Sub-lethal effects of thiamethoxam on Apis mellifera Linnaeus

Abstract Bees are the important natural resources, play a crucial role in maintaining diversity and sustaining food security. In the past couple of years, these tiny animals are facing problems due to various factors like climate change, loss of habitat, loss of bee pasturage, reduced immunity, pesticide poisoning, etc. Among these, the insecticides, particularly the ones belonging to the class neonicotinoids have been blamed worldwide. Thiamethoxam is the one among various insecticides in this group. It is a systemic insecticide whose residues have been reported to contaminate the nectar and pollen. Since it has been classified as a highly toxic insecticide to bees, several cases of acute toxicity to adult bees have been reported. Besides this, sub-lethal doses have also been reported to cause negative effects on workers, queen bee, and drones. Some of the negative effects on important physiological or behavioral processes are reduced brood development, altered locomotion, incapability in maintaining thorax temperature, sensitivity to sucrose, effect on olfactory learning and foraging, etc. At the same time, the effects on the reproductive capacity of the colony due to the negative effects on queen bee and drone have also been observed. The work has also been carried out to find the basis, at the molecular level, governing such effects. Since there are several negative effects even due to the sub-lethal doses of thiamethoxam, it becomes imperative to sum up all the generated knowledge on this topic. Hence, the present review has been prepared which will provide critical information to the various stakeholders who may use the information to safeguard the bees/apiaries in a better way.