Friday, July 20, 2012

Butterfly of the Week

Columbine Duskywing

Erynnis lucilius (Scudder and Burgess 1870)
Status: Infrequent breeding resident
Flight: Double brooded, with a spring brood from late April to mid May and a summer brood from late June to late July. A partial third brood may occasionally occur in mid to late August.
Distinguishing features: This species and the Wild Indigo Duskywing differ from other Iowa Erynnis by having very small clear spots on the fore wing and lacking dark brown mottling over both upper wing surfaces. Distinguishing these two species is quite problematic, however. Columbine Duskywings are often smaller and lighter brown than Wild Indigo Duskywings, but intermediate individuals are frequently encountered. Apparently no differences in genitalia exist (Burns 1964). The only consistent feature which can be used to separate them is their choice of larval hosts. Columbine Duskywings eat only columbine, and Wild Indigo Duskywings eat only wild indigo or crown vetch. Wingspan: 2.3 - 3.1 cm.
Distribution and habitat: Map 99. Generally limited to the northeastern tier of counties. Individuals were also noted from the Des Moines River valley in the 1960s. This species is limited to dry prairies that support columbine, often limestone or sandstone glades on south- or west-facing slopes. Interestingly, this species has never been observed in the more typical woodland habitat for columbine. 
Natural history: As noted above, larvae for this species only consume columbine. Populations may be limited to glades, which are sunnier and may provide more nectar than woodlands. Individuals from the spring brood are darker than individuals from the summer brood. 
Questions: Are the behaviors of Columbine Duskywing and Wild Indigo Duskywing different enough to allow for reproductive isolation, or do they interbreed? Why does the Columbine Duskywing occur only with grassland populations of columbine?

The Butterflies of Iowa, by Dennis W. Schlicht, John C. Downey, and Jeffrey C. Nekola

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