Researchers believe that by feeding on milkweeds, the butterflies may also obtain the sap's ability to repel potential predators.
At the present time, the monarch butterfly is denoted by the scientific name, Danaus plexippus. The Danaus subspecies is distinguished from most other Danaine butterflies by the fact that the males are unable to synthesize certain male pheromones. Thus, as the monarchs have evolved, the role of chemical communication during mating has diminished.
Danaus originated in the New World, and spread from South America into North America about 1.75 million years ago. However, the monarch is a well-known migrant; it has even been nicknamed "the wanderer." From its overwintering sites in California and Mexico, it expands throughout much of North America south of 50?N latitude. It is also found in both Central and South America. In South America, it generally inhabits areas north of the Amazon (i.e., Brazil, Venezuela, Colombia, and Ecuador). The butterfly is also found in the West Indies and the Galapagos Islands. Moreover, D. plexippus is established on many of the Pacific Islands. It occurs from Hawaii to New Zealand and Norfolk Island. It has also been recorded from the Solomon Islands westward to the Moluccas. The northern extent of its Pacific domain lies around the Philippines and Taiwan. The insect also occurs in Australia; it is most common on the eastern portion of the continent. The monarch has actually become a "very conspicuous element of the south-west Pacific butterfly fauna." Furthermore, the butterfly has moved east from North America also. D. plexippus has been recorded in Britain and western continental Europe. One recent sighting occurred in Spain.
The monarch is a polytypic species; hence, it displays a combination of features. The adult butterfly, however, is typically orange and black. The upper surface of the wings is bright reddish, with borders and...