11774_pair_Alpes-Maritimes_30Jun08

Minimus is common in France, often very common, and occasionally seen in huge numbers at altitude. The underside is very similar to the Osiris Blue (C. osiris), where minimus has (it seems to me) to have a great variety in the uns black spots, from quite light to very strong, from round to elongated, while the general arrangement of spots is very similar to osiris.

The principal differences are:

1) upperside colour (males), if visible, even in flight:

osiris clearly blue with a neat thin black border.

minimus may have a varying degree of blue scales but will not appear to be a clear bright blue.

2) unh series of four post-discal spots:

osiris in a straight line, although sometimes the lowest spot is very slightly displaced inwardly. However, sometimes the osiris spots in s2 and s3 are completely missing or just vestigial in s3 only.

minimus the lowest spot is usually more clearly displaced internally. It would be highly unusual for there not to be four spots in this series.

3) unf series of post-discal spots (except s6 at the top):

osiris fairly straight.

minimus more clearly arched.

4) unh marginal marks:

osiris unmarked.

minimus sometimes, but not typically,  has faint unh marginal markings.

5) upperside colour (females):

osiris is essentially plain dark brown to black with a varying degree of basal blue scaling.

minimus plain brown to bluish-grey with no blue scaling.

These pointers are for are general guidance. The range of natural variation means that there will always be a limited number of exceptions.

Osiris seems to be closely tied to its larval hostplant Sainfoin (Onobrychis viciifolia), especially the female, so if it's sitting on Sainfoin, the odds are that it is osiris.

The minimus underside sometimes needs a close look to differentiate it from the Mazarine Blue (Cyaniris semiargus) especially when the uns (unf in particular) spots are bolder and rounder. Both minimus and osiris could be confused with the Provençal Short-tailed Blue (C. alcetas) as they are of similar size and general markings, but alcetas has a hindwing bump, sometimes almost indiscernible, where the vestigial tail occurs, which minimus and osiris do not have.

observations

17364 was quite large, much larger than an average minimus, but the not the first time I have found an oversized minimus.

a female, as is evident from the body shape.

a typical male underside, the fourth unh spot in s2 clearly, but only slightly, displaced inwards.

a mating pair. I suspect the female is on the right, based on size and colouring, also that it is fresher. Whenever you see a mating pair, if one is worn or damaged, it is odds-on to be the male, because it emerges earlier on balance and fights territorial battles, while the females are sought out by the males to mate with almost immediately as soon as they emerge.