Modelling female mating success during mass trapping and natural competitive attraction of searching males or females

Simulation models of insects encountering sex pheromone with or without mass trapping in which the searching sex is either male (moths and many insect species) or female (some true bugs, beetles, and flies) were developed. The searching sex moved as a correlated random walk, while the opposite sex remained stationary (calling) and released an attractive sex pheromone. The searching sex was caught when encountering a pheromone-baited trap, and females mated when encountering a male. An encounter with pheromone was defined by the searcher’s interception of a circle termed the effective attraction radius (EARc). Parameters of movement (speed and duration), initial numbers of calling sex and searching sex, number of traps, area, and EARc of traps and calling sex were varied individually to evaluate effects on the percentage of females mating. In the natural condition without traps, female mating success in both models was identical. Increasing the EARc of the calling sex caused diminishing increases in female mating success, suggesting that evolution of larger pheromone release and EARc is limited by increasing costs (production/sensitivity) relative to diminishing increases and benefits of mating encounters. With mass trapping, increasing the EARc of traps or density of traps caused similar declines in female mating in both models, but the female-searching model predicted slightly lower mating success than the male-searching model. Increasing the EARc of calling insects or the initial density of insects caused similar increases in female mating in both models, but again the female-searching model had slightly lower mating success than the male searching model. The models have implications for mating lek formation and for understanding the variables affecting the success of mass trapping programs for insect pests with either male or female sex pheromones