Skeletal Crawlers are Undead enemies in Act V of Diablo III. They are a variant of Bile Crawlers.
"The Great Pestilence in Westmarch killed both humans and beasts alike. The panicked survivors then threw the corpses of both into the Plague Tunnels. Now the reapers' presence has revived many of those interred there, with the bones of beasts rising again as skeletal crawlers driven to kill the living"— Archangel Tyrael(src)
In-gameEditSkeletal Crawlers are only encountered in Plague Tunnels and Repository of Bones, none of which is mandatory for walkthrough, so one can finish the game without ever seeing these monsters. Despite being revived by the presence of Reapers, they count as simple Undead. They are just as fast as Bile Crawlers, but move faster, have more Life and deal more damage in melee. In return, Skeletal Crawlers are rarely encountered in groups of more than three at a time. They do not hide and do not spawn from any objects.
Skeletal Crawlers bear strong resemblance to the Skeletal Beasts from Dark Souls.