Pheromone is a secretion by an animal to influence the behavior or development of members of its own species. Pheromones, sometimes called "social hormones," are produced by a wide variety of animals, including insects, fish, and mammals. They affect or trigger many types of biological activities: growth, mating, movement, social grouping, alarm behavior, and numerous others. Animals may often leave scent trails of pheromones, which allow others of their species either to follow them or be warned away. Pheromones are distinct chemicals which, when used experimentally by man, achieve results identical to those obtained by the animals themselves. They are a strictly chemical means of communication among many creatures, which they smell, taste, or sense in some other way.
Among the more interesting pheromones are the sex attractants of certain insects. The female secretes a pheromone so potent that minute quantities can be detected by a male of her species from a distance of several miles, enabling him to follow the scent to the female and mate with her. Such pheromones are used by man to lure and trap injurious insects.
Other pheromones may regulate physiological changes. In certain species of grasshoppers, for example, the males secrete a hormone that speeds the growth of the young grasshoppers. Mature termites may release pheromones that arrest the sexual development of young termites.
Ants frequently use pheromones as scent trails that workers follow to sources of food and as alarms to mobilize the nest against impending danger. Substances resembling alarm pheromones also serve as chemical-warfare agents against other insects.
Many mammals secrete pheromones that help regulate their sexual, parental, and territorial behavior. For example, many female primates (including the human female) are known to release aliphatic-acid pheromones in vaginal secretions. Among most primates these pheromones are sex attractants, but to what extent they are functional in humans is not known.
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