Encounters by Locale: Anauroch - The Sword - Mountains/Hills (Night)

Swarm, Locust (CR 3)

Diminutive Vermin (Swarm)
Alignment: Always neutral
Initiative: +4 (Dex); Senses: darkvision 60 ft., Listen +4, and Spot +4

AC: 18 (+4 size, +4 Dex), touch 18, flat-footed 14
Hit Dice: 6d8-6 (21 hp)
Fort +4, Ref +6, Will +2
Speed: 10 ft., fly 30 ft. (poor)
Space: 10 ft./0 ft.
Base Attack +3; Grapple -
Attack: Swarm
Full Attack: Swarm
Damage: Swarm 2d6
Special Attacks: Distraction
Abilities: Str 1, Dex 19, Con 8, Int -, Wis 10, Cha 2
Special Qualities: immune to weapon damage, swarm, vermin
Feats: -
Skills: Listen +4 and Spot +4
Advancement: -
Climate/Terrain: Temperate Planes
Organization: Solitary, cloud (2-4 swarms), or plague (11-20 swarms)
Treasure: None

Source: Monster Manual

A whirling, clacking cloud of voracious, grasshopperlike insects flutters closer, filling the air with a high-pitched buzz.

A locust swarm is a cloud of thousands of winged vermin that devours any organic material in its path.

Faerûnian Random Encounters by Region and Locale