Spider Jockey

A spider jockey is the combination of a spider and a skeleton riding on top. Despite the skeleton and spider being treated as separate entities in the game (if the spider is killed, the skeleton will continue to attack and move and vice versa), a spider jockey possesses the ranged arrow attack of a skeleton plus the vision, agility, and wall-climbing ability of a spider with the sum of their aggression and respective health capacities. A spider has only a 1% chance to spawn with a skeleton rider, but the rare spider jockey is one of the most dangerous enemies the player can encounter.

Uses
The death of a spider jockey offers a potential three-in-one item drop special. Each spider jockey, when completely killed, will yield 0 - 2 pieces of string from the spider, and 0 - 2 bones plus 0 - 2 arrows from the skeleton.

Behavior
The spider controls the movement, so a spider jockey will wander aimlessly in the daytime and only pursue the player at night or in dimly lit areas when the spider is hunting. However, the skeleton will turn and fire at the player as soon as it sees them no matter the time of day (although the skeleton will quickly burn to death in sunlight, leaving the spider unharmed). Because spiders can "see" a player through solid blocks, spider jockeys can ambush unsuspecting players in sufficient darkness. If the skeleton shoots another hostile mob, it will focus its attack on the skeleton but not the spider being ridden even after the skeleton is killed.

Combat
Without some kind of armor, a bow and arrows, and plenty of space, the player is advised to make a tactical retreat when faced with a spider jockey as it can kill in seconds. Despite the spider's decreased leaping ability, this monster otherwise retains the spider's agility and sight, the skeleton's ranged attack, and the health of both, making it an unwise candidate for resource harvesting. Arrows can be crafted, and bones and string can be obtained in a less hazardous way by hunting individual spiders and skeletons.

Bolder players are advised to take out the skeleton first at a distance, taking care not to land any arrows on the spider before the skeleton dies. Even when armed with a diamond sword, the player is heavily disadvantaged when fighting the spider jockey.

An advisory on using wolves
Spider jockey battles involving wolves are slow and messy at best and fatal to everyone but the spider jockey at worst. Wolves are not recommended as a method of defense against one since they will not attack it as a whole - they will aim for either the spider or the skeleton, depending on which the player hit or was attacked by. Conversely, when a wolf attacks a spider jockey only the individual it managed to injure will try to go after it. Once hit, a wolf will focus its hostility on the mob that last attacked it. Since a skeleton's ranged attack makes it more likely to hit the player or a wolf, it will often be the first targeted. The wolves will then have a harder time attacking the skeleton because of its lofty arachnid perch, causing them to crowd around the spider in a futile effort to get at the skeleton while the spider continues to injure the player.

Defensive Measures
A spider jockey is vulnerable to falling, fire, lava, and contact with cacti. The player can decrease the chance of running into a spider jockey on the surface by regularly sleeping in a well-lit, sheltered bed at dusk since spider jockeys can spawn during the night.

If cornered or trapped in a cave with a spider jockey, the player can use a shovel or pick to quickly dig a 1-block shaft 3 blocks deep and seal off the top with another block before tunneling away to a safe location.

Construction Safeguards
Because a spider jockey can only spawn where an ordinary spider can, a spider-proofed area is also spider jockey-proof. Consult the spider article for more in-depth explanation. The usual guidelines of good lighting and installing doors from the outside apply.

If an overhang is built into a wall, not only will the spider jockey be unable to climb over it, but the skeleton will be suffocated in the process of being pressed into the overhang.

History
Spider jockeys were introduced in the Seecret Friday update 8. In Alpha, a spider jockey would drop 0 - 2 pieces of string from the spider and 0 - 2 arrows from the skeleton. This remained unchanged in Beta, but the skeleton could now drop 0 - 2 bones in addition to the arrows. When spiders were given the ability to climb and "see" the player through walls in Beta 1.2 spider jockeys became a much more formidable enemy.

Spider jockeys can be "passive aggressive" with the addition of rain in Beta 1.5. The light level is low enough in a rainstorm for the skeleton to not combust, but high enough for the spider to not be actively hunting. In this state, the skeleton will shoot the player with arrows but the spider will not give chase (unless the spider jockey wanders into a shady area) because movement is controlled by the spider. The player can safely observe this kind of spider jockey from a distance of 8 or more blocks away.

Trivia

 * A skeleton does not have a 1% chance of spawning riding a spider - a dungeon with a spider spawner can create a spider jockey, but a  skeleton dungeon cannot.
 * A spider jockey can kill itself - sometimes the skeleton arrows will injure the spider and other times the spider's pouncing will run the skeleton into its own arrow.
 * If the player exits a game after spider jockey has spawned, the skeleton will not be riding the spider when the player returns.
 * A spider jockey can attack two different players in SMP - this is caused by one player damaging one half of the spider jockey and not the other. This usually happens when a player chased by a spider jockey enters a structure that the spider can not crawl through. Because the spider can see through the walls, it will continue to target this player. Because the skeleton can't see through the walls it will look for a new target (such as another player walking by) and then fire arrows at them.
 * The world can create 1-2 spider jockeys at a time, but the spawn percentage is still 1%.