Tracking Varroa Parasitism Using Handheld Infrared Cameras: Is Eusocial Fever the Key?

The Varroa destructor is the most significant bee parasite and the greatest threat to bee health all around the world. Due to its hidden lifestyle, detection within the brood cell is only possible through invasive techniques. Enhancing detection methods is essential for advancing research on population dynamics, spread, selection efforts, and control methodologies against the mite. In our study, we employed infrared imaging to measure the thermal differences in parasite and intact Apis mellifera worker broods. Experiments were conducted over two years at the MATE Kaposvár Campus in Hungary involving five beehives in 2022 and five beehives in 2023. A FLIR E5-XT WIFI handheld infrared camera was used to create a heat map of capped brood frames. Our results indicate that the resolution of these cameras is sufficient to provide detailed IR images of a bee colony, making them suitable to detect temperature differences in intact and Varroa parasitized capped brood cells. Mite parasitism causes a time-dependent and sustained temperature increase in developing bee pupae, observable regardless of mite number. Our work demonstrates two different heating patterns: hotspot heating and heating cells that are responsible for the elevated temperature of the Varroa-infested cells as a social fever response by the worker bees. Based on our results, future research combined with AI-based image evaluation software could offer beekeepers and researchers practical and valuable tools for high-throughput, non-invasive Varroa detection in the field.

The function of OforOrco in the allogrooming behavior of Odontotermes formosanus (Shiraki) induced by Serratia marcescens Bizio (SM1).

Termites are consistently confronted with a complex microbial environment. In addition to the role of their innate immune system in resisting pathogen infection, social immune behavior also plays a significant role in helping termites withstand the stress caused by pathogenic microorganisms. The allogrooming behavior among different individuals is commonly observed in termites, and it plays a crucial role in the social immune interaction network. In the case of Odontotermes formosanus (Shiraki), Orco is specifically involved in detecting pheromones and volatile chemicals released by termites to communicate with each other. Nonetheless, the function of Orco in the social immunity remains unreported in O. formosanus. Consequently, in this study, we recorded the allogrooming behavior of O. formosanus workers under SM1 stress. The results indicated a significant increase in allogrooming behavior due to SM1 infection. The allogrooming behavior of workers under SM1 stress was significantly increased after the addition of soldiers. Compared with pronotum group treated by SM1, SM1 treatment of workers' heads significantly reduced the allogrooming behavior among workers. In addition, we found that SM1 could greatly increase the expression of OforOrco. Furthermore, interfering with OforOrco could markedly reduce the allogrooming behavior among workers under SM1 stress, and increase the mortality of worker under SM1 stress. This study demonstrated the significant role of OforOrco in the social immunity of O. formosanus, which offers a theoretical foundation for the advancement of research on termite RNA biopesticides, and the integration of RNA interference (RNAi) with pathogens. This study is valuable for elucidating the social immune behavior and interaction network of termites.

Wound-dependent leg amputations to combat infections in an ant society.

Open wounds pose major infection and mortality risks in animals.1,2 To reduce these risks, many animal species apply antimicrobial compounds on their wounds.1,2,3,4 Ant societies use antimicrobial secretions from the metapleural gland to combat pathogens,5,6,7,8,9,10 but this gland has been lost over evolutionary time in several genera, including Camponotus.11 To understand how infected wounds are handled without the use of antimicrobial secretions from the metapleural gland, we conducted behavioral and microbiological experiments in Camponotus floridanus. When we experimentally injured a worker's leg at the femur, nestmates amputated the injured limb by biting the base (trochanter) of the leg until it was severed, thereby significantly increasing survival compared to ants that did not receive amputations. However, when the experimental injury was more distal (at the tibia), nestmates did not amputate the leg and instead directed more wound care to the injury site. Experimental amputations also failed to improve survival in ants with infected tibia injuries unless the leg was amputated immediately after pathogen exposure. Micro-CT scans revealed that the muscles likely responsible for leg hemolymph circulation are predominantly in the femur. Thus, it is likely that femur injuries, by attenuating hemolymph flow, provide sufficient time for workers to perform amputations before pathogen spread. Overall, this study provides the first example of the use of amputations to treat infected individuals in a non-human animal and demonstrates that ants can adapt their type of treatment depending on the location of wounds.

