n large animal swarm 

Perception +18; darkvision

Skills Athletics +16, Stealth +19

Str +1 Dex +6 Con +4 Int -5 Wis +3 Cha -5

AC  28; Fort +19, Ref +19, Will +14

HP 130; Immunities precision, swarm; Weaknesses area damage 10, splash; Resistances bludgeoning 5, piercing 10, slashing 10

Cling [R] Trigger A creature leaves the swarm's space; Effect The swarm takes 1d6 damage as ticks cling to the creature and continue biting, dealing 3d6 persistent piercing damage. Immersion in water reduces the DC of the flat check to end this persistent damage to 5, and any area damage dealt to the creature destroys these clinging ticks.

Speed 25 feet, climb 25 feet

Swarming Bites [>] Each enemy in the swarm's space takes 3d6 piercing damage (DC 28 basic Reflex save) plus Cling and exposure to tick fever.

Tick Fever (disease) As giant tick but DC 27.

Bestiary 2, page 260.