Pheromones are special chemicals produced and secreted by living creatures, in small amounts, for a variety of purposes. Organisms use them to signal something (danger, territory, readiness to mate and so on) to another member of their social group or species.
In many ways, pheromones are like hormones that act outside of the body. In fact, they bore the name ectohormones before researchers Peter Karlson and Martin Lüscher proposed a new word in 1959, deriving the term "pheromone" from the Greek word pherein (to bear or transport) and hormone (to stimulate or excite). Pheromones produce two general categories of effects: releaser effects, which cause rapid behavioral changes, and primer effects, which prepare the body for a later behavioral change. Pheromones can also affect biological processes such as maturation [source: Winn].
Pheromones are found throughout the insect and vertebrate worlds, among crustaceans and even in plants. They play a particularly important role among certain social insects, such as ants and termites, which use a variety of pheromones to organize and direct the goings-on in their respective colonies. Even fungi, slime molds and algae use pheromones to attract one another for reproduction.
A few examples of pheromone uses include:
- Ants laying a trail of scent pheromones to lead other colony members to a food source
- Wounded minnows exuding a pheromone that causes the rest of the school to scatter
- Insects releasing a pheromone into the air, signaling their readiness to copulate
- Queen bees giving off a pheromone that inhibits ovarian development in other bees, eliminating competition
Organisms may distribute pheromones via a variety of mechanisms, including spraying them into the surrounding air or water or distributing them via urine. The chemicals linger for varying periods of time depending on their use. Danger signals disperse quickly, lest the recipients of the signal become overwhelmed by them or overly accustomed to them. Sexual signals persist longer to allow mates to locate the sender, but this also increases the danger of unwanted attention from parasites and predators. Marking signals, such as those used by animals to stake out territory or by egg-laying insects to warn others to lay their eggs elsewhere, last longer still.
Pheromones can be a powerful means of controlling behavior. Entomologists use them as a lure for trapping insects that they intend to study. Pheromones can also be employed to control undesirable populations by disrupting mating behaviors, preventing egg-laying and in general, introducing confusion.
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