This is one of a family of very similar hairstreaks of the Satyrium genus, including the Ilex (S. ilicis), the False Ilex (S. esculi), the White-letter (S. w-album), the Black (S. pruni) and the less-similar Blue-spot Hairstreak (S. spini). Acaciae has larger and rounder red spots on the unh with internal black triangles on the margin and black edging externally. The post-discal white line is also (usually) quite strong and almost straight (c.f. ilicis and w-album). Although it looks superficially similar to the other Satyrium species, with a clear view it can be identified with some confidence. It often flies in company with its Satyrium cousins, but can often be identified by its (usually) smaller size and rather rounder shape.

Prior to 2004 I had only seen it in one locality in the Alpes-Maritimes, but since I have seen it in a number of different localities, mostly at mid-altitude, but usually not more than a few in any locality. In 2006 I found it in large numbers in Var from late May to late June with a peak emergence around the second week in June when it was flying in company with ilicis, esculi, and spini.

The low-lying yellow flowers of the Helichrysum genus (see e.g. 10743) seem to be a strongly favoured nectar source of all the Satyrium species, often with several hairstreaks on each flowerhead. Sometimes the Satyrium hairstreaks can be counted in hundreds and maybe thousands.

The sexes are similar, but it appears that the female has a more prominent post-discal line, stronger lunules and markings and slightly longer tails. The tip of the female abdomen, where visible, is black. Thus 16239 and 10743 are clearly males, while 40951 and 49928 illustrate the difference very clearly.

observations

a male, for the same reasons as 10743.

a male, I suspect, based on the tip of the abdomen is just visible and does not appear to be black.