This mod adds some new spider enemies. They will spawn more at night. There is a chance a spider egg cluster will spawn too. This is a good source of eggs and spider silk, which is used to craft spider web traps. These traps slow and damage the enemy. Skinning spiders gives spider silk, and a very small chance to give you a mountable spider. Wild spiders will die after 5 minutes of being alive, to keep the population down and allow actual zombies the chance to spawn more often.
This is a modlet and does not require a world restart. Simply place into Mods folder and play!
Tested and works with Alpha 19 b173.
The forum topic of the mod is here.