All images © 2010-2021 Ana Carolina da Fonte (Masseran).
Taxonomy:
Animals Kingdom Animalia
Arthropods Phylum Arthropoda
Hexapods Subphylum Hexapoda
Insetos Class Insecta
Winged and Once-winged Insects Subclass Pterygota
Butterflies and Moths Order Lepidoptera
Butterflies Superfamily Papilionoidea
Monarcas, Borboletas-coruja e Afins Family Nymphalidae
Milkweed Butterflies Subfamily Danainae
Tribe Danaini
Tiger Butterflies Subtribe Danaina
Tiger Milkweed Butterflies Genus Danaus
Monarch Danaus plexippus
Danaus plexippus ssp. leucogyne
Danaus plexippus ssp. megalippe
Danaus plexippus ssp. nigrippus
Danaus plexippus ssp. nivosus
Danaus plexippus ssp. plexippus
Danaus plexippus ssp. portoricensis
Danaus plexippus ssp. tobagi
The monarch butterfly or simply monarch (Danaus plexippus) is a milkweed butterfly (subfamily Danainae) in the family Nymphalidae.[4] Other common names, depending on region, include milkweed, common tiger, wanderer, and black veined brown.[5] It may be the most familiar North American butterfly, and is considered an iconic pollinator species.[6] Its wings feature an easily recognizable black, orange, and white pattern, with a wingspan of 8.9–10.2 cm ( 3+1⁄2–4 in)[7] 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.
The eastern North American monarch population is notable for its annual southward late-summer/autumn migration from the northern and central United States and southern Canada to Florida and Mexico.[4] During the fall migration, monarchs cover thousands of miles, with a corresponding multi-generational return north. The western North American population of monarchs west of the Rocky Mountains often migrates to sites in southern California but has been found in overwintering Mexican sites as well.[8][9] Monarchs have been bred on the International Space Station.
Taxonomy
White morph of the monarch in Hawaii called white monarch
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.[11] The monarch was originally described by Carl Linnaeus in his Systema Naturae of 1758 and placed in the genus Papilio.[12] 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".[13] In the 10th edition of Systema Naturae, at the bottom of page 467,[14] 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.
There are three species of monarch butterflies:
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 and can be found in 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 mya, 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.[16]
D. cleophile, the Jamaican monarch, described by Jean-Baptiste Godart in 1819, ranges from Jamaica to Hispaniola.[17]
Six subspecies and two color morphs of D. plexippus have been identified:[5]
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.[18]
D. p. p. (as yet unnamed) – a color morph lacking some wing vein markings.[19]
D. p. nigrippus (Richard Haensch, 1909) – as forma: Danais [sic] archippus f. nigrippus. Hay-Roe et al. in 2007 identified this taxon as a subspecies:[20]
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 percentage of the white morph in Oahu is nearing 10%. On other Hawaiian islands, the white morph occurs at a relatively low frequency. White monarchs (nivosus) have been found throughout the world, including Australia, New Zealand, Indonesia, and the United States.
Some taxonomists disagree on these classifications.
Monarchs belong in the subfamily Danainae of the family Nymphalidae; Danainae was formerly considered a separately family Danaidae.
A 2015 paper identified genes from wasp bracoviruses in the genome of the North American monarch[22] leading to articles about monarch butterflies being genetically modified organisms.[23][24]
Description
Monarch butterfly
The monarch's wingspan ranges from 8.9 to 10.2 centimetres (3.5–4.0 in).[7] The upper sides of the wings are tawny orange, the veins and margins are black, and there are two series of small white spots 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.[25] The shape and color of the wings change at the beginning of the migration and appear redder and more elongated than later migrants.[26] Wings size and shape differ between migratory and non-migratory monarchs. Monarchs from eastern North America have larger and more angular forewings than those in the western population.[10] Monarchs are commonly and easily mistaken for the similar viceroy butterfly – the two species are Müllerian mimics.
Monarch flight has been described as "slow and sailing",[27] with a flight speed estimated at approximately 9 km/h or 5.5 mph.[28] For comparison, the average human jogs at a rate of 9.7–12.9 km/h (6–8 mph).
