ABSTRACT
The risk assessment of chemical pesticides on honey bees relies mainly on acute toxicity tests. Besides mortality, various aspects of the behavior of honey bees may be affected by sublethal doses of pesticides. Among the bees of a colony, foragers are the most likely to be exposed to chemicals. The foraging behavior is known to be based on a conditioning process, floral cues being associated with the food, memorized, and used for flower recognition during the following trips. The conditioning process occurring on the flower can be reproduced under laboratory conditions by using the olfactory conditioning of the proboscis extension response on restrained individuals. This bioassay has been adapted to screen the effects of various chemicals at sublethal concentrations. It allows threshold concentrations to be established above which a significant decrease in the olfactory learning abilities is observed. This method appears to be very promising for screening out pesticides, using a standard laboratory procedure. However, a wider range of compounds should be tested and the reliability of the assay still needs to be validated under more natural conditions before it can be proposed as a new method for regulatory guidelines.
