Fig. 5: The development and evolution of the wing blade from the lateral tergal margin.
A resemblance of the dorsoventral distribution of wg/ap/vg between Pedetontus10 and Gryllus indicates that nymphal terga are patterned in a similar fashion. The similar distribution is known in the Drosophila wing disc at the late second instar18, which implicates a timing shift of the patterning event from embryonic to larval stage. vgBE activity in Drosophila is required to initiate expansion of the wing compartment via vg FF signaling transduced through actions of vgQE, Wg, and Ft-Ds and Hippo pathways31. Analogously, the vg-dependent tergal margin organizes the wing growth in Gryllus, and Wnt, Ft-Ds and Hippo pathways drive dramatic expansion during postembryonic development. A growth mechanism like that in Drosophila was employed at the lateral tergum of an ancestral apterygote insect to form the body wall extension required for the evolution of insect flight.
