar chooses a safe place for pupation where it spins a silk pad on a downward facing horizontal surface At this point it turns around and securely latches on with its last pair of hind legs and hangs upside down in the form of the letter J After J hanging for about 12 16 hours it soon straightens out its body and goes into peristalsis some seconds before its skin splits behind its head It then sheds its skin over a period of a few minutes revealing a green chrysalis At first the chrysalis is long soft and somewhat amorphous but over a few hours it compacts into its distinct shape an opaque pale green chrysalis with small golden dots near the bottom and a gold and black rim around the dorsal side near the top 42 At first its exoskeleton is soft and fragile but it hardens and becomes more durable within about a day At this point it is about 2 5 cm 0 98 in long and 10 12 mm 0 39 0 47 in wide weighing about 1 2 g 0 042 oz At normal summer temperatures it matures in 8 15 days usually 11 12 days During this pupal stage the adult butterfly forms inside A day or so before emerging the exoskeleton first becomes translucent and the chrysalis more bluish Finally within 12 hours or so it becomes transparent revealing the black and orange colors of the butterfly inside before it ecloses emerges 43 44 Adult Edit This section needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed October 2021 Learn how and when to remove this template message An emergent monarch clinging to its chrysalis shell The adult emerges from its chrysalis after about two weeks of pupation The emergent adult hangs upside down for several hours while it pumps fluids and air into its wings which expand dry and stiffen The butterfly then extends and retracts its wings Once conditions allow it flies and feeds on a variety of nectar plants During the breeding season adults reach sexual maturity in 4 5 days However the migrating generation does not reach maturity until overwintering is complete 45 The adult s wingspan ranges from 8 9 to 10 2 centimetres 3 5 to 4 0 in 10 The upper sides of the wings are tawny orange the veins and margins are black and two series of small white spots occur in the margins Monarch forewings also have a few orange spots near their tips Wing undersides are similar but the tips of forewings and hindwings are yellow brown instead of tawny orange and the white spots are larger 46 The shape and color of the wings change at the beginning of the migration and appear redder and more elongated than later migrants 47 Wings size and shape differ between migratory and nonmigratory monarchs Monarchs from eastern North America have larger and more angular forewings than those in the western population 24 In eastern North American populations overall wing size in the physical dimensions of wings varies Males tend to have larger wings than females and are typically heavier than females Both males and females have similar thoracic dimensions Female monarchs tended to have thicker wings which is thought to convey greater tensile strength and reduce the likelihood of being damaged during migration Additionally females had lower wing loading than males which would mean females require less energy to fly 48 Adults are sexually dimorphic Males are slightly larger than females and have a black spot on a vein on each hindwing The spots contain scales that produce pheromones that many Lepidoptera use during courtship Females are often darker than males and have wider veins on their wings The ends of the abdomens of males and females differ in shape 46 49 24 50 51 52 The adult s thorax has six legs but as in all of the Nymphalidae the forelegs are small and held against the body The butterfly uses only its middle and hindlegs when walking and clinging 53 Adults typically live for 2 5 weeks during their breeding season 24 22 23 Larvae growing in high densities are smaller have lower survival and weigh less as adults compared with those growing in lower densities 54 Vision EditPhysiological experiments suggest that monarch butterflies view the world through a tetrachromatic system 55 Like humans their retina contain three types of opsin proteins expressed in distinct photoreceptor cells each of which absorbs light at a different wavelength Unlike humans one of those types of photoreceptor cells corresponds to a wavelength in the ultraviolet range the other two correspond to blue and green 56 In addition to these three photoreceptors cells in the main retina monarch butterfly eyes contain orange filtering pigments that filter the light reaching some green absorbing opsins thereby making a fourth photoreceptor cell sensitive to longer wavelength light 55 The combination of filtered and unfiltered green opsins permits the butterflies to distinguish yellow from orange colors 55 The ultraviolet opsin protein has also been detected in the dorsal rim region of monarch eyes One study suggests that this allows the butterflies the ability to detect ultraviolet polarized skylight to orient themselves with the sun for their long migratory flight 57 These butterflies are capable of distinguishing colors based on their wavelength only and not based on intensity this phenomenon is termed true color vision This is important for many butterfly behaviors including seeking nectar for nourishment choosing a mate and finding milkweed on which to lay eggs One study found that floral color is more easily recognized at a distance by butterflies searching for nectar than floral shape This may be because flowers have highly contrasting colors to the green background of a vegetative landscape 58 On the other hand leaf shape is important for oviposition so that the butterflies can ensure their eggs are being laid on milkweed Beyond the perception of color the ability to remember certain colors is essential in the life of monarch butterflies These insects can easily learn to associate color and to a lesser extent shape with sugary food rewards When searching for nectar color is the first cue that draws the insect s attention toward a potential food source and shape is a secondary characteristic that promotes the process When searching for a place to lay its eggs the roles of color and shape are switched Also a difference may exist between male and female butterflies from other species in terms of the ability to learn certain colors however no differences is noted between the sexes for monarch butterflies 58 Courtship and mating Edit source source source source source source source source source source source source Monarch butterfly mating video Monarch courtship occurs in two phases During the aerial phase a male pursues and often forces a female to the ground During the ground phase the butterflies copulate and remain attached for about 30 to 60 minutes 59 Only 30 of mating attempts end in copulation suggesting that females may be able to avoid mating though some have more success than others 60 61 During copulation a male transfers his spermatophore to a female Along with sperm the spermatophore provides a female with nutrition which aids her in laying eggs An increase in spermatophore size increases the fecundity of female monarchs Males that produce larger spermatophores also fertilize more females eggs 62 Females and males typically mate more than once Females that mate several times lay more eggs 63 Mating for the overwintering populations occurs in the spring prior to dispersion Mating is less dependent on pheromones than in other species in its genus 64 Male search and capture strategies may influence copulatory success and human induced changes to the habitat can influence monarch mating activity at overwintering sites 65 Distribution and habitat