Classified under the largest butterfly family Nymphalidae, the monarch originates in north and south America but globally distributed throughout tropical regions (4). They are brown and orange in color with black and white markings on their wings (2). There are distinct eastern and western populations in North America characterized by their different habitat and migratory patterns (4). A bi-annual migration of adult monarch begins during the fall where they migrate south from the northern region in the United States bordering Canada to southern Mexico (1). Breeding and production of successive generations occurs until spring, persisting during the northward migration period to escape harsher warm temperatures and the search for suitable milkweed, Aslepias spp., hosts for the larvae (1). The monarch adopts different morphologies and behaviors as thermoregulatory mechanisms to avoid freezing and heat stress (3). Monarchs are the first model species that indicate shivering as a behavior enacted by lepidopterans to increase thoracic temperature in addition to sun-basking (3). Their insulating scales situated on the thorax and abdomen segments participate in heat trapping along with the basal region of the wings for maintaining optimal flight temperature (3). Overheating is prevented through a sun-minimizing morphology adaptation that lowers the amount of heat gained when shading is not present (3).
- Wassenaar LI, Hobson KA. Natal origins of migratory monarch butterflies at wintering colonies in Mexico: new isotopic evidence. P Natl Acad Sci USA. 1998;95:
- Garth, J. S., Garth, J. S., & Tilden, J. W. (1986). California butterflies (Vol. 51). Univ of California Press
- Masters, A. R., Malcolm, S. B., & Brower, L. P. (1988). Monarch butterfly (Danaus plexippus) thermoregulatory behavior and adaptations for overwintering in Mexico. Ecology, 69(2), 458-467.
- Urquhart, F. A., & Urquhart, N. R. (1978). Autumnal migration routes of the eastern population of the monarch butterfly (Danaus p. plexippus L.; Danaidae; Lepidoptera) in North America to the overwintering site in the Neovolcanic Plateau of Mexico. Canadian Journal of Zoology, 56(8), 1759-1764.
(Photograph) T. W. Davies © California Academy of Sciences