Pheromones are chemicals produced as messengers that affect the behavior of other individuals of insects or other animals. They are usually wind borne but may be placed on soil, vegetation or various items. Tom Eisner, a foremost authority in the science of chemical use by insects, claims that each species of insect relies on some one hundred chemicals in its life, to engage in such routine activities as finding food and mates, aggregating to take advantage of food resources, protecting sites of oviposition, and escaping predation. It has been found that pheromones may convey different signals when presented in combinations or concentrations.
Pheromones differ from sight or sound signals in a number of ways.
They travel slowly, do not fade quickly, and are effective over a long range. Sound and sight receptors are not needed for pheromone detection, and pheromone direction is not limited to straight lines. Examples of pheromone use by insects and spiders. Pheromones have long been known to be important to the lives of insects in mating, as witnessed, for example, in some of the larger silkworm family moths, where males are noted to travel nearly 30 miles to a female, following a pheromone trail in the air. Male Cecropia moths are estimated to detect and respond to a few hundred molecules of pheromone in a cubic centimeter of air.