Negative effects of neonicotinoids on male honeybee survival, behaviour and physiology in the field

1. Agricultural chemicals such as neonicotinoid insecticides are believed to be one important factor responsible for the recent reduction in health of pollinating insects like the western honeybee (Apis mellifera). However, effects of neonicotinoids on male (drone) honeybee health remain severely understudied.

2. We examined for the first time the multi-dimensional effects of field-realistic concentrations of two common neonicotinoid insecticides (thiamethoxam and clothianidin) on drone honeybee survival, behaviour, and physiology using individuals reared and maintained as adults in the field.

3. Our data showed that neonicotinoids reduced honeybee drone survival by 51%, increased drifting behaviour to non-maternal colonies by 100%, delayed flight activities by three days, and reduced number of living sperm by 28%. However, they did not influence the sperm concentration produced by the drones, the strength of the drone's maternal colonies, or the total number of drones produced by those colonies.

4. 'Policy implications': Our study demonstrated that neonicotinoids can elicit a diverse array of lethal (survival) and sub-lethal (behaviour, reproductive physiology) effects on male honeybees (Apis mellifera) in the field. These findings should be considered by policy makers looking to adopt and implement science-based, holistic risk assessments to more comprehensively assess effects of chemicals on important ecosystem service providing insects like the honeybee. To date, risk assessment schemes do not specifically address potential effects on male bees.