Harvestmen

The Dripstone Caves need their own mob. Desperately. Spiders spawn commonly in these biomes, so why not add a new predator? Here is my idea: HARVESTMEN. These would spawn rarely in dripstone caves. They would have a body about the size of a player's head, but legs 5 blocks long (only one voxel in area, though). It would be hostile to spiders, cave spiders, endermites, and silverfish, but neutral to all other mobs. To get through smaller areas, it will fold its legs, which can fold at the one-block lines. It will only kill one spider a day, though, and then it will "rest", by lying on the ground with its near-invisible legs on the ground. If you try to mine a dripstone block, but discover it isn't a dripstone block... Well...

Anyway, I just thought this could be cool. Please consider it! :)