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Danaidae (the milkweed butterflies)
The monarch butterfly has brownish-orange wings with black to dark brown on the margins. The wings also have two rows of orange and/or white spots and veins outlined in black. Males have a black scent pocket on their hind wings.
The caterpillar is black with white and yellow bands. It has a pair of flexible appendages on its thorax and the second-to-last abdominal segment.
caterpillar = up to 70 mm (2.75 in)
butterfly = wingspan of 88-100 mm (3.5-4 in.)
0.27-0.75 g (0.0095-0.026 oz)
The larvae, or caterpillars, of this insect feed on the milkweed foliage, flower buds, and milky juice.
Adults feed on nectar.
The metamorphosis from egg to butterfly takes about 4 weeks.
– Monarch eggs are small, about the size of a pinhead. They hatch in about 3-4 days.
– The larva that hatches is about 0.5 cm (0.2 in.). This stage lasts about 2 weeks. Within this time, the larva will molt 5 times.
– The larva spins silk and attaches to a twig. This pupa is shiny green with gold spots. It will hang for about 2 weeks, until the adult emerges. This completes the metamorphosis.
Adult monarch butterflies that emerge in spring and early summer live 4-5 weeks.
Migrating generations, which emerge in late summer and fall, live 8-9 months.
The later emerging generations cannot survive a long, cold winter. Driven by daylight and temperature changes, they migrate to more temperate climates. Monarchs west of the Rocky Mountains travel to the California coast. Those east of the Rocky Mountains fly to the forests high in the mountains of Mexico, which is up to 6,437 kilometers (4,000 mi.) round-trip.
throughout North America
Monarch butterflies are found in meadows, roadsides, and sandy areas where milkweed plants grow.
It is estimated that up to 100 million migrate each fall.
The annual monarch migration is considered a 'threatened phenomena' by the IUCN.
As caterpillars, monarchs store poisonous compounds derived from the milkweed plants that serve as their food. These compounds, called glycosides, are poisonous helping monarchs avoid predation from birds and other vertebrate predators. The Viceroy is an edible species that mimics the Monarch in the western states.
Butterflies' colors come from tiny scales which cover the wings; colors may aid them in species recognition and camouflage, or by warning away predators.
Butterflies pollinate plants as they feed on nectar.
ECOLOGY AND CONSERVATION
Monarch butterflies and their annual migration face threats in their summer sites, as well as the wintering sites. In the north, milkweed is often destroyed, as it is seen as a harmful weed by some people. Milkweeds, as well as adult nectaring plants, are vulnerable to herbicides and monarchs themselves are vulnerable to pesticides. Monarch wintering sites are threatened mainly by habitat destruction. Real estate development in California and logging in areas of Mexico remove trees that are essential to the survival of migrating monarchs. Many organizations, in the United States and in Mexico, are working to protect the wintering sites of monarch butterflies.
Kane, E. 1999. "Danaus plexippus" (On-line), Animal Diversity Web. Accessed May 10, 2007 at animaldiversity.ummz.umich.edu/site/accounts/information/
Milne, L. and M. Milne, Eds. (1997).
National Audubon Society Fieldguide to North American Insects and Spiders
. New York, Albert A. Knopf, Inc.