Why do scientists think insect wings evolved only once?

Scientists believe that insect wings evolved only once because of the consistent pattern of venation—the arrangement of veins—found throughout the Pterygota. This structural uniformity suggests that all winged insects descended from a single common ancestor in the insect family tree.1

While the fossil record does not provide direct evidence of the transition from wingless apterygotes to winged insects, the shared venation pattern remains a primary indicator of a single evolutionary origin for flight in this group. Researchers have proposed various hypotheses for how these wings first emerged, such as the development of fixed thoracic planes for gliding or the modification of thoracic tracheal gills used by ancestral aquatic forms.1