Large Blue (Phengaris arion)

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2016 photographs highlighted in green. Click on any photograph to go to an enlarged picture, or simply scroll down the page.

21991_male_Hautes-Alpes_12Jul10 27108_female_Hautes-Alpes_14Jul11 25536_female_Alpes-Maritimes_08Jun11
35649_female_Drôme_28Jun14 17722_male_Hautes-Alpes_10Jul09 12817_male_Isère_12Jul08
30686_male_Hautes-Alpes_6Jul12 35659_female_Drôme_28Jun14 36343_pair_Valais, Switzerland_19Jul14

This species seems to be quite widespread in France. I have seen arion in a number of places in southern France, often at high altitudes such as 1800m, but never more than one or two at each location. The underside of fresh specimens is quite breathtakingly silvery blue and it is noticeably larger and darker than most blues, making it quite easy to spot in flight. Unusually, nearly all the specimens I have seen have been females, often egg-laying. High altitude forms are often quite dark, of the form obscura, where the dark upf spots extend and sometimes merge with the dark margins. There are also intermediate forms.

 

The larval hostplant is various species of Thyme, principally Large Thyme (Thymus pulegioides).

On a related theme, arion has been very successfully re-introduced into the UK using Swedish stock, with 10,000 individuals reportedly flying in 2006, and still doing well as at 2016; UK Butterfly Conservation are to be congratulated on this achievement, especially as arion has a larval stage that is entirely dependent on a complex relationship with ants of the Myrmica genus. In short, no ants, no arion. This was the big breakthrough - manage the habitat for the ants, not for arion or its larval hostplant.

 

This species was previously known as Maculinea arion.

ref sex

observations

alt. m
21991 M

a rare opportunity to get a shot of a male upperside.

1990
27108 F a very dusky female, or at least I suspect it is a female based on body length and shape. 27104 is the underside. 2020
25536 F a particularly heavily marked female. 1080
35649 F a female, slightly aberrant in that the upf marks are very heavy. 35659 is the underside. 960
17722 M

very odd. A dark and rather dirty ground colour and a strong basal blue flush. It can only be arion, as the markings are just too strong for Mountain Alcon Blue (P. alcon (rebeli)).

2100
12817 M

a female, fairly typical arion in terms of markings. At least I have assumed 12817 to be female based on the colouring, but the body length suggests male, so maybe the body length is a more reliable indicator of sex than the colouring. However, on studying the magnified image, the end of the foreleg appears to be hooked, which confirms that this is a male.

1020
30686 M a beautifully fresh arion at high altitude. On studying the magnified image, the end of the foreleg appears to be hooked, which confirms that this is a male. 2550
35659 F a female, the underside of 35649, egg-laying on what appears to be T. pulegioides. 960
36343 PAIR a mating pair, the fresh female on the right and the rather battered male on the left. 2090

 

21991_male_Hautes-Alpes_12Jul10

 

27108_female_Hautes-Alpes_14Jul11

 

25536_female_Alpes-Maritimes_08Jun11

 

35649_female_Drôme_28Jun14

 

17722_male_Hautes-Alpes_10Jul09

 

12817_male_Isère_12Jul08

 

30686_male_Hautes-Alpes_6Jul12

 

35659_female_Drôme_28Jun14

 

36343_pair_Valais, Switzerland_19Jul14