Chalkhill Blue (Polyommatus coridon)

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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.

17970_male_Isère_11Jul09 22951_male_Valais, Switzerland_24Jul10 31253_male_Valais, Switzerland_15Jul12
36450_male_Valais, Switzerland_20Jul14 38202_male_Hautes-Alpes_7Jul15 39197_male_Hautes-Pyrénées_24Jul15
8932_female_Hautes-Pyrénées_8Aug07 23388_female_Buckinghamshire, UK_8Aug10 36445_male_Valais, Switzerland_20Jul14
36591_male_Côte-d'Or_25Jul14 8599_male_Var_27Jul07 8907_male_Hautes-Pyrénées_5Aug07
22663_male_Isère_18Jul10 23424_female_Buckinghamshire, UK_8Aug10 05_24-21_female_Hautes-Pyrénées_Jul05 - form corydonis
 
27740_female_Valais, Switzerland_22Jul11 27002_pair_Hautes-Alpes_12Jul11  

Coridon and the Provence Chalkhill Blue (P. hispanus) can be difficult to tell apart, especially so from the female upperside. The male upperside of hispanus is a rather duller silvery blue, often being rather yellowish at the margins. Coridon can be quite variable, just to make things more difficult, but it is single-brooded and a relatively late emerger, even in the far south of France, so any specimens seen in May or early June will almost certainly be hispanus, and this has been borne out by other indicators. There is a second generation of hispanus later in the summer, when they and coridon fly at the same time and locations, although hispanus is on the wing into October. I have also found that the inner edge of the hispanus unf lunules are often larger and smudgily indistinct.

Lafranchis says that the coridon unh is tinged brown and contrasts with the paler grey unf, while the hispanus unh is also pale grey and there is minimal colour contrast; this seems to be true but there are grey (sic) areas. The female coridon I have seen in the Pyrénées, especially at altitude, were quite often greyish rather than the usual brown, and the extent of the ups marginal lunules varied quite significantly.

 

This species was previously known as Lysandra coridon.

ref sex

observations

alt. m
17970 M

I am not really 100% sure that this is coridon. The lack of blue tends to suggest that it may be hispanus but the date and location/altitude point to coridon. The upf marginal markings are quite pronounced.

1120
22951 M

a rather darker male, with well defined upf borders.

1800
31253 M a male, rather bluer than the norm, with quite wide black borders. 2180
36450 M a male, typical for a this species at altitude. 36445 is the underside. 1640
38202 M a male, from the Hautes-Alpes. 2020
39197 M a male, from the Hautes-Pyrénées, showing little difference from those from the Alpes. 1600
8932 F

a typical female, quite dark brown and with relatively small uph marginal lunules.

1600
23388 F

a UK female, quite dark and having a distinct greyish feel, especially on the uph.

90
36445 M a male, the underside of 36450. 1640
36591 M a male, from lower altitude in central France. 320
8599 M

this male has quite a pale underside, especially the unh, but with strong orange lunules.

780
8907 M

a very pale male underside especially in the basal area and unusually transitioning to a quite deep brown in the marginal areas. The markings are very light and the orange lunules uncharacteristically very thin, although quite distinct.

1500
22663 M

a rather lightly marked male underside, not uncommon I find in high altitude specimens.

1120
23424 F

a female, from the same UK location as 23388, also rather dark.

90
05_24-21 F

a dark grey female of the form corydonis. I have seen dark grey females in the Pyrénées before, but none that was as markedly so as this. The upperside was also noticeably greyer.

 
27740 F a typical female. 2160
27002 PAIR a mating pair, the paler, greyer, male on the right. 2010

 

17970_male_Isère_11Jul09

 

22951_male_Valais, Switzerland_24Jul10

 

31253_male_Valais, Switzerland_15Jul12

 

36450_male_Valais, Switzerland_20Jul14

 

38202_male_Hautes-Alpes_7Jul15

 

39197_male_Hautes-Pyrénées_24Jul15

 

8932_female_Hautes-Pyrénées_8Aug07

 

23388_female_Buckinghamshire, UK_8Aug10

 

36445_male_Valais, Switzerland_20Jul14

 

36591_male_Côte-d'Or_25Jul14

 

8599_male_Var_27Jul07

 

8907_male_Hautes-Pyrénées_5Aug07

 

22663_male_Isère_18Jul10

 

23424_female_Buckinghamshire, UK_8Aug10

 

05_24-21_female_Hautes-Pyrénées_Jul05 - form corydonis

 

27740_female_Valais, Switzerland_22Jul11

 

27002_pair_Hautes-Alpes_12Jul11