Description: Wingspan 38-44 mm. Forewings are reddish brown with a dark basal streak. Stigmata similar to base colour but edged with a fine pale line. Ante and postmedian lines are pale in colour; the latter has two tooth-shaped projections that extend to the terminal border of the wing. Hindwings fuscous brown with darker veining; darker discal lunule. Early May to late July.

World Distribution: Throughout western Europe as far north as the Arctic Circle.

Irish Distribution: Widespread and common throughout all counties including Rathlin Island.

Ecology: A woodland species, seen frequently at light and also visits flowers. The adults rest by day on the trunks of trees and occasionally fence posts. The larvae feed from July to September on oak Quercus spp., Hawthorn Crataegus monogyna, Broom Cytisus scoparius, Honeysuckle Lonicera periclymenum and probably other plants. It overwinters as a pupa.

Key Identification Features:

• Darker forewings with pale crosslines
• Tooth-shaped projections on postmedian line
• Darker fuscous hindwings with small discal lunules

Distribution Map from NBN: Lacanobia thalassina at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Lacanobia thalassina at iNaturalist World Species Observations database.