Spiders seem to be likely to spawn inside blocks of the floor or the wall
they also spawn inside stacks of carpet and die because of the Suffocation-Bug.
May be connected to the Carpet-Suffocation-Bug.

Tested on a flat world with Spider-spawners and the Snow-Golem-Pulling-turrets(which kill spiders) in the background. (difficulty=3)

I like the combination of the carpet damage with my pulling-turret but otherwise its a bad thing.

Jailbroken Device Taig installed (u can tell by the textures of the UI, that its jailbroken)