The caterpillar is black or greyish black, with reddish brown hairs, and a series of black-edged yellowish brown, or reddish brown blotches on each side of the back; these blotches are outlined in pale yellowish and occasionally connected by a line of the same colour. From the time they are hatched until nearly mature the caterpillars live in companies on a closely woven web of silk on a branch of hawthorn or sloe, only leaving their habitation to feed. These webs may often be seen on hedgerows from May to July. The brown chrysalis is enclosed in a solid-looking oval cocoon of a pale ochreous or whitish colour. Not all the moths emerge the following year: some will remain in the chrysalis over two or three winters, and occasionally they have been known to emerge seven years after pupation. The moth is said to be fully formed within the chrysalis all the time, but for some reason will not emerge, although if extracted from its shell, the moth has been known to expand its wings in the ordinary way. Barrett states that in the middle of February, after a moth had emerged, he "put a large number of cocoons upon a warm mantelpiece and obtained scores of moths within a few hours."
Generally distributed over the southern half of England; plentiful in some years in the Southern and Eastern Counties. Northwards and in Scotland it is local and less frequent. Kane states that in Ireland it is very locally abundant. The range abroad is through Central and Northern Europe to Southern Lapland, and eastward to Siberia and Amurland.
The Oak Eggar (Lasiocampa quercus).
The three moths, one male and two females, shown on Plate [52], were reared from caterpillars obtained in Kent, and they
represent the more or less ordinary South English forms of the species. Sometimes the ground colour of the male is more distinctly reddish, or rust tinted, and the yellowish bands narrower on all the wings. Or the bands may be much broader than in the male figured, and the widening is effected by extension in the form of rays towards the outer margins of the wings. A form that has been referred to, in error, as var. roboris, Shrank (= marginata, Tutt), has the outer margins of all the wings broadly yellow. I have not seen an English example of this form, but I have a reddish specimen in which the yellow band on the fore wings is broader than usual, and the whole of the outer third of the hind wings yellow, with a slight brownish shade on the external margin; this is semimarginata, Tutt, and is also identical with var. roboris of other British authors. The white spot usually present on the fore wings varies somewhat in size and shape; it is often seen on the under as well as the upper surface of the wings, except in the lighter coloured forms.
Var. callunæ (The Northern Eggar), is shown on Plate [54]. The chief features of this form are the generally darker coloration in both sexes, the yellow patch at the base of the fore wings of the male, and the outward turn of the lower ends of the yellow bands. All these characters are subject to modification; the yellow bands may be very narrow at one extreme, or greatly widened at the other, and the hind wings may occasionally be bandless; the basal patch is often of large size, but in some examples it is entirely absent. Sometimes the bands are greenish in colour (var. olivaceo-fasciata, Cockerell), and more rarely, perhaps, the greenish tinge extends over the whole of the wings (ab. olivacea, Tutt). It should be noted here that the var. olivaceo-fasciata has occurred once or twice in South England, but this phase of aberration seems to be more connected with callunæ than with quercus.
| Pl. 54. |
| Northern Eggar. |
| Pl. 55. |
| Oak Eggar. |
| Egg, natural size and enlarged; caterpillars and cocoon. |