| Pl. 51. |
| Pale Oak Eggar. |
| Eggs enlarged, and caterpillar. |
The caterpillar may be found from April to June on hawthorn and sloe, and it is said also on birch, oak, sallow, apple, bramble, etc. Those that I have found resting by day on shoots of hawthorn, apparently enjoying the sunshine, have almost invariably been "ichneumoned"; but others that came up after sunset to feed on the shoots were generally healthy. Usually the caterpillar feeds up and pupates the same year, but on the moors in Aberdeenshire and some other parts of Scotland it is said to hibernate and to complete its life cycle the following summer and autumn. Furthermore, the moths from these winter larvæ are much darker than normal, and have been doubtfully referred to var. ariæ, Hübn., a form found in the Alps, Scandinavia, and Finland.
The moth is out in August and September, and occurs in wooded districts throughout the southern half of England, but northwards from the Midlands it is uncommon; it is found in several parts of Scotland to Inverness. In Ireland it is reported (Birchall) to have occurred in Killarney, and Kane mentions that "a blackish form was taken at Magilligan, near Derry, by W. Salvage. Its larvæ were feeding on blackthorn." The range abroad extends through Europe to Armenia and Asia Minor.
The December Moth (Pœcilocampa populi).
This is a rather thinly scaled moth; the general coloration is sooty brown; the wings are suffused more or less with greyish; there are two pale ochreous cross lines on the fore wings, the first enclosing a reddish brown basal patch; hind wings rather paler with a diffuse whitish central band; fringes brown chequered with pale ochreous. Head brown, collar brownish, tipped with pale ochreous in the male. The female is rather larger than the male. The moth is figured on Plate [50], and the eggs and caterpillar on Plate [53].
The eggs, which are laid on the bark of trees, are whitish grey, variegated or mottled with darker grey.
The caterpillar hatches out in April, and when nearly full grown is ochreous, but so thickly dotted and freckled with black as to appear of a dark brown coloration; the back is clothed with dark short hairs, and the sides with long paler hairs; on the back of the first ring is a reddish brown mark divided by a white line; a double row of whitish dots along the back, most distinct on rings two and three, where they are placed on a velvety black bar; on each side of the white dots is a reddish brown interrupted line. Head ochreous brown, thickly dotted with black and clothed with pale hairs. Underparts ochreous, spotted and lined with blackish. Feeds on the foliage of most trees, and is said to eat lettuce. April to June.