White-letter Hairstreak (Satyrium w-album)

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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.

40694_male_Var_5Jun16 6242_sex?_Var_1Jun07 10550_sex?_Var_15May08
33690_female_Var_12Jul13 40689_female?_Var_5Jun16 41650_female_Rhône_17Jul16
   
41665_female_Rhône_17Jul16    

This is less common than its Satyrium cousins and superficially quite similar, although the "W" shape of the white band of the unh both gives it its name and leaves no room for doubt. It also seems to have longer tails than the others, and the female seems to have longer tails than the male. The marginal marks are otherwise quite similar to the Sloe Hairstreak (S. acaciae.

 

There appears to be a reliable way of differentiating the sexes: in the cell area of the unf there is a mark which is very slightly raised in the female and rather more so in the male. This is in addition to the clue given by the length of the tails.

There are varying amounts of blue scales on the black unh marginal mark in s1. Ironically, it occurs in the UK whereas the other Satyrium species do not (apart from the Black Hairstreak (S. pruni) which may be threatened with extinction). It is possibly one of the few butterflies that is actually more common in the UK than France.

A superb video of the life-cycle of w-album has been produced by Filming VarWild and can be viewed on YouTube here: https://www.youtube.com/watch?v=vdDNGF2HDr0

ref sex

observations

alt. m
40694 M a male, based on the shortness of the tails and the raised area of the unf cell. 200
6242 F

I'm guessing that 6242 is a female based only on the length of the tails, as there are virtually no other clues if the body shape is not visible.

200
10550 F

I suspect that this is also a female, based on the tail length, the visible body shape and the size - I recall that it was exceptionally large. However, I did see it on 15 May, very very early for any Satyrium species, and the early emergence would tend to argue for it being a male.

140
33690 F not quite square-on, so the colour looks a little greyish, but the white markings show up nicely. 680
40689 F? I'm not entirely convinced that this is a female, as the unf cell area is rather ambiguous, and the tails are rather sort. The abdomen appears quite wide, but maybe this is within the normal range for a male c.f. 41650. 200
41650 F clearly a female based on the length of the tails and the width of the abdomen. 180
41665 F a female based on the length of the tails. 180

 

40694_male_Var_5Jun16

 

6242_sex?_Var_1Jun07

 

10550_sex?_Var_15May08

 

33690_female_Var_12Jul13

 

40689_female?_Var_5Jun16

 

41650_female_Rhône_17Jul16

 

41665_female_Rhône_17Jul16