Edit String of monarchs wintering at California s Pismo State Beach Monarch Preserve 2015 Monarch flying away from a sunflower in Mexico The range of the western and eastern populations of D p plexippus expands and contracts depending upon the season The range differs between breeding areas migration routes and winter roosts 24 18 However no genetic differences between the western and eastern monarch populations exist 29 reproductive isolation has not led to subspeciation of these populations as it has elsewhere within the species range 24 19 In the Americas the monarch ranges from southern Canada through northern South America 5 It is also found in Bermuda Cook Islands 66 Hawaii 67 68 Cuba 69 and other Caribbean islands 24 18 the Solomons New Caledonia New Zealand 70 Papua New Guinea 71 Australia the Azores the Canary Islands Madeira continental Portugal Gibraltar 72 the Philippines and Morocco 73 It appears in the UK in some years as an accidental migrant 74 Overwintering populations of D p plexippus are found in Mexico California along the Gulf Coast of the United States year round in Florida and in Arizona where the habitat has the specific conditions necessary for their survival 75 76 On the East Coast of the United States they have overwintered as far north as Lago Mar Virginia Beach Virginia 77 Their wintering habitat typically provides access to streams plenty of sunlight enabling body temperatures that allow flight and appropriate roosting vegetation and is relatively free of predators Overwintering roosting butterflies have been seen on basswoods elms sumacs locusts oaks osage oranges mulberries pecans willows cottonwoods and mesquites 78 While breeding monarch habitats can be found in agricultural fields pasture land prairie remnants urban and suburban residential areas gardens trees and roadsides anywhere where there is access to larval host plants 79 Larval host plants Edit Mating monarchs in captivity The host plants used by the monarch caterpillar include Inflorescence of swamp milkweed one of many species of Asclepias milkweeds that serve as hosts for monarch caterpillars A second instar monarch caterpillar feeding on Asclepias fascicularis Asclepias angustifolia Arizona milkweed 80 Asclepias albicans whitestem milkweed Asclepias asperula antelope horns milkweed 80 Asclepias californica California milkweed 80 Asclepias cordifolia heartleaf milkweed 80 Asclepias curassavica Asclepias eriocarpa woolly pod milkweed 80 Asclepias erosa desert milkweed 80 Asclepias exaltata poke milkweed 80 Asclepias fascicularis Mexican whorled milkweed 80 Asclepias humistrata sandhill pinewoods milkweed 80 Asclepias incarnata swamp milkweed 81 82 83 84 Asclepias linaria pineneedle milkweed Asclepias nivea Caribbean milkweed 85 Asclepias oenotheroide zizotes milkweed 80 Asclepias perennis aquatic milkweed 80 Asclepias speciosa showy milkweed 80 86 87 88 89 Asclepias subulata rush milkweed 80 Asclepias syriaca common milkweed 90 Asclepias tuberosa butterfly weed 80 Asclepias variegata white milkweed 80 Asclepias verticillata whorled milkweed 80 Asclepias vestita woolly milkweed 80 Asclepias viridis green antelopehorn milkweed 80 91 92 93 94 Calotropis gigantea crown flower 95 Calotropis procera Cynanchum laeve sand vine milkweed 96 Sarcostemma clausa white vine 67 97 Monarch feeding from marigold flower Asclepias curassavica or tropical milkweed is often planted as an ornamental in butterfly gardens Year round plantings in the USA are controversial and criticised as they may be the cause of new overwintering sites along the U S Gulf Coast leading to year round breeding of monarchs 98 This is thought to adversely affect migration patterns and to cause a dramatic buildup of the dangerous parasite Ophryocystis elektroscirrha 99 New research also has shown that monarch larvae reared on tropical milkweed show reduced migratory development reproductive diapause and when migratory adults are exposed to tropical milkweed it stimulates reproductive tissue growth 100 Adult food sources Edit Nectaring on purple coneflower Echinacea purpurea An adult monarch sucking nectar from Salvia clevelandii Although larvae eat only milkweed adult monarchs feed on the nectar of many plants including 101 Apocynum cannabinum Indian hemp Asclepias spp milkweed Aster sp aster Cirsium sp thistle Daucus carota wild carrot Dipsacus sylvestris teasel Echinacea sp coneflower Erigeron canadensis horseweed Eupatorium maculatum spotted Joe Pye weed Eupatorium perfoliatum common boneset Hesperis matronalis dame s rocket Liatris sp blazing stars Medicago sativa alfalfa Solidago sp goldenrod Syringa vulgaris lilac Trifolium pratense red clover Vernonia altissima tall ironweed 76 Monarchs obtain moisture and minerals from damp soil and wet gravel a behavior known as mud puddling The monarch has also been noticed puddling at an oil stain on pavement 76 Flight and migration EditFurther information Monarch butterfly migration Migrating monarchs resting on a pine tree in Fire Island National Seashore on Long Island New York September 2021 In North America monarchs migrate both north and south on an annual basis in a long distance journey that is fraught with risks 5 This is a multi generational migration with individual monarchs only making part of the full journey 102 The population east of the Rocky Mountains attempts to migrate to the sanctuaries of the Mariposa Monarca Biosphere Reserve in the Mexican state of Michoacan and parts of Florida The western population tries to reach overwintering destinations in various coastal sites in central and southern California The overwintered population of those east of the Rockies may reach as far north as Texas and Oklahoma during the spring migration The second third and fourth generations return to their northern locations in the United States and Canada in the spring 103 Captive raised monarchs appear capable of migrating to overwintering sites in Mexico 104 though they have a much lower migratory success rate than do wild monarchs see section on captive rearing below 105 Monarch overwintering sites have been discovered recently in Arizona 106 Monarchs from the eastern US generally migrate longer distances than monarchs from the western US 107 Since the 1800s monarchs have spread throughout the world and there are now many non migratory populations globally 108 Flight speeds of adults are around 9 km h 6 mph 109 Interactions with predators EditIn both caterpillar and butterfly form monarchs are aposematic warding off predators with a bright display of contrasting colors to warn potential predators of their undesirable taste and poisonous characteristics One monarch researcher emphasizes that predation on eggs larvae or adults is natural since monarchs are part of the food chain thus people should not take steps to kill predators of monarchs 110 Larvae feed exclusively on milkweed and consume protective cardiac glycosides Toxin levels in Asclepias species vary Not all monarchs are unpalatable but exhibit Batesian or automimics Cardiac glycosides levels are higher in the abdomen and wings Some predators can differentiate between these parts and consume the most palatable ones 111 Butterfly weed A tuberosa lacks significant amounts of cardiac glycosides cardenolides but instead contains other types of toxic glycosides including pregnanes 112 113 114 This difference may reduce the toxicity of monarchs whose larvae feed on that milkweed species as a naturalist and others have reported that monarch caterpillars do not favor the plant 115 Some other milkweeds have similar characteristics 116 Types of predators Edit While monarchs have a wide range of natural predators none of these is suspected