Getting some Help

I had a great evening last night, and all because of one small fly. My obligatory after dark visit to the laundry shed found me eye-balling a fly sat on the light itself - and I mean a 'real' fly, not a midge or a gnat this time. Excitement levels were high as I gently slipped a pot over it and safely snapped the lid into place with the fly still inside. Cool, but what had I found this time?

Back indoors I found myself looking at a grey and yellow fly with skinny legs and long wings. No idea which family, so I ran it through the keys and it came out at Heleomyzidae. Great, I just need to find a key and give it a whirl...

Which is as far as I got for some time. The only key to Heleomyzidae that I could find was one to the genus Suillia and there are fourteen more genera in Heleomyzidae that I needed to work through. Time to find some help. Gilbert's Ghost had told me to ask if I needed anything, he has lots of fly-related literature including some quite obscure stuff. So I asked and he very quickly came back with a key. To Suillia. Grrrrr. Different key, to be fair, but same genus. I went back online and came up blank once more. The only literature that folks kept quoting were Collin (1943b) and a draft version to the family handed out a few years back at a workshop. Neither available online or to buy. Bugger, now what. 

The Ghost suggested I whack the pics up on iRecord, but I fancied my chances on a Facebook group first. These are the three images I added online, with a request for either key previously mentioned or a heads up to other keys that are still available. 

Two (not one) orbital bristles tell us that this is not a Suillia

It's a very smart fly, I spent quite a while visually exploring the various bristles and spines and whatnots. Blimey, it seems that I'm quite getting into this fly malarkey! 

After a short while I received a message from an extraordinarily helpful chap (a proper grown up dipterist, in fact) who pinged me across a modern key to Heleomyzidae. What a hero! With this key I would be able to ID the mystery fly, or so I hoped. 

Before I could make a start with it though, a second chap commented on my post and told me the sex and genus involved. Coolness! He too is a proper grown up dipterist, and a very good one too.

First thing I did was run it through to subfamily, it came out at Leriinae which I've never even heard of. Happily, there are only three genera in Leriinae and one of them matched what the dipterist said on my Facebook post. Even better than that, I scrolled down and discovered there are only FOUR species in the genus!! This would be a doddle. 

More pics for you

Dorsal preapical bristle on hind tibia - quite an important feature

Quite the looker - note the concave profile beneath the antennae

The single pre-sutural dorsoventral bristle (by my red dot) helps ID this to species

The only other feature I now needed to see concerned the precise placement of a line that runs between the front orbital bristles. Was it closer to the front ocelli or was it closer to the front of the frons? Two options leading to two species. I had to get this right.

Just look at those colours! Absolutely gorgeous!

The line in question is the narrow dark one separating the golden top half of the face from the orange lower half. Does it lie closer to the front ocelli (the three tiny 'eyes' in the silver triangle) or does it lie closer to the arched lower edge of the orange patch? I knew what I thought, but I measured anyway. It lies closer to the front ocelli.

All of which means I can confidently identify this fly as a female Heteromyza commixta, a widespread species and possibly more common in Scotland than in England. The NBN Map would suggest otherwise, it would also suggest it is new for Skye. Whether that's true or not I don't know, though I doubt it. What I do know is that it's new to me and I have a friendly online dipterist to thank for supplying me with a key. 

Sometimes it really is good to just ask for help.