www.ukbutterflies.co.uk

This is probably a Small Blue but could possibly be an Osiris Blue. If someone could confirm the ID I would be grateful.

http://www.youtube.com/watch?v=1TO9cvAxbdo[/video]

Thanks for looking.

The rather shallow obtuse angle formed by the upper three spots on the hindwing is common in little blue but I have never seen it in Osiris blue, where this angle is usually acute and occasionally very slightly obtuse. For that reason I would say this is a little blue. The shape and general appearance also fit little blue.

The rule of the three spots was given to me by a Swiss expert (although in connection with osiris/semiargus) and has proven itself consistently in Switzerland. I haven't read it in the books and don't have the evidence to say it is always true, everywhere.

Guy

Thanks G.

Just read the ID comments from GP which has blown me away. I know I'm a new 'leper' but I can't believe this level of analysis and can only read in wonder, oh well perhaps in a few years time (a good few years I think at that!)

Hi Gary. In the UK you very rarely need to do any deep analysis to identify at species level, though there are some tricky pairs (females of Adonis and chalkhill blues, small and Essex skippers or, if you are lucky, pale clouded and Berger's pale clouded yellows). Elsewhere in Europe there are certain groups that can be very difficult if, like most people on these forums, you like the butterfly to fly off unharmed after identification! It is great fun analysing photos and pictures trying to find constant features that work in all cases and before long you know the detailed markings of some butterflies much better than the proverbial back of your hand.

The problem is, markings, unlike genitalia, are accidental rather than essential and often rules that work in one locality don't work in another.

Little blue and Osiris blue are quite different butterflies in the field but superficially very similar when you only see the underside. Here are one of each:





The first is Osiris and the second little. The shallow angle in the second is a very strong indicator it is not Osiris (though I know it's not for other reasons). The deep angle in the first says nothing, as both species can be like this.

Guy

Interesting notes G.
The Osiris Blue shows the 4 spots on the forewing to be in a straight line whereas only 3 are in a straight line on the Small Blue.
The Small Blue photo looks extremely similar to the one in my video.

Thanks