The wings are greyish, thickly striped with darker grey; the markings similar to those of the next species, but the rings are nearly always reddish or purplish, and the central line is wavy. (Plate [53], Figs. 4 and 5.)
The egg (which, together with the caterpillar and chrysalis, is figured on Plate [51]) is at first bone-coloured; later, pink dots and patches appear.
The caterpillar is bright green with three lines along the back, the central one edged on each side with dark green and the others wavy; the sides are blotched with pink or pale purple, or sometimes whitish and unmarked; head slightly notched on the crown, pale brown, marked with darker; fore legs tipped with pink. (Porritt, abridged.) In another form of the green coloration, the sides are pinkish with dark-brown oblique stripes; in a third the general colour is pale brown. The first brood of caterpillars feeds in June on sallow and alder, and a second in August and September.
The moth appears in May and June, and again in July and August; sometimes a third brood has been reared in captivity. It is less frequently met with than the other species of Ephyra, even in its most favourite haunts, such as the New Forest, in Hampshire. Other localities for it are Abbots Wood, St. Leonards and Tilgate Forests, and elsewhere in Sussex; Redstone, Haslemere, and the Croydon districts, in Surrey; and in some Kentish woods. It has also been taken rarely in Dorset, Devon (Tiverton), S. Wales, and Suffolk (Lowestoft).
Birch Mocha (Ephyra pendularia).
The general colour of this species (Plate [53], Figs. 1, 2) is whitish, more or less powdered or suffused with grey; all the
wings have two blackish dotted cross lines and a greyish, sometimes reddish, central shade; not infrequently there is an interrupted grey or dark greyish band on the outer marginal area, and this margin itself is always dotted with black; the rings enclosing white dots on all the wings are usually black, but sometimes reddish. In some specimens having a reddish central shade, the general colour, especially of the fore wings, is delicately tinged with reddish. Var. subroseata, Woodforde (Fig. 3), a form of this species occurring in N. Staffs. is slaty grey, with the space between the inner and outer cross lines of fore wings rosy pink or reddish.
The caterpillar is of a green colour with slender yellowish lines along the back and sides; between the rings the colour inclines to yellowish, and the head, legs, and prolegs are reddish brown. In another form the general colour is greyish, inclining to reddish, and the lines paler grey. It feeds on birch in June and July, and again in August and September. It is said to eat alder and oak. The chrysalis, which is similar in shape to that of the last species (Plate [51]), is pale greyish-ochreous marked with dark brown.
The moth, which appears in May and June, and in some seasons in August, frequents woodlands and heaths where birch flourishes. Although fairly plentiful in most of the southern English counties, it appears to be rare in Dorset and Devon, and more or less so in the eastern counties. It is very local in Nottinghamshire and Yorkshire, but not uncommon at Strensall in the latter county; and although it has been recorded from Cumberland, it seems to be absent from Lancashire and Cheshire. Doubtfully reported from North Northumberland, but found in Wells Wood, Roxburghshire, and appears to be widely distributed in Scotland, although generally scarce in that country. In Ireland it is local, but not uncommon sometimes.
The range abroad extends to Eastern Siberia.