Descending protocerebral neurons in the male silkworm moth brain responding to the sexual pheromone (Bombykol) were identified. The neurons responded well with a tonic type of response and the high-frequency spikes evoked continued even after the end of the stimulus. Characteristics of the dose-response curves of the neurons to the pheromone remarkably resembled those of the wing vibration which is one of the mating behavioral components of the male moths.