Posted on: 02 March, 2017
Author: Alexander P
The maximum distance over which a ‘receiver’ insect can orient to pheromone emitted by a ‘sender’ insect depends upon many factors including: 1) pheromone emission rate of the ... The maximum distance over which a ‘receiver’ insect can orient to pheromone emitted by a ‘sender’ insect depends upon many factors including: 1) pheromone emission rate of the sender; 2) behavioral threshold for response to the pheromone by the receiver; 3) wind velocity; 4) length of time the sender releases pheromone; 5) ight speed of the receiver. The first three factors establish the foundation for estimating the theoretical maximum distance of pheromonal chemical communication (Bossert and Wilson 1963; Wilson and Bossert 1963) Less obvious are the factors of length of time the pheromone is released and ight speed of the receiver (Sower et al 1973). The latter variables will not affect the theoretical maximum communication distance if the sender emits pheromone for an indefinitely long, continuous period and the wind velocity is ideal for upwind ight by the receiver. Such ideal conditions probably often occur for some species. However, female moths of Trichoplusia release pheromone for an average period of only 20 min at any one time (Sower et al. 1971), the length of this release period decreasing even further with increased wind velocity (Kaae and Shorey 1972). The maximum distance for communication, then, is limited by the ability of the re- ceiver to reach the chemical source before pheromone emission ceases. Using data on pheromone release rates, male response thresholds and formulae concerning the dispersion of odor molecules in moving air, Sower et al. (1971) calculated that with a wind velocity of 50 cm/sec the mean maximum communication distance for T. ni is 20 m. However, due to the high individual variability of both female release rates and male threshold concentrations, a range of distances from one to approximately 100 m appears realistic. Learn about the pheromone perfume experience. Males have been reported in the literature to y exceptionally long distances (0.8 to 4.5 km) to reach a pheromone source (Rau and Rau 1929; Collins and Potts 1932; Holbrook et al. 1960; Teale 1961). Determinations of these long distances were based on captures of marked male moths released at various distances from female-baited traps. Because of possible upwind movement by the males prior to encountering an above threshold concentration of pheromone, these determinations should not be used as a basis for estimating the absolute maximum distance of communication; such estimates may be greatly exaggerated and unreliable. The above information can be integrated to establish a proposed system for the behavior of a hypothetical ying insect in response to a pheromone (fig. 5.3). When the insect perceives an above threshold concentration of pheromone it may either be resting on a substrate or ying. If the individual is stationary, it is stimulated to initiate ight. Once airborne, the insect steers its body upwind (if anemotaxis is used) and ies in the general direction of the source. If the insect is many meters downwind and the active space is several meters wide and contains a low concentration of molecules, the insect steers more or less in a straight line, turning only when it is in the vicinity of the boundaries of the active space. As the insect ies nearer to the source, the concentration increases and the active space becomes narrower. Source: Free Articles from ArticlesFactory.com Alexander P is a blogger from Los Angeles who studies pheromones.