This page lists all Spiders: currently, Spiders seem to have the most subtypes of all the Mobs.
“Spitters are a Cave-dwelling variety of a Spider, which can spit web-projectiles as well as...Spitter
“The Dangling Depth Dweller is a Spider variant found in the Ruins. They drop from the ceiling...Dangling Depth Dweller
“Cave Spiders are a Cave-dwelling type of Spider which have a shell-like carapace which they can...Cave Spider