Figure 1.

(A) Phylogenetic relationship of four major types of endopterygote insects and their wing morphology. The dendrogram was drawn based on the relationship reported in Zdobnov and Bork (2007)³⁹. This traces the divergence of 4 major orders of endopterygote insects for nearly 350 million years. Hymenopterans diverged first, then Coleopterans followed by separation of Lepidoptera and Diptera. They are represented by Apis, Tribolium, Bombyx and Drosophila, respectively. Forewing and hindwing morphology of each insect is shown in the panel on the right side. Note, while Apis and Bombyx show near identical fore- and hindwings, in Tribolium, the forewing is modified into a thick protective organ called elytra. In Drosophila, the hindwing is modified into small club shaped organ called haltere. (B–G) Expression patterns of Ubx in developing fore- and hindwing in Apis and Bombyx. (B,C) Forewing (B) and hindwing (C) buds of 5^th instar Apis larvae stained with anti-Ubx_Apis antibodies. Note, Ubx is expressed in both the wingbuds, while levels are marginally higher in the hindwing buds. (D,E) Forewing (D) and hindwing (E) buds of 4^th instar Bombyx larvae stained with anti-Ubx_Bombyx antibodies. While Ubx is expressed in the hindwing proper, its expression in the forewing bud is restricted to only the peripodial membrane (arrows). D’ and E’ show the same discs as in (D) and (E), respectively showing both DAPI (blue) and anti-Ubx_Bombyx (green) staining. (F,G) Wing (F) and haltere (G) discs of 3^rd instar Drosophila larvae stained with anti-Ubx_Drosophila antibodies. Ubx is strongly expressed in haltere cells, while its expression in the wing disc is restricted to the peripodial membrane. In (B–E), proximal end is shown towards the left and the distal end towards the right. In (F,G), anterior is towards left and ventral up.