The ground colour in the male ranges in tone from foxy red to dullish red brown or to greyish red brown. The cross lines in either sex may be widely apart, near together, or even united throughout their length, forming a band (var. _fasciata_, Tutt); sometimes one of the lines (var. _unilinea_, Tutt), or both lines, are absent from the fore wings, or from one of them. { 122}
The brown clouded greyish eggs are laid in batches, during June, on stems and stalks of plants, or on heather; sometimes they have been found on a fence, a rock, or a stone. The caterpillars hatch out at the end of June and through July. At first they are black, including the glossy head, and covered with long hairs which are black with some white ones amongst them; the ring divisions are pale yellow; later on they are more chocolate brown with yellow bands which, however, do not encircle the body entirely.
When full grown, in the autumn, the caterpillar is velvety black, and above this colour is most in evidence between the rings; the back is clothed with dense, short, bright reddish brown or tawny hair, and the whole body is covered with brownish hairs, varying in length, but always much longer than the tawny ones; along each side are some whitish hairs. Head blackish covered with brownish hairs. It feeds in August and onwards to October, when it seeks winter quarters, reappearing in the following spring, but not feeding again. After enjoying the sunshine whenever the opportunity offers through the early months of the year, it finally pupates in March or April. The cocoon is a long, more or less tubular, brownish construction of silk and larval hairs. It is spun up, usually somewhat upright, low down among the food plant, or at the roots of grass, etc.; sometimes among moss, when the rounded head end can just be seen above the moss (Plate 58).
In certain localities and seasons the caterpillars have been seen in enormous numbers, but such profusion only happens now and then. In some districts they may be abundant one year, and then scarce or quite absent for several years.
When handling the larvæ it will often be noted that the tips of one's fingers are thickly felted with the tawny hairs from the creature's back; if these hairs get transferred to the face or neck considerable irritation may be the result.