Household mosquito repellents may stop bumblebees from finding their way home

A chemical used in mosquito repellents may disorient bumblebees, stopping them from finding their way back to their nests, a recent study found.

Researchers in Finland exposed 123 buff-tailed bumblebees (Bombus terrestris), one of the most abundant bumblebee species in Europe, to a standard consumer mosquito repellent containing prallethrin, a type of pyrethroid insecticide.

One group of 44 bees was exposed to the repellant for 1 minute; 35 were exposed for 10 minutes; while 44 were exposed for 20 minutes. A control group of 43 bees was exposed to an identical device that did not release the insecticide. After exposure, the researchers released the bees 1 kilometer (0.6 miles) away from their colonies.

They found 16 bees from the control group made it home. However, only six bees exposed to the repellant for 10 minutes and just two bees exposed for 20 minutes returned.

“Bumblebee colonies depend on workers collecting food,” lead author Kimmo Kaakinen, a biologist at the University of Turku in Finland, wrote in a statement. “So if they cannot find their way back to the nest, the colony’s ability to obtain nutrition deteriorates.”