Spruce Carpet Geometridae

Thera britannica (Turner H.J., 1925)

Description: Wingspan 30-36mm. Adults are usually more richly marked than the other two species in this genus. The spring brood tends to be an overall brown rather than grey. The white lines that border the central band of the forewings are greatly reduced. Second generation adults are usually light grey with a well-defined central band edged with white. The sub-terminal line is generally well marked.

Key Identification Features:

Sets:  male upperside

Flight Period: A double-brooded species flying from mid April to late June and again from the end of August to mid October.

Status: Widely distributed in southern counties, sporadic further north. This species was unknown in Ireland before 1958 when it was found at Glenageary, Co. Dublin. Since then it has clearly increased its range and has now been recorded from all northern counties.

Ecology: As its name suggests this species is associated with spruce and it has clearly benefited from the large-scale planting of these in commercial plantations. Adults are attracted to light in moderate numbers. The larvae feed on Norway Spruce Picea abies and Douglas Fir Pseudotsuga menzieseii. It overwinters as a larva.

Bradley & Fletcher number: 1769 Agassiz number: 70.079

Additional information:

UK Moths account


 Thompson, R. S. & Nelson, B., 2003 (Oct 2). [In] The Butterflies and Moths of Northern Ireland