Estimating insect flight densities from attractive trap catches and flight height distributions

Methods and equations have not been developed previously to estimate insect flight densities, a key factor in decisions regarding trap and lure deployment in programs of monitoring, mass trapping, and mating disruption with semiochemicals. An equation to estimate densities of flying insects per hectare is presented that uses the standard deviation (SD) of the vertical flight distribution, trapping time, the trap's spherical effective radius (ER), catch at the mean flight height (as estimated from a best-fitting normal distribution with SD), and an estimated average flight speed. Data from previous reports were used to estimate flight densities with the equations. The same equations can use traps with pheromone lures or attractive colors with a measured effective attraction radius (EAR) instead of the ER. In practice, EAR is more useful than ER for flight density calculations since attractive traps catch higher numbers of insects and thus can measure lower populations more readily. Computer simulations in three dimensions with varying numbers of insects (density) and varying EAR were used to validate the equations for density estimates of insects in the field. Few studies have provided data to obtain EAR, SD, speed, and trapping time to estimate flight densities per hectare. However, the necessary parameters can be measured more precisely in future studies.