Great Long-tailed Winter Gnat Trichocera major

This came to light and was keyed using Stubbs. It keyed straight to major but a couple of things caused me to question this ID - firstly the aedeagus spine seemed to curve over the blade more than shown in the diagram (although the very round blade matched) and secondly the date - Stubbs gives a flight time of "October to December (exceptionally September and early January)". Clearly 25th March is well outside that period, so surely I must have gone wrong. I had got the impression that it was large for Trichocera but the wing only measured 7.1mm (possibly slightly more as I'd removed the wing to measure it and may not have quite got all of the base). That's in range for major, but at the lower end and also within range for most if not all the other species, so despite my impression that it was large the measured size is not conclusive.

If it isn't major then the most obvious possibility of error is with a plainer-than normal annulata. Stubbs doesn't provide a description of diagram of the genitalia for this species so I had to search the internet and eventually concluded that I was safe to eliminate this. The style was certainly a closer match to the diagram in Stubbs for major than for the other species, being long and slightly sinuous (depending on the angle - at some orientations they looked slightly curved but not sinuous). I took the bridge to be complete - certainly the sides met in the middle, though I'm not sure they were fused together (if they had been they came apart easily enough).

Eventually I found a key to European Trichocera which includes multiple photos of the genitalia for several species including major (and annulata)¹. The photos of the major aedeagus look exactly like mine. Looking back at the diagrams in Stubbs I realised that in fact mine matched the diagram for major better than I'd initially thought: although the angle of the spine relative to the blade meant mine curved over the blade more than shown in Stubbs, the spine itself is not more curved than Stubbs shows for major, and is straighter than Stubbs shows for other species. So in the end I am as satisfied as I can be that it's a late-flying major (but always happy to hear from anyone who has more experience).

¹Krzeminska, E (2021). Key and atlas to the genus Trichocera MEIGEN in Europe (Diptera, Trichoceridae). Acta Zoologica Cracoviensia 64(1). Accessed here.

male Great Long-tailed Winter Gnat Trichocera major showing wing, abdomen from above and genitalia (from different orientations including 3 views of the isolated aedeagus), Wendling Beck Environment Project (Norfolk, UK), 25th March 2025