Army worm

Army worm, any of several species of voracious caterpillars that travel in masses, causing severe crop damage; especially the common army worm (Pseudaletia unipuncta). The common army worm is the larva of a brown moth found in North America east of the Rocky Mountains. The eggs, laid in grass or on small grains, hatch into small worms that, if not controlled by parasites or pesticides, devour everything within reach and then migrate in armies to new feeding grounds.