Plebejus glandon

Glandon Blue (Plebejus glandon)

2023 photographs highlighted in green. Click on any photograph to go to an enlarged picture, or simply scroll down the page.


17613_male_Hautes-Alpes_09Jul09	17652_male_Hautes-Alpes_09Jul09	17770_male_Hautes-Alpes_10Jul09	22200_male_Hautes-Alpes_14Jul10

22309_male_Hautes-Alpes_15Jul10	21926_female_Hautes-Alpes_11Jul10	48605_female_Hautes-Alpes_20Jul21	17654_male_Hautes-Alpes_09Jul09

17637_male_Hautes-Alpes_09Jul09	22408_male_Hautes-Alpes_15Jul10	27009_male_Hautes-Alpes_12Jul11	27139_male_Hautes-Alpes_14Jul11

33439_male_Hautes-Alpes_7Jul13	38217_male_Hautes-Alpes_7Jul15	51423_male_Hautes-Pyrénées_10Jul23

Glandon is a high altitude species being found in the Alpes and the Pyrénées in France, the lower end of the altitude range being around 1800m. The male is a rather dull grey blue, but quite attractive nonetheless, and slightly smaller than the average Common Blue (Polyommatus icarus). It is not possible to confuse glandon with any other species in the Alpes, only the very similar Gavarnie Blue (P. pyrenaicus) which only occurs in the Pyrénées where both can fly together, something I first experienced in 2023.

Glandon is often seen puddling, in fact I only ever seen males when they are puddling, when it is often sedentary and can be quite hard to spot on a grey stony surface. I had never seen a female until 2010 when I managed to see 21926; they appear to be very reclusive. Until 2008 I had only seen glandon in odd ones or twos at a few locations each year, but in 2009 it appeared in greater numbers in quite a few sites, and in 2010 I visited several places in the Alpes where it was relatively frequently-encountered and occasionally common; in one spot in the Queyras National Park there were some fifty or so puddling together.

Having now seen good numbers of glandon, it seems to me to be quite variable in both the upperside and underside. The upperside seems to vary in the degree and darkness of the blue scales, some specimens appearing quite dark, and in the degree of marginal markings on the uph. The undersides seem to vary from the unh clean brown of 27139 to the dark grey basal suffusion of 22408. The underside markings are quite distinctive and unlike any other species in the western Alpes.

This species was previously known as Agriades glandon. In 2010 it was reclassified as Plebejus glandon and in 2017 it was again reclassified back to Agriades glandon. I'll give it a few years before changing the web page (and all the occurrences and links associated) as it is entirely possible that the taxonomists will change it again.

ref	sex	observations	alt. m
17613	M	a very dark male, probably an effect of the high altitude.	2100
17652	M	a slightly darker than average male, with quite pronounced uph marginal markings.	2100
17770	M	fairly normal, paler but still at the same altitude as the other two above.	2100
22105	M	fairly typical.	2020
22200	M	quite extensive uph blue scaling, well-defined thus suggesting a wide dark uph border, appearing not dissimilar to the Silvery Argus (Aricia nicias). The upf and uph discoidal spots are also unusually large.	2020
22309	M	a rather dark male, with only vestigial uph marginal markings.	2020
21926	F	lacking the blue scaling of the male and appearing a rather dull cold brown.	2020
48605	F	a female, a rather dull dark grey-blue, with a sign of some ageing, but females of these high altitude blues are seen only rarely.	2290
17654	M	slightly darker and more heavily marked than average.	2100
17637	M	fairly typical, seen at slightly lower altitude than the others on this page.	1890
22330	M	quite a clean unh brown ground colour.	2040
22408	M	quite a dark grey unh and a strong, almost black, basal suffusion.	2020
27009	M	a brownish and lightly marked underside.	2010
27139	M	a rather pale and lightly marked underside.	2040
33439	M	a fresh and very crisply marked male.	2040
38217	M	I only really noticed this aberration of glandon when I looked closely at the photograph of some hundred or so butterflies puddling at this small spot. I am rather assuming that it is glandon, mainly because it doesn't seem to fit anything else, and it is the only aberration I have ever seen of this species, even though its marking can be quite variable.	2020
51423	M	a male from the Pyrénées with a very much softer and warmer ground colour than its counterparts from the Alpes. It was flying in company with its very close cousin, the Pyrénées endemic Gavarnie Blue (P. pyrenaicus).	1700