This Least Black Arches is only the fourth record for Caithness (the last was in 1995) and was caught in mix woodland last night. It is very local in Scotland and not at all common. Although a "macro" moth, at only 10mm in length it is smaller than many "micro" moths. It over winters as a pupa on a cocoon stuck to a twig and the larvae feed on broadleaved trees including beech. The adults are on the wing in May and June.