A Horrid Phorid

I took myself off to Dunvegan Woods yesterday and remembered to bring my sieve and tray. The trees here consist of fairly dense coniferous plantings with a thick carpet of mosses as understorey. Lots of standing and some fallen deadwood, all covered in bryophytes. I shook handfuls of moss over the sieve, stripped loose bark over the sieve, threw rotten wood into the sieve. Springtails aplenty, a few woodlice and myriapods and a couple of spiders. Plus four pseudoscorpions, the most I've ever found in one session. Bugger all beetles whatsoever (apart from the husk of a long dead weevil minus its legs) but I did pot two small flies, both measuring around 2mm in length. One was a Lesser Dungfly (Sphaeroceridae), a family for which I lack a key to take any further, so that's just sitting on a pin for now. 

The second was a Scuttle Fly (Phoridae), happily one of the families for which I do have a key.

2mm of bristly, heavily gravid fly

Note the enlarged row of strong bristles along the wing costa, plus reduced wing venation. Here's the same image again, though I've added a red dot where each vein reaches the wing margin. Working clockwise from the uppermost left dot we have what The Key names Vein 1, Vein 2 and Vein 3 (all thickened and strong), followed by the much weaker, finer Vein 4, Vein 5, Vein 6 and Vein 7. It's a pretty radical naming system, I'm sure you'll agree. Must have taken them ages...

I've never needed to use the RES Scuttle Flies key before (currently available here for a mere three quid) and so was slightly dismayed to discover that it doesn't cover the large genus Megaselia (over 200 species) though it does cover the remaining genera, accounting for just 93 species. Before I'd even looked at the key, I realised there was a more than two thirds chance my fly wouldn't be in it. 

Thankfully The Ghost pointed out that there was a further work covering Megaselia (which can be downloaded here) and to stop my bleating and just get on with it. Or something like that. He may actually have just said 'good luck'. By sheer coincidence, he had just featured a phorid on his own blog which has better pics than mine showing the 'mini footballs for the third antennal segment and sideways pointing arista'. Well said, hope he doesn't mind me nicking it.

Mini footballs and sideways pointing arista!

The key to genera started off simply enough "does it have wings, does it lack wings..." and asked me to check the relative lengths of various veins against the length of the costal bristles and of each other, was one body part hairy or was it bare, etc etc. I did struggle a bit trying to decide if the hind tibia had transverse rows of bristles or whether the bristles were arranged in longitudinal palisades or not - but I think I got there in the end. And happily the key dropped me out at a genus with just one British member in it - sweet! My fly, apparently, was Beckerina with B.umbrimargo being the sole representative of the genus in Britain. 

Except that Beckerina umbrimargo really doesn't match my fly. I tried again and dropped out at Beckerina once more. Then I quit trying. I'll have another look later tonight, come at it with fresh eyes and try again. Must be those hind tibial bristles.

The good news is that whatever it is, it's nothing I've seen before. Or not knowingly, at least. 

In other news, a large Herring Gull that I found a few days back is now being touted as an American Herring Gull. Opinion is still out, but it's looking as though I may have jammed into a mega! Thankfully it's proving reliable and several local larophiles have taken a barrage of images both yesterday and today. We shall see...