In a general way the male is rather larger than the female, but this is not invariably the case. The colour of the male varies in shade, and very occasionally, perhaps, is of a lilac tint; the border varies in width, and is sometimes reduced to a mere line. In the female the orange marks may be of a brownish or yellowish tint, and now and then there may be a series of wedge-shaped blue spots above these marks on the hind wings. On the under side there is a good deal of modification of the black spots as regards size and shape, and occasionally there is at least one extra spot on the fore wings placed between the discal spot and the base of the wing; white markings sometimes appear on the fore wings between the outer series of black spots and the orange band, and with this there is generally a white band in a similar position on the hind wings. Female specimens with splashes of the male colour on one or more of the wings have been obtained, and, more rarely, examples entirely male on one side and female on the other have been recorded. Frohawk states that the egg both in colour and texture, resembles white porcelain; "all the depths produce a deep purplish-grey shade. The ova are deposited singly, and adhere firmly to the receptacle." Caterpillars hatched out from eggs, laid the previous summer, on April 1st to 3rd. They were reared on gorse (_Ulex europæus_), pupated towards the end of June, and the first butterfly, a male, appeared on July 10th. The caterpillar figured on Plate 104, when full grown, was reddish-brown, finely dotted with white, and from each dot a tiny hair arose; the stripe on the back and line on the side were black edged with white, head black and shining. This caterpillar was found on the last day of May, crawling on the ground under heather at Oxshott. It was then about half-grown, and was reared on heather, pupated in due course, and produced a female butterfly on July 11th. The chrysalis, of which two figures are given, had a pale brownish and rather shining head; the body was brown with a darker line on the back; the thorax and wing-cases dull yellowish-green, the former rather glossy. It was placed in an angle formed by a side and the floor of the cage, lying quite flat and secured by silken threads, which, owing to position, I was unable to examine. Some of the caterpillars that Mr. Frohawk reared were pale green with a dark purplish stripe on the back. Another food-plant is bird's-foot vetch (_Ornithopus perpusillus_).