Cave Spider

The Cave Spider is a hostile mob using the same model as the spider, but with a blue skin color and smaller size. They are more dangerous than the regular spider, but they in turn are much rarer than regular Spiders. Cave Spiders do not spawn naturally; they only spawn from monster spawners found in abandoned mine shafts. Their small size (0.7 x 0.7 x 0.5) allows them to fit through spaces one block wide and just half a block tall including those created by slabs, fence posts and two stair blocks facing each other. Cobwebs do not affect Cave Spiders.

Behavior
Aside from their small size and venom (see below), Cave Spiders inherit most of their behavior from regular Spiders. Cave Spiders behave just like normal Spiders in daylight or light levels of 9 or higher. Cave Spiders, like regular spiders, are pacified (made neutral) by bright light. Likewise, subjecting them to darkness will render them permanently hostile. They can climb walls, jump, track the player through solid blocks.. They are not affected by cobwebs or splash potions of Poison. Cave Spiders will climb or leap into an area three blocks high and wait for the player to get close enough to attack. If both cave and regular spiders are attempting to get to the player through a 1x1x1 size opening, the regular spiders crowd the opening and block the path of the smaller cave spider, greatly reducing its chance of getting through the opening. A cave spider can hold its breath underwater for about 16 seconds (320 world ticks/160 redstone ticks). It takes about 6 seconds (120 world ticks/60 redstone ticks) to suffocate a cave spider to death.

Venom
The most notable feature of the cave spider is its venomous bite. When bitten by a Cave Spider on any difficulty except Easy, the player's health bar turns yellow-green and gradually decreases. The venom inflicts half of a heart of damage about every second and a half, and lasts for 7 seconds on Normal difficulty, or 15 seconds on Hard. Armor does not protect from venom or reduce the damage received from it. Since 1.9 Pre-release 4 Jeb gave milk the ability to cure the player of the venom. Regardless of the difficulty, venom cannot kill the player, but it can drop the player's health to dangerously low levels. If they are suffering from the Weakness potion effect, then they will not do any damage or inflict poisoning.

Using milk
Because milk isn't stackable, drinking it during a battle is a waste; the best time to use the milk is after killing the spiders and lighting the spawner. The best ways to get past the spawners are to:


 * Block up all the passages to it, dig above and pour lava on the spawner.
 * Dig below and break the spawner.
 * Find another way around.
 * Build an Iron Golem in there, if you can.
 * Play on peaceful.
 * Light up the area.

Other tips

 * Cave Spiders are faster than normal spiders.
 * Cave Spider spawners are surrounded by cobwebs, making them difficult to get. Since as mentioned above, Cave Spiders are not slowed by Cobwebs, players can only take extreme caution when passing these areas, unless playing on Peaceful. Placing water over the cobwebs is an easy way to destroy them.
 * They may be able to go through a 1 block gap. The most effective method to farm spider eyes is via killing the spiders through the fence gaps; the player can hit them between the gaps with impunity, and spider eyes can be fermented then used to make Potions Of Harming, and that can kill them faster
 * Since the cave spider spawner is surrounded by cobwebs (which can only be burnt indirectly) you can set the cobwebs on fire to burn the spiders and (Temporarily) stop the Mob Spawner
 * When in doubt -- C-4! Yes, you can use explosives (TNT in this case) to blow up the mob spawner and kill most of the spiders in the area. Cave spiders only have twelve hitpoints so they die easily when there is an explosion. In the process, you'll also deal with a lot of cobwebs. However, you can get yourself killed if you're not careful.
 * A safe way to blow up the spawner is to get above it, dig a hole in the ceiling, remove any cobwebs above the spawner, drop the TNT in the space, and light it with your Flint and Steel.

Mob farming

 * Because of the cave spider's small dimensions, building a mob farm from a cave spider spawner would be considerably difficult (unless the player is on the Peaceful setting) and somewhat inefficient to build.
 * If building a mob farm for cave spiders, ensure the roof is greater than 3 blocks high on the player side wall or they will leap to the roof causing them to get stuck.
 * Cave Spiders do not drop more than one spider eye even after being killed by a looting-enchanted weapon, but the chance of one is increased.
 * Because of abundance of the cave spider spawners, they are quite commonly generated near each other. This can provide you with an extremely efficient XP farm: these spawners can work simultaneously (due to spawning behavior). A quite common 2-spawner XP farm can output a considerable amount of experience per hour. Sometimes it is possible to link together 3 or 4 spawners and generate a high amount of experience.

History
The Cave Spider was first introduced in the Beta 1.8 Pre-release.

SMP servers upgraded from older versions running in peaceful mode may begin spawning cave spiders, though no other monster appears in the world. This is because in older versions setting the Server.properties key  to   would place the server in peaceful mode. As of Beta 1.8, a separate key  must be set to zero to select peaceful difficulty; setting   to   prevents monsters from spawning randomly in dark areas but does not disable spawners. Because the  key defaults to 1 (easy), servers without the key configured at all changed from running in peaceful mode (prior to Beta 1.8) to easy mode (as of Beta 1.8).

Before the 1.0 update, Cave Spiders had health.

As of 1.2 both spiders and cave spiders have gained the ability to climb Ice blocks.

Cave spiders were added to the Xbox 360 Edition in the 1.2 (Beta 1.8.2) update.

Bugs

 * Because of the natural tendency of cave spider spawners being created with cobwebs and ceilings, but without walls such as the Moss Stone walls in dungeons, cave spiders can be spawned in the middle of a cavern or a ravine.

Trivia

 * The Cave Spider's texture appears to be at a higher-resolution than its normal counterpart - this is because the textures occupy a smaller space.
 * They have the same size shadow as a normal spider.
 * many speculations have been made about the possibility of a cave-spider-jockey. This however is impossible as cave spiders do not share an entity ID with spiders, like wither skeleton do with skeletons