Very similar to the Common Blue (P. icarus), usually slightly smaller. The male upperside is bright blue with a violet tinge, and there is a narrow, but strong and even, black border on both wings. The underside is very similar to icarus although the key identifier is the absence of a unf cell spot which icarus nearly always has, even if sometimes very small. It is not always easy to see this as it is near the base of the wing, especially if the forewing is tucked down and the cell spot (or lack of it) is not visible.

The unh submarginal orange lunules tend to be brighter and more elongated with pointed ends, and the black “dashes” inside the white marginal areas tend to be more centrally located within these white areas, compared to icarus where they are usually close to the orange, if not actually touching it.

The underside ground colour is pale brown in the female and greyish in the first brood males, although second brood males seem usually to have a brownish ground colour.

First brood females have a good degree of blue scales, whereas second brood females are more classically brown with orange lunules. First brood females could be confused with icarus - see the icarus page for possible means of differentiating. It is an early emerger, usually being on the wing in April in the south of France.

This species is referred to as Agrodiaetus thersites in T&L, but is now classified as a member of the Polyommatus genus.

observations

this male shows the strong deep blue, deeper than icarus, with the clear clean black border of constant width.

a male underside, quite a cold grey (even the male underside can be quite brownish, as shown on this page), and with some slight aberration of the unf black spots.

a male, puddling at an altitude of 2100m, about the upper limit of its altitude range.