Uncovering the function of insulin receptor substrate in termites' immunity through active immunization.

Insulin receptor substrate (IRS) proteins are key mediators in insulin signaling pathway. In social insect lives, IRS proteins played important roles in caste differentiation and foraging, but there function in disease defenses such as active immunization has not been reported yet. To investigate the issue, we successfully suppressed the IRS gene 3 days after dsRNA injection. Suppressing IRS gene increased the contents of glucose, trehalose, glycogen, and triglyceride and decreased the content of pyruvate in termites, and led to the metabolic disorder of glucose and lipids. IRS suppressing significantly enhanced grooming behaviors of nestmates of fungus-contaminated termites and hence increased the conidial load in the guts of the nestmates. Additionally, IRS suppressing led to significant downregulation of the immune genes Gram-negative bacteria-binding protein2 (GNBP2) and termicin and upregulation of the apoptotic gene caspase8, and hence diminished antifungal activity of nestmates of fungus-contaminated termites. The above abnormal behavioral and physiological responses significantly decreased the survival rate of dsIRS-injected nestmates of the fungus-contaminated termites. These findings suggest that IRS is involved in regulation of active immunization in termites, providing a better understanding of the link between insulin signaling and the social immunity of termites.

Subterranean termites raise the alarm when their anti-fungal weapon falters.

Termicin is an anti-fungal defensin that is disseminated from termite salivary glands. The peptide appears to be critical for the elimination with mutual grooming (allogrooming) of pathogenic spores (conidia) that have attached to the insect cuticle. There has been a recent selective sweep for an advantageous variant of this peptide in the subterranean termite Reticulitermes flavipes. We tested the anti-mycotic activity of a recombinant termicin corresponding with this variant against the conidia of different Metarhizium fungal isolates from soil close to foraging R. flavipes workers. Termicin was most effective against isolates that had previously been shown to elicit a relatively weak alarm response, as indicated by brief bouts of rapid longitudinal oscillatory movement (LOM). These isolates that elicited weak alarm were also the deadliest apparently because the survival of termites exposed to the fungus depends on a strong social immune response (LOMs and allogrooming). The selective pressure for a single termicin variant may have been driven by the most dangerous isolates that elicit a weak behavioral response. The correlation between termicin anti-fungal activity and LOM suggests that pathogen-associated molecular patterns that affect termite recognition of conidial contamination and the onset of elevated allogrooming also affect the vulnerability of conidia to the disruption of their cell membranes by termicin.

Trade-offs between immunity and competitive ability in fighting ant males.

BACKGROUND: Fighting disease while fighting rivals exposes males to constraints and trade-offs during male-male competition. We here tested how both the stage and intensity of infection with the fungal pathogen Metarhizium robertsii interfere with fighting success in Cardiocondyla obscurior ant males. Males of this species have evolved long lifespans during which they can gain many matings with the young queens of the colony, if successful in male-male competition. Since male fights occur inside the colony, the outcome of male-male competition can further be biased by interference of the colony's worker force. RESULTS: We found that severe, but not yet mild, infection strongly impaired male fighting success. In late-stage infection, this could be attributed to worker aggression directed towards the infected rather than the healthy male and an already very high male morbidity even in the absence of fighting. Shortly after pathogen exposure, however, male mortality was particularly increased during combat. Since these males mounted a strong immune response, their reduced fighting success suggests a trade-off between immune investment and competitive ability already early in the infection. Even if the males themselves showed no difference in the number of attacks they raised against their healthy rivals across infection stages and levels, severely infected males were thus losing in male-male competition from an early stage of infection on. CONCLUSIONS: Males of the ant C. obscurior have a well-developed immune system that raises a strong immune response very fast after fungal exposure. This allows them to cope with mild pathogen exposures without compromising their success in male-male competition, and hence to gain multiple mating opportunities with the emerging virgin queens of the colony. Under severe infection, however, they are weak fighters and rarely survive a combat already at early infection when raising an immune response, as well as at progressed infection, when they are morbid and preferentially targeted by worker aggression. Workers thereby remove males that pose a future disease threat by biasing male-male competition. Our study thus reveals a novel social immunity mechanism how social insect workers protect the colony against disease risk.

Group size rather than social status influences personal immune efficacy in a socially polymorphic bee.

