Spiders consistently spawning inside a tree in Toxx
 

There is a tree in Toxxulia Forest (Loc = -1808, 876) above which on the hillside a Large Wood Spider spawns. Inside this tree a Widow Hatchling and another Large Wood Spider spawns.

I have been farming Spiderling Silks there lately and have confirmed that these two spiders spawn inside the tree at least 5 times.