The upperside ground colour of the nominate form of alveus is usually a dark grey-brown sometimes with a yellowish flush, with smallish white marks on the upf, especially in the cell, and very weak marks on the uph. The unh has no particular distinguishing features, the discal marks in s2 and s3 being quite small, but this is not unique to alveus. It is perhaps the most difficult of the French Pyrgus species to identify with any degree of confidence, and I have included some on this page that I am not at all confident are alveus in order to invite comment. It usually seems to be a case of the "balance of probabilities" rather than "beyond reasonable doubt".

The Lafranchis ID book simply says that the uph marks are dull, which is hardly a unique differentiator. The unh ground colour is olive brown. Alveus is a relatively large Pyrgus, but only slightly larger than most of its cousins, so identification may be based more on this rather than analysis of the photograph. It has a wide altitude range, from 0 to 2100m and flies in June-August.

The subspecies accretus (also, but now largely historically, called centralhispaniae or centralitaliae) is completely different to the nominate form P. a. alveus in that the upf white marks are very well-defined and the uph marks are strong and well-contrasted. The undersides of nominate alveus and accretus appear to be very similar as far as I can ascertain. Accretus flies in south-west Europe including, as its alternative names imply, central Spain and Italy. There seems to be very little information available of the exact distribution of accretus and its relationship to alveus, particularly in respect of whether it can be considered as a separate species.

With regard to accretus in the Pyrénées, see also the general and species-specific comments on the Oberthur's Grizzled Skipper (P. armoricanus) page.

observations

this male matches the illustration in T&L perfectly for the subspecies accretus (centralhispaniae).

a rather colder grey-brown colour than average. The cell spot is not sufficiently well-defined to suggest other species, nor is it outwardly concave which would suggest the Carline Skipper (P. carlinae).

I suspect this may be a male from the body length. I had some doubts as to whether this is actually alveus; the upf marks are rather strong, and the cell spot has just a suggestion of external concavity which might suggest carlinae, but having seen the underside, this clearly rules out carlinae.

I am fairly certain that this is a male alveus as I also have an underside shot and it was ID'd with certainty by a local expert. The upperside markings are just about spot-on for alveus and I recall that it was a large Pyrgus.

the unh marks here all point to alveus. The discal s2/3 are completely empty, ruling out armoricanus. Basal s7 is rather rounded suggesting carlinae but the marginal mark on v5 is not sufficiently large or well defined, and the altitude is some way below the normal range for carlinae.