of causing harm to the overall population or are the cause of the long term declines in winter colony sizes Several species of birds have acquired methods that allow them to ingest monarchs without experiencing the ill effects associated with the cardiac glycosides cardenolides The black backed oriole is able to eat the monarch through an exaptation of its feeding behavior that gives it the ability to identify cardenolides by taste and reject them 117 The black headed grosbeak though has developed an insensitivity to secondary plant poisons that allows it to ingest monarchs without vomiting 118 As a result these orioles and grosbeaks periodically have high levels of cardenolides in their bodies and they are forced to go on periods of reduced monarch consumption This cycle effectively reduces potential predation of monarchs by 50 and indicates that monarch aposematism has a legitimate purpose 117 The black headed grosbeak has also evolved resistance mutations in the molecular target of the heart poisons the sodium pump The specific mutations that evolved in one of the grosbeak s four copies of the sodium pump gene are the same as those found in other milkweed butterflies like the common crow that also evolved to resist cardiac glycosides 119 Other bird predators include brown thrashers grackles robins cardinals sparrows scrub jays and pinyon jays 111 The monarch s white morph appeared in Oahu after the 1965 1966 introduction of two bulbul bird species Pycnonotus cafer and Pycnonotus jocosus These are now the most common avian insectivores in Hawaii and probably the only ones that eat insects as large as monarchs Although Hawaiian monarchs have low cardiac glycoside levels the birds may also be tolerant of that toxin The two species hunt the larvae and some pupae from the branches and undersides of leaves in milkweed bushes The bulbuls also eat resting and ovipositing adults but rarely flying ones Because of its color the white morph has a higher survival rate than the orange one This is either because of apostatic selection i e the birds have learned the orange monarchs can be eaten because of camouflage the white morph matches the white pubescence of milkweed or the patches of light shining through foliage or because the white morph does not fit the bird s search image of a typical monarch so is thus avoided 120 Some mice particularly the black eared mouse Peromyscus melanotis are like all rodents able to tolerate large doses of cardenolides and are able to eat monarchs 121 Overwintering adults become less toxic over time making them more vulnerable to predators In Mexico about 14 of the overwintering monarchs are eaten by birds and mice and black eared mice can eat up to 40 monarchs per night 75 121 In North America eggs and first instar larvae of the monarch are eaten by larvae and adults of the introduced Asian lady beetle Harmonia axyridis 122 The Chinese mantis Tenodera sinensis will consume the larvae once the gut is removed thus avoiding cardenolides 123 Predatory wasps commonly consume larvae 124 though large larvae may avoid wasp predation by dropping from the plant or by jerking their bodies 125 Aposematism Edit Chemical structure of oleandrin one of the cardiac glycosides Monarchs are toxic and foul tasting because of the presence of cardenolides in their bodies which the caterpillars ingest as they feed on milkweed 64 Monarchs and other cardenolide resistant insects rely on a resistant form of the Na K ATPase enzyme to tolerate significantly higher concentrations of cardenolides than nonresistant species 126 By ingesting a large amount of plants in the genus Asclepias primarily milkweed monarch caterpillars are able to sequester cardiac glycosides or more specifically cardenolides which are steroids that act in heart arresting ways similar to digitalis 127 It has been found that monarchs are able to sequester cardenolides most effectively from plants of intermediate cardenolide content rather than those of high or low content 128 Three mutations that evolved in the monarch s Na K ATPase were found to be sufficient together to confer resistance to dietary cardiac glycosides 126 This was tested by swapping these mutations into the same gene in the fruit fly Drosophila melanogaster using CRISPR Cas9 genome editing These fruit flies turned monarch flies 129 were completely resistant to dietary ouabain a cardiac glycoside found in Apocynaceae and even sequestered some through metamorphosis like the monarch 126 Different species of milkweed have different effects on growth virulence and transmission of parasites 130 One species Asclepias curassavica appears to reduce the symptoms of Ophryocystis elektroscirrha OE infection The two possible explanations for this include that it promotes overall monarch health to boost the monarch s immune system or that chemicals from the plant have a direct negative effect on the OE parasites 130 A curassavica does not cure or prevent the infection with OE it merely allows infected monarchs to live longer and this would allow infected monarchs to spread the OE spores for longer periods For the average home butterfly garden this scenario only adds more OE to the local population 131 After the caterpillar becomes a butterfly the toxins shift to different parts of the body Since many birds attack the wings of the butterfly having three times the cardiac glycosides in the wings leaves predators with a very foul taste and may prevent them from ever ingesting the body of the butterfly 127 To combat predators that remove the wings only to ingest the abdomen monarchs keep the most potent cardiac glycosides in their abdomens 132 Mimicry Edit Monarch left and viceroy right butterflies exhibiting Mullerian mimicry Monarchs share the defense of noxious taste with the similar appearing viceroy butterfly in what is perhaps one of the most well known examples of mimicry Though long purported to be an example of Batesian mimicry the viceroy is actually reportedly more unpalatable than the monarch making this a case of Mullerian mimicry 133 Human interaction EditThe monarch is the state insect of Alabama 134 Idaho 135 Illinois 136 Minnesota 137 Texas 138 Vermont 139 and West Virginia 140 Legislation was introduced to make it the national insect of the United States 141 but this failed in 1989 142 and again in 1991 143 Homeowners are increasingly establishing butterfly gardens monarchs can be attracted by cultivating a butterfly garden with specific milkweed species and nectar plants Efforts are underway to establish these monarch waystations 144 An IMAX film Flight of the Butterflies describes the story of the Urquharts Brugger and Trail to document the then unknown monarch migration to Mexican overwintering areas 145 Sanctuaries and reserves have been created at overwintering locations in Mexico and California to limit habitat destruction These sites can generate significant tourism revenue 146 However with less tourism monarch butterflies will have a higher survival rate because they show more protein content and a higher value of immune response and oxidative defense 147 Organizations and individuals participate in tagging programs Tagging information is used to study migration patterns 148 The 2012 novel by Barbara Kingsolver Flight Behavior deals with the fictional appearance of a large population in the Appalachians 149 Captive rearing Edit Humans interact with monarchs when rearing them in captivity which has become increasingly popular However risks occur in this controversial activity On one hand captive rearing has many positive aspects Monarchs are bred in schools and used for butterfly releases at hospices memorial events and weddings 150 Memorial