Fig. 4.

Pesticides affect odour discrimination during olfactory recall tests. A discrimination index was calculated to measure when bees responded to the conditioned stimulus (CS) at a greater rate than to a novel odour during the 10 min and 24 h recall tests. Values greater than zero reflect a preference for the CS over the novel odour; negative values reflect a preference for the novel odour. (A–C) Bees tested after massed conditioning with imidacloprid (A), coumaphos (B) or imidacloprid plus coumaphos (C). (D–F) Bees tested after spaced conditioning with imidacloprid (D), coumaphos (E) or imidacloprid plus coumaphos (F). Sample sizes and pairwise comparison statistics for all treatments and doses are shown in Table 4; recall response rates to the CS and the novel odour are reported in supplementary material Fig. S1.