Mesotype didymata
Mesotype didymata, the twin-spot carpet, is a moth of the family Geometridae. The species was first described by Carl Linnaeus in his 1758 10th edition of "Systema Naturae". Its genus is sometimes included in "Perizoma". Distribution. It is found in northern and central Europe; further south and east it seems to be confined to the mountains Pyrenees, Alps, Urals. Description. The wingspan is 24–29 mm. The ground colour of the forewings is generally pale or dark grey. There are two dark stains near the apex and the costa of the forewing. The wavy crosslines delimit a darker  mid field and a darker marginal field. It is very variable in colour, with the male considerably darker than the female; in some districts the sexual dimorphism is quite striking. This sex is also appreciably smaller and narrower-winged than the male and has a much stouter abdomen. - ab. "ochroleucata" Auriv. is unicolorous grey yellow or yellow brown without markings except the light subterminal line. - In ab. "nigrofasciata" Rbl. The ground colour is darkened and the median band narrow, almost black. - ab. "nigra" Prout has uniform blackish brown wings. In "hethlandica" Rbl. the male is more or less bright orange  brown, the female lighter ochreous brown or fawn colour. Biology. Adults are on wing from June to August. There is one generation per year. The larva feed on various plants, including "Vaccinium myrtillus", "Salix" and "Calluna".Unlike most "Perizoma" the species lives openly on the nutrient plant, not inside the seed capsules, and it can use a variety of different nutrient plants. This may provide the basis for assigning this species (and some others) to the genus "Mesotype".