In laboratory wind tunnel studies, quiescent Korscheltellus gracilis (Grote) females initiated wing fanning as light intensity was reduced to 25–11 lx at the end of a 16-h, 450-lx photophase. Males downwind of a wing-fanning female initiated wing fanning, rapid walking, or both, and upwind flight toward the female typically ensued shortly thereafter. Wing-fanning females whose abdomens had been removed, and excised hind wings of females evoked the same male responses, but females whose hind wings had been removed evoked no male response. The sex pheromone of K. gracilis evidently is released from the female’s hind wings, a so far unique site of pheromone release in female Lepidoptera. The importance of this finding to understanding the mating system of hepialids and the ancestral form of pheromone release among the Lepidoptera is considered.