\Ar"my worm`\ (Zo["o]l.)
   (a) A lepidopterous insect, which in the larval state
       often travels in great multitudes from field to field,
       destroying grass, grain, and other crops. The common
       army worm of the northern United States is {Leucania
       unipuncta}. The name is often applied to other related
       species, as the cotton worm.
   (b) The larva of a small two-winged fly ({Sciara}), which
       marches in large companies, in regular order. See
       {Cotton worm}, under {Cotton}.