The Effect of Insecticides Considered Harmless to Honey Bees <I>(Apis mellifera)</I>: Proboscis Conditioning Studies by Using the Insect Growth Regulators Tebufenozide and Diflubenzuron

Abstract

Experiments were designed to examine the effects of the IGRs tebufenozide and diflubenzuron on Pavlovian conditioning of harnessed foragers. In one set of experiments, animals learned a simple task in which they associated a conditioned stimulus with feeding. A second set of experiments required the animal to learn a complex discrimination task. Within each experiment, separate groups of bees were pretreated with the insecticide, whereas others received the insecticide imbedded in the sucrose solution used as the unconditioned stimulus. Results indicated that exposure to both tebufenozide and diflubenzuron influence the performance of honey bees. Bees pretreated with 10 μl of tebufenozide, 10 min before learning a simple Pavlovian task, produced lower levels of acquisition when the concentrations were administered in dosages equivalent to 0.22, 0.29, and 1.0 liter/ha. When animals were given a series of 1-μl droplets of diflubenzuron over the course of 12 training trials, the effect on acquisition and extinction was even more pronounced. No such effects were seen when tebufenozide was used. Discrimination learning was also influenced in bees pretreated with the insecticides or having the insecticides imbedded in the unconditioned stimulus.