Effects of a Common Neonicotinoid Pesticide on Mason Bee (Osmia lignaria) Locomotion

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Bees have long since been important pollinators—contributing to plant biodiversity across ecosystems, and by increasing agricultural yield around the world. While many stressors have been thought to affect bee health, researchers now hypothesize that neonicotinoid pesticides have a larger impact on these pollinators than previously thought. In particular, we investigated the behavioral effects of field realistic, sub-lethal doses of a neonicotinoid pesticide, clothianidin, which is commonly used in agriculture. To better understand how this pesticide influences bee health, we studied its effects on the locomotion and phototaxis of Osmia lignaria (mason bees), Megachile rotundata (leafcutter bees), and Apis mellifera (honey bees) by using a phototaxis arena and video tracking software. The goal of this experiment is to determine if sub-lethal neonicotinoid exposure alters typical bee motor functions, activity and phototaxis —including an inability to walk in a coordinated manner and perhaps even premature death. While this is an on-going research project, preliminary results from our testing on Osmia lignaria indicate that exposure to clothianidin has a significant effect on hyperactivity, as seen through increased velocity (p=0.038), and decreased time spent stationary (p< 0.001). There was also a significant (p=0.018) increase in falls thirty minutes after exposure to clothianidin when compared with mason bees given the control sucrose solution treatment. While there is more data to be analyzed, these early results may suggest a decrease in the mason bee’s ability to serve as an effective pollinator, due to a combination of hyperactivity and loss of coordination. This work is important in helping us determine, at least in part, why multiple bee species have declined globally. It is especially vital to look critically upon the health of these pollinators given their economic value to agriculture, food security, and their importance for pollinating natural ecosystems.