The Monarch Butterfly

The monarch butterfly, Danaus plexippus, is a widespread insect species. In North America, it is a most characteristic large, ornate butterfly. There has even been an effort in the United States to adopt the monarch as the national insect. Moreover, D. plexippus is the only insect listed by the Bonn Convention for the Conservation of Migratory Species of Wild Animals. In fact, the extraordinary attention that the butterfly has received over the years has led some authors to doubt whether it is justified. The monarch butterfly certainly is not endangered; actually, relatively large numbers of the organism exist. Perhaps it is the monarch's combination of intriguing characteristics though, which have made it the focus of so much scientific investigation.

Butterflies, in general, show a great diversity of biological features. The most important of these probably involve the organism's life cycle. The insects undergo "complete metamorphosis." Female adults lay eggs which give rise to larvae, or caterpillars. These larvae then grow by a series of moults, or instar stages, and eventually transform into a resting stage (i.e., the pupa or chrysalis). It is during the chrysalis stage that the organism's body is broken down and reorganized into the adult butterfly form. Variations on this basic pattern generally occur either between butterfly groups or species. These variations typically represent some attempt to make optimal

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ty lots) rich in asclepiad flora. Flowers are very attractive to the insects. In addition, they drink from puddles and streams. They may therefore be found around gullies. The butterflies normally live below 3000 feet, although they have been recorded at much higher elevations (Ackery 70, 201-202). As an insect, Danaus plexippus is one of the links in the food chain. Luckily though, the butterfly has evolved a remarkable mechanism for avoiding predation. The sap of the milkweed plant contains digitoxin glucosides. These compounds are poisonous to predatory birds. By feeding on the milkweed, and selectively storing such substances, the monarch caterpillar is able to repel most insectivores. Moreover, the chemical defenses are believed to also carry over into the adult forms. Its bright colors serve to alert predators to the organism's toxicity. In the past, researchers have even hypothesized that the similarly colored viceroy butterflies were attempting to repel predators through their resemblance to the monarch. However, it is now known that the viceroy butterflies, like the monarchs are also distasteful. Hence, the monarch and viceroy butterflies form a Mullerian (formerly described as Batesian) mimicry complex.
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Approximate Word count = 2600
Approximate Pages = 10 (250 words per page)

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