Kenna, D. | Search bioRxiv

bioRxiv2025

Pesticide-exposed bees fail to thermoregulate leading to cold colonies with consequences for offspring development

For many organisms, effective thermoregulation is needed to cope with changing environmental temperatures. But if exposure to pesticides in the environment were to impair this homeostatic process, reproduction and population viability could be at risk. Focusing on an important insect pollinator, we conducted three complementary experiments exposing bumblebees to a pesticide under different temperature challenges and measuring the impacts on thermoregulatory ability and brood development. First, we reveal that pesticide-exposed individuals cannot maintain a stable thorax temperature, especially at lower temperatures. Second, reductions in body temperature are accompanied by behavioural changes and that pesticide-exposed colonies fail to maintain appropriate brood temperatures. Third, such collective impairment on brood thermoregulation (not the pesticide toxicity to offspring per se) leads to delayed pupal development and reduced adult population growth. Our study provides a valid mechanistic explanation for why terrestrial insects requiring brood thermoregulation have declined. With frequent extreme weather events forecasted, our findings have concerning implications for how populations will adequately persist and grow under current pesticide-use regimes with ramifications on pollination services.

ecology↗

bioRxiv2018

Pesticide exposure affects flight dynamics and reduces flight endurance in bumblebees

The emergence of agricultural land use change creates a number of challenges that insect pollinators, such as eusocial bees, must overcome. Resultant fragmentation and loss of suitable foraging habitats, combined with pesticide exposure, may increase demands on foraging, specifically the ability to reach resources under such stress. Understanding the effect that pesticides have on flight performance is therefore vital if we are to assess colony success in these changing landscapes. Neonicotinoids are one of the most widely used classes of pesticide across the globe, and exposure to bees has been associated with reduced foraging efficiency and homing ability. One explanation for these effects could be that elements of flight are being affected, but apart from a couple of studies on the honeybee, this has scarcely been tested. Here we used flight mills to investigate how exposure to a field realistic (10ppb) acute dose of imidacloprid affected flight performance of a wild insect pollinator - the bumblebee, Bombus terrestris audax. Intriguingly, intial observations showed exposed workers flew at a significantly higher velocity over the first [3/4] km of flight. This apparent hyperactivity, however, may have a cost as exposed workers showed reduced flight distance and duration to around a third of what control workers were capable of achieving. Given that bumblebees are central place foragers, impairment to flight endurance could translate to a decline in potential forage area, decreasing the abundance, diversity and nutritional quality of available food, whilst potentially diminishing pollination service capabilities.\n\nSummary StatementAcute neonicotinoid exposure impaired flight endurance and affected velocity of Bombus terrestris workers, which may dramatically reduce colony foraging potential and pollination provision in pesticide applied landscapes.

ecology↗