Monarch Butterfly (Danaus plexippus). The enlarged swelling of a vein on the hind wing, a scent patch, identifies this specimen as a male. Widespread throughout the US and much of southern Canada. Famous for its autumn migration to its wintering ground in northern Mexico. Larvae feed on members of the milkweed genus and absorb these plants' toxic chemicals, causing them and the adult butterfly to be unpalatable to predators. Its bright colors are thought to advertise this fact (aposematic coloring).