Prior to 2006, I had seen a few arethusa in various places in the south of France, never in great numbers, and it was always a pleasure to see them. It is a very appealing and intricately marked butterfly, especially when fresh. In 2006 I stayed in Var throughout August and September and found that there was a strong emergence in mid-August extending through until mid-September when I counted at least 20 in one locality alone.

It is a semi-altitude specialist and most of these were seen at 800-1000m although I have seen them at 2000m whereas the books indicate that its altitude range is normally up to 1100m and exceptionally 1600m. In subsequent years in this same locality, there has been a mass emergence at the beginning of August and they could be counted in hundreds, staying on the wing until mid-September.

The subspecies dentata has a more tooth-shaped (dentate) pattern to the unh post-discal area, also reflected in the rather tooth-shaped upperside orange markings, and a lesser degree of contrast across the unh discal line. Dentata is said (in T&L) to be the normal subspecies in southern France, the nominate form occurring in the north, although I believe that at least some of these photographs are of the nominate form, not dentata. Higgins & Riley, a very authoritative work if now 45 years since publication, says that dentata is found in south-west France and is "transitional to" arethusa in the Basses Alpes and this would seem to explain the similarity as the Var locations were in the north of the département on the edge of the Basses Alpes.

observations

a male, very fresh with a nice rich dark brown ground colour, and a rich orange post-discal band on both wings. The extent of the orange is much less than shown in T&L. The rather tooth-shaped external edges of the orange markings, the uph in particular, suggests that this may be the subspecies dentata.

a female upperside, a quick flash before closing up. There is a small upf black spot in s2, and a strong uph black spot in s2. This appears to be of the nominate species, not dentata.

probably a male, as I believe the undersides of both sexes are almost indistinguishable. In fact, T&L only gives one underside illustration. This seems fairly typical of the mass emergence of arethusa.

a male, I think, with rather dull colouring, even though fresh.

a fresh male, nice orange but not the fiery colouring that arethusa sometimes has.

a nice fresh female, bright orange and a strong discal line. I am assuming it is a female as it was lurking in the undergrowth.