Reverdin's Blue (Plebejus argyrognomon)

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2016 photographs highlighted in green. Click on any photograph to go to an enlarged picture, or simply scroll down the page.

8109_male_Côte-d'Or_17Jul07 27868_male_Côte-d'Or_26Jul11 8099_male_Côte-d'Or_17Jul07
32630_male_Côte-d'Or_13Jun13 20605_female_Côte-d'Or_11Jun10

8134_male_Côte-d'Or_17Jul07

8096_male_Côte-d'Or_17Jul07 20601_female_Côte-d'Or_11Jun10 40894_pair_Alpes-de-Haute-Provence_3Jul16

I first saw argyrognomon (couldn't it have a simpler name?) in 2001 in a field adjacent to a service station in central France, on our way south. It initially looked like idas/argus but had a much darker and deeper blue upperside differentiating it from both, although the specimen was rather worn. I have also seen argyrognomon at several places near Beaune in central France and at altitude near Isola, in 2006 in Italy, and in 2007 near Dijon and again near Digne-les-Bains, the most southerly location in which I have seen it. It tends to have an easterly European distribution and occurs in France mainly in the east, although there are some localities in the west and I saw it near Poitiers in 2008.

The male underside ground colour is pale silvery-grey, almost white in some cases. The key characteristic is that the unh orange band is continuous, extending almost to the forewing costa, and the adjacent black unh “chevrons” are more rounded on the internal edge (idas is more v-shaped) and flatter on the external side. It is generally considered to be similar to the Idas Blue (P. idas), although I would say that it would be difficult to confuse the two.
ref sex

observations

alt. m
8109 M

a male with quite pronounced uph marginal black spots. There is a very slight chequering of the fringes where the veins meet the margins.

320
27868 M the shot captures very well the strong deep blue of the male argyrognomon upperside. 320
8099 M

a male, with the uph margin unmarked by a series of black spots.

320
32630 M a male, showing the characteristic strong blue upperside, although the uph has slightly chequered margins. 320
20605 F

a relatively fresh female, with large and strong orange uph lunules. It is the same individual as 20601 as can be seen from the blade of grass it is resting on.

320
8134 M

a typical male, with a strong continuous orange band, although only just reaching the forewing costa.

320
8096 M

a male with generally reduced markings, such that the orange band is only just continuous. The silver studs are also much reduced and only s2 has more than a few silver scales.

320
20601 F

the same female as 20605. Clearly a female as confirmed by the upperside, despite the silvery-grey ground colour which would strongly suggest male. This illustrates one the characteristics of argyrognomon, that the orange band is continuous and extends to the costa on both wings. The black chevrons are rather more sagittate than normal for argyrognomon.

320
40894 PAIR I believe these to be argyrognomon, female above, on the grounds that the orange band extends to the costa, and that the black marks on the internal edges of the hindwing lunules are rather rounded. 580

 

8109_male_Côte-d'Or_17Jul07

 

27868_male_Côte-d'Or_26Jul11

 

8099_male_Côte-d'Or_17Jul07

 

32630_male_Côte-d'Or_13Jun13

 

20605_female_Côte-d'Or_11Jun10

 

8134_male_Côte-d'Or_17Jul07

 

8096_male_Côte-d'Or_17Jul07

 

20601_female_Côte-d'Or_11Jun10

 

40894_pair_Alpes-de-Haute-Provence_3Jul16