services for the September 11 attacks include the release of captive bred monarchs 151 152 153 Monarchs are used in schools and nature centers for educational purposes 154 Many homeowners raise monarchs in captivity as a hobby and for educational purposes 155 On the other hand this practice becomes problematic when monarchs are mass reared Stories in the Huffington Post in 2015 and Discover magazine in 2016 have summarized the controversy around this issue 156 157 The frequent media reports of monarch declines have encouraged many homeowners to attempt to rear as many monarchs as possible in their homes and then release them to the wild in an effort to boost the monarch population Some individuals such as one in Linn County Iowa have reared thousands of monarchs at the same time 158 Some monarch scientists do not condone the practice of rearing large numbers of monarchs in captivity for release into the wild because of the risks of genetic issues and disease spread 159 One of the biggest concerns of mass rearing is the potential for spreading the monarch parasite Ophryocystis elektroscirrha into the wild This parasite can rapidly build up in captive monarchs especially if they are housed together The spores of the parasite also can quickly contaminate all housing equipment so that all subsequent monarchs reared in the same containers then become infected One researcher stated that rearing more than 100 monarchs constitutes mass rearing and should not be done 160 In addition to the disease risks researchers believe these captive reared monarchs are not as fit as wild ones owing to the unnatural conditions in which they are raised Homeowners often raise monarchs in plastic or glass containers in their kitchens basements porches etc and under artificial lighting and controlled temperatures Such conditions would not mimic what the monarchs are used to in the wild and may result in adults that are unsuited for the realities of their wild existence In support of this a recent study by a citizen scientist found that captive reared monarchs have a lower migration success rate than wild monarchs do 105 A 2019 study shed light on the fitness of captive reared monarchs by testing reared and wild monarchs on a tethered flight apparatus that assessed navigational ability 161 In that study monarchs that were reared to adulthood in artificial conditions showed a reduction in navigational ability This happened even with monarchs that were brought into captivity from the wild for a few days A few captive reared monarchs did show proper navigation This study revealed the fragility of monarch development if the conditions are not suitable their ability to properly migrate could be impaired The same study also examined the genetics of a collection of reared monarchs purchased from a butterfly breeder and found they were dramatically different from wild monarchs so much so that the lead author described them as franken monarchs 162 An unpublished study in 2019 compared behavior of captive reared versus wild monarch larvae 163 The study showed that reared larvae exhibited more defensive behavior than wild larvae The reason for this is unknown but it could relate to the fact that reared larvae are frequently handled and or disturbed Threats EditIn February 2015 the U S Fish and Wildlife Service reported a study that showed that nearly a billion monarchs had vanished from the butterfly s overwintering sites since 1990 The agency attributed the monarch s decline in part to a loss of milkweed caused by herbicides that farmers and homeowners had used 164 Western monarch populations Edit See also Threats to monarch butterfly in California Western monarch populations from 1997 to 2013 from Xerces Society data Based on a 2014 20 year comparison the overwintering numbers west of the Rocky Mountains have dropped more than 50 since 1997 and the overwintering numbers east of the Rockies have declined by more than 90 since 1995 According to the Xerces Society the monarch population in California decreased 86 in 2018 going from millions of butterflies to tens of thousands of butterflies 165 The society s annual 2020 2021 winter count showed a significant decline in the California population One Pacific Grove site did not have a single monarch butterfly A primary explanation for this was the destruction of the butterfly s milkweed habitats 24 166 This particular population is believed to comprise less than 2000 individuals as of 2022 update 167 Eastern and midwestern monarch populations Edit Area covered by monarchs D plexippus eastern migratory population in their overwintering areas in Mexico between 1993 and 2018 A 2016 publication attributed the previous decade s 90 decline in overwintering numbers of the eastern monarch population to the loss of breeding habitat and milkweed The publication s authors stated that an 11 57 probability existed that this population will go almost extinct over the next 20 years 168 Chip Taylor the director of Monarch Watch at the University of Kansas has stated that the Midwest milkweed habitat is virtually gone with 120 150 million acres lost 169 170 To help fight this problem Monarch Watch encourages the planting of Monarch Waystations 155 Habitat loss due to herbicide use and genetically modified crops Edit Declines in milkweed abundance and monarch populations between 1999 and 2010 are correlated with the adoption of herbicide tolerant genetically modified GM corn and soybeans which now constitute 89 and 94 of these crops respectively in the U S 168 GM corn and soybeans are resistant to the effect of the herbicide glyphosate Some conservationists attribute the disappearance of milkweed to agricultural practices in the Midwest where GM seeds are bred to resist herbicides that farmers use to kill unwanted plants that grow near their rows of food crops 171 172 In 2015 the Natural Resources Defense Council filed a suit against the United States Environmental Protection Agency EPA The Council argued that the agency ignored warnings about the dangers of glyphosate usage for monarchs 173 However a 2018 study has suggested that the decline in milkweed predates the arrival of GM crops 174 Losses during migration Edit Monarch nectaring on a zinnia flower during its migration southward to Mexico late September of 2022Eastern and midwestern monarchs are apparently experiencing problems reaching Mexico A number of monarch researchers have cited recent evidence obtained from long term citizen science data that show that the number of breeding adult monarchs has not declined in the last two decades 175 176 177 The lack of long term declines in the numbers of breeding and migratory monarchs yet the clear declines in overwintering numbers suggests a growing disconnect exists between these life stages One researcher has suggested that mortality from car strikes constitutes an increasing threat to migrating monarchs 178 A study of road mortality in northern Mexico published in 2019 showed very high mortality from just two hotspots each year amounting to 200 000 monarchs killed 179 Loss of overwintering habitat Edit This section needs to be updated Please help update this article to reflect recent events or newly available information August 2021 The area of Mexican forest to which eastern and midwestern monarchs migrate reached its lowest level in two decades in 2013 The decline was expected to increase during the 2013 2014 season Mexican environmental authorities continue to monitor illegal logging of the oyamel trees The oyamel is a major species of evergreen on which the overwintering butterflies spend a significant time during their winter diapause or suspended development 180 A 2014 study