Results/Conclusions We used a reversal learning paradigm to establish that monarch butterflies learn to discriminate against colored artificial flowers that contain salt solution, decreasing both number and duration of probes to flowers of a preferred color and altogether avoiding those of a non-preferred color. In addition, when we offered butterflies artificial flowers of two different colors, both of which contained the same mean nectar volume but which differed in variance (flowers of one color all contained 2 ul of sucrose solution; flowers of the other color contained 4 ul sucrose or none at all), the monarchs exhibited risk-averse foraging: they probed the constant flowers significantly more than the variable ones, regardless of flower color. Our results demonstrate that monarchs can respond to aversive as well as appetitive stimuli, and can also adjust their foraging behavior to avoid floral resources with high variance rewards.