This early stage is a sort of fat wormlike eating machine, whose only goal is to stuff itself with lots of greenery. Like snakes, larvae can only get bigger by shedding their tight old skin every now and then. Once they're big and full up, they spin themselves a cocoon. Inside this protective chamber, they pupate. Pupation is a remarkable process - the insects more or less disintegrate, and then reconstruct themselves in a totally different shape, which is the adult.
Flour beetles are pesky bugs that creep into warehouses and tuck into flour and cereals.
Normally, they make themselves a cocoon once they get to the right size, and pupate into an adult. It ends up twice as big as it should, and never pupates. In other words, it never turns into an adult, and never reproduces. These larvae are infected by a parasite called Nosema . Nosema makes one of the larva's own hormones.