Giant Ant Lion (CR 5)

Large Vermin
Alignment: Always neutral
Initiative: -1 (Dex); Senses: darkvision 60 ft. and Listen +5

AC: 14 (-1 size, -1 Dex, +6 natural), touch 8, flat-footed 14
Hit Dice: 8d8+24 (60 hp)
Fort +9, Ref +1, Will +3
Speed: 20 ft., burrow 20 ft.
Space: 10 ft./5 ft.
Base Attack +6; Grapple +14
Attack: Bite +9 melee
Full Attack: Bite +9 melee
Damage: Bite 2d8+6 plus poison
Special Attacks/Actions: Constrict 2d8+6 plus poison, improved grab, pit, poison, sand burst
Abilities: Str 19, Dex 8, Con 17, Int -, Wis 12, Cha 7
Special Qualities: vermin traits
Feats: -
Skills: Hide -1* and Listen +5
Advancement: 9-16 HD (Large); 17-24 HD (Huge)
Climate/Terrain: Temperate deserts
Organization: Solitary
Treasure: None

Source: Sandstorm

At the bottom of a sandy pit lies a bristled horror with enormous, hooked jaws. It looks like a fat-bodied louse but is the size of a warhorse.

A giant ant lion is the larval form of a giant insect that resembles a dragonfly. It spends almost its entire life in larval form, voraciously consuming giant ants or anything that stumbles into its trap.

Giant ant lions are perfectly adapted to trapping and devouring prey. They dig slippery pits in loose sand and hide themselves at the bottom, with only their outsized jaws protruding. If a creature comes too close to the pit's edge, it falls in and slides toward the waiting predator. A giant ant lion is expert at knocking down hapless creatures that try to escape the trap, and its body has thick, forward-pointing bristles that keep it from being pulled out of its pit once it has seized its prey.