Junonia coenia (also known as Precis coenia) is a beautiful butterfly with conspicuous eyespots on both the fore- and hind-wings. This species occurs through much of the United States, northern Mexico and Cuba, and frequents open, sunny habitats with some bare ground. Caterpillars feed on plantain, snapdragon, Gerardia spp. (3), figworts, and vervains (2). By incorporating toxins (iridoid glycosides) from these plants, the caterpillars deter predatory ants (2). It cannot survive winters in the North, and in the autumn migrates to overwinter in the deep South. Junonia coenia has several generations each year. In the autumn generation the underside of the wings is dark brown, but in the generations that grow up in the summer the undersides are a pale tan. This difference in pigmentation is controlled by ecdysone, a steroid hormone, whose secretion is affected by the shortening days in the autumn.
(2) Opler, P.A. and G.O. Krizek, Butterflies East of the Great Plains, (1984), Baltimore, Johns Hopkins University Press.
(3) Rountree, D.B. and Nijhout, H. F., Hormonal control of a seasonal polyphenism in Precis coenia (Lepidoptera: Nymphalidae), J. Insect Physiol., vol. 41, (1995), pp. 987-992.
(4) Scott, J.A., The Butterflies of North America: A Natural History and Field Guide, (1992), Stanford, CA, Stanford University Press.
(5) Triplehorn, C.A. and N.F. Johnson, Borror and Delong’s Introduction to the Study of Insects, 7th ed., (2005), Thomson Brooks/Cole.