Spider Jockey

A Spider Jockey is the rare appearance of a Spider being ridden by a Skeleton. A Spider Jockey possesses the ranged arrow attack of a Skeleton plus the vision, agility, and wall-climbing ability of a Spider, and the two creatures attack and take damage individually. The Skeleton and Spider are treated as separate entities in the game (i.e. if the Spider is killed, the Skeleton will continue to attack and move, and vice-versa). A Spider Jockey can spawn above and below ground. However, generally, underground Skeleton riders die of suffocation, due to the spider scaling walls, causing the skeleton to have its head raised into the ceiling and suffocate.

Origins
A Spider has a 1% chance to spawn with a Skeleton rider. As of 12w36a, spiders spawned using Spawn Eggs in the Nether have a small chance(0.8% of the time) of a Wither Skeleton spawning on them.

Uses
The death of a Spider Jockey offers a potential five-in-one item drop special. Each Jockey, when completely killed, will yield 0-1 spider eyes, 0-2 string, 0-2 bones, 0-2 arrows, and a rare chance of a bow or enchanted bow.

Behavior
The Spider controls the movement, so a Spider Jockey will wander aimlessly in the day 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 in sunlight, leaving the Spider unharmed). Because Spiders can detect 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.

When exposed to sunlight, the Skeleton will burn and die like a normal Skeleton, but the Spider will remain active and not deadly

a Skeleton can not get off a Spider after a certain amount of time. This happens because of code within every entity's AI to occasionally decide to not dismount the entity it is currently riding, which is used for when they are on boats or minecarts.

Combat
Without some kind of armor, a bow and arrows, and plenty of space, the player is generally 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.

Spider Jockeys are hardly a threat in SMP because of their bugginess. The Skeleton rarely appears to be riding on the Spider but rather next to it, so it usually shoots the Spider. They are so glitchy that they sometimes disappear or suffocate.

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 a Spider Jockey, because of the jockey's incredible agility and damage. Another way to kill it is to get the Spider Jockey on a block above you, but in a way so that it doesn't fall, leading to the Skeleton shooting the Spider; the lone Skeleton can then be dispatched easily.

However, even with something as basic as a stone sword and good combat skills, the player can kill the Jockey if at close range.

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 the Jockey 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. It is recommended that you do not use wolves, unless you are in possession of a strong enchanted bow.

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, like regular Spiders and skeletons, can only spawn during the night. They can also spawn in dimly lit rooms with a light measurment of 7 or less. See construction safeguards to prevent this from happening.

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. You can also make a 2x2 tunnel and lead it in. Because the spider is one block tall you can place another block over the spider after making the 2x2 tunnel to suffocate the skeleton and then easily dispatch the spider later. If you aggravate a spider jockey, by accident, run into your house and get a bow (if you do not already have one with you) and dispatch it from a safe distance.

Construction safeguards
Because a Spider Jockey can spawn anywhere 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 able to climb over it, but the Skeleton will be not be suffocated in the process of being pressed into the overhang. However, the Spider-Jockey is rare enough not to pose an extreme hazard, but more a rare enemy, therefore it would not create much of a difference to construct a safe guard on your house. Always make sure to have glass as windows due to the Skeleton's arrows.

Trivia

 * Presumably because of the above, Cave Spider Jockeys do not spawn at all in Minecraft unless hacked into the game.
 * They are one of the few "mobs" that do not have a spawn egg, due to the fact that they are not unique mobs at all, just a stack of two different mobs.
 * 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 and then returns while a Spider Jockey is spawned, the Skeleton will stop riding the Spider.
 * 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.
 * In earlier updates the Spider Jockey would move in glitched movement, often the Skeleton would "bob" in and out of the Spider. This bug still happens in SMP, especially with large amounts of lag.
 * When a Spider Jockey rides a minecart, the Spider will suffocate and the Skeleton will remain.
 * If the Skeleton on the Spider Jockey is shot by another Skeleton, it will jump off and leave the spider.
 * In Creative mode, it is possible to have only the Skeleton attack you, and vice versa (as seen above), due to the fact that they are two different mobs.
 * Sometimes, if you are far away enough from this mob that it doesn't give chase, the spider may just despawn.
 * Sometimes, the spider despawns,and the skeleton remains. However, it is still sitting and cannot be hurt.

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