Adults are sexually dimorphic. Males are slightly larger than females[10][25] and have a black patch or spot of androconial scales on each hindwing (in some butterflies, these patches disperse pheromones, but are not known to do so in monarchs). The male's black wing veins are lighter and narrower than those of females.[29]
One variation, the "white monarch", observed in Australia, New Zealand, Indonesia and the United States, is called "nivosus" by lepidopterists. It is grayish white in all areas of its wings that are normally orange and is only about 1% or less of all monarchs, but populations as high as 10% exist on Oahu in Hawaii.[18]
The monarch has six legs like most adult insects, but uses only its middle legs and hindlegs in walking as its forelegs are small, as in all Nymphalidae, and held against its body.[30]
Monarch flying away from a Mexican sunflower
Detailed measurements
Male and female monarch measurements
A study in 2015 examined a preserved collection of male and female monarch specimens from eastern North America to evaluate the sex-based differences in fine-scale wing and body structure.[31] The study found significant differences in overall wing size and in the physical dimensions of wings. Males tended to have larger wings than females, and were heavier than females, on average. Both males and females had similar thorax dimensions (wing muscles are contained in the thorax). Female monarchs tended to have thicker wings, which is thought to convey greater tensile strength. This would make female wings less likely to be damaged during migration. Also, females had lower wing loading than males (wing loading is a value derived from the ratio of wing size to body mass), which would mean females require less energy to fly.[32]
Distribution and habitat
String of monarchs wintering at the Pismo State Beach Monarch Preserve, 2015
The range of the western and eastern populations of D. plexippus plexippus expands and contracts depending upon the season. The range differs between breeding areas, migration routes, and winter roosts.[10]:(p18) However, no genetic differences between the western and eastern monarch populations exist;[33] reproductive isolation has not led to subspeciation of these populations, as it has elsewhere within the species' range.[10]:(p19)
In the Americas, the monarch ranges from southern Canada through northern South America.[4] It has also been found in Bermuda, Cook Islands,[34] Hawaii,[35][36] Cuba,[37] and other Caribbean islands[10]:(p18) the Solomons, New Caledonia, New Zealand,[38] Papua New Guinea,[39] Australia, the Azores, the Canary Islands, Madeira, continental Portugal, Gibraltar,[40] the Philippines, and Morocco.[41] It appears in the UK in some years as an accidental migrant.[42]
Overwintering populations of D. plexippus plexippus are found in Mexico, California, along the Gulf Coast, year round in Florida, and in Arizona where the habitat has the specific conditions necessary for their survival.[43][44] On the US East Coast, they have overwintered as far north as Lago Mar, Virginia Beach, Virginia.[45] 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.[46] 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.
Habitat restoration is a primary goal in monarch conservation efforts. Habitat requirements change during migration. During the fall migration, butterflies must have access to nectar-producing plants. During the spring migration, butterflies must have access to larval food plants and nectar plants.
Life cycle
The monarch butterfly undergoes four stages of complete metamorphosis:
Eggs
The eggs are derived from materials ingested as larvae and from the spermatophores received from males during mating.[48] Eggs are laid singly on the underside of a young leaf of a milkweed plant during the spring and summer months.[49] The eggs are cream colored or light green, ovate to conical in shape, and about 1.2×0.9 mm in size. The eggs weigh less than 0.5 mg each and have raised ridges that form longitudinally from the point to apex to the base. Though 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.[48] The number of eggs laid by a female, who may mate several times, ranges from 290 to 1180.[50] Females lay their eggs on the underside of the milkweed leaves; the offspring's consumption of the milkweed benefits health and helps defend them against predators.[51][52] Eggs take 3 to 8 days to develop and hatch into larva or caterpillars.[10]:(p21) Monarchs will lay eggs along the southern migration route.[53]
Larvae
Size comparison between an eastern black swallowtail caterpillar (top), a monarch caterpillar (middle), and a queen caterpillar (bottom) all on a human hand.
A monarch caterpillar in the third instar, eating tropical milkweed.
