The Moths of the British Isles Second Series/Chapter 6

By some systematists this small group of moths is treated as a subfamily of the Geometridæ. Brephos, however, which is typical of the family, does not seem to have any close affinities with the Noctuidæ or with the Geometers, and is therefore better considered as apart from both those families. Meyrick includes Brephos with Aplasta, Erannis, and Baptria, in his family Monocteniadæ.

Only five species are known to inhabit the Palæarctic Region, and two of these occur in Britain.

The white markings of the fore wings vary a good deal in size; in some specimens, chiefly males, they are very small and confined to the front margin; in others, mainly females, they are much enlarged, and the central one is continued as a band across the wings. On the orange hind wings the blackish central band is usually more or less complete, but sometimes it is nearly or quite absent above the blackish triangular patch on the inner margin. Occasionally, there is a yellow blotch at the anal angle, and frequently another on the costal area. Still more rarely the whole ground colour is yellow. (Figured on Plate 38, Figs. 1 ♂ and 2 ♀.) The caterpillar is green, with six white lines along the back, and white stripes along the sides. When young it feeds on the catkins of birch, and afterwards on the foliage. April to early June. (Plate 39, Fig. 1.)

The moth is out in March and April, and on sunny days the males may be seen flying, generally pretty high up, on the lee side of the birch trees growing on heaths; also in open spaces in or around birch woods. The females rest on the twigs, as also do the males when the sun is obscured. Both sexes have been found sitting on the ground in sunny glades.

The species is widely distributed over the southern and eastern counties, common in many parts; but its range extends through England to Durham, and it has been recorded from Wales. Although it does not seem to have been noted in Scotland south of Kincardineshire, it occurs on the east to Moray. Westmeath is the only Irish locality that has so far been mentioned.

Its distribution abroad extends to East Siberia and Amurland.

Very similar to the last species, but rather smaller in size, and the fore wings are much less variegated. The antennæ of the male of this species are bipectinated, whilst those of parthenias are finely serrated. (Plate 38, Figs. 4 ♂ and 5 ♀.)

The caterpillar feeds in May and June on aspen, eating the foliage and hiding between two leaves drawn together. The head is greenish or greenish-brown, with three conspicuous black spots. Body, green, olive-green, or reddish; line along middle of the back darker green edged with white; two thin white lines on each side, and a whitish stripe along the spiracles. When mature it burrows into decayed bark or wood (virgin cork in confinement), and before changing to a reddish-brown chrysalis, it spins a thin covering of silk and woody particles over the mouth of the chamber. The caterpillar and the chrysalis are shown on Plate 39, Figs. 2 and 2a. Although the bulk of the moths emerge the following April, some have been known to remain until the following or even the third year. The males fly about aspen, but only in the sunshine; in other respects its habits are pretty much those of the last species.

The distribution of the species in England seems confined to two areas: a western one represented by Worcester, Gloucester, with Monmouth, Wales, Wilts, and Dorset; and an eastern one by Norfolk, Cambridgeshire, Suffolk, Essex, Middlesex, Kent, Surrey, and Sussex. In Scotland only recorded from Moray.

The range abroad extends to Amurland.