The Scotch Argus (Erebia Æthiops = Blandina)
The butterfly figured on Plate 77 is deep velvety brown, appearing almost black in very fresh male specimens. There is a broad fulvous band on the outer area, but not reaching either the costa or the inner margin; it is contracted about the middle, the upper part encloses two white pupilled black spots, and the lower part has one such spot. The hind wings have a narrow fulvous band, usually enclosing three white pupilled black spots. The under side is more distinctly brown and not velvety, band of fore wings similar to above; the hind wings have a greyish band beyond the middle, with three small white pupilled black spots on its outer edge; the basal area is often greyish also. The female is generally less dark and velvety, the bands are rather wider, more orange in colour, and the white pupils of the spots are more conspicuous; on the under side the alternate dark and pale bands are more striking, and sometimes the grey colour is replaced by ochreous, which seems to constitute the aberration named ochracea, Tutt. The spots on the fore wings, upper side, are often increased to four by the addition of a small one between those previously mentioned. More rarely there is an extra spot above the upper pair, and still less frequently, and in the female sex, an additional pair is found below the usual lower spot, thus making six in all. On the other hand, the only spots in evidence may be the pair in the upper part of the band. The spots on the hind wings range in number from two to five, but occasionally all are absent. The fulvous bands on the fore wings may be reduced to rings around the upper and lower spots respectively, and altogether wanting on the hind wings. Such an aberration would be referable to obsoleta, Tutt, which is considered to be very rare. There are many other modifications, but these mentioned will serve to show the variable character of this local butterfly.
The egg is ochreous white, or bone colour, finely freckled with pale brown or pinkish-brown; it has a number of ribs, and is also reticulated.
The caterpillar in its last skin is pale drab, the warts pale whitish-brown, emitting short tapering bristles; dorsal stripe blackish-brown, enclosed by two paler drab lines; subdorsal stripe paler drab, becoming narrow towards the anal point, edged above with a greenish-brown thread, and below with blackish or brownish dashes, that almost form a continuous line; below this come two thin pale lines, above the lower of which are the circular black spiracles; the under parts and the legs are of a somewhat warmer tint of the ground colour of the back. It changed on June 22nd to a pupa, unattached, but placed in an upright position amongst the grass near the ground.
The chrysalis has the body ochreous, with a darker stripe down the back, and other lines; the eye covers are black, and the thorax, antennæ cases, and wing covers are dingy, dark purplish-brown.
The above descriptions of caterpillar and chrysalis are adapted from Buckler, whose figures of these stages are also reproduced on the plate.
Aira præcox, A. cæspitosa, and Poa are the grasses that seem to be the food of the caterpillar.
Mr. Haggart, of Galashiels, who had exceptional opportunities for observing the habits of this butterfly in its natural home, gives a most interesting account of it in the Entomologist for November, 1895. He writes—
“The haunt of this species is, almost without exception, the margin of a plantation or wood where the different species of Poa grow abundantly, and always situated in such a position as to receive the first rays of the rising sun. This last-mentioned fact is so plainly evident, that the least observant cannot fail to notice it. The insect is truly sun loving, and no collector need go in search of it with any thought of success if the day be dull.
“It is most interesting to observe the extreme sensibility of the insect to shine and shade. A very good day to illustrate this is one when heavy clouds at intervals obscure the sun; the moment it disappears so also does the butterfly, and no sooner does it shine forth again than, as if by magic, scores of the insect are on the wing.
“The under side of the insect bears a marked resemblance to that of a dead leaf, and I have often watched the males being deceived by withered leaves lying among the moss. They would flutter down quite close to the leaf, immediately rise with a disappointed air and fly a little further, only to be deceived again and again.
“The ova are deposited amongst the Poa grass, and hatch in September. Towards the end of October the larvæ go down and hibernate throughout the winter and spring, coming up to feed again in May; they are generally full-fed about the end of June; and the insect appears in July or August. The larvæ are nocturnal feeders, coming up to feed on the grass just about dusk. The method of procuring the larvæ is by no means enviable, even to the most ardent entomologist, as in the uncertain light it necessitates crawling on one’s hands and knees amongst the grass, and there is always the risk of grasping those little brown slugs in mistake, which resemble the larvæ very much in shape and colour. No artificial light can be used, as the larvæ immediately drop down amongst the grass if this is done. The only alternative, therefore, is to use one’s eyes to the best advantage until the darkness makes that impossible.
“They are not difficult to rear in confinement if the larvæ are kept properly supplied with food.”
This butterfly, which as a British species was discovered in the Isle of Arran in 1804, only occurs in the north of England and in Scotland. Its localities in the latter country are Glen Tilt and other valleys in the Perthshire highlands, Strathglass in Inverness, Altyre woods at Forres; Selkirk, Roxburgh, and various parts of Argyleshire; around the Lowther Hills, Dumfrieshire; also in Arran and the Isle of Skye. In most of the places it is plentiful. In England it occurs in the counties of Durham, Westmoreland, Cumberland, Lancashire, and Yorkshire. It is common in Castle Eden Dene, Durham; at Grassington, in Yorkshire; at Witherslack and Arnside, in Westmoreland; and at Grange and Silverdale, in Lancashire.
Abroad, it is distributed through Central and Southern Europe, and its range extends into Northern Asia Minor, Kurdistan, and Armenia; the Altai and South Siberia.
It may be noted here that E. ligea was supposed to have been taken in Arran at the same time as E. blandina, that is in 1804. If this were so, it would seem that the captor must have exterminated the species, for, although the island has often been closely explored, no one has been able to detect the “Arran Brown” again.