Phase Wasp (CR 2)

Tiny Magical Beast
Alignment: Always neutral
Initiative: +4 (Dex); Senses: darkvision 60 ft., low-light vision, see invisibility, Listen +6, and Spot +6

AC: 17 (+2 size, +4 Dex, +1 natural), touch 16, flat-footed 13
Hit Dice: 2d10 (11 hp)
Fort +3, Ref +7, Will +2
Speed: 10 ft., fly 60 ft. (perfect)
Space: 2 1/2 ft./0 ft.
Base Attack +2; Grapple -10
Attack: Sting +0 melee
Full Attack: Sting +0 melee
Damage: Sting 1d4-4
Special Attacks/Actions: Magic missile
Abilities: Str 3, Dex 19, Con 10, Int 2, Wis 13, Cha 6
Special Qualities:
Feats: Alertness
Skills: Listen +6, Spot +6, and Survival +3
Advancement: 3-4 HD (Tiny); 5-6 HD (Small)
Climate/Terrain: Any temperate or warm land
Organization: Swarm (5-20)
Treasure/Possessions: None

Source: Monster Manual II

Magic Missile (Sp): A phase wasp can produce an effect that functions like a magic missile spell (caster level 3rd). Once it has used this ability, it must wait 1d4 rounds until it can do so again.

See Invisibility (Sp): A phase wasp produces an effect like that of a see invisibility spell (caster level 3rd), except that it is always active.

Normally, phase wasps attack only to defend themselves and their nests. They converge on intruders in swarms, fire their magic missiles, and then swoop in to sting until they can use their missiles again.