Multiattack

The swarm makes a Bite attack against every target in its spaces.

Bites

Melee Weapon Attack: +3 to hit, reach 0 ft., every target in the swarm's space. Hit: 22 (6d6 + 1) piercing damage, or 11 (3d6 + 1) piercing damage if the swarm has half of its hit points or fewer. The target also takes 10 (3d6) poison damage and becomes poisoned for 1d4 rounds; a successful DC 13 Constitution saving throw reduces poison damage by half and prevents the poisoned condition.