uncommon n gargantuan animal swarm 

Variant army ant swarm (Bestiary 2 20)

Perception +30; darkvision, scent (precise) [object Object] feet

Skills Athletics +27

Str -1 Dex +9 Con +7 Int -5 Wis +6 Cha -4

AC  41; Fort +31, Ref +33, Will +27

HP 260; Immunities precision, swarm mind; Weaknesses area damage 20, splash damage 20; Resistances bludgeoning 10, piercing 20, slashing 20

Inexorable The apocalypse ant swarm recovers from the slowed and stunned conditions at the end of its turn. It's immune to penalties to its Speeds and ignores difficult terrain and greater difficult terrain.

Cling [R] Trigger A creature leaves the swarm's space; Effect The swarm loses 2d8 HP as ants cling to the creature and continue biting, dealing 7d8 persistent piercing damage. High winds or immersion in water reduces the DC of the flat check to end this persistent damage to 5. Any area damage dealt to the creature destroys these clinging ants.

Speed 30 feet, fly 30 feet

Swarming Bites [>] Each enemy in the swarm's space takes 7d8 piercing damage (DC 39 basic Fortitude save). A creature that fails its save against Swarming Bites becomes clumsy 1 for 1 round (1 minute on a critical failure). If the creature attempts a concentrate or manipulate action while affected, it must succeed at a DC 5 flat check or the action is lost; roll the check after spending the action, but before any effects are applied.

Strength of Thousands #6: Shadows of the Ancients, page 56.