Minecraft wiki entry for Summoning_jockeys, associated text: /summon spider ~ ~1 ~ {Passengers:[{id:skeleton,HandItems:[{Count:1,id:bow},{Count:1,id:shield}],ArmorItems:[{Count:1,id:diamond_boots},{Count:1,id:diamond_leggings},{Count:1,id:diamond_chestplate},{Count:1,id:diamond_helmet}],CustomName:Killer,Visible:1,HandDropChances:[1.0f,1.0f],ArmorDropChances:[1.0f,1.0f,1.0f,1.0f],ActiveEffects:[{Id:1,Amplifier:1,Duration:999999},{Id:5,Amplifier:1,Duration:999999},{Id:8,Amplifier:1,Duration:999999},{Id:12,Amplifier:0,Duration:999999}]}]}