Friday, July 6, 2012

Butterfly of the Week

Mottled Duskywing

Erynnis martialis (Scudder 1870)
Status: Rare breeding resident.
Flight: Up to four: from mid April to early May, late May to mid June, and early to late July. A partial fourth brood may occur in mid August.
Distinguishing features: The Mottled Duskywing is one of the most easily identified species in its genus. Particularly in the spring brood, the upper wing surface has a distinct mottling of light and brown patches. Wingspan: 3-3.4 cm.
Distribution and habitat: Map 94. Although collections are scattered across the state, it is absent from the northeastern quarter except in the vicinity of the Mississippi River. Most of the collections from south-central Iowa are over 100 years old, and it is probably now absent from this region. Only two collections have been made in eastern Iowa in the last twenty years, so it may soon be extirpated there as well. Its last stronghold is in the western third of the state, where it is limited to xeric prairie in the Loess Hills and on gravel ridges associated with the terminal moraines and outwash channels of the Des Moines Lobe.
Natural history: This species appears limited in Iowa to dry grasslands supporting an abundance of New Jersey tea.
Questions: Why have populations of this species apparently been more stable in western than in eastern Iowa? The presumed host plant (New Jersey tea) is found commonly throughout the state: what other factors limit it to so few sites? How much mortality do populations face when colonies of New Jersey tea are burned? 

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