August Thorn Geometridae

Maps updated: April 2008

Ennomos quercinaria (Hufnagel, 1767)

Description: Wingspan 42-50mm. Adults are usually an orange-yellow colour. Males are generally lighter than females, although individuals can appear lighter or darker. The forewings are lightly speckled with a dark marginal edge, scalloped at the edges and have double cross-lines.

Similar Species: It is similar in appearance to the Canary-shouldered Thorn E. alniaria, but distinguished by the postmedian line, which according to Skinner is angled inwards around the discal spot.

Key Identification Features:

Sets:  male upperside

Flight Period: Late July to early October, most commonly encountered throughout August and early September.

Status: Widely distributed in southern counties especially north Armagh and much of Down. Sporadic further north, although there may be small isolated populations in some suitable areas.

Ecology: As its name suggests this is a late summer species commonly encountered in woodland, gardens and heaths. Adults are sometimes found by day resting on the trunks of trees, or occasionally beaten from the branches. They are attracted to light and frequently appear in traps, but usually in small numbers. The larvae can be found from May to July on oak Quercus spp., Beech Fagus sylvatica, birch Betula spp. and Hawthorn Crataegus monogyna. It overwinters as an egg attached to the twigs of the foodplant.

Caterpillar: 

 Thompson, R. S. & Nelson, B., 2003 (Oct 2). [In] The Butterflies and Moths of Northern Ireland
http://www.ulstermuseum.org.uk/lepidoptera/species.asp?item=6003

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