Friday, June 22, 2012

Butterfly of the Week

Wild Indigo Duskywing

Erynnis baptisiae (Forbes 1936)
Status: Once a very rare breeding resident. Populations have recently expanded. Now uncommon, but occurs regularly across the state.
Flight: Up to four broods over the growing season. The first occurs in May, the second from late June to early July, and the third from late July to mid August, with a possible fourth brood emerging from early September to early October. Native populations in Loess Hills prairies appear double brooded, with early May and July flights.
Distinguishing features: This species is very similar to the Columbine Duskywing, being on average larger and darker. It often possesses a lighter brown patch just proximal to the row of upper fore-wing spots. The only consistent distinguishing characteristic for these species, however, are their larval host plant choices. Wingspan: 2.8-4.4 cm.
Distribution and habitat: Map 98. Until the mid 1980s very rare and limited in Iowa to dry prairies supporting large colonies of wild indigo. Most verified colonies were restricted in the west to the Loess Hills and in the northeast to limestone and sandstone glades. Since that time, however, a race originating in Pennsylvania that eats crown vetch has moved rapidly through Iowa along roadside ditches where this plant has been established. It is now known from scattered sites across the entire state.
Natural history: Depending upon the population, wild indigo (especially cream wild Indigo) or crown vetch is used as the larval host.
Questions: Are there genetic, morphological, or behavioral traits that separate the races that feed on wild indigo and crown vetch? Do the populations that feed on wild indigo have two broods, while the population that feed on crown vetch have three to four broods? Do these two populations interbreed? If so, does the crown vetch population pose the risk of genetically swamping the wild indigo population?

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