D&D Basic Monsters: Swarm of Insects

Ants, earwigs, centipedes, millipedes, bedbugs, carpet beetles, spider beetles, pillbugs, silverfish and cockroaches are just some of the critters you might find in one of these, and they're sure to gross quite a few players out.

Swarms weren't really a thing in D&D before 3rd edition, however, since then they've been a constant danger to player characters everywhere, specially those without large area effects or spells.