David Baracchi

Invasive insect pests present escalating threats to agricultural productivity and environmental stability, often necessitating the intensive use of broad-spectrum insecticides that jeopardize non-target organisms and ecosystem services. Endotherapy (i.e., trunk injection) is increasingly proposed as a sustainable alternative to conventional sprays to minimize environmental dispersion and reduce off-target impact. In the present study, we used the highly polyphagous Japanese beetle Popillia japonica, a quarantine priority pest in European Union due to its significant economic and environmental risks, as a model to evaluate the ecological trade-offs of systemic pest management. We assessed the efficacy of three active ingredients, acetamiprid, abamectin, and emamectin benzoate, in controlling the invasive pest. The compounds were injected into linden trees, Tilia spp., at the resumption of vegetative growth, and their translocation to floral tissues was quantified to determine potential risks to the non-target honey bee, Apis mellifera. Results indicate that while acetamiprid provided effective control of adult beetles, its residues detected in flowers significantly reduced honey bee survival and altered feeding behavior in a dose-dependent manner. Crucially, sublethal concentrations of both acetamiprid and abamectin impaired bee cognitive performance, highlighting hidden costs often overlooked in standard ecotoxicity assessments. These findings underscore that the perceived safety of endotherapy is contingent upon active ingredient selection and application timing relative to blooming. Our work demonstrates the necessity of evaluating systemic treatments within a sustainability-oriented framework that balances immediate pest suppression with the long-term safeguarding of pollination services. Such integrated approaches are essential for aligning agricultural practices with global mandates for pesticide reduction and biodiversity conservation.

The idea that invertebrates may exhibit basic forms of emotion, and possibly sentience, is gaining traction as evidence of their advanced cognitive abilities continues to mount. While high-level cognition does not imply emotional states, invertebrates offer a unique window into whether such states can arise in small-brained animals. With their relatively simple yet highly structured nervous systems, they serve as tractable models for dissecting the mechanisms underlying emotional expression. To probe these processes, researchers have developed behavioural paradigms exposing different species to contexts likely to elicit emotional responses. From a phylogenetic perspective, studying emotional expression in invertebrates can reveal whether basic emotional systems are conserved across species. This review synthesizes current knowledge of non-verbal emotional expression in social insects, focusing on mechanisms and functional roles. We apply a multi-component approach to examine key building blocks shared across emotions and taxa, offering insights into their evolutionary origins. We also identify critical gaps in knowledge and propose directions for future research. By examining the proximate and ultimate causes of emotion, this framework enhances our understanding of the biological basis and evolutionary significance of emotions, promoting interdisciplinary research that bridges neuroscience, ethology and evolutionary biology. This article is part of the theme issue ‘Mechanisms, development, phylogeny and functions of emotional expressions’.

The increasing use of microbial biopesticides in sustainable agriculture requires a deeper understanding of their potential impact on non-target pollinators. Although biocontrol agents are generally considered safer than synthetic pesticides, they may still cause subtle but ecologically relevant adverse effects on non-target organisms, especially when exposed to multiple stressors that are often overlooked in current risk assessment frameworks. Among these, nutritional stress, caused by habitat loss, fragmentation and reduced floral diversity, is becoming increasingly widespread. In this study, we investigated the lethal and sublethal effects of the bacterial biopesticide Bacillus velezensis (formerly B. amyloliquefaciens ) strain QST713 at field-relevant concentrations on two key pollinators: Apis mellifera and Bombus terrestris . For the first time for a biopesticide, oral toxicity was assessed under environmental stress represented by diets with varying sugar concentrations (optimal and suboptimal) to identify potential synergistic effects on bee health. Sublethal effects were examined by studying learning performance and memory retention through a conditioning experiment under laboratory conditions. The results showed marked species-specific differences. While B. velezensis did not impact bee survival under realistic nutritional conditions, we observed a synergistic lethal effect in B. terrestris when biopesticide exposure was coupled with extreme nutritional stress (sugar deprivation). Similar species-specific differences emerged at the behavioral level: unlike A. mellifera, B. terrestris showed impaired visual learning and early long-term memory recall. Taken together, these results show that sublethal cognitive endpoints and multi-stressor contexts may reveal vulnerabilities not immediately evident through mortality-based assessments alone. Our findings also highlight the importance of including multiple pollinator species in risk assessment, as sensitivity to biopesticides might greatly vary among species.

While foraging, pollinators encounter a wide array of molecules, some of which may influence their internal states and behaviors. Among these, biogenic amines – nitrogenous compounds that serve as essential neuromodulators in animals – have only recently been detected in floral nectar. As a result, little is known about the effects of nectar concentrations of these compounds on pollinators. In this study, we tested how two key biogenic amines, octopamine and its precursor tyramine, affect bumble bee behavior by examining: 1) consumption and survival, 2) locomotion, and 3) feeding behavior. Our findings show a preference for low concentration of octopamine (0.1 mM) and a dose‐dependent effect on flight behavior. Specifically, a concentration equal to 0.1 mM of octopamine reduces the bee's motivation to fly, whereas a concentration of 1 mM increases flight duration. Tyramine has no significant effect on any of the behaviors tested. Our results demonstrate that nectar‐borne biogenic amines have the potential to influence various bumble bee behaviors critical to flower visitation.

