Hi Steve,
just by looking at their mouth parts I do not think they would bee able to kill varroa as varroa has a hard exoskeleton and the mites only have soft tissue and no mandibles to crush with. I have seen these mites on pieces of wax so I am not sure if they eat wax or not. I think they also eat pollen which there is an abundance of on the bottom of the hive. Apart from that I cant be any more forthcoming with info.
The mites may be found in great numbers in active bumblebee colonies, moving rapidly over the nest floor, nectar pots, and brood cells where they feed on nectar and pollen.
These mites are of the genus Pneumo[COLOUR="Red"]laelaps [/COLOUR]from North America*
females note the red highlighted words I think they must bee related to Tropelaelaps not sure need to checxk that out.
I will try to take a couple of photos of them at work.