The Small Mountain Ringlet (Erebia epiphron).
The typical form of this butterfly, epiphron, Knock, has the tawny bands unbroken on the fore wings, and almost so on the hind wings; the black dots on the hind wings of the female are often pupilled with white, and more rarely this is so in the male also. It has been stated that specimens occur in Perthshire which exhibit these characters. All the British examples of the Small Mountain Ringlet that I have seen are referable to the form known as cassiope, Fab. (Plate [77]). The tawny, or orange, bands are rarely so entire on the fore wings as in epiphron, and are generally rather narrower; and that on the hind wing is broken up into three or four rings. The black dots are usually smaller and without white pupils. The female is somewhat larger and the bands or rings paler.
Variation in the markings is extensive. The bands on the fore wings become less and less complete, until they are reduced to a series of mere rings around the black dots. The black dots decrease in size and in number until they, together with the tawny marking, entirely disappear, and a plain blackish-brown insect only remains. This extreme form has been named obsoleta, Tutt. The earliest rings to vanish seem to be the third on the fore wings and the first on the hind wings. Similar modifications occur on the under side also, but there may be aberration on the upper side of a specimen, and not, or at least not in the same way, on the under side.
The egg, when first laid, is yellow, changing afterwards to fawn colour with darker markings, especially towards the top. It is laid in July on blades of grass. The larva hatches in about sixteen days.
The young caterpillar, before hibernation in October, is greenish, with darker green and yellow lines. Head brownish. Feeds in July and after hibernation on various grasses, among which Poa annua, Festuca ovina, Aira præcox, and A. cæspitosa have been specified as eaten by caterpillars in confinement. A distinct preference, however, has been shown for mat grass (Nardus stricta), and it has been suggested that this may be the natural food. The full-grown caterpillar appears to be undescribed.
The chrysalis is described by Buckler as being "little more than three-eighths of an inch in length, rather thick in proportion, being less dumpy in form than hyperanthus, but more so than blandina. The colour of the back of the thorax and wing cases is a light green, rather glaucous; the abdomen a pale drab or dirty whitish; a dark brown dorsal streak is conspicuous on the thorax, and there is the faintest possible indication of its being continued as a stripe along the abdomen. The eye-, trunk-, antenna-, and leg-cases are margined with dark brown, and the wing nervures are indicated by the same colours."
Pl. 74.
Marbled White.