‘It would be too bad if the question of head segmentation ever should be finally settled; it has been for so long such fertile ground for theorizing that arthropodists would miss it as a field for mental exercise’. Snodgrass, 1960 (cited by Rempel, 1975)
The development of the Drosophila embryo has provided an excellent model system for the analysis of embryonic pattern formation. In little more than a decade, many of the elements of the molecular genetic cascade underlying early development have been identified. However, these studies have focused primarily on the development of the central, overtly segmented region of the fruitfly embryo. As the influential insect morphologist R. E. Snodgrass pointed out, understanding of the formation of the complex embryonic head region has advanced quite slowly. Recently, however, substantial progress has been made in the identification and analysis of the genes determining head development. These studies are generating...
