n large animal swarm 

Perception +12; tremorsense (imprecise) 60 feet

Skills Acrobatics +10, Stealth +12

Str -1 Dex +3 Con +4 Int -5 Wis +1 Cha -4

AC  20; Fort +15, Ref +12, Will +8

HP 60; Immunities acid, precision, swarm mind; Weaknesses area damage 4, splash damage 4, water 8

Speed 15 feet, burrow 30 feet

Swarming Bites [>] Each enemy in the swarm's space takes 3d6 acid damage (DC 22 basic Reflex save). Creatures that fail this save become sickened 1 from the swarm's painful bites.

Bestiary 3, page 36. Expanded in LOIL.