I just commented below, but I have been in this very tree (it is in Corcovado National Park in Costa Rica) and there were bats in there, and it was pretty scary going in there- but amazing once you got inside. The local guides take people in there regularly. The guide did say there had been some scorpions and other critters in there in the past, but that enough people go in there to keep out too many other animals.
Corcovado does have jaguars, pumas, caimen, and fer-de-lance snakes, so plenty to be careful about. Also tapir, coatis, and thousands on birds. The place is amazing.
