Cave Spider

The Blue Spider is a hostile mob that it is believed will be introduced in Minecraft Beta 1.8. It is a spider with a blue retextured skin and is presumably stronger than its brown brethren. Blue spiders are much more rare than regular spiders. When bitten by a blue spider, your health bar turns yellow and gradually decreases. Blue Spiders are also smaller than the regular black spiders Blue spiders can only be found in Abandoned Mine Shafts, which will also be introduced in 1.8.

Trivia

 * It was originally going to be called a tree spider according to Jeb, but that wouldn't make any sense due to it spawning in mine shafts.
 * In the 1.8 Preview, a Blue(?) Spider was called a "poisonous spider", but "venomous spider" would be a more defining name.