Saw several on hike including a large group feeding on an oil beetle
Seems like they are feeding on an oil beetle carcass
This observation is for the smaller hitchhiker on the Meloe beetle.
Specimen on hand, further photos can be taken for more accurate ID (if needed to be revised)
BugGuide entry:
https://bugguide.net/node/view/913519
~4-8mm body length. Flying over leaf litter in woods