Cosmia affinis (Linnaeus, 1767)

Host plants:
Usually, the caterpillars live on elm (Ulmus), but according to literature rarely also on other hardwoods.

Habitat:
Cosmia affinis inhabits elm-rich forests (hardwood floodplains) and other elm stocks. I found larvae together with those of Satyrium w-album on the eastern Swabian Alb at an elm-rich, semi-shady spot on a dry limestone slope. I also observed many young caterpillars on Ulmus minor in webbed leaf tips in fully shaded areas in the Upper Rhine Valley in April 2009.

Life cycle:
The eggs overwinter and the caterpillars are found from mid-April to mid-June. The flight time is from late June to September.

Endangerment factors:
Cosmia affinis is threatened by the decline of elm (destruction of riparian forests, elm disease, monocultures). But this species is still much more recorded than the more demanding C. diffinis.

Remarks:
The distribution extends from Morocco across Southern and Central Europe and large parts of temperate Asia to Japan.