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Monarch butterfly
The monarch butterfly (Danaus plexippus) is a well-known North American butterfly. Its wings feature an easily recognizable orange and black pattern. The butterfly is especially noted for its lengthy annual migration. The population east of the Rocky Mountains overwinters in Mexico, and the Western population overwinters in various sites in central coastal California, notably in Pacific Grove, California and Santa Cruz, California. The length of these journeys far exceeds the lifetime of any given butterfly. How the species manages to return to the same overwintering spots over a gap of several generations remains a mystery.
In larval form, the Monarch feeds on milkweed[?], and sequesters substances called cardenolides[?], related to the cardiac glycoside digitalis: the amount 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 has resulted in the evolution of mimics, which are colored like the monarch to ward off animals but are not themselves poisonous.
The species was described by Carolus Linnaeus in 1758.
