Comparison of Acoustical Detection of Several Species of Stored-Grain Beetles (Coleoptera: Curculionidae, Tenebrionidae, Bostrichidae, Cucujidae) Over a Range of Temperatures

Abstract

Acoustical detection of five species of adult stored-product insects in 1-kg samples of wheat was compared. Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) were detected during more 10-s intervals than Rhyzopertha dominica (F.); Cryptolestes ferrugineus (Stephens) and Oryzaephilus surinamensis (L.) were detected less frequently than other species. These species were also distinguishable by differences between the probability distributions of the numbers of sounds per 10-s interval. The probability distributions decreased logarithmically with increasing numbers of sounds. The number of sounds for three species varied with temperatures between 17.5 and 37.5°C. The number of sounds of S. oryzae increased as the temperature increased from 17.5 to 35°C and then decreased at higher temperatures. The number of sounds of T. castaneum tended to be lowest at <25°e and then increased steadily as temperature increased. The number of sounds of R. dominica increased as temperature increased from 17.5 to 30°C and then became level at higher temperatures. We also investigated the possibility of finding larger differences in acoustical signals between species by using different instrument settings for the filter which eliminates sounds above and below a selected frequency range and the counter which determines the number of sounds producing voltages above a selected threshold. Widening the filter frequency range increased the number of background sounds as much as it increased the number of insect sounds; thus, it did not increase our ability to distinguish between species. Raising the counter voltage threshold resulted in a logarithmic decrease in the number of sounds for all insect species. These data should make it possible to distinguish between some species of adult insects using acoustical detection data, and to adjust the estimates of insect density made using acoustical detection by removing the effects of temperature.