The neonicotinoid insecticide imidacloprid disrupts bumblebee foraging rhythms and sleep

SUMMARY Neonicotinoids have been implicated in the large declines observed in flying insects such as bumblebees, an important group of pollinators[1]. Neonicotinoids are agonists of nicotinic acetylcholine receptors that are found throughout the insect central nervous system, and are the main mediators of synaptic neurotransmission[2]. These receptors are important for the function of the insect central clock and circadian rhythms[3, 4]. The clock allows pollinators to coincide their activity with the availability of floral resources, favourable flight temperatures, as well as impacting learning, navigation and communication[5]. Here we show that exposure to the field relevant concentration of 10 µg/L of imidacloprid can cause a reduction in foraging activity and reduce both locomotor and foraging rhythmicity in Bombus terrestris . Foragers showed an increase in daytime sleep and an increase in the proportion of activity occurring at night. This would likely negatively impact foraging and pollination opportunities, reducing the ability of the colony to grow and reproduce, endangering crop yields.