Locusts have been a fixture in mythology and folklore since the Bible—by which I of course mean the collected issues of Bone. (And also the actual Bible, though you have to admit it would be hella badass if Jeff Smith illustrated that too.)
So if you want to visit the eighth plague of the Torah/Old Testament upon your characters, the locust swarm has you covered. And if you want a more standard giant vermin, the giant locust is ready to vomit on you and devour your scrolls.
A charlatan is using shrieker paste to draw locust swarms to the fields of Evenhome in an attempt to turn the faithful against Aya the Merciful. Adventurers must uncover his trickery and destroy the locusts before a cloud turns into a plague. Worse yet, Evenhome is where the navy’s sailcloth is dyed. If the locusts get into the storehouse, the navy’s spring launch could be delayed by weeks.
A buzzing, swarming thing of locusts and hate, the worm that walks known as Acrides was destroyed in year 8 of the Crown Age. But perhaps some essence of him lingers on, for the locusts swarms that prey upon Sevenridge seem to seek out the crops, homes, and bodies of gnomes…and it was a gnomish militia` that laid Acrides low.
Skewered giant locusts are a delicacy to stone giants, one that the great goliaths rarely get to enjoy, living high in the mountains as they do. Adventurers trying to solve a murder at a building site will find the stone-faced masons much more likely to talk if they can provide a colony of the vermin to snack on.
—Pathfinder Bestiary 4 183
Don't forget the plague locust swarm from Pathfinder Adventure Path #79: The Half-Dead City.
Speaking of the Old Testament, I did get a copy of Green Ronin’s 3.0 book Testament: Roleplaying in the Biblical Era for crazy cheap in some sale. It looks really cool and has decent reviews, but I’ve never done more than flip through the pages. Any good?
And you guys have to stop being awesome when my back is turned. The Creature Chronicle just tackled the nagpa!