Spider jockey spawned with the skeleton's head inside glass. This is … They can also spawn in a 1 high space with a transparent block above, so the skeleton is stuck in the transparent block. It is very rare for a spider jockey to spawn naturally in the game, but you can summon a spider jockey whenever you want using a cheat (game command) in Minecraft PC. A spider jockey has a 1% chance of spawning out of every spider or cave spider [ Bedrock Edition only ] spawned, and in the Nether, there is an 80% chance of a spider jockey becoming a Wither skeleton jockey, in snowy biomes there is 80% chance of cave spider jockey with stray rider.
Cave spiders can also spawn as spider jockey. Spider jockeys spawned in narrow enclosures can cause the skeleton rider to die of suffocation, due to the spider scaling the walls.