Cockroaches, mayflies, cicadas haven't changed much since then Articulated body with head, thorax, abdomen. One pair antennae from head. Simple and compound eyes. Mouth parts pierce, chew, suck, lap. Gas exchange by trachea.
Spiracles are holes in body wall that let air into tracheal tubes.
Excretion by Malpighian tubules receive metabolic waste from blood Concentrate waste and discharge waste into intestine. Conserve water Sexes separate, internal fertilization primitive, wingless insects like silverfish have direct, simple development. Pupa in cocoon doesn't feed, does change form to adult with functional wings and reproductive organs. Why bugs took over the world tough exoskeleton protects from predators, prevents evaporation of body fluid segmented exoskeleton allows mobility and flexibility Body plan is amazingly adapted to lifestyle. Segmentation allows regional specialization.