Summon swarm

Summon swarm is a conjuration spell that conjures a swarm of small crawling or flying creatures. It requires as a material component a square of red cloth.

Effect
When cast, summon swarm causes a swarm of little creatures to carpet an area, viciously attacking all other creatures there. Spellcasting or concentrating on spells within the swarm is impossible. The caster has no choice as to what type of creature he summons; typical swarms include rats, bats, poisonous spiders, centipedes, and flying beetles.

The swarm cannot be fought effectively with weapons, but fire and damaging area effects can force it to disperse. Certain area or effect spells, such as gust of wind and stinking cloud, disperse a swarm immediately if appropriate to the swarm summoned. (For example, only fliers are affected by a gust of wind.)

The swarm is stationary once summoned, not leaving the original area. A druid caster, however, can direct the swarm to move up to thirty feet every few seconds (or ninety feet if she has summoned bats or beetles).