Eros Blue (Polyommatus eros)

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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.

21692_male_Alpes-Maritimes_7Jul10 22091_male_Hautes-Alpes_14Jul10 22201_male_Hautes-Alpes_14Jul10
17682_female_Hautes-Alpes_09Jul09 41637_female_Hautes-Alpes_16Jul16 21966_male_Hautes-Alpes_11Jul10
13216_male_Valais, Switzerland_18Jul08 17675_male_Hautes-Alpes_09Jul09 26410_male_Alpes-Maritimes_07Jul11
 
31356_male_Savoie_20Jul12 27294_pair_Hautes-Alpes_15Jul11  

A species of the higher ranges of the Alpes and Pyrénées. The male upperside is a shining pale blue with strong uneven uph black borders sometimes having detached black spots in each space, and with slight chequering of the fringes. The males shown here are from different locations but look very different, though. T&L shows it as being very pale and with a medium but constant width upf black border. You would have difficulty identifying these upperside photographs as eros from the T&L illustrations.

The underside is very similar to the Common Blue (P. icarus) even to the extent of having a unf cell spot, which other French Polyommatus blues do not have (excluding the erstwhile Lysandra species which have been reclassified as Polyommatus). The ground colour is usually a cold clean mid-grey.

 

In the past few years I have found eros at a number of locations, almost all males and nearly always puddling. Only at one location did I see them in good numbers. I have only twice seen a female eros.

ref sex

observations

alt. m
21692 M

a male, with a black upf border of neatly consistent width and a uph border just about breaking up into discrete black spots. It has a Safflower Skipper (Pyrgus carthami) for company.

1400
22091 M

a male, not unlike 22088 but rather lighter in colour, with a Glandon Blue (Plebejus glandon) for company.

2020
22201 M a male with quite wide black borders, and uph marginal marks that are large and detached from the margin. 2020
17682 F

a rarely-seen female, only ID'd for certain because I had seen the underside, at least, that's what my notes said at the time I saw it. Male eros were flying within a few metres and no escheri were seen at that location. Since then, I have received comments from a French lepidopterist who is confident it is a female Escher's Blue (P. escheri) for the following reasons:

1. there does not appear to be a cell spot on the unf. It is very difficult to see from this angle, but it appears this is so, in which case escheri is very much more likely.

2. the curvature of the wing shape points to escheri.

3. the colours are "warm", pointing to escheri whereas eros tends to have "cold" colours.

4. the lunules are arched in the normal manner for escheri.

5. it appears that the plant it is on is Astragalus monspessulanus, the larval hostplant of escheri, from what little I can see, and if this is true, then maybe this is compelling evidence.

However, on a subsequent visit to the UK Natural History Museum to study the archives for eros and escheri, 17682 looked identical to the female eros, and all the female escheri had were brown with no blue scales and a full set of orange lunules. This mirrored the illustrations in T&L. No female escheri I have ever seen - and I have also seen quite a number since 2009 - has had any blue scales. I also saw, in 2016, 41637, which looks more or less identical to 17682, and this clearly has a unf cell spot. I feel this is fairly conclusive evidence that 17682 is eros

2100
41637 F I believe this to be a female eros, mainly because the unf cell spot is visible and this limits the options to eros and icarus and I'm fairly sure it's not the latter. 2290
21966 M

a male, typically grey and with rather heavy internal edging to the unf marginal lunules.

2050
13216 M

a male underside, very similar to icarus, but more lightly marked at the margins.

2200
17675 M

a male underside, slightly browner than 13216 but still quite a "cold" grey.

2100
26410 M  a beautifully pure light grey ground colour, very typical of eros. 1400
31356 M a male underside, quite dark grey. 2070
27294 PR a mating pair, female above, showing the contrast in the ground colour between the sexes. 2550

 

21692_male_Alpes-Maritimes_7Jul10

 

22091_male_Hautes-Alpes_14Jul10

 

22201_male_Hautes-Alpes_14Jul10

 

17682_female_Hautes-Alpes_09Jul09

 

41637_female_Hautes-Alpes_16Jul16

 

21966_male_Hautes-Alpes_11Jul10

 

13216_male_Valais, Switzerland_18Jul08

 

17675_male_Hautes-Alpes_09Jul09

 

26410_male_Alpes-Maritimes_07Jul11

 

31356_male_Savoie_20Jul12

 

27294_pair_Hautes-Alpes_15Jul11