Cave spiders are similar to normal spiders, but smaller and blue-ish grey in color. In addition to their small size, which allows them to pass through any gap that’s half a block high and 1 block wide, the attack of a cave spider will also poison you, though this does not happen on easy difficulty.
When a cave spider is killed, it’ll drop 0-2 pieces of string and 0-1 spider eye. The string is always dropped, no matter how it dies, while the spider eyes are only dropped when the spider is killed by a player. Like most hostile mobs, a cave spider will drop 5 experience points in the form of orbs.
Cave spiders will only spawn from monster spawners found in abandoned mineshafts, which often makes it more difficult to fight the spiders who can hide behind the wooden planks found in mineshafts. The spawners can be found on peaceful difficulty, but the spiders will not spawn. The spawners are often hidden in a large cobweb construction inside a mineshaft, which makes it all the more difficult to get to. Cave spiders and normal spiders are unaffected by cobwebs and will gladly use that ability to swiftly move in for a kill.
Cave spiders are also similar to normal spiders in terms of AI. Like a normal spider, cave spiders can climb walls. They will often ‘hang’ in the air, waiting for a player to pass by the opening, before it jumps down to attack the player. In combination with the often confined spaces of abandoned mineshafts, their home territory, and their venomous attacks, killing or surviving cave spiders can be quite a pain.
Like normal spiders, cave spiders will be neutral when they’re in a light level of 9 or higher, but spiders that are already attacking you will continue to do so, no matter how much you light up the place.
As mentioned, cave spiders are smaller and faster than normal spiders. Their size allows them to climb through any gap they can find. This includes the gaps created by fences and stone slabs, even 2 stair blocks facing each other with the lower part create a gap big enough for a cave spider to slip through.
Cave spiders are the only venomous monsters in minecraft. When a player is struck, poison will do half a heart of damage per 1,5 seconds, for 7 seconds on normal difficulty and 15 seconds on hard difficulty. You will know you’re poisoned as your health bar turns into a yellow-brown color.
Poison cannot kill you, but it can drop your health to half a heart, leaving you incredibly vulnerable to any other attack.
Drinking milk works as an antidote against this poison, however, after drinking the milk, spiders can immediately poison you again, so it’s not advised to drink milk during a battle.
Disabling spawners can be a little tricky due to the large amounts of cobweb surrounding the spawner. The easiest way to overcome this obstacle is to simply dig around or under the spawner and destroy it when you get close enough. This way you won’t have to deal with any spiders that may spawn and aren’t affected by the cobwebs. Swords are the best tool to use if you do chose to slice your way through the webs in order to get to the spawner.
Due to the way abandoned mineshafts are generated, several spawners can be very close to each other. It’s not uncommon to find 3-4 spawners close to each other. This means cave spiders can make a great xp farm by simply directing the spiders to a single point with water flows.