The caterpillar varies in general colour from pale green to a dark olive green approaching black. In the white dotted paler green forms there are several transverse whitish lines, some of them wavy, between the yellowish spiracular line and the dark green line along the middle of the back; head, marked with black on each cheek. It will eat almost every kind of low-growing vegetation, either wild or cultivated, and in some years may be found throughout the summer. Small larvae were recorded as seen at the end of October, 1901. The blackish chrysalis is enclosed in a whitish cocoon, often placed under leaves of thistle, burdock, etc. The moth is seen in the spring and early summer (most probably immigrants), and again in the autumn, when it is generally more abundant. This well-known migrating species has been observed in greater or lesser numbers over the whole of the British Isles. Its distribution abroad embraces the Palaearctic Region, North Africa, and North America. {73} THE SCARCE SILVER Y (_Plusia interrogationis_). Portraits of two examples of this species will be found on Plate 26, Figs. 4 and 5. The metallic central marks on the fore wings vary a good deal in size and in form, and are sometimes almost absent; these wings have the general greyish colour more clouded or suffused with blackish in some specimens than in others. Kane states that Irish specimens, when freshly emerged, have a tinge of violet purple, and Tutt notes some British specimens as beautifully tinted with rose colour (ab. _rosea_). The caterpillar, which feeds on heather (_Calluna_) and bilberry (_Vaccinium_), is green inclining to blackish on the sides and underparts, with six white lines along the back; two of which are irregular; the raised dots are white and the bristles therefrom dark; head, green dashed with purple, shining. (Fenn.) After hibernation it may be found without much difficulty in May and June on its food plants, either in the daytime, or by the aid of a lamp at night. Large numbers fall victims to parasitical flies. (Plate 28, Fig. 2.) The white cocoons enclosing the black chrysalids are spun up on or under the twigs of bilberry and heather. The moth is out in July and August, and may be found on moorlands, in the north of England from Shropshire (with Radnor) and Staffordshire on the west, and Lincolnshire on the east, through Scotland to Sutherland, and in all suitable localities in Ireland. THE DARK SPECTACLE (_Abrostola triplasia_).