In its typical form the fore wings are white, inclining to greyish, with a number of brownish or dark-grey cross lines; two pairs on the central area are marked with black. Sometimes the wings are greatly suffused with smoky grey, and this tint in examples from the Sheffield and Rotherham districts of Yorkshire assumes a much darker hue, so that all the markings are obscured, but the veins are blacker.
The caterpillar is green, marked with some irregular reddish blotches; a yellowish line along the back. It feeds in August, earlier or later in some seasons, on mountain ash (Pyrus aucuparia), and the moth, which rests by day on tree-trunks, is out in July and early August. The haunts of the species are chiefly in hilly localities of the northern counties of England, but it has also been reported from Gloucestershire (Cotswolds), Somersetshire (Weston-super-Mare), and Devon (Dulverton). In Wales it occurs in Merionethshire, as well as in Cardiganshire; and in Scotland it spreads from Roxburghshire, where it is locally common among mountain ash, through Clydesdale to Inverness. It is widely distributed in Ireland. The range abroad extends to Japan and North America.
Grey Mountain Carpet (Entephria cæsiata)
The typical greyish form, with blackish wavy cross lines and dark central band, is shown on Plate [80], Fig. 1 ♂ and 2 ♀. Figure 3 represents a specimen from Shetland in which the band is sooty black (ab. annosata, Zetterstedt = nigristriaria, Gregson). The interesting blackish suffused form from the Isle of Arran (Fig. 4) leads up to a still blacker variety, occurring in the same isle, and also in the Shetlands, in which the whole of the fore wings is nearly as dark as the central band of Fig. 3, and the hind wings are also much darkened; such specimens are referable to ab. glaciata, Germar. Ab. prospicuata, Prout = gelata, Staud., is a form with the fore wings whitish, and the
base and the central band thereof blackish; some Shetland specimens closely approach this pretty variety.
The caterpillar is green, with a brownish line along the middle of the back, and a series of pinkish or purplish-red oblique streaks which nearly meet at the central line and so form V-shaped marks; a whitish or yellowish stripe low down along the sides, sometimes edged above with reddish. In some examples the general colour is reddish brown. It feeds in April and May, after hibernation, on bilberry, ling, and heath in a wild state, but may be reared on knot-grass or sallow.
The moth is out from June until early August, and may be found resting, often in numbers, on rocks and stone walls in mountain and moorland districts, from Herefordshire, northwards through England, North Wales, and over the whole of Scotland, including the isles, and Ireland. Kane states that in the latter country melanic forms, such as those from Yorks, etc., are nowhere met with.
Yellow-ringed Carpet (Entephria flavicinctata).
The general colour of the fore wings of British specimens of this species (var. obscurata, Staud.) is slaty grey; the basal, central, and outer marginal cross bands are thickly sprinkled with yellowish-brown, and it is this feature that at once separates this species (Plate [80], Figs. 5, 6) from that last referred to.
The bristly caterpillar is green, chocolate, or red brown, but always of a dull shade; on the back is a series of black V-shaped marks, and a central dark, slender line; the front part of each V-mark filled up with pink or lilac, forming a triangle, the apex of which is yellow; a yellowish stripe low down along the side (adapted from Fenn). It feeds in the spring till April, after hibernation, on saxifrage (Saxifraga aizoides, S. hypnoides, etc), and also on stonecrop (Sedum), and is most partial to the flowers of these plants.