Neonicotinoid exposure makes bees less social, causing them to neglect their young… experts say this could stunt the growth of bee colonies

A team of animal behavior biologists from Harvard University has tracked the exact way neonicotinoids, the world’s most commonly used insecticide, affect the behavior of bees. Their study, published in Science, highlights the dangers of using this class of neuro-active chemicals, especially as they appear to have insidious effects on vital pollinators. Using an innovative tracking technique, the Harvard researchers saw that neonicotinoids significantly reduce the activity in bumblebee colonies, making the insects less likely to care for their young, and being less active in regulating nest temperature.

Previous research on the topic have confirmed that neonicotinoids represent a risk to wild bees and honeybees. In 2013, the European Commission severely restricted the use of three types of neonicotinoids (clothianidin, imidacloprid, and thiamethoxam) to protect honeybees. This was further validated by several studies made the European Food Safety Authority (EFSA) that concluded that this type of insecticide had a confirmed effect on the behavior and health of bees.

Tracking bees with unique tags

Researchers were stymied by how exactly the insecticide affected the bees, and damaged entire colonies, which can contain hundreds or even thousands of bees, all interacting as one complex “superorganism.” The difficulties lay in the tracking of the insects themselves.

Lead researcher, James Crall, came up with an innovative solution. He and his colleagues glued 3-by-4-millimeter tags onto the backs of hundreds of bumblebees. The team then adapted robotic equipment from a fruit fly lab to assemble a movable platform with two high-resolution cameras. These cameras were able to “spy” on up to a dozen bumblebee colonies, picking up the movement of the tags, and then transferring the data into computers for analysis.

Social interactions decreased

Nine colonies were given sugar syrup laced with six parts per billion of imidacloprid, a common neonicotinoid. Bees were allowed to feed on it whenever they wanted. Over the 12-day experiment period, Crall and his team saw that the overall level of social interaction among the bees decreased. They saw that whereas bees in the control colonies spent about 25 percent of the night caring for their young, the pesticide-consuming bees spent less than 20 percent. Worryingly, the lethargy was more profound at night.

Bees regulate their temperature, as well as that of their nest, by flexing their muscles and fanning their wings. It is important that bees work together and keep the hive at a constant temperature so that larvae can develop properly. When bees become “lazy,” this can have negative effects on their young.

Richard Gill, a bee ecologist at Imperial College London explains, “[Their] brood is their future. If they don’t take care of them, then there’s a likelihood of an effect on the colony.” He surmises that neonicotinoid-induced damage could stunt the growth of a bee colony.

On neonicotinoids

Neonicotinoids (neonics) are a class of insecticides that affect the central nervous system of insects, resulting in paralysis and death. Chemically speaking, neonicotinoids are quite similar to nicotine, hence why the name literally means “new nicotine-like insecticides.”

Neonicotinoids are systemic pesticides, which means that the chemicals are taken up by plants and transported through its entire system (i.e. leaves, flowers, stems, as well as pollen and nectar). Because of this mode of action, neonics represent a potential risk to pollinators.

Sources include:

ScienceMag.org

EFSA.Europa.eu

EC.Europa.eu

BeyondPesticides.org