Sunday, 1 August 2010

Venus Pool - Brown Argus beats the blues

I was busy photographing female Common Blues to try and get as good a range as possible of the variation in upperwing 'blueness' (see the previous post for more) so I reckon I'd got my eye in!

All of a sudden, I became aware of something quite out of the ordinary! There basking on a grass stem was a pristine brown 'blue'. I wasn't sure what I'd got initially until it dawned on me (and my field guide pointed that way) this couldn't be a Common Blue - I was looking at a Brown Argus! Now, I don't 'do' butterflies that seriously and had no idea of the status of this species locally but after a couple of phone calls, I was left in no doubt - this was rather special!!

It's a male - the orange marks (lunes) are faded out at the wing tips, the abdomen is relatively long, reaching at least to the edge of the white fringe. The two black spots on the upper forewing add up to the classic appearance of a Brown Argus.......






Most of the key indicators are found on the underwing and obligingly (although I nearly lost it) it soon flew, and perched with wings closed on another grass stem.....

Two key features are apparent. Two of the black spots on the hindwing are arranged in the form of a colon (check my other pictures, in the Common blue these are aligned with the top of this wing). The orange lunes on the forewing are also bright and clearly defined (much more so than in Common Blue). Finally the shape of the forewing is more rounded than in the latter species.






Unconvinced? Here's a Common Blue female for comparison....






The only other distinguishing feature of the underside which I never managed a shot of - there is a 'missing spot' on the forewing (present in Common Blue). The shot below shows how close I came to getting this feature (not)....






Nevertheless, the compelling evidence you can see leads to only one conclusion - male Brown Argus and another gem onto the Shropshire list! Many thanks to Steve Cheshire by the way for his help and advice with identification. I've added a link to his amazing site 'British Butterflies' which you will find amongst my links on the right menu.....

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