A phylum of the Metazoa that includes the classes Crustacea (crabs, shrimps, crayfish, lobsters), Insecta, Arachnida (spiders, scorpions, mites, ticks), Chilopoda (centipedes), Diplopoda (millipedes), Merostomata (horseshoe crabs), and various other extinct or lesser known groups. Arthropoda forms the largest assemblage of living organisms, 75% insects, of which over a million species are known.


[arthro- + G. pous, foot]