All olfactory discrimination experiments were performed using three modified eight- channel olfactometers ([61], Knosys, Bethesda, Maryland, United States of America) operated by custom-written software in Igor (Wave Metrics, Lake Oswego, Oregon, United States of America) on Pentium I, II, and III PCs running Microsoft Windows 98. Great care was taken to counterbalance groups between setups. In brief, animals were presented with odor from one out of eight possible odor channels and rewarded with a 2- to 4-μl drop of water in a combined odor/reward port (Figure 1B), ensuring tight association of the water-reward with a presented odorant. Head insertion into the port was monitored by an IR beam and photodiode (Figure 1B). Odors used were n-amyl acetate, ethyl butyrate, pelargonic acid, valeric acid, and binary mixtures of cineol and eugenol. If not otherwise noted, odors were diluted to 1% in mineral oil (Fluka Chemie, Steinheim, Germany) and further diluted by airflow to a final concentration of approximately 0.15%. All dilutions in the text refer to the dilution in mineral oil. All chemicals were obtained from Fluka Chemie.