December 12, 2017

Brown Argus (Aricia agestis) or Common Blue?

Whilst taking some exciting macros of yesterdays Dragonfly species, I was briefly distracted by this butterfly.

I thought it was a female Common Blue (Polyommatus icarus), photographed it and got back to the Dragons, but when I got home and looked at the files on the big screen I started to wonder.

There’s more to ID-ing the Brown Argus than meets the eye. Mainly because the female Common Blue isn’t blue, she’s brown, mostly. Pretty sneaky eh? Of course, this cryptic colouration is not uncommon in the bird world, females often being dowdier than males, but it’s quite unusual among butterflies, except in the Lycanidea family, the Blues. To further confuse matters, the Brown Argus is also a Lycanid and so taxonomically at least, also a ‘Blue’.

Anyway, the crux of the ID relies on some fiddly little details on which I had intended to expound, but this would be a bit esoteric without some comparative shots of a female Common Blue. I don’t have any of those. I thought I did, but funnily enough, when I came to look at them in preparation for adding them to this post, I discovered that they too were of a female Brown Argus.

Instead I refer you to Steven Cheshire who has written a superb guide to identifying the two species, which can be downloaded from his excellent site www.britishbutterflies.co.uk. I’m indebted to him for this PDF as its helped me to add another insect to my species list and that’s always a good day, despite the fact that I’ve unwittingly already seen and photographed it!

Oystercatcher (Haematopus ostralegus)

Thanks to Aneurin Owen both for the inspiration for this post and for the Scientific name. Once you start getting into taxonomy, you start dropping these arcane species names into conversations hoping to look erudite (I probably don’t, but that’s never stopped me before). Tonight. for the first time ever and without any prompting, I was asked the common name for Haematopus ostralegus. I got as far as working out there was a reference to blood (haema) but that was it. Bah! It’s a common misconception that scientific names a re Latin but there’s alot of Greek going on in taxonomy and this species’ name literally it means “blood footed collector”.

To be fair there’s a lot of binomial nomenclature out there to memorise. This is the system of identifying every organism on earth by Genus and Species, created by the Father of Taxonomy, Carolus Linneus. It’s just a shame I dropped the first ball thrown to me, which incidentally, is the reason I failed to get into the house cricket team at school. No second chances at public school.

Anyhoo, Oystercatchers! They remind me of cartoon snowmen with a particularly impressive carrot for a nose, or bulked up smaller waders, wearing several overcoats and a partial Groucho mask. They have an unmistakable squeaking alarm call and aren’t at all shy about using it. Unless you’ve got good field craft, this sound, along with a spectacular white flash of the trailing wing edge, as rapid wing beats propel their equally spectacular white rump away from you, are the the best you can hope for.

Their common name is actually a bit of a misnomer, as although physical size and powerful bill mean they’re one of the few waders actually capable of opening an oyster, smaller molluscs like Mussels and crusatceans, even earthworms, form a major part of their diet.

Aneurin Owen