acknowledged that while the protection of overwintering habitat has no doubt gone a long way towards conserving monarchs that breed throughout eastern North America their research indicates that habitat loss on breeding grounds in the United States is the main cause of both recent and projected population declines 181 Parasites Edit Pteromalus cassotis on monarch chrysalis Parasites include the tachinid flies Sturmia convergens 182 and Lespesia archippivora Lesperia parasitized butterfly larvae suspend but die prior to pupation The fly s maggot lowers itself to the ground forms a brown puparium and then emerges as an adult 183 Pteromalid wasps specifically Pteromalus cassotis parasitize monarch pupae 184 These wasps lay their eggs in the pupae while the chrysalis is still soft Up to 400 adults emerge from the chrysalis after 14 20 days 184 killing the monarch The bacterium Micrococcus flacidifex danai also infects larvae Just before pupation the larvae migrate to a horizontal surface and die a few hours later attached only by one pair of prolegs with the thorax and abdomen hanging limp The body turns black shortly thereafter The bacterium Pseudomonas aeruginosa has no invasive powers but causes secondary infections in weakened insects It is a common cause of death in laboratory reared insects 183 Ophryocystis elektroscirrha is another parasite of the monarch It infects the subcutaneous tissues and propagates by spores formed during the pupal stage The spores are found over all of the body of infected butterflies with the greatest number on the abdomen These spores are passed from female to caterpillar when spores rub off during egg laying and are then ingested by caterpillars Severely infected individuals are weak unable to expand their wings or unable to eclose and have shortened lifespans but parasite levels vary in populations This is not the case in laboratory rearing where after a few generations all individuals can be infected 185 Infection with O elektroscirrha creates an effect known as culling whereby migrating monarchs that are infected are less likely to complete the migration This results in overwintering populations with lower parasite loads 186 Owners of commercial butterfly breeding operations claim that they take steps to control this parasite in their practices 187 although this claim is doubted by many scientists who study monarchs 188 Confusion of host plants Edit The black swallow wort Cynanchum louiseae and pale swallow wort Cynanchum rossicum plants are problematic for monarchs in North America Monarchs lay their eggs on these relatives of native vining milkweed Cynanchum laeve because they produce stimuli similar to milkweed Once the eggs hatch the caterpillars are poisoned by the toxicity of this invasive plant from Europe 189 Climate Edit Climate variations during the fall and summer affect butterfly reproduction Rainfall and freezing temperatures affect milkweed growth Omar Vidal director general of WWF Mexico said The monarch s lifecycle depends on the climatic conditions in the places where they breed Eggs larvae and pupae develop more quickly in milder conditions Temperatures above 35 C 95 F can be lethal for larvae and eggs dry out in hot arid conditions causing a drastic decrease in hatch rate 190 If a monarch s body temperatures is below 30 C 86 F a monarch cannot fly To warm up they sit in the sun or rapidly shiver their wings to warm themselves 191 Climate change may dramatically affect the monarch migration A study from 2015 examined the impact of warming temperatures on the breeding range of the monarch and showed that in the next 50 years the monarch host plant will expand its range further north into Canada and that the monarchs will follow this 192 While this will expand the breeding locations of the monarch it will also have the effect of increasing the distance that monarchs must travel to reach their overwintering destination in Mexico which could result in greater mortality during the migration 193 Milkweeds grown at increased temperatures have been shown to contain higher cardenolide concentrations making the leaves too toxic for the monarch caterpillars However these increased concentrations are likely in response to increased insect herbivory which is also caused by the increased temperatures Whether increased temperatures make milkweed too toxic for monarch caterpillars when other factors are not present is unknown 194 Additionally milkweed grown at carbon dioxide levels of 760 parts per million was found to produce a different mix of the toxic cardenolides one of which was less effective against monarch parasites 195 Conservation status EditOn July 20 2022 the International Union for Conservation of Nature added the migratory monarch butterfly the subspecies common in North America to its red list of endangered species 196 2 The monarch butterfly is not currently listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora or protected specifically under U S domestic laws 197 On August 14 2014 the Center for Biological Diversity and the Center for Food Safety filed a legal petition requesting Endangered Species Act protection for the monarch and its habitat 24 based largely on the long term trends observed at overwintering sites The U S Fish and Wildlife Service FWS initiated a status review of the monarch butterfly under the Endangered Species Act with a due date for information submission of March 3 2015 later extended to 2020 On December 15 2020 the FWS ruled that adding the butterfly to the list of threatened and endangered species was warranted but precluded because it needed to devote its resources to 161 higher priority species 198 The number of monarchs overwintering in Mexico has shown a long term downward trend Since 1995 coverage numbers have been as high as 18 hectares 44 acres during the winter of 1996 1997 but on average about 6 hectares 15 acres Coverage declined to its lowest point to date 0 67 hectares 1 66 acres during the winter of 2013 2014 but rebounded to 4 01 hectares 10 acres in 2015 2016 The average population of monarchs in 2016 was estimated at 200 million Historically on average there are 300 million monarchs The 2016 increase was attributed to favorable breeding conditions in the summer of 2015 However coverage declined by 27 to 2 91 hectares 7 19 acres during the winter of 2016 2017 Some believe this was because of a storm that had occurred during March 2016 in the monarchs previous overwintering season 199 200 201 though this seems unlikely since most current research shows that the overwintering colony sizes do not predict the size of the next summer breeding population 202 In Ontario Canada the monarch butterfly is listed as a species of special concern 203 In fall 2016 the Committee on the Status of Endangered Wildlife in Canada proposed that the monarch be listed as endangered in Canada as opposed to its current listing as a species of concern in that country This move once enacted would protect critical monarch habitat in Canada such as major fall accumulation areas in southern Ontario but it would also have implications for citizen scientists who work with monarchs and for classroom activities If the monarch were federally protected in Canada these activities could be limited or require federal permits 204 In Nova Scotia the monarch is listed as endangered at the provincial level as of 2017 update This decision as well as the Ontario decision apparently is based on a presumption that the overwintering colony declines in Mexico create declines in the breeding range in Canada 205 Two recent studies have been conducted examining long term trends in monarch abundance in Canada using either butterfly atlas