Figure 31.28 The Origin of Insect Wings? Insect wings may be derived from an ancestral appendage similar to that of modern crustaceans. (A) A diagram of the ancestral, multibranched arthropod limb. The uppermost dorsal branch may have been used for gas exchange. (B, C) The pdm gene, a Hox gene, is expressed throughout the dorsal limb segment of the thoracic limb of a crayfish (B) and in the wings of Drosophila (C).