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Harvard Research Identifies Foraging and Social Impacts of Neonics on Bees

Two studies at Harvard have linked a decrease in foraging and social behavior in bumblebees to sublethal exposure to imidacloprid.


Bombus impatiens, or the common eastern bumblebee, is predominantly found across eastern North America. They nest underground and have many food sources including roses, goldenrods, and impatiens.

Harvard postdoc James Crall and PhD student Callin Switzer have conducted two studies observing the effects of neonicotinoid exposure on the common eastern bumblebee.

Crall created an artificial nest area for a group of bumblebees, and allowed them time to adjust to their surroundings. Each bee in the colony was tagged so that a computer could track the movement of individual bees within the nest. After tagging, the bees were observed before and after being exposed to imidacloprid, one of the more common neonicotinoid pesticides.

Evaluation of the data points tracked by the computer indicated that after exposure, bees reduce the frequency of brood care and spend more time alone on the perimeter of the nest. In healthy nests, the larvae are at the center and are cared for by smaller bees, while larger workers and foragers are on the periphery. When these behaviors change, populations are more susceptible to decline.

Switzer studied the effects of neonicotinoid exposure on buzz pollination, which is the ability of bumblebees to forage on and pollinate plants using vibrations. Bees were recorded foraging on tomato blossoms. They were exposed to imidacloprid and allowed to resume foraging.

Bees exposed to the pesticide at levels similar to what would be encountered in a single day were less likely to resume foraging than bees that had no pesticide exposure at all. This could lead to lessened crop production and food supplies for the colony.

Both research projects were presented separately at the Society for Integrative and Comparative Biology's 2017 Annual Meeting, held Jan. 4-8.

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August 22, 2019, 1:20 am PDT

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