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Social networks mediate the spread of information and disease. The dynamics of spreading depends, among other factors, on the distribution of times between successive contacts in the network. Heavy-tailed (bursty) time distributions are characteristic of human communication networks, including face-to-face contacts and electronic communication via mobile phone calls, email, and internet communities. Burstiness has been cited as a possible cause for slow spreading in these networks relative to a randomized reference network. However, it is not known whether burstiness is an epiphenomenon of human-specific patterns of communication. Moreover, theory predicts that fast, bursty communication networks should also exist. Here, we present a high-throughput technology for automated monitoring of social interactions of individual honeybees and the analysis of a rich and detailed dataset consisting of more than 1.2 million interactions in five honeybee colonies. We find that bees, like humans, also interact in bursts but that spreading is significantly faster than in a randomized reference network and remains so even after an experimental demographic perturbation. Thus, while burstiness may be an intrinsic property of social interactions, it does not always inhibit spreading in real-world communication networks. We anticipate that these results will inform future models of large-scale social organization and information and disease transmission, and may impact health management of threatened honeybee populations.

This review seeks a deeper functional understanding of wild bee microbiomes by focusing on a tribe of bees where natural history and behavioral ecology are well known but investigations of microbiology are just beginning. Opportunities to improve our future knowledge of pathogens to insect pollinators are explored—which have broad ramifications for crop pollination services, considering the current overdependence on a few managed species that face a multitude of health threats. The bee tribe Allodapini (Apidae: Xylocopinae) has the potential to offer comparative insights on the evolution of bee microbiomes, owing to a unique combination of life history traits relevant to pollination service delivery across sub‐Saharan Africa, Southern Asia, and Australia. Allodapines exhibit facultatively social colony organization that offer evolutionary perspectives on the formation of group living not afforded by obligately eusocial insects, which have already transgressed the solitary‐social threshold. Progressive provisioning of brood (in the absence of brood cells) facilitates a network exchange of nutrients (via trophallaxis) that we speculate may culminate in an intra‐colony “network microbiome”. A literature review of pathogenic (bacterial, fungal, viral, and protozoan) associates of allodapine bees reveals considerably less research than for carpenter (Ceratina, Xylocopa), bumble (Bombus), and honey (Apis) bees. Interrogation of published genomes (Exoneura, Exoneurella) discovered novel microsporidian and protozoan parasites and relatives of known bee bacteria (Commensalibacter, Sodalis). Some Xylocopa exhibit microbial profiles typical of corbiculate bee core gut microbiomes, but no comparative evidence among allodapines was found. Allodapines visit flowers of 13 horticultural crops (fruits, vegetables, oilseeds, tree‐nuts) and 50 native genera (predominantly Myrtaceae, Proteacae, Myoporaceae, Goodeniaceae). The ability to parse intrinsic and extrinsic factors influencing microbiome patterns within and between species means that allodapine bees provide the opportunity for an integrated approach to bee socio‐eco‐evo‐immunology.

Many factors can negatively affect honey bee ( Apis mellifera L.) health including the pervasive use of systemic neonicotinoid insecticides. Through direct consumption of contaminated nectar and pollen from treated plants, neonicotinoids can affect foraging, learning, and memory in worker bees. Less well studied are the potential effects of neonicotinoids on queen bees, which may be exposed indirectly through trophallaxis, or food-sharing. To assess effects on queen productivity, small colonies of different sizes (1500, 3000, and 7000 bees) were fed imidacloprid (0, 10, 20, 50, and 100 ppb) in syrup for three weeks. We found adverse effects of imidacloprid on queens (egg-laying and locomotor activity), worker bees (foraging and hygienic activities), and colony development (brood production and pollen stores) in all treated colonies. Some effects were less evident as colony size increased, suggesting that larger colony populations may act as a buffer to pesticide exposure. This study is the first to show adverse effects of imidacloprid on queen bee fecundity and behavior and improves our understanding of how neonicotinoids may impair short-term colony functioning. These data indicate that risk-mitigation efforts should focus on reducing neonicotinoid exposure in the early spring when colonies are smallest and queens are most vulnerable to exposure.

