Friday, May 11, 2012

Butterfly of the Week

Northern Cloudywing

Thorybes pylades (Scudder 1870)
Status: Common breeding resident
Flight: Essentially single brooded, with adults flying from early May to mid August. Most individuals have been collected from the last few days of May through the first week of July.
Distinguishing features: Like T. bathyllus, this species is dark brown, with white spots on the fore wing above and darker brown bands on the hind wings below. It differs by having narrow, oblong fore-wing white spots, darker wing fringes, and hollow (rather than solid) dark brown hind-wing bands. Males possess a costal fold. Wingspan: 3.4-4 cm.
Distribution and habitat: Map 48. This species is relatively frequent in the southern two-thirds of the state. It occurs in a variety of dry, open habitats, including prairies and old fields.
Natural history: The larvae of the Northern Cloudywing have been reported to feed on a variety of legumes, including clover, bush clover, and tick-trefoil. These plants are more common in Iowa than those used by T. bathyllus, so it is not surprising that T. pylades is more common.
Questions: Is the apparent higher frequency of T. pylades populations, compared to T. bathyllus, due to the higher frequency of its larval host plants? How variable are the hyaline fore-wing spot patterns within and between populations?

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