Thaumatomyia hallandica

My previous attempts at identifying the deceptively tricky black-and-yellow Chloropids have been fairly unscientific and therefore with only tentative identifications. This one was keyed using Mike Hackston's key and, rather surprisingly, turned out not to be notata (which I think is the really common one).

The key character was the width of the gena, deeper than the first flagellomere but not 1.5x as deep. The arista was clearly hairy (clear at least under high magnification). The scutellum had much more than 20 bristles and the frontal triangle was shiny and lined with a row of bristles. The only slight query I had with the key was that the first flagellomere is described as narrowly pale ventrally (as opposed to broadly pale ventrally): it appeared entirely dark, though on close inspection there was a vague dull yellowy area on the ventral surface.

Thaumatomyia hallandica showing frontal triangle, scutellum, antenna and side of head (close-up with measurements) Wendling Beck Environment Project (Norfolk, UK), 3rd August 2023