Esculi and its very close cousin the Ilex Hairstreak (S. ilicis) co-exist in southern Var and in June the Satyrium species emerge in large numbers, literally in thousands, and appear to be mostly esculi, which can be exceptionally abundant. They are quite sedentary and can be missed, even in large numbers, but once you've seen them, you start to notice that they're everywhere, with three or four individuals were sitting on almost every flower head. They are strongly attracted to the yellow flowers of Helichrysum species, abundant in southern Var in June.

Esculi is principally an Iberian species with the distribution "spilling" into the far south of France, whereas the distribution of ilicis extends across nearly all of France.

There are several key differentiators between esculi and ilicis:

1. colour of unh lunules: the ilicis unh lunules are more orange-red than red, and appear rather pale. In esculi the unh lunules are a deeper red, albeit still slightly orange.

2.  unh lunule edging: ilicis has clear black internal edging and sometimes a slight white edging as well, and usually some black external edging, especially in s1 and s2. Esculi has slightly thinner black internal edging but - most significantly - no black external edging.

3. unh lunule width: the esculi lunules usually seem to be thinner than ilicis.

4. marginal line: the unh marginal white line seems to be stronger in ilicis, strongest at the base, while for esculi it is weaker and may not extend past s3 or s4.

5. uns post-discal white line: in esculi this is almost straight and continuous. It extends across the unh but is faint on the unf and may not reach the costa. There is usually an internal black edging, which is rarely strong and can be quite weak. The ilicis line is irregular and therefore often discontinuous. It usually reaches the costa. The internal black edging is usually stronger than that of esculi, producing a marked contrast.

observations

could possibly be considered a male based on the shorter tail and forewing margin straightness, but on studying the magnified image, the end of the foreleg appears to be articulated and identical to the mid-leg and hind-leg and not hooked, which confirms that this is a female.

possibly a female based on the longer tail and forewing margin curvature. On studying the magnified image, the end of the foreleg appears to be articulated and identical to the mid-leg and hind-leg and not hooked, which confirms that this is a female.

could possibly be considered a male based on the shorted tail and forewing margin straightness, but on studying the magnified image, the end of the foreleg appears to be articulated and identical to the mid-leg and hind-leg and not hooked, which confirms that this is a female.

a female, based on body shape and length of tails.