Detection of Hidden Insect Infestations by Feeding-Generated Ultrasonic Signals

Abstract

Insects living hidden within seeds, wood, and certain other fibrous plant materials can be detected by the ultrasonic signals emitted when the insects feed on their organic substrate. Using cowpea weevil, Cal/osobruchus macuJatus (E), developing in cowpea seeds as our model, we have detected feeding activity by monitoring ultrasonic emissions at 40 KHz. The ultrasonic signals are produced when the insects strike the seed tissue during feeding, but not when they move in their tunnels. With cowpea weevil, feeding events can be detected from the early first ins tar through the last ins tar. The numbers of feeding events per unit time is directly proportional to the number of insects per seed. Many different species f hidden feeders can be detected by this technique, including other bruchids in a variety of legume seeds, SitophiJus spp. feeding in maize, lesser grain borer, Rhyzopertha dominica (E), feeding in rice, and termites feeding in wood. Ultrasonic monitoring should enable far greater insight into the life histories of insects feeding hidden within dry materials than has been possible by conventional techniques. Because the natural environment is relatively free of ultrasonic noise, monitoring insect activity is subject to little interference by extraneous signals. The biomonitor, the electronic detector device developed to study the biology of feeding behavior, may have numerous practical applications, including early detection of hidden infestations, grain quality assessment, and rapid evaluation of efficacy of fumigation procedures.