More than a quarter million wasps filled the skies of the northeastern province of Khon Kaen (see map) on Saturday. The hope is that the wasps will attack mealybugs, which have been infesting the country's valuable cassava crop.

The pill-shaped mealybugs suck sap from the crops—a main ingredient of tapioca—causing them to shrivel and die.

But that's nothing compared with the killing technique of female Anagyrus lopezi wasps, which inject their eggs directly into the mealybugs' bodies. When the eggs hatch, the larvae eat their way out of their hosts, killing them.

(See "'Zombie' Roaches Lose Free Will Due to Wasp Venom.")

Like the wasp and cassava, the Phenacoccus