No evidence for neonicotinoid preferences in the bumblebee Bombus impatiens

Neonicotinoid pesticides can have a multitude of negative sub-lethal effects on bees. Understanding their impact on wild populations requires accurately estimating the dosages bees encounter under natural conditions. This is complicated by the possibility that bees might influence their own exposure: two recent studies found that bumblebees (Bombus terrestris) preferentially consumed neonicotinoid-contaminated nectar, even though these chemicals are thought to be tasteless and odourless. Here we used Bombus impatiens to explore two elements of these reported preferences, with the aim of understanding their ecological implication and underlying mechanism. First, we asked whether preferences persisted across a range of realistic nectar sugar concentrations, when measured at a series of time points up until 24 hours. Second, we tested whether bees’ neonicotinoid preferences were driven by an ability to associate their post-ingestive consequences with floral stimuli such as color, location,...