The European honeybee (Apis mellifera L., Hymenoptera, Apidae) is facing a drastic decrease in the last decade. Colonies are experiencing sudden drops in population number, leading to bees death and colony losses. Although many reasons have been questioned, no clear answer has been pointed out yet. It seems that these colony losses are a result of multiple factors. In fact, bees are not exposed to one risk, but to a large amount of stresses that can interact among themselves. Pesticides are recognised as one of the main causes. Pesticides residuals can strongly affect honeybees and the effects on cognition and mortality are well known. Much attention has been paid to the insecticide class of neonicotinoids. These are very effective, systemic, wide spectra neurotoxic molecules largely used in agriculture. However, they do not only affect crop pests, but also non-target species such as pollinators. The hazard of poisoning results not only for direct contact but also for oral assumption of contaminated food source. Indeed, neonicotinoids persistence in the environment is strong enough to allow detection of residuals in nectar and pollen long after applications.
Bee colonies exposure to continuous repeated doses of pesticides may have serious long-term consequences, including the colony death. In this research, I am investigating the effect of long-lasting dietary exposure to sub-lethal doses of neonicotinoids on honeybee colonies and individuals. Possible impairments of antennal odour perception are measured through variation of signal transduction using the EAG and GC-EAD approach. Using the Proboscis Extension Reflex technique, I focus on the effects on honeybees learning capacity and memory. Neonicotinoids impairs associative learning and memory in foraging age honeybees and reduces their gustatory sensitivity. Forager honeybees experience changes in waggle dance communication, orientation and navigation. Studies on the colonies are carried out in field, where many beehives are running under a long-lasting exposition to sub-lethal doses of neonicotinoids. Real-time remote monitoring systems and performance estimation methods allows to evaluate the effects of such intoxication on the colony.