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Monarch Butterfly (Danaus Plexippus)

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Monarch butterfly male

Male monarch butterfly - note the black scent glands which appear as dots on the hindwings.

Photo: © Debbie Hadley, WILD Jersey

Ask any grade school student the name of this orange and black butterfly, and you'll likely get the right answer - the Monarch butterfly, Danaus plexippus. The Monarch's famous migration makes it a fascinating insect for study by schoolchildren and scientists alike.

Description:

The Monarch butterfly's large orange wings are veined and outlined in black, with white dots decorating the black outer edges of each wing. Showy wings sometimes hide the body, which is just as pretty with white polka dots on a black background. Males and females are easy to differentiate, as the males have black scent glands along a vein on each of their hindwings (see photo). Males also have thinner veination on their wings than females.

Monarch caterpillars are also easy to recognize, with distinctive coloration. The caterpillars display alternating bands of yellow, white, and black, with a black stripe between pairs of white. Paired black tentacles at each end, with the longer pair at the head, collect sensory data for the caterpillar.

Monarch eggs appear on the undersides of milkweed leaves, usually near the top of the plant, and appear egg-shaped and white. Monarch females lay just one egg on a milkweed leaf. Not to be outdone by the colorful caterpillars and adults, the Monarch chrysalis displays a vibrant shade of green with gold flecks of trim.

Classification:

Kingdom - Animalia
Phylum - Arthropoda
Class - Insecta
Order - Lepidoptera
Family - Nymphalidae
Genus - Danaus
Species - plexippus

Diet:

Monarch caterpillars feed exclusively on milkweed. Monarch butterfly adults drink nectar from a variety of flowers.

Life Cycle:

Like all butterflies, Monarchs undergo complete metamorphosis with four stages in their life cycle: egg, larva, pupa, and adult. From egg to adult, the life cycle takes about 30 days.

Egg - Eggs are laid singly and usually hatch in four days.
Larva - The caterpillars go through five instars, growing from 2 mm to nearly 25 mm in about 15 days.
Pupa - It takes 8-14 days for the adult to emerge from the chrysalis.
Adult - Most live 2-5 weeks, but migrant generations live as long as 8 months.

Special Adaptations and Defenses:

Caterpillars feed exclusively on milkweed, ingesting toxic glycosides present in the plants. While the Monarchs themselves are not bothered by these toxins, predators who eat them do feel their affects. The toxins remain within the Monarch through the transformation from larva to adult. The bright, contrasting colors of the caterpillar's skin and the butterfly's wings advertise their unpalatability to potential predators.

Habitat:

In spring and summer, Monarch habitat includes open fields, meadows, roadsides, and backyard gardens with milkweed. Fall migrants require nectar sources along their migratory route. Populations from the eastern U.S. and Canada overwinter in the oyamel forests of central Mexico's mountains. Monarchs from the western regions require pine and eucalyptus forests along the central California coast.

Range:

Native to North and South America, with long-established populations in Australia and New Zealand as well. Also known throughout the South Pacific and Caribbean islands.

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