Cave Spider

The Blue Spider is a hostile mob that is to be introduced in Minecraft Beta 1.8. It is a Spider with a blue re-textured skin and is more dangerous than the regular spider, but in turn they are much more rare than regular Spiders. The increased danger comes from the fact that Blue Spiders have a venomous bite, which is represented by your health bar turning yellow and gradually decreasing. Blue Spiders can only be found in Abandoned Mine Shafts, which will also be introduced in Beta 1.8. Blue Spiders are also smaller than regular spiders ; presumably so that they can fit through the mine shafts that they spawn in.

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, not trees.
 * In the Beta 1.8 preview, Blue Spiders were called "Poison Spiders", but "venomous spider" would be a more grammatically correct name.
 * A possible cure for the spider venom could be milk, as tweeted by Jeb when someone suggested it.