Parasites can influence host physiology and behavior, often impairing cognition. We investigated how infection and parasite load affect olfactory learning and memory in the paper wasp Polistes dominula workers parasitized by the insect parasite Xenos vesparum (Strepsiptera). We adapted a Pavlovian conditioning assay based on the proboscis extension reflex protocol. We tested three groups: unparasitized workers, singly parasitized workers, and superparasitized workers. Wasps were conditioned to associate a floral odorant with sucrose and later assessed in a memory assay. Unparasitized workers outperformed superparasitized workers in both assays, while single parasitized individuals showed intermediate performance. Superparasitized workers were less responsive during the conditioning and exhibited greater generalization during the memory test. Our results revealed that not only parasitization, but also parasite load correlates negatively with host cognition. These findings highlight the cognitive costs of parasitism in social insects and align with previously observed behavioral patterns in this complex host-parasite system.

Neuropeptides are crucial molecules in the nervous system, regulating various biological processes. Neuropeptide F (NPF) and its shorter form, short neuropeptide F (sNPF), serve functions in invertebrates analogous to those of neuropeptide Y (NPY) in vertebrates, modulating growth, reproduction, nociception, circadian rhythms and feeding behaviours. In the honeybee, a social insect that adjusts foraging strategies based on colony needs, sNPF is a key regulator of foraging-related behaviours, including food intake, sucrose sensitivity, olfactory perception and visual memory formation. This study investigates the role of sNPF in olfactory learning and memory across different seasons and nutritional states by artificially elevating sNPF levels in honeybees. Our findings reveal that enhancing sNPF in well nourished winter bees does not affect cognitive performance. In contrast, increased sNPF levels in poorly or intermediately nourished summer bees significantly enhance learning and memory. These results indicate that while sNPF plays a role in olfactory learning and memory, its effects are modulated by seasonal and nutritional factors. The distinct physiological states and foraging demands faced by winter and summer bees likely influence sNPF signalling, modulating neural activity in olfactory and reward-processing circuits. Our study highlights the dynamic nature of sNPF signalling, emphasizing its tuning to external environmental conditions.

The ability to resist immediate temptation for a better, delayed outcome is thought to underpin advanced cognition. Traditionally, this ability has been studied in large-brained animals. However, to understand its evolutionary origins, it is necessary to expand the study to species with different life histories and ecological pressures, such as insects. Here, we investigated the ability to endure delayed gratification in the bumble bee Bombus terrestris using a delay maintenance task that assessed the capacity to sustain a delay for a large reward. Bees were first individually trained in a foraging arena to associate two differently coloured flowers either with an immediately accessible small reward (a 5 µl drop of 30% sucrose) or a delayed large reward (four 5 µl drops with a 15-s delay). Bumble bees were then tested over 10 delay choices between the two flowers/rewards. Finally, bees were tested in a delay maintenance test in which the 15-s delay was extended indefinitely. Overall, our findings suggest that bumble bees did not consistently choose the delayed reward over the immediate one across the ten trials, and their ability to sustain delay was highly variable across individuals. Although a small subset of bees (n = 5) exhibited prolonged waiting times comparable to those observed in mammals, birds, and fish (with one individual resisting for up to 364-s), the overall lack of consistency suggests that self-control in bumble bees may be limited and related to either ecological constraints or their foraging strategy. These results provide new insights into the evolutionary origins and drivers of self-control.

Biopesticides have gained increased attention as sustainable substitutes for synthetic pest control products. Nonetheless, in recent years, a growing body of research has highlighted their undesired effects on non‐target organisms, including sublethal impacts on social behavior. Here, we investigate the potential adverse effects of a common biopesticide, the entomopathogenic fungus Beauveria bassiana, on the nestmate recognition ability of the paper wasp Polistes dominula. Nestmate recognition, based on individual cuticular hydrocarbons (CHCs) profiles, plays a key role in the colony integrity of social insects, avoiding foreign intrusion and the spread of pathogens inside the nest. P. dominula workers were topically exposed to the biopesticide, and subsequent presentation behavioral assays and GC–MS chemical analyses were carried out to evaluate possible changes both in the nestmate recognition ability and chemical profile induced by B. bassiana. Biopesticide exposure altered the CHCs profile of exposed wasps and triggered increased aggression toward both exposed nestmates and foreign individuals, while not disrupting the colony nestmate recognition system. The higher aggressive response toward exposed wasps likely represents an adaptive strategy to prevent the entrance of pathogen‐infected individuals into the nest. The present study demonstrates how an integrated approach based on behavioral bioassays and chemical analyses can effectively evaluate the sublethal effects of plant protection products on non‐target organisms.

Microplastics pose a significant ecological threat, yet their actual impact on terrestrial ecosystems and organisms remains poorly understood. This study investigates the effects of two common microplastics, poly(methyl methacrylate) (PMMA) and polystyrene (PS), on the pollinator Bombus terrestris , exploring their combined and sublethal effects at three different concentrations (0.5, 5 and 50 mg l ^–1 ). PMMA and PS single exposure reduced bee survival in a concentration-dependent manner, whereas combined exposure (MIX) had no significant effect. PS reduced bee sucrose responsiveness, PMMA had no significant effect and MIX enhanced it. Learning and memory tests showed impaired mid-term and early long-term memory in bees exposed to PMMA and PS, with concentration-dependent effects. Interestingly, MIX exposure had no effect on memory retention. Our findings emphasize the differential effects of individual microplastics on bumblebee behaviour, suggesting potential risks to pollinator survival, cognitive function and possibly overall colony health, but also unexpected antagonistic interactions between these pollutants. The PS–PMMA antagonistic interactions highlight a challenge in assessing the toxicity of microplastics. Combined effects may not mirror the individual toxicity of PS and PMMA, highlighting the need for a careful assessment of polymer interactions, especially in environments or organisms contaminated by different microplastics.