Pheromones are chemicals secreted in small amounts by an organism, that triggers a social response in members of the same .
These chemicals are secreted by special glands or incorporated in other substances like urine. Chemically pheromones affect the nervous system and bring about physiological changes , inflammatory signalling, immune system changes or behavioural changes in the recipient.
Pheromones are widely found in insects, vertebrates and crustaceans, but are unknown in birds.
Ants usually lay scent pheromones trails leading to a food source. Some animals use it to signal the prescence of danger. Territorial pheromones mark the boundaries and identity of an organism’s territory. Pheromones are widely used to promote aggregation or transmit messages needed to co ordinate the complex activities of a colony of insects. Pheromones are also used by some fungi, slime moulds and algae as attractants in reproduction.