A chemical secreted by an animal, especially an insect, that influences the behavior or development of others of the same species. Pheromones are found throughout the living world. The complex but primitive single-celled amoeba Dictyostelium, for example, uses a pheromone to attract others of its kind for reproduction. Insects regularly use pheromones for the same purpose. Ants, for example, usually have a pheromone for marking trails to food, another for starting attacks on enemies, a third that signals the need to flee, and others that identify their larvae in the darkness of the nest.
Pheromones are also common in vertebrates.
Mammals regularly mark their territorial boundaries with pheromones from specialized glands. These odors can be detected at great distances and can alter behavior dramatically. Vertebrates also have additional odors that identify animals individually. Neighboring mammals of many species recognize one another by the odors that each leaves along mutual boundaries or at traditional scenting posts, and intruders are detected almost immediately . Even mates and offspring often recognize one another by odor.