Posted on: 02 March, 2017
Author: Alexander P
Pheromones are produced by specialized glands in insects of one sex and elicit a behavioral response in the opposite sex. In most cases, the producing sex does not release the pheromone continuously t... Pheromones are produced by specialized glands in insects of one sex and elicit a behavioral response in the opposite sex. In most cases, the producing sex does not release the pheromone continuously throughout its adult life. Nor does the responding sex typically display a constant degree of responsiveness to the pheromone. Instead, certain physiological factors within the insects themselves and certain properties of the environment in which the insects live control the occurrence and the timing of pheromone communication. The manner in which sex pheromones are used in the premating communication between a male and female may vary considerably from one species to the next. Males of many species, perceiving the sex pheromone released from conspecific females, exhibit a sequence of behavioral steps, in a hierarchical manner. For in- stance, the female sex pheromone of many species of Lepidoptera and Coleoptera may cause: 1) activation of a resting male; 2) his oriented approach toward the pheromone source; and 3) various short-range behavioral reactions, often termed ‘courtship’, that serve to stimulate the female to mate (Shorey 1973). Most investigators of the inuence of environmental and physiological variables on pheromone behavior have not examined the effect of these factors on each step in the behavioral hierarchy. Rather, most experiments designed to evaluate pheromone responsive- ness as inuenced by these variables have been conducted using laboratory bio- assays, which mainly measure the activation reaction, or pheromone-baited traps, which measure the oriented approach reaction. Experiments evaluating the inuence of the variables on the pheromone-producing sex are also often conducted under conditions far removed from the natural situation. Despite the necessary artificiality of most experiments, the accumulating published data are starting to show how adaptive — how appropriate to the conditions existing in and around them — is the sex pheromone communication system of insects. Three aspects of pheromone communication have been investigated with regard to the controlling inuence of environmental and physiological variables. This can be altered by dealing with pheromones signals. Insect sex pheromone behavior The release of pheromone by the sex which initiates the communication sequence; and 3) response to the pheromone by a member of the opposite sex. Unfortunately, investigators have often failed to differentiate the first two aspects, and experiments demonstrating the amount or timing of release of pheromone are often erroneously claimed to give the amount or timing of pheromone produced. Where possible, quantitative changes in levels of these three aspects, as influenced by changes in the controlling variables, will be considered in this chapter. The relative level of responsiveness by the sex receiving the pheromone can be determined for many species by laboratory bioassay techniques. The relative level of pheromone production can also be determined quantitatively by extracting the pheromone glands or even the entire bodies of the producing insects in an appropriate solvent, followed by bioassay or gas chromatographic analyses. The level of pheromone release, however, is often not determined. Rather, the extrusion of a pheromone gland or the attraction of members of the opposite sex to the releasing individual are commonly used as all-or-none indications of the occurrence of releasing behavior. Article Tags: Pheromone Behavior, Pheromone Communication, Many Species Source: Free Articles from ArticlesFactory.com Alexander P is a blogger in Los Angeles who studies pheromones.