Megaselia latifemorata

The RES key to scuttle flies (Phoridae) took me to the genus Megaselia simply enough, but this is such a huge genus that it's dealt with in a separate RES key. Both are really simple and easy to use, well-illustrated with helpful figures.

It took me a while to work out what the description of tibial hairs in couplet 15 meant but apart from that my only slight problem keying this was determining the femora colour at couplet 149 - I took them to be yellowish. This forced me to spend a chunk of time working through the next few couplets. Pushing past an apparent dead-end at couplet 150 I reached another block at couplet 152, but then I noticed the comment at the end of the couplet, “If anal tube is longer than in figs 392 and 393 and three notopleural bristles are present, try couplet 153.” Well, the anal tube was longer, and couplet 153 was where I would have gone if I’d interpreted the femora as being “dominantly brown or at least a dirty, greyish yellow if pale”. From there it was an easy ride to latifemorata.

male Megaselia latifemorata showing wing, North Elmham (Norfolk, UK), 28th March 2020

The mesopleural furrow (arrowed in green below) was an important character used in determining the genus, especially as I initially misunderstood the tibial bristle characters detailed in the same couplet (which prompted me to check the alternative route, which lead to a dead end).

same male Megaselia latifemorata showing forewing, North Elmham (Norfolk, UK), 28th March 2020

When I went wrong with the genus key after misunderstanding tibial bristle characteristics, I came to a choice between Diplonevra (which didn't seem right as mine only had one dorsal hair palisade) and Dohrniphora (which didn't seem right as the mesopleuron was bare). I prepared this femora and trochanter (and the rest of a hind leg) with a view to trying to key it as Diplonevra - the key advises this treatment. But before wasting too much time on that I re-checked the earlier steps and the presence of a mesopleural furrow highlighted my error. Still, having a cleared hind leg proved useful when keying it as Megaselia. In particular it made it much easier to determine whether or not there were 2 or more bifurcated apical bristles on the tibia (there weren't - one looked like it might have been bifurcated but certainly not the others).

same male Megaselia latifemorata showing hindleg (trochanter, femur, tibia, close ups of both sides of the tibia apex), North Elmham (Norfolk, UK), 28th March 2020

These photos show the extent of hairs on the abdominal tergites and the two pairs of bristles on the scutulum.

same male Megaselia latifemorata showing abdomen and scutulum, North Elmham (Norfolk, UK), 28th March 2020

And finally a couple of views of the epandrium and anal tube.

same male Megaselia latifemorata showing epandrium and anal tube, North Elmham (Norfolk, UK), 28th March 2020