Monarch butterfly

Monarch butterfly
	File:Monarch by LeoSynapse.jpg
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Lepidoptera
Family:	Nymphalidae
Subfamily:	Danainae
Genus:	Danaus
Species:	D. plexippus
Binomial name
	Danaus plexippus; (Linnaeus, 1758)

The Monarch butterfly (Danaus plexippus) is a well-known North American butterfly. Its wings feature an easily recognizable orange and black pattern. The females have darker veins on their wings, and the males have a spot in the center of each hindwing from which pheromones are released.

Migration

Monarchs are especially noted for their lengthy annual migration. They make massive southward migrations from August through October. A northward migration takes place in the spring. Female Monarch butterflies deposit eggs for the next generation during these migrations. The population east of the Rocky Mountains overwinters in Michoacán, Mexico, and the western population overwinters in various sites in central coastal California, United States, notably in Pacific Grove and Santa Cruz. The length of these journeys far exceeds the lifetime of any given butterfly (lives 4 days as egg, 2 weeks as caterpillar, 10 days as chrysalis, and 2-6 weeks as a butterfly). How the species manages to return to the same overwintering spots over a gap of several generations is still subject of a research; the flight patterns are inherited, based on a combination of circadian rhythm and the position of the sun on the sky.[1] A recent study suggests that butterflies have special ultraviolet photoreceptors that provide them with a sense of direction.[2] This is one of the few insects to manage transatlantic crossings. A few Monarchs turn up in the far southwest of Great Britain in any year when the wind conditions are right. Monarchs can also be found in New Zealand during the summer period, but are noticeably absent the rest of the year.

On the Island of Hawaii no migrations have been noted. The monarchs will live a life of 6 to 8 weeks in a garden having their host asclepias plants and sufficient flowers for nectar. This is especially true if the flower garden happens to be surrounded by native forest that seems to be lacking in flowers.

Metamorphosis

The life cycle of a Monarch butterfly includes a change of form called complete metamorphosis. This process goes through four radically different stages.

Egg

First, as mentioned above, the eggs are laid by the females during spring and summer breeding months.

Caterpillar

File:Monarchrsh3.jpg

Monarch caterpillar

Second, the eggs hatch, revealing worm-like larva, the caterpillars. The caterpillars consume their egg cases, then feed on milkweed, and sequester substances called cardenolides, related to the cardiac glycoside digitalis. During the caterpillar stage, Monarchs store energy in the form of fat and nutrients to carry them through the non-feeding pupa stage.

Pupa

File:Monarchrysalis.jpg

Monarch Butterfly Chrysalis

Third is the pupa, or chrysalis stage. The caterpillar spins a silk pad on a twig, leaf, etc. and hangs from this pad by its last pair of prolegs. It hangs upside down in the shape of a 'J', and then molts, leaving itself encased in an articulated green exoskeleton. At this point, hormonal changes occur, leading to the development of a butterfly.

Butterfly

Fourth, the mature butterfly emerges after about two weeks.

Protection

The amount of cardenolides accumulated depends on the level present in the milkweed. This accumulation makes the adult butterfly distasteful and poisonous to Blue Jays and other would-be predators, and many such animals avoid consuming it. This defense is shared by the even more distasteful (and similar-appearing) Viceroy, in an example of Müllerian mimicry (they are often believed to be Batesian mimics, but this is not true).

Monarch butterflies are brightly colored in order to ward away potential predators. This defence works because most predators associate bright colors (especially orange and black or yellow and black) with poison and other unpleasant properties. This phenomenon is called aposematism.

Popularity

File:Wiki monarchbutterfly.JPG

1999 stamp issued by the United States of America. The text on the back reads: "This remarkable migrating butterfly resides throughout the United States and southern Canada during the summer. In the fall, monarchs fly in massive numbers to aggregation sites in Mexico and California, where they spend the winter. The return journey is completed mostly by the subsequent generation of monarchs."

The monarch butterfly is the state insect of Alabama, Idaho, Illinois, Texas and Vermont, and the state butterfly of Minnesota and West Virginia. It was nominated in 1989 as the national insect of the United States, and is the national insect of Canada. The monarch's name and color were also the inspiration for the name and home strip of the Michoacán-based CA Monarcas Morelia professional football team.

Threats

Recent illegal deforestation of the Monarch's overwintering grounds have led to a drastic reduction in the butterfly's population. Efforts to classify it as a protected species and to restore its habitat are under way. Mexican authorities expected a significant increase in the Monarch population in the 2005-2006 butterfly season. [3]

External links