Despite being a coleopterist, I was somewhat surprised when I realized that I have not yet posted a Lepidoptera photo on this site – especially considering their abundance, diversity (2nd largest order of insects), and overall photogenicity. Time to change that. I encountered this pretty little moth at Reifsnider State Forest in Warren Co., Missouri.
Pyromorpha dimidiata (orange-patched smoky moth) is one of the so-called “leaf-skeletonizer moths” in the family Zygaenidae. This particular species is distinguished from a similar, though unrelated species in our area, Lycomorpha pholus (black-and-yellow lichen moth, one of the subfamilies of the tiger moths, or family Arctiidae), by the black hind margin of the forewing and its phenology – L. pholus adults don’t appear until late summer.
Larvae of P. dimidiata are reported to feed on leaf litter, especially oak leaves. Oaks are present in great quantity and diversity here in Missouri, and in fact this species was photographed in one of Missouri’s finest examples of a mature white oak (Quercus alba) forest – uncommon in Missouri due to the generally less mesic conditions of our upland habitats.
Perhaps I like this moth because it apparently belongs to a mimicry complex involving net-winged beetles (family Lycidae), in particular the species Calopteron terminale (end band net-wing). Lycomorpha pholus also participates in this mimicry complex; however, unlike that species, P. dimidiata is itself toxic as well - all life stages of this moth contain hydrogen cyanide, which they manufacture rather than obtaining from host plants (Scoble 1992). Thus, the Calopteron-Pyromorpha mimicry complex appears to be an example of Müllerian mimicry, where both the model and the mimic are toxic.
Scoble, M. J. 1992. The Lepidoptera. Form, Function and Diversity. Oxford University Press, Oxford, 404 pp.