The dorsal head vertex of Drosophila is specified mainly by the orthodenticle (otd) gene. The expression and the function of otd are regulated by the concerted action of many genes including hedgehog (hh) and notch (N). These genes are components of a meshwork of signaling transduction pathways that interact to form the dorsal head capsule of the fruit fly. Loss-of-function Hh mutants lack ocelli; however, loss-of-function N mutants lack a different domain of the dorsal head vertex. This report provides new evidence that the Hh and N pathways are two epistatic signaling cascades that act genetically upstream of the dorsal head capsule specification gene.