All our Tephrochlamys species (two native and two introduced) have only 3 pairs of (postsutural) dorsocentrals, whereas this fly appears to have a fourth (presutural) pair. The wing spines also seem a little large for Tephrochlamys. From the location and what I can see, I would guess this is a species of Heleomyza.

I've reexamined this one and it is indeed a Heleomyza. I must have missed the setae on the prosternum, and yes it does have a pair of presutural DCs (the postsutural DCs are 3 on one side and 4 on the other).

Looking at Gill (1), his terminology is somewhat confusing (e.g. the "posterior margin of the mesopleuron" is what sclerite exactly). The only hairs on the mesopleuron (in the broad sense) are anteriorly and dorsally on the katepisternum.

In any case, the male terminalia are nicely exposed on the specimen and are clearly not the common H. serrata but are closer to H. genalis and H. pleuralis, neither of which should be in Kentucky as far as I can tell.

A cryptic species described from Europe in 1962, with a more "hockey stick" shaped surstylus rather than the "banana" shaped surstylus seen in true H. serrata. They are externally indistinguishable. It's definitely not genalis or pleuralis, which both have a dark abdomen.

Do you happen to have a copy of the paper where it was described?

Gill used mesopleuron to refer to the anepisternum specifically. For the other pleural sclerites, he used pteropleuron for anepimeron, sternopleuron for katepisternum, and propleuron for proepisternum. I find these older terms more intuitive and easier to remember, but I figure they've fallen out of use for good reason.

Wow. Thank you!!

Thank you.
Already have it waiting.