(Science: endocrinology) A volatile hormone or behaviour modifying agent. Normally used to describe sex attractants for example bombesin for the moth bombyx, but includes volatile aggression stimulating agents (e.g. Isoamyl acetate in honey bees). A chemical substance secreted externally by some animals (especially insects) that influences the physiology or behavior of other animals of the same species.A chemical that is used by animals (and some plants) as a method of communication. Examples include pheromones present in dog urine which marks its territory or can also be used in organisms to attract a mate of the opposite sex.