Evening Bat

Nycticeius humeralis is a small vespertilionid, 8–10 cm long with a 26–30 cm wingspan and 7–14 g in weight, with dull brown fur, blackish ears and membranes and a short, curved, blunt tragus that separates it from Myotis species. It ranges through the southeastern and midwestern United States. Unusually among North American bats, females regularly bear twins, born in late May to June, and maternity colonies of 30 to several hundred females form in buildings and tree cavities. Northern populations migrate south in autumn rather than hibernating locally.

Foraging begins early, often before full dark, with slow fluttering flight over pastures, forest clearings and water, taking beetles, leafhoppers, moths and flying ants. Colonies are strongly philopatric and females frequently nurse pups other than their own, which is rare among bats. Health significance is the same as other structure-dwelling species: guano accumulation, odour, staining and histoplasmosis potential, plus the standard rabies precaution for any bat found on the ground or inside living space. It does not damage wood or wiring — the damage is contamination and the entry gaps that also admit other pests.