Insects are hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body, three pairs of jointed legs, compound eyes, and a pair of antennae. Insects are the most diverse group of animals, with more than a million described species; they represent more than half of all animal species.
Insect
Insect: Six legs, three-part body (head, thorax, abdomen), up to two pairs of wings
Spider: eight legs, two-part body
Woodlouse: seven pairs of legs, seven body segments (plus head and tail)
The subphylum Hexapoda or hexapods comprises the largest clade of arthropods and includes most of the extant arthropod species. It includes the crown group class Insecta, as well as the much smaller class Entognatha, which includes three orders of wingless arthropods that were once considered insects: Collembola (springtails), Protura (coneheads) and Diplura. The insects and springtails are very abundant and are some of the most important pollinators, basal consumers, scavengers/detritivores and micropredators in terrestrial environments.
Hexapoda