|Not sure exactly what this is but it was flying across a track carrying
what looks like a Bath white Pontia daplidice.
care to put a name to it, and a little background would be interesting too...
David Nash wrote in reply;
"It looks to me like a fine photograph of a robber fly - A member of the
family Asilidae (within the order Diptera). I can't tell you which species I'm afraid, but the strong, hairy legs and "beard" are pretty typical
('though I'm not a Dipterist, and there are a few other small families of similar large flies. It's definitely a Dipteran!). The robber flies are all
predators of other insects, often catching them on the wing, after which they take the insect to a roosting site and suck out it's innards... which
sounds exactly what you observed. They are also some of the biggest flies (i.e. Diptera) - I remember seeing some in
Australia a good three inches long."
Bart Vanholder replied;
I promised the name of the predator fly you had in your pages: Last friday
at the entomological meeting we had a glimp at your pic of the fly and the butterfly. It turned out to be Dasypogon diadema
Dear Mr. Coombes,
I found the photograph of an asilid fly on your web page "andal15.htm", which is
named "Dasypogon diadema". I must correct this, you can find a b/w photograph of
this species on:
D. diadema is a bee-hunter and a member of another subfamily (Dasypogoninae).
Your photograph shows a member of the subfamily Asilinae. I believe that this animal is a
species of the genus Machimus and the species-group of setibarbus. A better determination
is not possible, because you have to check the genitalia of this male. [I need also the
place of this record]
Robber flies catch a lot of different insects, most of them are not specialized, an
important parameter is the size of the potential prey.