Monarch butterfly
The monarch butterfly or simply monarch is a milkweed butterfly in the family Nymphalidae. Other common names, depending on region, include milkweed, common tiger, wanderer, and black-veined brown. It is among the most familiar of North American butterflies and an iconic pollinator, although it is not an especially effective pollinator of milkweeds. Its wings feature an easily recognizable black, orange, and white pattern, with a wingspan of. 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 instinctive migration from the northern and central United States and southern Canada to Florida and Mexico. 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 have been found in overwintering Mexican sites, as well. Populations are found further south in the Americas, and in parts of Europe, Oceania, and Southeast Asia.
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. The monarch was originally described by Carl Linnaeus in his Systema Naturae of 1758 and placed in the genus Papilio. In 1780, Jan Krzysztof Kluk used the monarch as the type species for a new genus, Danaus. However, many works published between at least 1883 and 1964 identified the species as Anosia plexippus or Anosia archippus.In 2005, investigators reported that the monophyletic genus Danaus s.l. had previously been divided into three subgenera. However, based on their own studies, which combined mitochondrial DNA and nuclear DNA sequence information with morphological data, they concluded that the earlier classification was unsustainable and should be abandoned.
Danaus, a great-grandson of Zeus, was a mythical king in Egypt or Libya, who founded Argos; Plexippus 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". In the tenth edition of Systema Naturae, at the bottom of page 467, 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.".
Robert Michael Pyle suggested Danaus is a masculinized version of Danaë, 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.
Taxonomy
Monarchs belong to the subfamily Danainae of the family Nymphalidae. Danainae was formerly considered a separately family Danaidae. The three species of monarch butterflies are:- D. plexippus, described by Linnaeus in 1758, is the species known most commonly as the monarch butterfly ranging from North America to northern South America. Its range 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 two 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.
- D. cleophile, the Jamaican monarch, described by Jean-Baptiste Godart in 1819, ranges from Jamaica to Hispaniola.
- 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.
- * D. p. p. – a color morph lacking some wing vein markings.
- D. p. nigrippus – South America - as forma: Danais ''archippus f. nigrippus. Hay-Roe et al. in 2007 identified this taxon as a subspecies
- D. p. megalippe – nonmigratory subspecies, and is found from Florida and Georgia southwards, throughout the Caribbean and Central America to the Amazon River.
- D. p. leucogyne − St. Thomas
- D. p. portoricensis Austin Hobart Clark, 1941 − Puerto Rico
- D. p. tobagi'' Austin Hobart Clark, 1941 − Tobago
Genome
The monarch was the first butterfly to have its genome sequenced. 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. More recently, the genetic basis of monarch migration and warning coloration has been described.No genetic differentiation exists between the migratory populations of eastern and western North America. 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.
A 2015 publication identified genes from wasp bracoviruses in the genome of the North American monarch leading to articles about monarch butterflies being genetically modified organisms.
Life cycle
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.Egg
The egg is derived from materials ingested as a larva and from the spermatophores received from males during mating. Female monarchs lay eggs singly, most often on the underside of a young leaf of a milkweed plant during the spring and summer. 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.Eggs are cream colored or light green, ovate to conical in shape, and about in size. The eggs weigh less than each and have raised ridges that form longitudinally from the point to apex to the base. Although each egg is 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. The number of eggs laid by a female, which may mate several times, can reach 1,180.
Eggs take three to eight days to develop and hatch into larvae or caterpillars. The offspring's consumption of milkweed benefits health and helps defend them against predators. In the US Monarchs lay eggs along the southern migration route.
Larva
The larva has five stages, molting at the end of each instar. Instars last about 3 to 5 days, depending on factors such as temperature and food availability.The first-instar caterpillar that emerges from the egg is pale green or grayish-white, shiny, almost translucent, with a large, black head. It lacks banding coloration or tentacles. The larva or caterpillar eats its egg case and begins to feed on milkweed in 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 long.
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 and long.
The third-instar larva has more distinct bands and the two pairs of tentacles become longer. Legs on the thorax differentiate into smaller pairs 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 long. The fourth-instar larva has a different banding pattern. It develops white spots on the prolegs near its back, and is usually between long.
The fifth-instar larva has a more complex banding pattern and white dots on the prolegs, with small front legs very close to the head. Its length ranges from.
The larvae typically chew through a latex vein to relieve the pressure and feed above it. Fifth-instar larvae often chew a notch in the petiole of the leaf they are eating, which relieves the latex pressure and causes the leaf to fall into a vertical position.
As the caterpillar completes its growth, it is long and wide, and weighs about, compared to the first instar, which is long and 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. A monarch caterpillar can travel up to 10 meters from its milkweed plant to find a safe place to pupate.
In a laboratory setting, the fourth- and fifth-instar caterpillar stages showed aggressive behavior with lower food availability. Attacked caterpillars were found to be attacked when feeding on milkweed leaves, and the caterpillars attacked when foraging for milkweed. This demonstrates the aggressive behavior of monarch caterpillars due to the availability of milkweed.