Sublethal effects of a commercial imidacloprid formulation on appetitive, defensive, and motor behaviors in Africanized honey bees (Apis mellifera)

Honey bees (Apis mellifera) are essential pollinators in both agricultural and natural ecosystems, yet exposure to neonicotinoid insecticides such as imidacloprid poses a recognized risk to their behavior and physiology. We evaluated the sublethal effects of a commercial formulation of imidacloprid (Confidor 350 CS) on appetitive, defensive, and motor behaviors in Africanized honey bees using three experimental protocols: the proboscis extension reflex (PER), the sting extension reflex (SER), and analyses of individual and group locomotion. Imidacloprid exposure produced dose- and time-dependent reductions in both PER and SER, with significant impairments at intermediate and high concentrations. At the motor level, exposed bees exhibited reduced activity and altered movement dynamics across body segments, with heterogeneous reductions in head and abdominal motion, as well as decreased angular displacement and angular speed during group movement. Together, these results indicate that sublethal imidacloprid exposure disrupts multiple sensorimotor behavioral domains, resulting in broad functional impairment under controlled conditions. These findings add to growing evidence that sublethal neonicotinoid exposure can substantially alter honey bee behavior and highlight the need for careful evaluation of their use in agroecosystems.