Osiris Blue (Cupido osiris)
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2020 photographs highlighted in green. Click on any photograph to go to an enlarged picture, or simply scroll down the page.
Osiris is very similar to the Small Blue (C. minimus) based on the underside alone. Details of the differences are given on the minimus page. It is probably much easier to differentiate them in the field where the blue upperside of the male osiris is clearly apparent, and I believe the females can be identified by the visible uppersides in flight as well. Osiris seems to be closely tied to its larval hostplant Sainfoin (Onobrychis viciifolia), especially the female, so if it's sitting on Sainfoin, the odds are that it is osiris. The converse is also true. The theory about the series of four unh post-discal spots being in a straight line in osiris seems only to hold true for the female in my experience. The males can vary significantly, as indicated by the comments on the specific individuals below.
Osiris is considered to be uncommon, but I am coming to the conclusion, after fourteen seasons in Var, that it is more widespread than is generally reported stated in the books, although often in low densities. I suspect it is often missed as it is very similar to several other small bright blues, notably the Chapman's Blue (Polyommatus thersites), which has a similar deep blue colouring and well-defined black border, and perhaps also to the Common Blue (P. icarus). It is about the same size as thersites and icarus, maybe sometimes slightly smaller. It is an early season butterfly in Var, and I have not seen it later than about the first week in June, although it does have a second brood in other areas.
|29351||M||a male, showing the slightly violet tint to the blue.||220|
|34701||M||a male, in typical territorial pose.||185|
a courting pair, male above. The female is the same as 10264, but I included the photograph because it captured both sexes in the same shot.
a sprinkling of blue scales on the basal area of the forewing.
|34574||F||a female, and unusual in that it had a slight kink at the base of hindwing v2, which made me seriously wonder if it could be a Provenšal Short-tailed Blue (C. alcetas). Also the colouring was almost completely black, with no (or very few) blue scales, also indicative of alcetas. It was in a region where osiris was common and alcetas had not previously been recorded, although alcetas does have a habit of popping up unexpectedly in singles in the PACA region. Other female osiris were examined but none showed the kink of this one. It disappeared soon after this shot, otherwise it might have been conclusive to see if it was strongly attracted to Sainfoin. However, on the balance of probabilities, given that the kink is only mild and not of the length expected for alcetas, I think it must be a non-typical osiris.||220|
|34635||F||a female, and I've just noticed that it is almost identical to, and in the same pose, as 10264. 34616 is the underside.||220|
very fresh and appealing with nice basal blue flush. The unh series of four spots: the fourth spot in s2 is missing, not unusual, and the third spot in s3 is vestigial. The unf series is nice and straight, an indicator of osiris, but not definitively so: see the minimus page.
|45080||M||A male with a rather bluer than average underside ground colour, in territorial pose, ready to see off intruders.||140|
|31961||M||a male, nectaring, as is usually the case, on Sainfoin.||185|
a very clean underside with a strong basal blue flush. As noted above, there are usually four post-discal spots in a straight line, but for some reason this specimen only has the top two in s4 and s5, with no sign of even vestigial lower spots in s2 and s3. The just-visible blue of the uph confirms osiris, rather than minimus.
a typical osiris, except that the fourth post-discal spot is clearly displaced internally.
|24510||M||another typical male.||210|
|34555||F||a female, as seen in flight and just enough of the uph is visible to confirm this. The photo has been rotated through 90 degrees for convenience.||185|
|34616||F||a female, the underside of 34635. It is in its typical head-down pose.||220|
|29555||F||a female egg-laying on Sainfoin.||185|