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.

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.