The evolution of group living is associated with increased pressure from parasites and pathogens. This can be offset by greater investment in personal immune defences and/or the development of cooperative immune defences (social immunity). An enduring question in evolutionary biology is whether social-immune benefits arose in response to an increased need in more complex societies, or arose early in group living and helped facilitate the evolution of more complex societies. In this study, we shed light on this question through investigating how immunity varies intraspecifically in a socially polymorphic bee. Using a novel immune assay, we show that personal antibacterial efficacy in individuals from social nests is higher than that of solitary individuals, but that this can be explained by higher densities in social nests. We conclude that personal immune effects are likely to play a role in the social/solitary transition in this species. These patterns are consistent with the idea that social immunity evolved secondarily, following the evolution of group living. The flexibility of the individual immune system may have favoured a reliance on its use during the facultative phase early in social evolution.

Overcoming Immune Deficiency with Allogrooming.

Allogrooming appears to be essential in many social animals for protection from routine exposure to parasites. In social insects, it appears to be critical for the removal of pathogenic propagules from the cuticle before they can start an infectious cycle. For subterranean termites, this includes fungal spores commonly encountered in the soil, such as Metarhizium conidia, that can quickly germinate and penetrate the cuticle. We investigated whether there is a difference in reliance on social and innate immunity in two closely related subterranean termites for protection from fatal infections by two locally encountered Metarhizium species. Our results indicate that relatively weak innate immunity in one termite species is compensated by more sustained allogrooming. This includes enhanced allogrooming in response to concentrations of conidia that reflect more routine contamination of the cuticle as well as to heavy cuticular contamination that elicits a networked emergency response.

Influence of Honey bee Nutritive Jelly Type and Dilution on its Bactericidal Effect on Melissococcus plutonius, the Etiological Agent of European Foulbrood.

To defend themselves against pathogenic microorganisms, honey bees resort to social immunity mechanisms, such as the secretion of antibiotic compounds in the jelly they feed to their larvae. Whereas the bactericidal activity of jelly fed to queen larvae is well studied, little is known about the bioactivity of compositionally different jelly fed to worker larvae. However, the numerous worker larvae are likely to drive the spread of the microorganism and influence its virulence and pathogenesis. Diluted jelly or extracts are mostly used for jelly bioactivity tests, which may bias the evaluation of the pathogen's resistance and virulence. Here, we compared the bactericidal effect of pure and diluted jellies destined for queen and worker larvae on Melissococcus plutonius, the etiological agent of the European foulbrood (EFB) disease of honey bees, and on a secondary invader bacteria, Enterococcus faecalis. We tested three strains of M. plutonius with varying virulence to investigate the association between resistance to antibacterial compounds and virulence. The resistance of the bacteria varied but was not strictly correlated with their virulence and was lower in pure than in diluted jelly. Resistance differed according to whether the jelly was destined for queen or worker larvae, with some strains being more resistant to queen jelly and others to worker jelly. Our results provide a biologically realistic assessment of host defenses via nutritive jelly and contribute to a better understanding of the ecology of M. plutonius and of secondary invaders bacteria in the honey bee colony environment, thus shedding light on the selective forces affecting their virulence and on their role in EFB pathogenesis.

The effect of ergosterol on the allogrooming behavior of termites in response to the entomopathogenic fungus Metarhizium anisopliae.

Termites have physiological and behavioral immunities that make them highly resistant to pathogen infections, which complicates biocontrol efforts. However, the stimuli that trigger the pathogen-avoidance behaviors of termites are still unclear. Our study shows that workers of Coptotermes formosanus exposed to the conidia of Metarhizium anisopliae exhibited a significantly higher frequency and longer duration of allogrooming behaviors compared with untreated termites. Volatile compounds in the cuticle of control termites and termites previously exposed to a suspension of M. anisopliae conidia were analyzed and compared using a gas chromatography-mass spectrometer (GC-MS). Our results showed that the amount of ergosterol differed between the fungus-exposed and control termites. Choice tests showed that termites significantly preferred to stay on filter paper treated with ergosterol (0.05, 0.1, or 1.0 mg/mL) compared with control filter paper. In addition, termites exposed to ergosterol followed by M. anisopliae conidia were allogroomed at a significantly higher frequency and for a longer duration than termites exposed to alcohol (the solvent used with the ergosterol in the ergosterol trials) alone followed by M. anisopliae conidia. These results showed that ergosterol may enhance the allogrooming behavior of termites in the presence of entomopathogenic fungi.

