army worm(n = noun.animal) armyworm, pseudaletia unipuncta - noctuid moth larvae that travel in multitudes destroying especially grass and grain;
is a kind of caterpillar
is a member of genus pseudaletia, pseudaletia

1.  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 the noctuid moth (Pseudaletia unipuncta, formerly Leucania unipuncta. The name is often applied to other related species, as the cotton worm. [1913 Webster]

2.  the larva of the fungus gnat; -- they march in large companies in regular order. [WordNet 1.5]

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