Description: Wingspan 17-22mm. Adults are generally whitish-brown with a series of small dark coloured dots the upper surface of the forewings. There is also a dark patch near the outer margin on each forewing and a dotted line that is continuous around the outer margins of all wings. Mid-June to the end of August.

Irish Distribution: Common and widely distributed especially in the south but much more localised in the north.

Ecology: Normally associated with damper parts of woodland, heaths and bogs. Its scarceness further north, especially in Londonderry, may well be due to limited fieldwork at the appropriate time of year. Adults are attracted to light and appear in small numbers. The larvae can be found from September to May on Cow Parsley Anthriscus sylvestris and Burnet-saxifrage Pimpinella saxifraga. It overwinters as a larva.

Key Identification Features:

• Dark patch near the outer margin on each forewing
• Small discal spot on the hindwing

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

iNaturalist: Idaea dimidiata at iNaturalist World Species Observations database.