The term FLIES, FLEAS ETC is referring to INSECTS. INSECTS are a class of invertebrates within the arthropod phylum that have a chitinous exoskeleton, a three-part body, three pairs of jointed legs, compound eyes, and two antennae. They are among the most diverse groups of animals on the planet, including more than a million described species and representing more than half of all known living organisms. INSECTS may be found in nearly all environments, although only a small number of species reside in the oceans, which are dominated by another arthropod group, crustaceans.