Flight or protection: the genes and in the determination of membranous and sclerotized wings in insects.

Present-day pterygote insects have two pairs of wings, one in the mesothorax (T2), the other in the metathorax (T3), and both have diverged in structure and function in different groups. Studies in endopterygote and paraneopteran species have shown that the gene () specifies the identity and wing structure in T3, whereas the gene () significantly contributes to forming modified T2 wings. We wondered whether these and mechanisms operate in the lineage of polyneopterans. To explore this possibility, we used the cockroach (Polyneoptera and Blattodea), in which the T2 wings are sclerotized (tegmina), whereas those of the T3 are membranous. We found that determines the structure of T3 and the membranous wing, while significantly contributes to form the sclerotized T2 tegmina. These results along with the studies carried out on the beetle by Tomoyasu and collaborators suggest that plays an important role in the sclerotization and melanization of the T2 wings in neopteran groups that have sclerotized forewings. In turn, the sclerotizing properties of demonstrated in beetles and cockroaches suggest that the origin of this function goes back to the emergence of Neoptera, in the mid Devonian.