Male heliothine moths can discriminate and respond to the sex pheromone of conspecific females by using a sophisticated olfactory receptor system. Several different types of olfactory sensilla housing functionally identical olfactory receptor neurons (ORNs) are involved in the reception of conspecific as well as interspecific pheromone components. The olfactory signals elicited in each neuron are received and processed by the interneurons in knots of neuropil, called glomeruli, in the antennal lobe. We examined the projection pathways of ORNs into their target glomeruli in the antennal lobe, using a cobalt backfilling method after electrophysiologically identifying the ORNs within the sensilla of male Helicoverpa zea moths. The pheromone-compound-specific characteristics and the topographic arrangement of the target glomeruli of each type of ORN were further clarified with use of a calcium imaging technique in which the real-time synaptic activities involving calcium release with glomeruli were recorded in response to individual pheromone-related compounds. The results from single-sensillum recording, cobalt staining, and calcium imaging showed that there is a highly consistent linear pathway specific to each pheromone compound from ORN to glomerulus to higher-order interneurons.