First time I've ever seen one of these. It's hard to make out much detail, but there are six legs, a single ommatidium near the rear corner of the head on each side, and thin antennae that seems to be comprised of three segments, the first two antennomeres being somewhat thick and elongate and the last being threadlike and about as long as the first two combined. Posteriorally, there is a pair of fairly elongate setae poking out obliquely from the penultimate abdominal segment. the terminal abdominal segment is longer than wide and a bit tapered. I'm not familiar with what parasitizes sarcophagids, but this seems to match well with images of Macrosiagon.

This came from a restored prairies. Collected with a flight intercept trap.