The collective noun for Caterpillars is an army. This term is derived from the way in which Caterpillars move in large groups, resembling an army marching in formation. The term is also used to describe the large number of Caterpillars that can be found in a single area. The etymology of the collective noun an army in relation to Caterpillars is thought to have originated from the Latin word armata, which means armed.
