a figure from the essay
Homeotic Genes and the Evolution of Anthropods and Chordates
by Sean B. Carroll

Figure 4 (from page 78 of Shaking the Tree: Readings from Nature in the History of Life edited by Henry Gee)

Hox genes and the morphological divergence of homologous structures. The forewings and hindwings differ between insects, and usually from each other. Based on the developmental genetics of wing formation in Drosophila and comparisons of homeotic gene expression and function between insects, it appears that forewing patterns evolve independently of homeotic genes, whereas hindwing patterns are Ubx-regulated modifications of the respective forewing patterns. In primitive four-winged insects the forewings and hindwings appear similar but have evolved quite different morphologies in various insect orders. The different hindwing morphologies are probably due in part to the divergence of the potentially large sets of wing-patterning genes regulated by Ubx in different orders. This divergence is brought about by changes in cis-regulatory sequences in target genes that affect their regulation by Ubx.

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About the book: Shaking the Tree: Readings from Nature in the History of Life edited by Henry Gee, published by the University of Chicago Press.