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In hemimetabolan insects, the transcription factor Broad complex (Br–C) promotes wing growth and development during the nymphal period. We wondered whether Br–C could trigger the initiation of wing development, using the cockroach Blattella germanica as a model. We show that first instar nymphs have their unique identity of these three thoracic segments specified. During embryogenesis, the expression of Br–C and some wing-related genes show two matching waves. The first takes place before the formation of the germ band, which might be involved in the establishment of various developmental fields including a potential “wing field”, and the second wave around organogenesis, possibly involved in the initiation of wing development. However, the expression of Br–C in early embryogenesis concentrates in the developing central nervous system, thus not co-localizing with the expression of the typical wing-related gene vestigial, which is expressed at the edge of the thoracic and abdominal segments. This suggests that Br–C is not specifically involved in the establishment of a potential “wing field” in early embryogenesis. Moreover, maternal RNAi for Br–C depletes the first wave of Br–C expression but does not affect the early expression of wing-related genes. As maternal Br–C RNAi did not deplete the second expression wave of Br–C, we could not evaluate if Br–C is involved in the initiation of wing development. Alternatively, using nymphal RNAi of Br–C and Sex combs reduced (Scr), we show that Br–C contributes to the formation of ectopic wing structures that develop in the prothorax when Scr is depleted. The gene most clearly influenced by Br–C RNAi is nubbin (nub), which, in nymphs is crucial for wing growth. Together, these results suggest that Br–C does not specifically contribute to the establishment of the “wing field”, but it does seem important later, in the initiation of wing development, enhancing the expression of wing-related genes, especially nub. This supports

The acquisition of wings has facilitated the massive evolutionary success of pterygotes (winged insects), which now make up nearly three-quarters of described metazoans. However, our understanding of how this crucial structure has evolved remains quite elusive. Historically, two ideas have dominated in the wing origin debate, one placing the origin in the dorsal body wall (tergum) and the other in the lateral pleural plates and the branching structures associated with these plates. Through studying wing-related tissues in the wingless segments (such as wing serial homologs) of the beetle, Tribolium castaneum, we obtained several crucial pieces of evidence that support a third idea, the dual origin hypothesis, which proposes that wings evolved from a combination of tergal and pleural tissues. Here, we extended our analysis outside of the beetle lineage and sought to identify wing-related tissues from the wingless segments of the cockroach, Blattella germanica. Through detailed functional and expression analyses for a critical wing gene, vestigial (vg), along with re-evaluating the homeotic transformation of a wingless segment induced by an improved RNA interference protocol, we demonstrate that B. germanica possesses two distinct tissues in their wingless segments, one with tergal and one with pleural nature, that might be evolutionarily related to wings. This outcome appears to parallel the reports from other insects, which may further support a dual origin of insect wings. However, we also identified a vg-independent tissue that contributes to wing formation upon homeotic transformation, as well as vg-dependent tissues that do not appear to participate in wing formation, in B. germanica, indicating a more complex evolutionary history of the tissues that contributed to the emergence of insect wings.