The caterpillar goes through five major distinct stages of growth, and after each one it molts. Each caterpillar, or instar, is larger than the previous after molting, as it eats and stores energy in the form of fat and nutrients to carry it through the nonfeeding pupal stage. Each instar lasts about 3 to 5 days, depending on various factors such as temperature and food availability.[4]
The first instar caterpillar that emerges from the egg is pale green and translucent. It lacks banding coloration or tentacles. The larvae or caterpillar eats its egg case and begins to feed on milkweed. It is during this stage of growth that the caterpillar begins to sequester cardenolides. The circular motion a caterpillar uses while eating milkweed prevents the flow of latex that could entrap it. The first instar is usually between 2 and 6 mm long.
A monarch caterpillar in the fifth instar, feeding on the end of Asclepias fascicularis.
The second instar larva develops a characteristic pattern of white, yellow and black transverse bands. It is no longer translucent but is covered in short setae. Pairs of black tentacles begin to grow, one pair on the thorax and another pair on the abdomen. Like the first instar, second-instar larvae usually eat holes in the middle of the leaf, rather than at the edges. The second instar is usually between 6 mm and 1 cm long.
Fifth instar with the white spots visible on the prolegs
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. These third-stage caterpillars begin to eat along the leaf edges. The third instar is usually between 1 and 1.5 cm long.
The fourth instar has a different banding pattern. It develops white spots on the prolegs near the back of the caterpillar. It is usually between 1.5 and 2.5 cm long.
The fifth instar has a more complex banding pattern and white dots on the prolegs, with front legs that are small and very close to the head. A caterpillar at this stage has an enormous appetite, being able to consume a large milkweed leaf in a day. Its length ranges from 2.5 to 4.5 cm.[4]
As the caterpillar completes its growth, it is 4.5 cm long (large specimens can reach 5 cm) and 7 to 8 mm wide, and weighs about 1.5 grams, compared to the first instar, which was 2 to 6 mm long and 0.5 to 1.5 mm wide. Fifth-instar larvae increase in weight 2000 times from first instars. Fifth-stage instar larva can chew through the petiole or midrib of milkweed leaves and stop the flow of latex. After this, they eat more leaf tissue. Before pupation, larvae must consume milkweed to increase their mass, after which they stop feeding and search for a pupation site.
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 caterpillar attacked when it was foraging for milkweed.[54] This demonstrates the aggressive behavior of monarch caterpillars due to the availability of milkweed.
Pupa
Monarch larvae begin to pupate alongside other monarch chrysalises
Adult monarch emerges from its chrysalis shell
To prepare for the pupa 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 hindlegs and hangs upside down, in the form of the letter J. After "J-hanging" for about 12–16 hours, it will suddenly straighten out its body and go 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.[55] 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 (1") long and 10–12 mm (3/8–7/16") wide, weighing about 1.2 grams. 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).
Adult
An adult butterfly emerges after about two weeks as a chrysalis, and hangs upside down for a few hours until its wings are dry. Fluids are pumped into the wings, which expand, dry, and stiffen. The monarch extends and retracts its wings, and once conditions allow, flies and feeds on a variety of nectar plants. During the breeding season, adults reach sexual maturity in four or five days. However, the migrating generation does not reach maturity until overwintering is complete.[57] Monarchs typically live for two to five weeks during their breeding season.[10]:(pp22–23) Larvae growing in high densities are smaller, have lower survival, and weigh less as adults compared with those growing in lower densities.[58] Monarch metamorphosis from egg to adult occurs during the warm summer temperatures in as little as 25 days, extending to as many as seven weeks during cool spring conditions. During the 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. However, this is a natural attrition rate for most butterflies, since they are low on the food chain.
Reproduction
File:Monarch butterfly mating.webm
Monarch butterfly mating
Females and males typically mate more than once. Females that mate several times lay more eggs. Mating for the overwintering populations occurs in the spring, prior to dispersion. Mating is less dependent on pheromones than other species in its genus. Male search and capture strategies may influence copulatory success, and human-induced changes to the habitat can influence monarch mating activity at overwintering sites.
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.[62] Only 30% of mating attempts end in copulation, suggesting that females may be able to avoid mating, though some have more success than others. During copulation, a male transfers his spermatophore to a female. Along with sperm, the spermatophore provides a female with nutrition, which aids her in egg laying. An increase in spermatophore size increases the fecundity of female monarchs. Males that produce larger spermatophores also fertilize more females' eggs.
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