Trophallaxis, a fundamental social behavior observed among honeybees, involves the redistribution of food and chemical signals. The automation of its detection under field-realistic conditions poses a significant challenge due to the presence of crowding, occlusions, and brief, fine-scale motions. In this study, we propose a markerless, deep learning-based approach that injects short- and mid-range temporal features into single-frame You Only Look Once (YOLO) detectors via temporal-to-RGB encodings. A new dataset for trophallaxis detection, captured under diverse illumination and density conditions, has been released. On an NVIDIA RTX 4080 graphics processing unit (GPU), temporal-to-RGB inputs consistently outperformed RGB-only baselines across YOLO families. The YOLOv8m model improved from 84.7% mean average precision (mAP50) with RGB inputs to 91.9% with stacked-grayscale encoding and to 95.5% with temporally encoded motion and averaging over a 1 s window (TEMA-1s). Similar improvements were observed for larger models, with best mAP50 values approaching 94–95%. On an NVIDIA Jetson AGX Orin embedded platform, TensorRT-optimized YOLO models sustained real-time throughput, reaching 30 frames per second (fps) for small and 23–25 fps for medium models with temporal-to-RGB inputs. The results showed that the TEMA-1s encoded YOLOv8m model has achieved the highest mAP50 of 95.5% with real-time inference on both workstation and edge hardware. These findings indicate that temporal-to-RGB encodings provide an accurate and computationally efficient solution for markerless trophallaxis detection in field-realistic conditions. This approach can be further extended to multi-behavior recognition or integration of additional sensing modalities in precision beekeeping.

Associations with symbionts within the gut lumen of hosts are particularly prone to disruption due to the constant influx of ingested food and non-symbiotic microbes, yet we know little about how partner fidelity is maintained. Here we describe for the first time the existence of a gut morphological filter capable of protecting an animal gut microbiome from disruption. The proventriculus, a valve located between the crop and midgut of insects, functions as a micro-pore filter in the Sonoran Desert turtle ant ( Cephalotes rohweri ), blocking the entry of bacteria and particles ⩾0.2 μm into the midgut and hindgut while allowing passage of dissolved nutrients. Initial establishment of symbiotic gut bacteria occurs within the first few hours after pupation via oral–rectal trophallaxis, before the proventricular filter develops. Cephalotes ants are remarkable for having maintained a consistent core gut microbiome over evolutionary time and this partner fidelity is likely enabled by the proventricular filtering mechanism. In addition, the structure and function of the cephalotine proventriculus offers a new perspective on organismal resistance to pathogenic microbes, structuring of gut microbial communities, and development and maintenance of host–microbe fidelity both during the animal life cycle and over evolutionary time.

Transmission routes impact pathogen virulence and genetics, therefore comprehensive knowledge of these routes and their contribution to pathogen circulation is essential for understanding host–pathogen interactions and designing control strategies. Deformed wing virus (DWV), a principal viral pathogen of honey bees associated with increased honey bee mortality and colony losses, became highly virulent with the spread of its vector, the ectoparasitic mite Varroa destructor . Reproduction of Varroa mites occurs in capped brood cells and mite-infested pupae from these cells usually have high levels of DWV. The removal of mite-infested pupae by worker bees, Varroa Sensitive Hygiene (VSH), leads to cannibalization of pupae with high DWV loads, thereby offering an alternative route for virus transmission. We used genetically tagged DWV to investigate virus transmission to and between worker bees following pupal cannibalisation under experimental conditions. We demonstrated that cannibalization of DWV-infected pupae resulted in high levels of this virus in worker bees and that the acquired virus was then transmitted between bees via trophallaxis, allowing circulation of Varroa -vectored DWV variants without the mites. Despite the known benefits of hygienic behaviour, it is possible that higher levels of VSH activity may result in increased transmission of DWV via cannibalism and trophallaxis.

Social insects frequently engage in oral fluid exchange – trophallaxis – between adults, and between adults and larvae. Although trophallaxis is widely considered a food-sharing mechanism, we hypothesized that endogenous components of this fluid might underlie a novel means of chemical communication between colony members. Through protein and small-molecule mass spectrometry and RNA sequencing, we found that trophallactic fluid in the ant Camponotus floridanus contains a set of specific digestion- and non-digestion related proteins, as well as hydrocarbons, microRNAs, and a key developmental regulator, juvenile hormone. When C. floridanus workers’ food was supplemented with this hormone, the larvae they reared via trophallaxis were twice as likely to complete metamorphosis and became larger workers. Comparison of trophallactic fluid proteins across social insect species revealed that many are regulators of growth, development and behavioral maturation. These results suggest that trophallaxis plays previously unsuspected roles in communication and enables communal control of colony phenotypes. Ants, bees and other social insects live in large colonies where all the individuals work together to gather food, rear young and defend the colony. This level of cooperation requires the insects in the colony to be able to communicate with each other. Most social insects share fluid mouth-to-mouth with other individuals in their colony. This behavior, called trophallaxis, allows these species to pass around food, both between adults, and between adults and larvae. Trophallaxis therefore creates a network of interactions linking every member of the colony. With this in mind, LeBoeuf et al. investigated whether trophallaxis may also be used by ants to share information relevant to the colony as a form of chemical communication. The experiments show that in addition to food, carpenter ants also pass small ribonucleic acid (RNA) molecules, chemical signals that help them recognize nestmates, and many proteins that appear to be involved in regulating the growth of ants. LeBoeuf et al. also found that trophallactic fluid contains juvenile hormone, an important regulator of insect growth and development. Adding juvenile hormone to the food that adult ants pass to the larvae made it twice as likely that the larvae would survive to reach adulthood. This indicates that proteins and other molecules transferred mouth-to-mouth over this social network could be used by the ants to regulate how the colony develops. The next steps following on from this work will be to investigate the roles of the other components of trophallactic fluid, and to examine how individual ants adapt the contents of the fluid in different social and environmental conditions. Another challenge will be to determine how specific components passed to larvae in this way can control their growth and development.

