Bumblebee preference for nicotine-enriched nectars. Individual preferences (mean value of 100 choices) of bees (n = 60, 20 each nicotine concentration) for the flower type associated with nicotine-laced sucrose solution during a foraging choice test. Bees are deterred only by unnaturally high nicotine concentrations (50-ppm). This deterrence disappears or turns into attraction at lower nectar-relevant concentrations (1 and 2.5-ppm). Red dots represent individual bees, while the black bars indicate the mean value for each group. The grey line indicates random choice level. *P = 0.001.