Identification

Care required to separate from Swallow Prominent; use the following. The prominent clean white wedge extending from the apex never reaches halfway across the forewing, this being diagnostic.

Life cycle

Two overlapping generations. Overwinters as a pupa underground. Larvae are present June and July, again, late August to September.

Larval foodplants

Downy Birch and Silver Birch.

Habitat

Downland, heathland, moorland and woodland.

History 1860-2010

Stainton (1859) mentioned Edinburgh as the only Scottish locality for this moth, but Lennon (1864) found four larvae in the Crichton Institution garden, but had described it as rare. All Gordon (1913) had to say was that larvae were occasionally taken on birch. Sir Arthur Duncan (1909-84) during his lifetime had found it at Closeburn, Tynron and Castlehill, Dumfries (all VC72).

Fewer than ten records were recorded in the early 1970s, four from the Moffat area (VC72), and Silver Flowe, Woodhall Loch, Ravenshall and Glen Trool being the others from VC73. But during 1974 to 1982 there were just under sixty records from all of the Rothamsted stations, apart from Caerlaverock, with further RIS data from Mabie Forest during 1985-90. There were a number of records, also, from the Hensol Estate in the period 1982-85.

From 1992 to 2010 the regular trapped sites at Kirkton, Cally Woods, Carsfad near Dalry, Forest Moor and Old Torr contributed a portion of the 200 records, with the remainder from widespread sites across the region.