These moths mainly inhabit deciduous forests, hedgerows, parks and gardens, at an elevation up to 1,600 metres (5,200 ft) above sea level.[2]
Description
Acronicta psi has a wingspan of 34–45 mm (1.3–1.8 in).[3] These moths have grey forewings with bold black dagger-shaped markings. (The Latin specific name also refers to these markings, as resembling the Greek letter psi, ψ.)[3] The hindwings are dirty grey, generally paler in the male.
The moth is very similar to the dark dagger (Acronicta tridens) and identification is generally only possible by minute examination of the genitalia.[3] See Townsend et al.[4] However, in general this moth is generally darker in colour than the dark dagger and always lacks the white hindwings often present in the male of that species. Moreover, the larvae of the two species are very different.
Figures 2, 2a, 2b show larvae after their final moult
The larva of Acronicta psi is quite hairy, greyish or brownish below and black above, with red spots along the sides and a bold yellow stripe along the back. It has a distinctive horn just behind the head (absent from the larva of dark dagger).
Biology
The grey dagger flies at night from June to August[a][3] and is attracted to light and sometimes to sugar.
It feeds on a wide range of plants, mainly trees and shrubs (see list below). The species overwinters as a pupa.
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