Entity "minecraft:cavespider" is invalid when run through a command

When i was experimenting with commands, i run into this little problem

when i run this command: /entitydata @e[type=CaveSpider]

{CustomNameVisible:1,NoAI:1,Silent:1}

what i expected: Updating the data of a minecraft:cavespider to have a data tag of CustomNameVisible to a 1, NoAI to a 1, and Silent to a 1

outcome: Entity type 'minecraft:cavespider' is invalid