Multiattack

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

Bites

Melee Weapon Attack: +6 to hit, reach 0 ft., every target in the swarm's space. Hit: 24 (6d6 + 3) piercing damage, or 13 (3d6 + 3) piercing damage if the swarm has half of its hit points or fewer. The target also takes 17 (5d6) poison damage and becomes poisoned for 1d4 rounds; a successful DC 15 Constitution saving throw reduces poison damage by half and prevents the poisoned condition.