Sublethal Effects of Pesticides on Visually-Guided Bee Behaviours

European honeybees (Apis mellifera) are abundant and effective natural pollinators contributing enormously to mass production of agricultural crops through extensive foraging. They possess visual systems that are highly sensitive to motion and rely on motion of visual elements (optic flow) to efficiently navigate their complex environment with high precision. Optic flow stimulates an innate response known as the optomotor response, which enables the bees to orient and maintain a straight course during flight. The persistent use of pesticides in seed treatments and bees’ exposure negatively impact honeybee’s ability to engage in these ecologically relevant behaviours. Previous studies showed that neonicotinoids and sulfoxaflor impaired flight performance and walking tracks associated with optomotor responses in workers. This study is investigating the responses of different honeybee castes and worker age groups to optomotor stimuli in a 360° visual stimulus arena and how nicotinic acetylcholine receptors (nAChRs) agonists – imidacloprid (IMD), sulfoxaflor (SFX) and their mixture (MIX), impair these responses. Bees were tethered on air-supported ball where I provided optomotor stimuli consisting of alternating black and white stripes rotating in clockwise and counterclockwise directions. Workers exposed to SFX exhibited significantly faster reaction times and an enhanced preference for clockwise stimulus direction, while queens in all pesticide-treated groups showed a preference for leftward orientation bias. Drones remained largely unaffected by any of the pesticide treatments. Among worker age groups, nurses exhibited slower movement and delayed responses compared to foragers and nest bees. No interactive effects between age and pesticide exposure were observed. These findings highlight potential impairments in foraging efficiency and navigation, with significant implications for pollination services and pesticide risk assessments.