Idas Blue (plebejus idas)
2008 photos highlighted green. Click on any photo to go to an enlarged picture, or simply scroll down the page.
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| 12735_male_Isere_11Jul08 | 7347_male_Alpes Maritimes_24Jun07 | 12968_male_Valais, Switzerland_15Jul08 |
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| 12513_male_Isere_10Jul08 | 12733_male_Isere_11Jul08 | 3109_female_Alpes Maritimes_25Jul06 |
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| 13398_female_Valais, Switzerland_20Jul08 | 3145_female_Alpes Maritimes_26Jul06 | 12968_male_Valais, Switzerland_15Jul08 |
Idas can sometimes be hard to differentiate from the Silver-studded Blue (P. argus), not to mention possible confusion with Reverdin's Blue (P. argyrognomon) where the latter occurs. Idas is a very variable species with many subspecies across Europe, although only the more lightly-marked subspecies calliopsis occurs in France. The male upperside is a strong bright blue with a narrower black border than argus and wide white fringes, sometimes with uph marginal black spots or more triangular indents which are generally smaller than those of argus. The female upperside is brown with varying amounts of blue, with marginal lunules more prominent than argus (although this has not always been my experience) especially on the uph and there is sometimes a basal blue flush. T&L shows the nominate female as being largely blue with strong uph lunules, but this has not been my experience and I have seen a lot of idas. The unh black edging to the marginal lunules (the "studs") is usually chevron-shaped and quite sharply pointed especially in s2 and s3. There are sometimes no silver centres to the marginal spots, or at least, that's how it appears - the silver is often a question of the viewing angle. Also the orange on the unf lunules does not extend to the apex as it does on argyrognomon.
There is quite a common form, calliopsis, in which the male has a chequered black uph margin and reduced uns discal and post-discal spots. According to T&L, calliopsis is found in the Basses and Hautes Alpes between 500-1000m, although I have seen it in locations up to 1800m. Altitude ranges given in books, even the more authoritative ones, should, from my experience, be viewed only as a guide, not an absolute.
Another feature to differentiate idas from argus, which allegedly holds true 100% of the time, is the foreleg spine. Argus has this spine, idas does not. However, the books do not seem entirely consistent about this, and I am not remotely convinced about this. Please see the close-up photo and commentary on 12968 below and the argus page for more detailed discussion.
12735: a dark blue male with quite heavily chequered margins, especially the uph where the border is effectively a series of heavy black triangles. I believe this of the form calliopsis.
7347: a male, with the typical chequered uph marginal pattern characteristic of the alpine form calliopsis. Altitude 2100m.
12968: a male with very elongated and pointed black chevrons, for me this is 100% idas but see the comments on the spine close-up below.
12513: a male which did not look like classic idas, perhaps because it is in the shade and the white chevrons inside the unh lunules show up clearly. It was quite large and I did wonder about Zephyr Blue (plebejus pylaon) which is a larger plebejus although I have never knowingly seen one, but pylaon does not have silver studs and this clearly does. Idas it is, then.
12733: a male, large and with a classic idas elongated (as opposed to argus rounded) shape, and pointed black chevrons.
3109: female calliopsis, basically brown with only a dusting of basal blue scales (less blue than the book illustrations). The uph lunules are very clear and appealing, with delicate blue edging externally. These are much more pronounced than the book illustrations of calliopsis, and the books show either no or vestigial uph lunules, whereas in 3109 they are very pronounced. Altitude 1800m.
13398: a female with only vestigial lunules on a dull dark brown ground colour. I am fairly sure this was idas even though it looks like the female argus in T&L and nothing like the idas illustration.
3145: a female of the form calliopsis, with reduced uns markings. The pointed black chevrons indicate idas as compared to argus. Altitude 1800m.
12968 spine: the mid-leg spine shown looks to me very much like the strong spine that is supposed to characterise argus, but for me 12968 is 100% idas. Either I have got it wrong (and I never discount this possibility) or the spine theory is not sound, or, of course, this isn't actually a spine. Does anyone know for sure? Comment actively invited.
7347_male_Alpes Maritimes_24Jun07
12968_male_Valais, Switzerland_15Jul08
3109_female_Alpes Maritimes_25Jul06
13398_female_Valais, Switzerland_20Jul08
3145_female_Alpes Maritimes_26Jul06