records 206 or citizen science butterfly surveys 207 and neither shows evidence of a population decline in Canada Conservation efforts EditSee also Monarch butterfly conservation in California Although numbers of breeding monarchs in eastern North America have apparently not decreased reports of declining numbers of overwintering butterflies have inspired efforts to conserve the species 175 176 177 Federal actions Edit On June 20 2014 President Barack Obama issued a presidential memorandum entitled Creating a Federal Strategy to Promote the Health of Honey Bees and Other Pollinators The memorandum established a Pollinator Health Task Force to be co chaired by the Secretary of Agriculture and the Administrator of the Environmental Protection Agency and stated The number of migrating Monarch butterflies sank to the lowest recorded population level in 2013 14 and there is an imminent risk of failed migration 208 In May 2015 the Pollinator Health Task Force issued a National Strategy to Promote the Health of Honey Bees and Other Pollinators The strategy laid out federal actions to achieve three goals two of which were Monarch Butterflies Increase the Eastern population of the monarch butterfly to 225 million butterflies occupying an area of approximately 15 acres 6 hectares in the overwintering grounds in Mexico through domestic international actions and public private partnerships by 2020 Pollinator Habitat Acreage Restore or enhance 7 million acres of land for pollinators over the next 5 years through Federal actions and public private partnerships 209 Many of the priority projects that the national strategy identified focused on the I 35 corridor which extends for 1 500 miles 2 400 km from Texas to Minnesota The area through which that highway travels provides spring and summer breeding habitats in the United States key monarch migration corridor 209 The U S General Services Administration GSA publishes sets of landscape performance requirements in its P100 documents which mandate standards for the GSA s Public Buildings Service Beginning in March 2015 those performance requirements and their updates have included four primary aspects for planting designs that are intended to provide adequate on site foraging opportunities for targeted pollinators The targeted pollinators include bees butterflies and other beneficial insects 210 211 212 On December 4 2015 President Obama signed into law the Fixing America s Surface Transportation FAST Act Pub L 114 94 213 The FAST Act placed a new emphasis on efforts to support pollinators To accomplish this the FAST Act amended Title 23 Highways of the United States Code The amendment directed the United States Secretary of Transportation when carrying out programs under that title in conjunction with willing states to encourage integrated vegetation management practices on roadsides and other transportation rights of way including reduced mowing and encourage the development of habitat and forage for Monarch butterflies other native pollinators and honey bees through plantings of native forbs and grasses including noninvasive native milkweed species that can serve as migratory way stations for butterflies and facilitate migrations of other pollinators 214 The FAST Act also stated that activities to establish and improve pollinator habitat forage and migratory way stations may be eligible for Federal funding if related to transportation projects funded under Title 23 214 The United States Department of Agriculture s Farm Service Agency helps increase U S populations of monarch butterfly and other pollinators through its Conservation Reserve Program s State Acres for Wildlife Enhancement SAFE Initiative The SAFE Initiative provides an annual rental payment to farmers who agree to remove environmentally sensitive land from agricultural production and who plant species that will improve environmental health and quality Among other things the initiative encourages landowners to establish wetlands grasses and trees to create habitats for species that the FWS has designated to be threatened or endangered 215 216 217 218 Other actions Edit Agriculture companies and other organizations are being asked to set aside areas that remain unsprayed to allow monarchs to breed In addition national and local initiatives are underway to help establish and maintain pollinator habitats along corridors containing power lines and roadways The Federal Highway Administration state governments and local jurisdictions are encouraging highway departments and others to limit their use of herbicides to reduce mowing to help milkweed to grow and to encourage monarchs to reproduce within their right of ways 172 219 National Cooperative Highway Research Program report Edit In 2020 the National Cooperative Highway Research Program NCRHP of the Transportation Research Board issued a 208 page report that described a project that had examined the potential for roadway corridors to provide habitat for monarch butterflies A part of the project developed tools for roadside managers to optimize potential habitat for monarch butterflies in their road rights of way 220 221 Such efforts are controversial because the risk of butterfly mortality near roads is high Several studies have shown that motor vehicles kill millions of monarchs and other butterflies every year 178 Also some evidence indicates that monarch larvae living near roads experience physiological stress conditions as evidenced by elevations in their heart rate 222 The NCRHP report acknowledged that among other hazards roads present a danger of traffic collisions for monarchs stating that these effects appear to be more concentrated in particular funnel areas during migration 223 Nevertheless the report concluded In summary threats along roadway corridors exist for monarchs and other pollinators but in the context of the amount of habitat needed for recovery of sustainable populations roadsides are of vital importance 223 Butterfly gardening Edit Further information Butterfly gardening A monarch waystation near the town of Berwyn Heights in Prince George s County Maryland June 2017 While scientific studies on the subject have been reported the practice of butterfly gardening and creating monarch waystations is commonly thought to increase the populations of butterflies 224 225 226 227 228 229 230 Efforts to restore falling monarch populations by establishing butterfly gardens and monarch waystations require particular attention to the butterfly s food preferences and population cycles as well to the conditions needed to propagate and maintain milkweed 231 232 For example in the Washington DC area and elsewhere in the northeastern United States monarchs prefer to reproduce on common milkweed A syriaca especially when its foliage is soft and fresh Because monarch reproduction in that area peaks in late summer when milkweed foliage is old and tough A syriaca needs to be mowed or cut back in June through August to assure that it will be regrowing rapidly when monarch reproduction reaches its peak Similar conditions exist for showy milkweed A speciosa in Michigan and for green antelopehorn milkweed A viridis where it grows in the Southern Great Plains and the Western United States 80 233 234 235 236 237 In addition the seeds of A syriaca and some other milkweeds need periods of cold treatment cold stratification before they will germinate 238 239 240 241 242 243 To protect seeds from washing away during heavy rains and from seed eating birds one can cover the seeds with a light fabric or with an 0 5 inch 13 mm layer of straw mulch 244 245 However mulch acts as an insulator Thicker layers of mulch can prevent seeds from germinating if they