The Speckled Wood (Pararge Egeria)
Quite early in the eighteenth century Petiver met with the butterfly shown on Plate 80 at Enfield, so he figured it as the “Enfield Eye” in that curious old book entitled “Papiliorium Britanniæ Icones.” Later on, Wilkes named the butterfly the “Wood Argus,” thus indicating its favourite haunts, as well as a prominent character in its ornamentation. Harris changed the name to the “Speckled Wood Butterfly,” which seems even more suitable.
The general colour is blackish-brown, and the spots are yellowish. The fore wings have one white-pupilled black eye spot towards their tips, and the hind wings have three such eye spots on the outer area. The male has a long oblique patch of blackish scales on the middle of the fore wings, which is, perhaps, more easily detected if the insect is held up to the light. The female is usually slightly larger than the male, the wings rather rounder, and the yellowish spots, are, as a rule, distinctly larger. The typical or southern form of this butterfly has the spots of a tawny colour, but it does not occur in Britain. Our form, in all its modifications, belongs to egerides, Staudinger. Occasionally, in the south of England, specimens are found in which the spots are tinged with fulvous; others have almost white spots. The spots are sometimes much reduced in size in the male, or greatly enlarged in the female.
The egg is pale greenish, finely reticulated; as the caterpillar matures within, the shell becomes less glossy than at first, and the upper part is blackish.
The caterpillar has a green head, which is larger than the first ring of the body (1st thoracic), covered with short fine whitish hairs, with which are mixed a few dark hairs. The body is rather brighter green, with darker lines, edged with yellowish, along the back and sides; the skin is transversely wrinkled, the rings being subdivided, and the whole of the body is clothed with fine whitish hair and a few dark hairs arising from warts; the anal points are whitish and also hairy. It feeds on various grasses, among which are Triticum repens and Dactylis glomerata.
The chrysalis is pale green, tinged with yellowish or whitish; the edges of the wing covers are brown, and there are whitish dots on the body. According to Hellins the colour varies, and green chrysalids may be covered all over with very fine smoky freckles. Barrett states that they are occasionally brownish with darker brown lines. Suspended by the cremaster from a silken pad.
From eggs laid in early May butterflies were reared at the end of June; and from eggs laid at the end of June butterflies resulted during middle August. Early July eggs produced perfect insects in early September, and from caterpillars fed up in October butterflies were obtained in November. These observations were not all made in the same year.
Barrett writes, “In the south of Surrey in 1862, the first emergence took place in April in abundance, these specimens became worn and disappeared, and a second emergence took place at the end of May, a third at the end of July, and a fourth in September; the next year the first emergence was in the third week in March, and again four broods were observed, but this is not the case every year, three emergences being probably the rule.”
Mr. Joy has recorded that of caterpillars, resulting from a pairing induced in captivity, in August, eighty per cent. hibernated as pupæ, twenty per cent. as half-fed caterpillars. Butterflies from the winter pupæ emerged in May, but the caterpillars that had gone through the winter in that state did not produce butterflies until June. Possibly something of this sort occurs in the open, and we may suppose that the early and late spring butterflies are not separate broods, but early and late emergences of one brood. Butterflies seen on the wing in November may be a few individuals that, owing to favourable weather, have emerged from chrysalids which under ordinary conditions would have remained as such during the winter.
Shady lanes, rides in woods, as well as the borders of the same, are its favourite haunts. It is not a sun-loving butterfly, but is generally found to frequent places where the sun’s rays are more or less intercepted by a leafy screen. It seems to be more abundant in wet seasons than in dry ones. It is generally distributed throughout England and Wales, but more plentiful in southern and western counties than in the eastern and northern. In Ireland, Kane says, it is “everywhere abundant and double brooded.” It is local in Scotland, and rare north of the Caledonian Canal.
Abroad our form of the butterfly egerides is found commonly in Central and Northern Europe, except in the extreme north, and in Northern Asia Minor and Armenia. The typical form, egeria proper, occurs in South-Western Europe, North Africa, and Syria.