Protean Spawn

There are many blood elf corpses in Arcatraz which will spawn these small larvae in pairs. The spawn is triggered by either getting too close or attacking the corpse (ranged attacks included so it is possible to aggro these one pair at a time).

Prior to 2.0.10 you were able to avoid the worm spawn by using some sort of crowd control effect on the corpses. Note that this is no longer works.