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o aim of identifying the neural mechanisms that underpin condi- by two pathways: either by association of an odor withalmond-nectar toxin, amygdalin. To assess whether the gusta-hibited PER toward the odor on the third trial was 70%–90% less than its expected level for sucrose alone (Figure 2A).*Correspondence: jeri.wright@ncl.ac.ukthe honeybee’s sensitivity to two toxins, quinine and thetioned food aversions. We first established whether bees could preingestively detect toxins in food. Using a combination of behavioral and electrophysiological techniques, we tested tory sensilla on the proboscis (mouthparts) were sensitive to the presence of toxins (Figures 1A and 1B), we stimulated a reflexive taste aversion toward a toxin or by association of an odor with the malaise caused by toxin ingestion. Using an olfactory conditioning paradigm for PER, honeybees were conditioned to associate an odor with either a sucrose-quinine solution or a sucrose-amygdalin solution by first touching the antenna with 1.0 M sucrose and then presenting the sucrose-toxin solution to the proboscis. When conditioned with the sucrose-quinine solution, the probability that a honeybee ex-Parallel Reinforcement Path