The Effects of Silver and Potassium Iodide on Honey Bee (Apis mellifera) Learning

Silver iodide (AgI) and potassium iodide (KI), which are used in cloud seeding, were administered to bees in a variety of pretreatments (low or high dosing) and analyzed through a series of experiments to determine the effect on bees' ability to learn. Cloud seeding is the process of dispersing chemicals into an already-formed cloud to attract water molecules that fall to Earth as rain or snow. These chemicals then enter the ecosystem through water and soil. Honey bees were used because they represent a robust and ecologically appropriate model organism to study the behavioral impacts of cloud seeding. The first experiment utilized a shuttle box to test whether honey bees could avoid shock in a punishment experiment. Results revealed that the majority of the pretreatments did inhibit bees' ability to learn to avoid shock. Experiment 2 consists of two proboscis extension reflex experiments (PER) where bees are trained to associate an odor with a sucrose feeding. Using the PER paradigm, we investigated simple conditioning and odor discrimination. Results revealed that in both the simple conditioning and discrimination experiments, learning was inhibited by the pretreatment of chemicals regardless of dosing amount. The final experiment explored reward discrimination in a free-flying flower patch paradigm. Results revealed that learning ability was not affected; however, return times were greatly impacted. Overall, results showed that AgI and KI throughout each experiment (i.e., shuttle box, PER, and free-flying discrimination) had some degree of negative effect on honey bee behavior.