prevent soil temperatures from rising enough when winter ends Further few seedlings can push through a thick layer of mulch 246 Although monarch caterpillars will feed on butterfly weed A tuberosa in butterfly gardens the plant has rough leaves and is typically not a heavily used host plant for the species 247 The plant s low levels of cardenolides may also make the plant unattractive to egg laying monarchs 115 While A tuberosa s colorful flowers provide nectar for many adult butterflies the plant may be less suitable for use in butterfly gardens and monarch waystations than are other 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has a clear sap and the level of toxic cardiac glycosides is consistently low although other toxic compounds may be present Mikkelsen Lauge Hjorth Hamoudi Hassan Altuntas Gul Cigdem Heegaard Steffen 2017 Corneal Toxicity Following Exposure to Asclepias tuberosa The Open Ophthalmology Journal Bentham Science Publishers 11 1 4 doi 10 2174 1874364101711010001 PMC 5362972 PMID 28400886 The latex of A tuberosa seems to be different from other Asclepias species due to the fact that even though cardenolides are normally present in Asclepias species these cardenolides have not been found in A tuberosa Instead some unique pregnane glycosides are found in A tuberosa Warashina Tsutomu Noro Tadataka February 2010 8 12 8 20 Diepoxy 8 14 secopregnane Glycosides from the Aerial Parts of Asclepias tuberosa Chemical and Pharmaceutical Bulletin Pharmaceutical Society of Japan 58 2 172 179 doi 10 1248 cpb 58 172 PMID 20118575 Retrieved September 11 2020 Though cardenolides are considered to be 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by Monarch Butterflies PDF Washington D C Transportation Research Board OCLC 1152199695 Pre publication draft of NCHRP Research Report 942 Archived PDF from the original on July 8 2021 Retrieved July 8 2021 via Northwestern University Library Davis Andrew K Schroeder Hayley Yeager Ian Pearce Jana May 31 2018 Effects of simulated highway noise on heart rates of larval monarch butterflies Danaus plexippus implications for roadside habitat suitability Biology Letters 14 5 20180018 doi 10 1098 rsbl 2018 0018 PMC 6012697 PMID 29743264 a b Cariveau A B Caldwell W Lonsdorf E Nootenboom C Tuerk K Snell Rood E Anderson E Baum K A Hopwood J Oberhauser K 2019 Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies PDF Washington D C Transportation Research Board pp 2 3 OCLC 1152199695 Pre publication draft of NCHRP Research Report 942 Archived PDF from the original on July 8 2021 Retrieved July 8 2021 via Northwestern University Library Glassberg J 1995 Enjoying butterflies more attract butterflies to your backyard Marietta Ohio Bird Watcher s Digest Press ISBN 1880241080 LCCN 96202681 OCLC 35808599 Retrieved March 9 2020 via Google Books Butterfly Gardening Introduction University of Kansas Monarch Watch Archived from the original on February 2 2020 Retrieved March 9 2020 Monarch Garden Plants PDF San Francisco California Pollinator Partnership Archived from the original PDF on March 9 2020 Retrieved March 9 2020 Monarch Waystation Program University of Kansas Monarch Watch Archived from the original on June 2 2017 Retrieved June 5 2017 Abugattas Alonzo January 3 2017 Monarch Way Stations Archived from the original on June 5 2017 Retrieved June 5 2017 via Blogger Plants for Butterfly and Pollinator Gardens Native and Non native Plants Suitable for Gardens in the Northeastern United States PDF Monarch Watch Archived PDF from the original on August 9 2020 Retrieved October 18 2020 Wheeler Justin November 21 2017 Picking Plants for Pollinators The Cultivar Conundrum Xerces Blog The Xerces Society for Invertebrate Conservation Archived from the original on April 14 2021 Retrieved August 1 2021 Borders Brianna Lee Mader Eric 2014 Milkweed Propagation and Seed Production PDF Milkweeds A Conservation Practitioner s Guide Plant Ecology Seed Production Methods and Habitat Restoration Opportunities Portland Oregon The Xerces Society for Invertebrate Conservation pp 21 95 Archived PDF from the original on July 4 2021 Retrieved July 12 2021 Landis Thomas D Dumroese R Kasten 2015 Propagating Native Milkweeds for Restoring Monarch Butterfly Habitat PDF International Plant Propagators Society Combined Proceedings 2014 64 299 307 Archived PDF from the original on March 8 2021 Retrieved July 11 2021 via United States Department of Agriculture United States Forest Service Cariveau Alison B Caldwell Wendy Lonsdorf Eric Nootenboom Chris Tuerk Karen Snell Rood Emilie Anderson Eric Baum Kristen A Hopwood Jennifer Oberhauser Karen 2020 Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies Washington D C National Academies Press pp 79 80 doi 10 17226 25693 ISBN 9780309481328 LCCN 2020935714 OCLC 1229163481 S2CID 218854539 National Cooperative Highway Research Program NCRHP Research Report 942 Archived from the original on July 29 2020 Retrieved July 8 2021 Could roadside mowing stimulate milkweed growth and support monarch breeding Limited research in eastern North America has shown that spring or summer mowing can promote new growth and extend the availability of milkweed plants for monarch breeding Mowing may stimulate growth of some milkweed species particularly those that spread through rhizomes like common milkweed A syriaca and showy milkweed A speciosa Summer June or July mowing in Michigan resulted in more monarch eggs on regenerated stems than unmowed stems Summer July mowing and burning can increase green antelopehorn milkweed A viridis availability in the late summer and early fall in the Southern Great Plains whereas in areas without mowing the milkweed has senesced by August In the West showy milkweed will regrow after summer mowing and continue to support monarch breeding Stephanie McKnight personal observation However more research is needed in other areas to determine the optimal timing and frequency of mowing that promotes not only milkweed but also nectar plants It is also unknown if the benefit of additional milkweed availability in the fall outweighs the costs of the larval mortality caused by summer mowing The benefits are likely greater in areas that primarily have breeding monarchs in the spring and fall and where the dominant species of milkweed spread by rhizomes Sources Alcock et al 2016 Baum and Mueller 2015 Bhowick 1994 Haan and Landis 2019 Fischer et al 2015 cite news first Adrian last Higgins url http www washingtonpost com lifestyle home creating a rest stop for the monarch 2015 05 26 cd81a75c ffcb 11e4 805c c3f407e5a9e9 story html 7Ctitle A gardener s guide to saving the monarch department Home amp Garden newspaper The Washington Post access date October 17 2020 date May 27 2015 archive url https web archive org web 20150531181342 http www washingtonpost com lifestyle home creating a rest stop for the monarch 2015 05 26 cd81a75c ffcb 11e4 805c c3f407e5a9e9 story html 7Carchive date May 31 2015 url status live quote The monarch doesn t care where the milkweed grows and putting it in residential neighborhoods makes perfect sense said Doug Tallamy an entomologist at the University of Delaware author and expert on wildlife habitat gardens The Smithsonian Gardens Gardens and landscapes Smithsonian Institution s Butterfly Habitat Garden and the Ripley Garden are both good places to see milkweed integrated into a garden setting At the butterfly garden you can see the common milkweed now looking pretty good in fresh unblemished clumps By late summer it looks tall tired and tough Tallamy says if you grow it you should cut it back at least by half in June to produce soft foliage in late summer that will be more munchable for the caterpillars