Cosmia diffinis (Linnaeus, 1767)

Host plants:
The larvae feed on elm trees (Ulmus), especially Ulmus laevis and U. minor.

Habitat:
Cosmia diffinis inhabits riparian woodlands and other humid, warm habitats with elm in the lowlands.

Life cycle:
The egg hibernates. The larvae develop between mid-April and mid-June and live between spun leaves. I recorded the larvae in the penultimate instar on smaller branches coming directly from the trunk of old Ulmus laevis trees in a riparian forest in the lower Elbe valley (N-Germany). They are also reported from youn elm scrub. The moths fly between mid-June and August.

Endangerment factors:
Cosmia diffinis has already lost many sites due to destruction of riparian woodlands ad dewatering of lowland swamps, but temporarily also due to the elm disease. The last habitats are dependent on the protection and whereever possible restoration of elm-rich humid woodlands.

Remarks:
Cosmia diffinis occurs locally in central and southern Europe. To the north it is found up to central England, Gotland and Lithuania.