The Brown Argus (Lycæna Astrarche)
Fore wings blackish or sooty-brown with a black discal spot, and a row of reddish-orange spots on the outer margin of all the wings; the fringes are white, sometimes with blackish interruptions. The under side is greyish or greyish-brown, and the black spots are distinctly ringed with white. On the fore wing there are seven of these spots, one at the end of the cell, and the others in an irregular series beyond; the last in this series is sometimes double, or it may be absent. On the hind wings the spots comprise a series of four preceding the white discal mark, and a series of seven beyond; the second spot in this series is placed directly under the first, forming a colon-like mark, and this character will help to distinguish the Brown Argus from the blackish or brown females of the next species.
The female has larger orange markings, and the outline of the fore wings is rather rounder on the outer margin, otherwise the sexes are very similar.
The orange spots referred to in the male are sometimes absent towards the tips of the fore wings, and in this respect lead up to the form known as the Durham Argus (var. salmacis, Stephens), which is blackish above and ochreous-brown below; the black spots on the under side are much smaller then in typical specimens, and some may be absent altogether. The male has a black discal spot, and the female a white one, on the upper side of the fore wings; the hind wings have a red or orange band on both surfaces. Sometimes the male also has a white spot on the fore wings. Specimens with the orange spots on upper side almost entirely absent are referable to var. allous.
Artaxerxes is the form occurring in Scotland, and is known as the “Scotch White Spot.” Both sexes have a conspicuous white discal spot on the fore wings, and the spots on the under side are white, and rarely centred with black. In var. quadripuncta, Tutt, all four wings have a white discal spot above. Occasionally an odd specimen with white discal spots is found in the south.
Figures of the butterfly will be found on Plate 105, and of its life history on Plate 104; the upper egg is that from a typical female, and the lower one was laid by a female artaxerxes.
The egg, which is whitish, with a faint greyish tinge, is laid on the upper side of a young leaf of the rock-rose (Helianthemum chamæcistus). The caterpillar has a black shining head; the body is green with whitish hairs, a pinkish line along the back, a whitish one bordered with pinkish along the sides; the green colour becomes dingy as the caterpillar matures. The chrysalis is obscure yellowish-green, the front of the thorax is edged with pinkish, and there are bands of the same colour on the back and sides of the body; the thorax and the wing-cases are rather glossy. Held in position by a few silken threads between leaves of the food-plant.
The ordinary form of the butterfly is on the wing in May and June, and again in August. It is widely distributed throughout the southern half of England, and also in Wales.
Although chiefly associated with rock-rose, especially in chalky districts, it occurs too among stork’s-bill (Erodium cicutarium), upon which plant the caterpillar also feeds, in sandy places inland as well as on the coast.
Caterpillars from the first flight of butterflies may be found in July, and those from the second flight hibernate and feed up in April.
The butterfly has a marked liking for roosting on the flower stems of long grasses, and quite a number may often be found resting together towards sundown, or on dull days, in sheltered hollows. Sometimes several specimens of this species and of the Common Blue may be found on the same perch. It is rather less frequently seen in the Midland counties, but it is more or less common in some parts of Derbyshire, Yorkshire, and Lancashire.
The intermediate form, salmacis and its modifications, is found in the neighbourhood of Richmond, Yorks, and thence northward to the Scottish border.
Var. artaxerxes occurs in Scotland from Roxburgh to Aberdeenshire on the east, and from Dumfries to the Clyde on the west. Kane records four specimens from Co. Galway, and these are all that are known of the species from Ireland. This form, together with the var. salmacis, are not found anywhere outside the United Kingdom, and, it may be added, the latter appears to be getting scarce—at least, in some of its old haunts in Durham.
The species is distributed throughout the Palæarctic Region, except the Polar parts.