If you do that make sure there are no larvae on the plant before you chop it Abugattas Alonzo January 3 2017 Monarch Way Stations Capital Naturalist Archived from the original on March 8 2021 Retrieved July 5 2021 via Blogger Virginia is blessed for instance with 13 native Asclepias species plus 4 climbing vines that Monarch caterpillars can feed on For the best results cut the some of the stems back in late summer after they ve bloomed Fall is the when we get the most Monarchs laying eggs on our milkweeds Since the mother butterflies prefer young more tender growth you can provide this by timing your pruning so there are new leaves by September or so for the arriving Monarchs Just make sure to leave a few to produce pods for seeds The local monarch favorite is Common Milkweed A syriaca Gomez Tony Asclepias syriaca Common Milkweed for Monarch Caterpillars Monarch Butterfly Garden MonarchButterflyGarden net Archived from the original on March 16 2015 Retrieved October 17 2010 Cut At mid season after the blooms have faded cut some common plants back by about a third This promotes fresh plant growth and could get you an extra generation of monarchs on the fresh new leaves Leave some plants uncut if you want to harvest milkweed seeds in fall Stevens Michelle Plant guide for common milkweed Asclepias syriaca PDF United States Department of Agriculture Natural Resources Conservation Service National Plant Data Center Archived PDF from the original on July 5 2021 Retrieved July 5 2021 Borders Brianna Lee Mader Eric 2014 Milkweed Propagation and Seed Production Stratification PDF Milkweeds A Conservation Practitioner s Guide Plant Ecology Seed Production Methods and Habitat Restoration Opportunities Portland Oregon The Xerces Society for Invertebrate Conservation pp 28 29 Archived PDF from the original on July 4 2021 Retrieved July 12 2021 Landis Thomas D Dumroese R Kasten 2015 Propagating Native Milkweeds for Restoring Monarch Butterfly Habitat PDF International Plant Propagators Society Combined Proceedings 2014 64 302 Archived PDF from the original on March 8 2021 Retrieved July 11 2021 via United States Department of Agriculture United States Forest Service Many sources of milkweed seeds require stratification cold moist treatment before sowing In a review of stratification requirements for common milkweed recommendations varied from as short as 7 days to as long as 11 months at 5 C 41 F Luna and Dumroese 2013 Butterfly milkweed A tuberosa germination increased from 29 to 48 to 62 as stratification duration increased from 0 to 30 to 60 days respectively Bir 1986 Our informal natural stratification trial with showy milkweed and narrow leaf milkweed A fascicularis in southern Oregon revealed that seeds began to germinate after 15 weeks in stratification Fig 3A Higgins Adrian May 27 2015 7 milkweed varieties and where to find them Home amp Garden The Washington Post Archived from the original on September 26 2020 Retrieved October 17 2020 Seed may be stubborn to germinate and may need a period of cold treatment Gomez Tony Asclepias syriaca Common Milkweed for Monarch Caterpillars Monarch Butterfly Garden MonarchButterflyGarden net Archived from the original on March 16 2015 Retrieved October 17 2010 Start seeds indoors 2 months before final frost seeds must be cold stratified Stevens Michelle Plant guide for common milkweed Asclepias syriaca PDF United States Department of Agriculture Natural Resources Conservation Service National Plant Data Center Archived PDF from the original on July 5 2021 Retrieved July 5 2021 If planting in flats or in a greenhouse common milkweed seeds should be cold treated for three months Asclepias syriaca Butterfly gardening amp all things milkweed Archived from the original on July 7 2015 Retrieved July 7 2015 germination seed requires cold moist period Mader Eric Shepherd Mathew Vaughan Mace Black Scott Hoffman LeBuhn Gretchen 2011 Establishing Pollinator Habitat from Seed Sowing Seed Attracting Native Pollinators Protecting North America s Bees and Butterflies The Xerces Society guide North Adams Massachusetts Storey Publishing pp 113 114 ISBN 9781603427470 LCCN 2010043054 OCLC 776997073 Retrieved July 7 2021 via Internet Archive Landis Thomas D Dumroese R Kasten 2015 Propagating Native Milkweeds for Restoring Monarch Butterfly Habitat Propagating Native Milkweeds Seed Propagation PDF International Plant Propagators Society Combined Proceedings 2014 64 302 Archived PDF from the original on March 8 2021 Retrieved July 11 2021 via United States Department of Agriculture United States Forest Service Any of the standard seed propagation methods Landis et al 1999 are effective with milkweed Direct sowing of non stratified seeds during the fall followed by exposure to ambient winter conditions can be effective but the seeds must be mulched and protected Cover sown seeds with a thin mulch research has found that common milkweed seeds germinated better when planted 1 to 2 cm 0 4 to 0 8 in deep than when at the soil surface Jeffery and Robison 1971 Bush Brown James Bush Brown Louise 1958 Chapter 32 Mulches America s garden book New York Charles Scribner s Sons p 768 LCCN 58005738 OCLC 597041748 via Internet Archive a b Gomez Tony Asclepias tuberosa Butterfly Weed for Monarchs and More Monarch Butterfly Garden MonarchButterflyGarden net Archived from the original on July 29 2016 Retrieved October 17 2010 Rough leaves for monarch caterpillars not typically a heavily used host plant Pocius Victoria M Debinski Diane M Pleasants John M Bidne Keith G Hellmich Richard L January 8 2018 Monarch butterflies do not place all of their eggs in one basket oviposition on nine Midwestern milkweed species Ecosphere Ecological Society of America ESA 9 1 1 13 doi 10 1002 ecs2 2064 Retrieved July 6 2021 via Wiley Online Library Asclepias incarnata North Carolina Extension Gardener Plant Toolbox Raleigh North Carolina North Carolina State University N C Cooperative Extension Archived from the original on November 28 2020 Use in a naturalized area pollinator garden or along a pond or stream in full sun to partial shade Asclepias incarnata St Louis Missouri Missouri Botanical Garden Archived from the original on February 25 2021 Retrieved July 5 2021 Uses Sunny borders stream pond banks butterfly gardens Gomez Tony Asclepias incarnata Swamp Milkweed for Monarch Butterflies and Caterpillars Monarch Butterfly Garden Archived from the original on April 22 2021 Retrieved July 5 2021 Vogt Benjamin February 19 2015 Great Design Plant Asclepias incarnata for a Butterfly Garden Beautiful swamp milkweed makes it easy to help monarchs and other pollinators in eastern U S gardens Palo Alto California Houzz Archived from the original on May 7 2021 Retrieved July 5 2021 a b Abugattas Alonzo January 3 2017 Monarch Way Stations Capital Naturalist Archived from the original on March 8 2021 Retrieved July 5 2021 via Blogger A better option for most gardeners might be Swamp Milkweed A incarnata which despite its name does fine in regular garden soil and doesn t spread by runners a b Asclepias incarnata Bring Back The Monarchs Monarch Watch Archived from the original on June 12 2021 Retrieved July 5 2021 Life span In gardens most plants live two five years but known to survive up to 20 years Propagation Slow to spread via seeds Overhead Conditions Not shade tolerant An early successional plant that tends to grow at the margins of wetlands and in seasonally flooded areas It is not a good vegetative competitor and tends to disappear as vegetative density increases and habitats dry out External links Edit section, wikipedia, wiki, book, books, library,

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