The Wall Butterfly (Pararge Megæra)
The butterfly now under consideration is figured on Plate 82. It is bright fulvous in colour, with blackish-brown veins, margins, and transverse lines. There is one white pupilled black spot on the fore wings, and four of such spots on the outer area of the hind wings; the fourth, which is generally blind, is placed at the end of the series near the anal angle. The male has a very conspicuous sexual brand on the central area. The under side of the fore wings is paler than above, but the markings are similar, except that the brand is absent and the margins are greyer; the hind wings on the under side are greyish marked with brown and traversed by dark lines; there is a row of six eyed spots on the outer area; that nearest the anal angle is double. The female has more ample wings, and as the brand is absent on the fore wings in this sex, the central black transverse lines are more distinct.
Variation is chiefly in the size of the eyed spots; sometimes the apical one of the fore wings has a smaller one attached to its lower margin, or in the interspace (i.e. between the veins) above it or below it; or both extra spots, which are usually without white pupils, may be present. Very rarely the apical spot may be almost absent on one fore wing, but well defined on the other. The central transverse lines on the fore wings of the female are sometimes broad, and very occasionally the space between the lines is blackish; blackish-banded male specimens are also found in some localities, such as the slopes of Dartmoor, Devon, as mentioned by Barrett.
The ground colour varies in tint, darker or lighter than normal, but specimens of a bright golden yellow-brown, straw colour, or whitish are known to occur, although such extreme aberrations are exceptional.
The egg is pale green when first laid, and in shape it is almost spherical, but rather higher than broad; it is finely ribbed and reticulated, but unless examined through a lens it appears to be quite smooth.
The caterpillar when full grown is whitish-green, dotted with white. From the larger of these dots on the back arise greyish bristles; the three lines on the back (dorsal and subdorsal) are whitish, edged with dark green; the line on the sides (spiracular) is white, fringed with greyish hairs; anal points green, hairy, extreme tips white. Head larger than the first ring (1st thoracic segment), green dotted with white and hairy, jaws marked with brownish. It feeds on grasses.
The chrysalis is green, with yellow-tinted white markings on the edge of the wing covers and ridges; the spots on the body are yellowish, or sometimes white. Occasionally the chrysalids are blackish, with white or yellow points on the body.
There are certainly two broods of this butterfly in the season, and in favourable years there may be three broods. In an ordinary way the first flight is in May and June, and the second flight in July and August. The caterpillars feed on Poa annua, Dactylis glomerata, etc. Those hatched in autumn hibernate more or less completely, and become full grown in early or late spring according to the season. Sometimes, however, they seem to feed during the winter, and assume the chrysalis in March. Probably it is from such precocious caterpillars that the butterflies sometimes seen in April result.
The Speckled Wood, it was noted, prefers shady places; the present butterfly is more partial to sunshine and plenty of it. As its English name suggests, it is fond of basking on walls, but it does this also on dry hedge banks, sides of gravel pits, tree-trunks—in fact, wherever it can enjoy the full sunshine. It is not at all shy, and will be pretty sure to introduce itself to the notice of the collector as soon as he enters its domain. Although it now seems to be absent from certain districts in which it was once abundant, it may still be regarded as a generally common species in England and Wales, and even plentiful, in some years, in the southern, eastern, and western counties; it appears to be more local in North England. In Scotland it seems fairly distributed, and not scarce in the south; its range extends to Aberdeenshire. Kane states that it is everywhere abundant throughout Ireland. Abroad it is common throughout Europe, except the extreme north, and extends into North Africa, Asia Minor, and Armenia.