Tiny Aberrations with high Dex and Weapon Finesse for a decent melee attack?
Actually, it looks like the warriors and nobles are Diminutive, and the Calipha is Tiny (advancing to Small).
Let's figure out ability scores.
Giant Soldier Ant (M): Str 14, Dex 10, Con 13, Int —, Wis 13, Cha 11
...Downsized to (D): Str 4, Dex 16, Con 11, Int —, Wis 13, Cha 11
Tiny Monstrous Centipede: Str 1, Dex 15, Con 10, Int —, Wis 10, Cha 2
Tiny Monstrous Scorpion: Str 3, Dex 10, Con 14, Int —, Wis 10, Cha 2
Tiny Monstrous Spider: Str 3, Dex 17, Con 10, Int —, Wis 10, Cha 2
Mulworm (D): Str 1, Dex 12, Con 11, Int —, Wis 14, Cha 4
Wiggling Maggot (D): Str 1, Dex 12, Con 11, Int —, Wis 14, Cha 2
The warrior has Int 8-10, the noble 11-12, and the calipha 11-12. The calipha appears to have a Con penalty. The giant ant queen has poorer Dex, and the calipha's description doesn't seem to suggest otherwise.
Since they most closely resemble ants, I propose...
Warrior (D): Str 3, Dex 16, Con 11, Int 10, Wis 13, Cha 11
Noble (D): Str 4, Dex 16, Con 11, Int 12, Wis 13, Cha 13
Calipha (T): Str 5, Dex 11, Con 9, Int 12, Wis 13, Cha 15
Revising...
Pitfall (Ex): Pasari-nimal can bury an opponent by opening a pitfall beneath them. This requires a standard action by the pasari-nimal, who must be free to move by burrowing. If the target succeeds at a DC X Reflex save they will not fall into the pitfall. A single pasari-nimal can create a pitfall big enough for an opponent of Tiny size or smaller; it takes 2 pasari-nimal to create a pitfall for a Small-sized opponent, 4 for a Medium-sized opponent and 16 for a Large-sized opponent. If the pasari create an oversized pitfall the Reflex save DC increases by +4? for every size the pitfall is bigger than the opponent. Pasari-nimal are too small to create a pitfall for Huge-sized or larger opponents as a standard action special attack, although they can still excavate standard pit traps for such big creatures.
A pasari-nimal's pitfall collapses as soon as it is created, leaving the victim trapped and partially buried in the ground. The pitfall is deep enough that the pasari-nimal has total cover and total concealment against any other opponents on the surface. The pasari-nimal have cover and concealment against its buried victim, giving the pasari-nimal +4 AC and the victim a 20% miss chance. The confined quarters of the pit the victim is in means they can only wield light slashing or piercing weapons. The pasari-niml fight without penalty due to their burrow speed. If the victim has a burrow speed, they can move and fight normally by burrowing.
The buried victim, or their allies, can attempt to drag the victim from the ground with a DC Y Strength check, or the buried victim can wiggle free with a DC Z Escape Artist check (+4? DC for every size the pitfall is bigger than the opponent). The pasari-nimal can try to prevent the victim leaving the pit by grappling or other means. The save DCs are Strength-based and include a +4 racial bonus?
Remove the "-sized" bits, and I think it's looking pretty good!