But to answer the question I didn't answer before, yes they can be dangerous to a tarantula. If left in there unsupervised, they can actually kill and eat a tarantula in premolt or as it's molting. If there's more in there, I would swap out the substrate
No I fed it a dubia roach a while ago and maybe it burrowed and died. They didn’t start coming up until I gave it that roach one time last month they just start popping up a couple weeks ago I take them out every time I see them.