44. Diastatidae – known unknown

It is a continual surprise to find that whatever I scoop up in my net, someone busybody has been there before me, describing what I’ve found, fitting it into taxonomy, documenting its habits and distribution. Even those specks that look like they could squeeze through the mesh of the net or might be missed when emptying out a pooter have all already been described. On the one hand it’s comforting to know that even this small-scale territory is known, and their diminutive features known. But it’s also somehow disturbing to think that it has all been done, that new discoveries aren’t waiting for me when I walk out the back door. †

This is quite a natty fly, with its unnecessarily long head bristles that point every which way, a tousle-headed rascal. The antennae are delicately plumose (feathered) and there is a nice balance of grey for the body, yellow for the legs and face and a classy red for the eyes. Also rather pleasing are the graded bristles along the front edge of the wing, ending with a big spike before the subcostal break. Six species in the family are found in the UK, and according to Peter Chandler’s 1985 key only one (Diastata fuscula) has wings that are unmarked apart from a blush of brown above the subcosta, just beneath that fine row of bristles.

When I arrived at Stirling for the Dipterists Forum field meeting, a couple of enthusiasts were already heading out to see what they could find in a patch of wet woodland they had spotted at the University entrance. I rushed to unpack my collecting gear and follow them and found some woods, but though I scoured the slopes and diligently swept my net over flowers, foliage, rotting tree trunks and mud there was no sign of the others. At least I found this fly, which according to the NBN map is only the fifth Scottish record south of Perth. And when I gave up on the woods I did find a legendary dipterist working the muddy edge of the campus pond and so I tagged along to learn how it should be done properly. All nice and tidy. Except that it turns out that the larvae of this family are unknown – there are yet some chinks in the armour of knowledge. I’m off to check my local woods for flies and glory!

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