armyworm has 2 distinct synonyms spread across 2 of its 3 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
noctuid moth larvae that travel in multitudes destroying especially grass and grain
Synonyms, antonyms and the broader and narrower relations for armyworm come from Princeton University’s WordNet. Full sources and licences.
larva of fungus gnat that feed on cereals and other grains; they march in large companies in regular order when the food is exhausted