All the available information concerning the occurrence of this species in England has already been given. No doubt the localities from which specimens were recorded have been closely investigated during the past twenty years, but no further captures of this butterfly have been recorded. This seems to indicate that it is not really indigenous, but that its presence here may possibly have been due to accidental introduction.
The spring form, polysperchon, is smaller than the specimens occurring in the summer, but so far that form has not been seen in England.
The species is widely distributed over Central and Southern Europe, and its range extends through Northern Asia to Amurland, Corea, and Japan. It is also represented in Northern and Central America by var. comyntas, and has been recorded from Australia.
The Silver-studded Blue (Lycæna argus = ægon).
The male of this butterfly (Plate [105]) is purplish-blue with a black border on the outer margins, and sometimes black dots on that of the hind wings. The female is sooty-brown, powdered to a greater or lesser extent with blue scales on the basal area; there is generally a series of orange marks forming a more or less complete band on the outer margin of the hind wings, and sometimes on the fore wings also. The under side is bluish-grey in the male, and brownish-grey in the female; the black spots are ringed with white, and on the fore wings there is one at the end of the discal cell and a series of seven beyond; the hind wings have from three to five spots before the discal spot, and a curved series of seven beyond; there is a black-edged orange band on all the wings, and beyond this on the hind wings there is a series of metallic blue centred spots; hence the English name of the butterfly, given to it by Moses Harris, which is certainly more suitable than Petiver's "Lead Argus."
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.