Insects
Class Insecta: most diverse and most abundant arthropods
live in every terrestrial and freshwater system; only 1 marine species
Old name: Hexapoda ? 6 legs (3 pairs) on thorax; no legs on abdomen but segmentation visible in abdomen; 1 pair of antennae
Thorax: 3 segments, each with 2 legs, muscles if 2 pairs of wings: middle and last segment; if 1 pair of wings: middle segment