How did primitive wingless insects contribute to the evolution of winged insects?

Primitive wingless insects, or apterygotes, are considered survivors of the ancestral stock from which all winged insects (Pterygota) evolved. While the fossil record does not explicitly document the transition from wingless to winged forms, scientists have developed two primary hypotheses regarding how these primitive ancestors contributed to the development of flight.12

One hypothesis suggests that wings originated as fixed, lateral outgrowths from the thorax that initially functioned as gliding planes for leaping insects. Over time, these structures evolved muscles to control inclination and eventually enabled flapping flight.2

A second hypothesis proposes that wings evolved from large, movable thoracic tracheal gills, similar to those found on the abdomen of some mayfly larvae. These structures may have originally helped insects navigate aquatic environments or disperse via wind.2

Regardless of the specific mechanism, the consistency of wing venation across all winged insects suggests that the evolution of flight occurred only once, with the primitive wingless stock giving rise to the diverse lineages of the Pterygota.21