A species with restricted range in the UK, but occurring in nearly every French département, sometimes very common, and often found where the larval hostplant Horseshoe Vetch (Hippocrepis comosa) grows. It is slightly larger than the Common Blue (Polyommatus icarus) with which it is most likely to be confused, at least on a frequency basis. The male upperside is a very distinctive bright blue, often discernible in flight, with the characteristic black chequering on the white margins where the veins cut the margin. There are occasionally black spots in the marginal areas of the uph; there is a species known as the Spotted Adonis Blue but this does not occur in France.

The female upperside is basically brown, as with most blues, but it has varying amounts of blue according to locality. Generally in my experience the female is plain brown at low altitudes but with increasing amounts of blue as the altitude increases, with a very blue form known as ceronus and intermediary forms which could perhaps be described as semi-ceronus.

The underside is superficially similar to icarus, especially as bellargus has a unf cell spot which many Polyommatus species do not have. The male underside ground colour can vary from grey to pale brown, especially the unh, and the female is usually a deeper but more consistent brown.

Bellargus is actually related to the Chalk-hill Blue (Lysandra coridon) which becomes more apparent on comparison of the underside patterns. The normal brown form of the female can be very similar, sometimes almost indistinguishable, from the female coridon.

In the new European taxonomy, this species now has the scientific name Polyommatus bellargus.

observations

quite lightly chequered fringes.

by contrast with 21694, a male with quite heavily chequered fringes.

a female with almost completely blue hindwings, with the orange lunules merging into the blue.

a fabulously marked female, with a full set of orange uph lunules and even a reasonable set on the upf. There is a smattering of blue scales, most pronounced at the outer edges of the uph lunules. The female is quite variable, usually plain brown, 5908 being quite strongly marked compared to the norm.

a female with considerable amounts of blue, suggesting the form ceronus so could be described as semi-ceronus.

another delicately marked female, with blue scales setting off the strong hindwing lunules.

a female, with virtually no blue scales.

a typical male underside, with clear contrast in the brown ground colour of the unh and the grey of the unf.

a cleanly marked fresh male. The unh is quite pale brown, as even the male can be quite deep brown here.

a male, with rather browner colouring, especially the hindwing, fairly typical.

a mating pair, female above.

this female has a fairly standard deep brown underside ground colour, particularly on the unh, contrasting well with the bright orange lunules.