Fly ID please

agrumpycow · #1 (**permalink**) 17-10-2009, 02:21 PM

Can anyone help to identify this fly please. Seen today near the Thames in Berkshire. The closest I've got is 'fly'

so any help would be great

ChrisR · #2 (**permalink**) 17-10-2009, 03:46 PM

Can you tell me how big it was? It looks a lot like a tachinid (a parasite fly) but the colour and shape is a bit confusing because it doesn't look like any of the normal ones.

agrumpycow · #3 (**permalink**) 17-10-2009, 04:24 PM

It was small - my guess would be around 5-7 mm body length. It didn't hang around long but I got this other photo, a bit blurred and of a slightly different angle if it helps. Thanks

ChrisR · #4 (**permalink**) 17-10-2009, 04:30 PM

Ahh, that second photo is better - you can clearly see a long, hinged proboscis extending forward from the head, which (along with the slightly hunched-back shape and sandy brown colour) means it is a species of Siphona - probably a female S.geniculata, but that is impossible to confirm for sure

It is a parasitoid of cranefly larvae, which means they attack the cranefly 'leather jackets' and eat then from the inside out, eventually killing them

EDT: Roger Thomason got some quite nice shots of one recently and posted them here.

EDIT2: They are a fairly common genus with a few very common species (eg. geniculata) and a lot more rare species (usually restricted to Scotland). I saw quite a few down the road from you in Moor Copse reserve (Tidmarsh) and Hartslock Reserve (Goring-on-Thames)

agrumpycow · #5 (**permalink**) 17-10-2009, 04:39 PM

Many thanks, Chris.
Just had a look at your website - very interesting, and you must be very close to me, Moor Copse it my favourite and most visited reserve as it's just own the road from me

p.s. you must have been writing you edit2 as I posted!