The moth is out in March and April; and after their short evening flight the males may be seen in numbers on hedgerows and the twigs of trees. It is not infrequent at sallow catkins, and sometimes is not scarce on palings and tree-trunks. The female may occasionally be detected in the crevices of bark on tree-trunks, but is more easily obtained on the twigs at night.
The species is common over the whole of England and Wales, also in Ireland. As regards Scotland, it is abundant in the south, but its range does not seem to extend beyond Aberdeen; the var. fuscata occurs in Renfrewshire.
Mottled Umber (Hybernia defoliaria).
A female (Fig. 3) and four examples of the male of this variable species are shown on Plate [122]. The ground colour of the fore wings in the male varies from whitish, through ochreous brown to dull russet brown; the cross bands (when present) range in colour from reddish brown to dark purplish, almost blackish, brown; in all the paler specimens the ground colour is more or less sprinkled or suffused with brownish; the darker specimens are sprinkled with dark purplish or blackish. Ab. obscurata, Staud., is almost uniformly dull brownish, and an example approaching this form is represented by Fig. 4.
When deposited the eggs (Plate [125], Fig. 1b) were deep straw yellow.
The caterpillar (figured on Plate [125], Fig. 1, from a coloured drawing by Mr. A. Sich) has various shades of reddish brown on the back, and yellowish on the sides and beneath; the line above the red-marked white spiracles is black, and this has an interrupted edging of white. Fig. 1a shows a pale form. It feeds on the foliage of birch, oak, and other forest trees, also on fruit trees, rose, honeysuckle, etc. It often occurs in great abundance, and is largely responsible for the leafless condition of the trees, sometimes noticed in May.
The moth appears from October to December, and occasionally in January, February, or March.
Generally abundant throughout England and Wales; widely distributed, and often common in Ireland; not uncommon in the south of Scotland, but becoming less frequent northwards to Perthshire and Aberdeen.