Silver-studded Blue (plebejus argus)
2008 photos highlighted green. Click on any photo to go to an enlarged picture, or simply scroll down the page.
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| 11088_male_Bouche du Rhone_4Jun08 | 12058_male_Alpes de Haute Provence_6Jul08 | 11087_male_Bouche du Rhone_4Jun08 |
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| 12051_female_Alpes de Haute Provence_6Jul08 | 11138_female_Bouche du Rhone_4Jun08 | 13639_female_Lozere_21Aug08 |
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| 13647_female_Lozere_21Aug08 | 2756_female_Italy_16Jul06 | |
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| enlargement of 2756 showing middle leg spine - argus | enlargement of 3364 - idas |
Common in most of France, sometimes occurring in thousands, but can be difficult to differentiate from the Idas Blue (P. idas). The argus upperside usually has a broader black border (clear in 12058) than idas, often with marginal black uph spots. My feeling is that the unh black interiors to the marginal lunules are quite pointed for idas and more rounded for argus. However, TLID describes both argus and idas as "sagittate". It also says that the argus unf spots are more arched, having a "?" shape, than idas - this is clear in 13647. In my experience, argus is fairly consistent in terms of size and noticeably smaller than idas, but this would only be a guide at best - TLFra gives the argus wingspan at 10-16mm and idas 11-16mm. Argus also seems more rounded, whereas idas seems to me to be more angular.
Argus has a small spine on the foreleg tibia (see above) but you need to be very close to see it, or have a digital camera with high resolution. Idas has a minute spine, clearly too small to be confused with an argus spine. However, this ID pointer as described by the leading books (see the introductory page for the key to the book abbreviations) does not seem to add up:
1) does it occur on the male only? T&L, TLFra, TLID and H&R all say "male". The enlargement of 2756 - which is clearly a female (from the brown ground colour and the apparent curvature of the body shape) - shows a very strong spine on the mid-leg. Are the books wrong? In many respects, T&L is very much a straight lift from H&R, so if H&R got it wrong, T&L would probably follow. My feeling is that it occurs on both sexes, as I have studied many photos of females that appear to have the same strong spine.
2) which leg does it occur on? They have three pairs of legs. It always seems to be on the middle leg. Is this what the books mean by foreleg?
3) which way is it pointing? In all of these photos, and many more that I have studied, the spine is clearly and consistently pointing backwards, but in H&R and TLID the illustrations show it pointing forward.
4) several authors refer to it as a "hook". It doesn't look like a hook to me.
11088: a very light border for male argus. Where the uph border is light, it tends to break up into black spots rather than a smooth border.
12058: a more typical broad male argus border.
11087: a typical male underside. The black interiors to the unh lunules do not appear sagittate to me (see comment above).
12051: a very lightly marked female, with a narrow forewing.
11138: a well-marked female, with a spattering of blue scales on the uph.
13639: a less well-marked female with rather indistinct and faint orange lunules on the upf.
13647: a strongly-marked female underside, with good arching of the unf post-discal spots. The strong brown ground colour sets off the white areas inside the unh lunules.
2756: a female with the middle leg spine clearly visible in the blow-up shot. The silver studs are quite thin. Other shots of males show exactly the same spine.
11088_male_Bouche du Rhone_4Jun08
12058_male_Alpes de Haute Provence_6Jul08
11087_male_Bouche du Rhone_4Jun08
12051_female_Alpes de Haute Provence_6Jul08
11138_female_Bouche du Rhone_4Jun08
