Cave Spider

The Cave Spider is a neutral mob that can inflict poisoning.

Monster spawners
Cave spiders are spawned by monster spawners in abandoned mine shafts.

Drops
They drop 0-2 string. They also have a $1/3$ chance to drop a spider eye if killed by a player.

Behavior
Cave spiders inherit most of their behavior from regular spiders:
 * They are pacified (made neutral) by bright light—daylight or light levels of 9 or higher. Likewise, subjecting them to darkness will render them hostile.
 * They can climb walls when needed and leap at the player.
 * They are not affected by cobwebs or splash potions of poison.
 * A cave spider can hold its breath underwater for about 16 seconds (320 game ticks), as with other mobs and the player. It takes about 6 seconds (120 game ticks) to suffocate a cave spider to death.

They have two big differences from regular Spiders: One is the much smaller size of the cave spider: they take up only a fraction of a block space, specifically 0.7 x 0.7 x 0.5 of a block. Note that if both cave and regular spiders are trying to reach the player through the same 1x1x1 size opening, the regular spiders tend to crowd the opening (which they can't pass), and block the path of the cave spiders.

Venom
The cave spider's other special feature is its poisonous bite. When bitten by a cave spider on any difficulty except Easy, the player is inflicted with Poison I effect, which lasts for 7 seconds on Normal difficulty, or 15 seconds on Hard. If they are suffering from the Weakness potion effect, or the difficulty is on Easy, they will not inflict poisoning.

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.
 * Despite being smaller, they have the same size shadow as a normal spider.
 * Cave spiders are one of the five mobs that give a debuff to the player, the other four being the Wither, the Wither skeleton, the witch, and the Elder Guardian.
 * If cave spiders are allowed to spawn naturally via hacks, they will only spawn if the light level is 7 or below (like most other hostile mobs).