Eagle-eyed readers will have already spotted the Phoretic mites on the elytra (and one at the back of the head):
The mites are not parasitic on the beetle, but are carnivorous, eating fly larvae that could be a threat to the beetle larvae. They use the beetle as transport, so we have a good symbiotic relationship, here.
I also coincidentally photographed this Harvestman with phoretic mites on the same day:
