A substance that acts as a molecular messenger, transmitting information from one member of a species to another member of the same species. The first pheromone to be characterized chemically was bombykol, an unsaturated, straight-chain alcohol that is secreted in microgram amounts by females of the silkworm moth (Bombyx mori) and is capable of attracting male silkworm moths at large distances. The electroantennogram (EAG) technique was developed in connection with this work; the electrical signals that are generated by the pheromone stimulation of an insect's chemoreceptor cells are recorded and analyzed.