It is a well-documented fact that pheromones are chemicals that are secreted by animals and insects. These chemicals are secreted in very small quantities but affect social behavior within the same species. These chemicals are secreted externally. Insects in particular are believed to secrete these bio-chemicals. There is a specific purpose behind the secretion of these chemicals. These chemicals trigger a social or physiological response in members of the same species.

For instance, at the time of mating many female elephants secrete a special chemical that tells a male elephant that she is ready to mate. This is a sexual response. Sometimes animals and insects like to leave a trail behind them as a marker. Lions and tigers mark their territory with such secreted chemicals. In such a case, these chemicals are a part of the urine of the tiger or lion marking its territory. Urine is sprayed in the region to be market as its territory.