Barcode-based tracking of individuals is revolutionizing animal behavior studies, but further progress hinges on whether in addition to determining an individual’s location, specific behaviors can be identified and monitored. We achieve this goal using information from the barcodes to identify tightly bounded image regions that potentially show the behavior of interest. These image regions are then analyzed with convolutional neural networks to verify that the behavior occurred. When applied to a challenging test case, detecting social liquid transfer (trophallaxis) in the honey bee hive, this approach yielded a 67% higher sensitivity and an 11% lower error rate than the best detector for honey bee trophallaxis so far. We were furthermore able to automatically detect whether a bee donates or receives liquid, which previously required manual observations. By applying our trophallaxis detector to recordings from three honey bee colonies and performing simulations, we discovered that liquid exchanges among bees generate two distinct social networks with different transmission capabilities. Finally, we demonstrate that our approach generalizes to detecting other specific behaviors. We envision that its broad application will enable automatic, high-resolution behavioral studies that address a broad range of previously intractable questions in evolutionary biology, ethology, neuroscience, and molecular biology.

Individual variation in sociability is a central feature of every society. This includes honey bees, with some individuals well connected and sociable, and others at the periphery of their colony’s social network. However, the genetic and molecular bases of sociability are poorly understood. Trophallaxis—a behavior involving sharing liquid with nutritional and signaling properties—comprises a social interaction and a proxy for sociability in honey bee colonies: more sociable bees engage in more trophallaxis. Here, we identify genetic and molecular mechanisms of trophallaxis-based sociability by combining genome sequencing, brain transcriptomics, and automated behavioral tracking. A genome-wide association study (GWAS) identified 18 single nucleotide polymorphisms (SNPs) associated with variation in sociability. Several SNPs were localized to genes previously associated with sociability in other species, including in the context of human autism, suggesting shared molecular mechanisms of sociability. Variation in sociability also was linked to differential brain gene expression, particularly genes associated with neural signaling and development. Using comparative genomic and transcriptomic approaches, we also detected evidence for divergent mechanisms underpinning sociability across species, including those related to reward sensitivity and encounter probability. These results highlight both potential evolutionary conservation of the molecular roots of sociability and points of divergence.

The cuticular hydrocarbon (CHC) profile and the gut microbiome (GM) are crucial traits which have a significant impact on the life of bees. In honey bees, the CHC profile and the GM interact finely through trophallaxis, such that the characteristics of the GM are partially defined by the chemical recognition among sisters. However, most of the known primitively eusocial bees show simpler social traits, including moderate genetic relatedness among colony members, often due to workers' nest drifting or dispersal, and lack of trophallaxis. Hence, primitively eusocial bees offer a great opportunity to evaluate the respective role of worker‐worker genetic relatedness and of the environment in which the adult lives (residency nest) on the interaction between CHC profile and GM. Here, we investigated such relationships in the primitively eusocial digger bee Halictus scabiosae (Halictidae). We found a high rate of nest‐drifting by workers, which leads to a consequent highly variable intra‐colonial genetic relatedness. Genetically closely related workers, even occupying distant nests, did possess both a more similar microbiome profile and a more similar CHC profile. Additionally, sharing the same nest seemed to account for the similarity of both CHC profile and GM among workers. Interestingly, differences in microbiome profile and in CHC profile were highly and positively correlated across workers, even after controlling for genetic relatedness. The results of our study point towards an impact of genetic relatedness on the GM and the CHC profile, but also suggest that microbiome and CHC profile are partially acquired through adult nest environment, and that microbiome possibly has a role in shaping the cuticular chemistry. The relationship between cuticular hydrocarbon (CHC) profile and the gut microbiome (GM) is poorly known in bees. In the primitively eusocial bee Halictus scabiosae we found a high rate of nest‐drifting by workers, which leads to a consequent highly variable intra‐colonial genetic relatedness. Genetically closely related workers, even occupying distant nests, did possess both a more similar microbiome profile and a more similar CHC profile, and sharing the same nest seemed to also account for the similarity of both CHC profile and GM among workers.