I found a couple of these on my B. smithi tarantula, by the mouth (I think they are the same, but I lost the one I picked off the tarantula so these are from the terrarium). I found a few in the water dish, floating on top. They aren't mites (antennae and six legs), but I'm not sure if their being on the tarantula is coincidental or they are directly harming him. He hasn't been behaving normally. I looked at the terrarium after dark with a flashlight, and didn't see a lot of them. They look dark here, but on the black tarantula and in the terrarium they looked light. They are pretty soft-bodied, since putting a cover slip over the drop smashes them.