Effects of sublethal doses of acetamiprid and thiamethoxam on the behavior of the honeybee (Apis mellifera).

Acetamiprid and thiamethoxam are insecticides introduced for pest control, but they can also affect non-target insects such as honeybees. In insects, these neonicotinoid insecticides are known to act on acetylcholine nicotinic receptors but the behavioral effects of low doses are not yet fully understood. The effects of acetamiprid and thiamethoxam were studied after acute sublethal treatment on the behavior of the honeybee (Apis mellifera) under controlled laboratory conditions. The drugs were either administered orally or applied topically on the thorax. After oral consumption acetamiprid increased sensitivity to antennal stimulation by sucrose solutions at doses of 1 microg/bee and impaired long-term retention of olfactory learning at the dose of 0.1 microg/bee. Acetamiprid thoracic application induced no effect in these behavioral assays but increased locomotor activity (0.1 and 0.5 microg/bee) and water-induced proboscis extension reflex (0.1, 0.5, and 1 microg/bee). Unlike acetamiprid, thiamethoxam had no effect on bees' behavior under the conditions used. Our results suggest a particular vulnerability of honeybee behavior to sublethal doses of acetamiprid.