Light knot grass

Description

Acronicta menyanthidis, the light knot grass, is a moth of the family Noctuidae. It is distributed through northern, central and eastern Europe, east to Siberia and the Russian Far East. For a key to the terms used, see Glossary of entomology terms. The wingspan is 33–41 mm. Forewing bluish white, dusted and shaded with dark grey; a short black streak from near base; marginal area darker, sometimes blackish, grey; orbicular stigma quite small.- In the ab. suffusa Tutt the whole forewing is suffused with dark grey. - ab. obsoleta Tutt has the forewing quite pale with all markings faint; on the contrary ab. scotica Tuff from the west coast of Scotland is larger and brighter than the type, with all markings clear and distinct. The adults fly at night from May to July. They are attracted to light. The caterpillar is blackish brown with a red spiracular line with white dots. It feeds on moorland plants like bog myrtle and bilberry. Recorded food plants include Myrica, Calluna, Vaccinium, Salix, Betula, Ranunculus aconitifolius, Comarum palustre, Lysimachia nummularia and Menyanthes trifoliata. Acronicta is a genus of noctuid moths containing about 150 species distributed mainly in the temperate Holarctic, with some in adjacent subtropical regions. The genus was erected by Carl Linnaeus in his 1758 10th edition of Systema Naturae. Caterpillars of most Acronicta species are unmistakable, with brightly colored hairy spikes, and often feed quite visibly on common foliate trees. The hairy spikes may contain poison, which cause itchy, painful, swollen rash in humans on contact. The larva of the smeared dagger moth (A. oblinita) is unusually hairy even for this genus. Acronicta species are generally known as dagger moths, as most have one or more black dagger-shaped markings on their forewing uppersides. But some species have a conspicuous dark ring marking instead. Its eyes are naked and without eyelashes. The proboscis is fully developed. Antennae are simple in both sexes. Thorax and abdomen tuftless. Abdomen with long coarse hair on the dorsal part of proximal segments. Legs spineless. Forewings with non-crenulate cilia. Inner margin slightly lobed towards base.