Analysis of Physiological Alterations in Development and Mating Behavior by Ultrasound Treatment in the Beet Armyworm, Spodoptera exigua

Some high frequency sounds alter physiological processes of the beet armyworm, Spodoptera exigua. This study investigated the effect of ultrasound ( 20 kHz) on larval feeding, pupal development, and adult mating behavior of S. exigua. Ultrasound suppressed feeding behavior of fifth instar larvae, and 30 or 45 kHz treatment inhibited more than 50% of feeding activity. Larvae treated with ultrasound exhibited alterations in major nutrient compositions in the hemolymph plasma. Plasma protein levels decreased with an increase in ultrasound frequency. In contrast, sugar levels increased with an increase in ultrasound frequency. Lipid levels increased with an increase in ultrasound frequency up to 30 kHz and then decreased at treatments > 30 kHz. Hemocytes, the fat body, and epidermis expressed three heat shock proteins and apolipophorin III. Ultrasound treatment markedly inhibited expression of some stress-related genes. Ultrasound treatment also inhibited S. exigua pupal development by extending the pupal developmental period and preventing adult emergence. Last, ultrasound treatment significantly inhibited adult mating behavior, which resulted in a significant decrease in female fecundity. These results show that ultrasound is a physiological stress to S. exigua.