Distinct and enhanced hygienic responses of a leaf-cutting ant toward repeated fungi exposures.

Leaf-cutting ants and their fungal crops are a textbook example of a long-term obligatory mutualism. Many microbes continuously enter their nest containing the fungal cultivars, destabilizing the symbiosis and, in some cases, outcompeting the mutualistic partners. Preferably, the ant workers should distinguish between different microorganisms to respond according to their threat level and recurrence in the colony. To address these assumptions, we investigated how workers of Atta sexdens sanitize their fungal crop toward five different fungi commonly isolated from the fungus gardens: Escovopsis sp., Fusarium oxysporum, Metarhizium anisopliae, Trichoderma spirale, and Syncephalastrum sp. Also, to investigate the plasticity of these responses toward recurrences of these fungi, we exposed the colonies with each fungus three times fourteen days apart. As expected, intensities in sanitization differed according to the fungal species. Ants significantly groom their fungal crop more toward F. oxysporum, M. anisopliae, and Syncephalastrum sp. than toward Escovopsis sp. and T. spirale. Weeding, self-, and allogrooming were observed in less frequency than fungus grooming in all cases. Moreover, we detected a significant increase in the overall responses after repeated exposures for each fungus, except for Escovopsis sp. Our results indicate that A. sexdens workers are able to distinguish between different fungi and apply distinct responses to remove these from the fungus gardens. Our findings also suggest that successive exposures to the same antagonist increase hygiene, indicating plasticity of ant colonies' defenses to previously encountered pathogens.

First insights into the honey bee (Apis mellifera) brain lipidome and its neonicotinoid-induced alterations associated with reduced self-grooming behavior.

Introduction: Honey bees (Apis mellifera) play key roles in food production performing complex behaviors, like self-grooming to remove parasites. However, the lipids of their central nervous system have not been examined, even though they likely play a crucial role in the performance of cognitive process to perform intricate behaviors. Lipidomics has greatly advanced our understanding of neuropathologies in mammals and could provide the same for honey bees. Objectives: The objectives of this study were to characterize the brain lipidome of adult honey bees and to assess the effect of clothianidin (a neurotoxic insecticide) on the brain lipid composition, gene expression, and performance of self-grooming behavior under controlled conditions (cage experiments). Methods: After seven days of exposure to oral sublethal doses of clothianidin, the bees were assessed for self-grooming behavior; their brains were dissected to analyze the lipidome using an untargeted lipidomics approach and to perform a high throughput RNAseq analysis. Results: Compared to all other organisms, healthy bee brain lipidomes contain unusually high levels of alkyl-ether linked (plasmanyl) phospholipids (51.42%) and low levels of plasmalogens (plasmenyl phospholipids; 3.46%). This could make it more susceptible to the effects of toxins in the environment. A positive correlation between CL 18:3/18:1/14:0/22:6, TG 6:0/11:2/18:1, LPE 18:0e and intense self-grooming was found. Sublethal doses of a neonicotinoid altered PC 20:3e/15:0, PC 16:0/18:3, PA 18:0/24:1, and TG 18:1/18:1/18/1 levels, and affected gene expression linked to GPI-anchor biosynthesis pathway and energy metabolism that may be partially responsible for the altered lipid composition. Conclusion: This study showed that lipidomics can reveal honey bee neuropathologies associated with reduced grooming behavior due to sublethal neonicotinoid exposure. The ease of use, unusual brain lipidome as well as characterized behaviors that are affected by the environment make honey bees a promising model organism for studying the neurolipidome and associations with neurobehavioral disorders.

Context-Dependent Viral Transgenerational Immune Priming in Honey Bees (Hymenoptera: Apidae).

Transgenerational immune priming is the process of increased resistance to infection in offspring due to parental pathogen exposure. Honey bees (Apis mellifera L. (Hymenoptera: Apidae)) are hosts to multiple pathogens, and this complex immune function could help protect against overwhelming infection. Honey bees have demonstrated transgenerational immune priming for the bacterial pathogen Paenibacillus larvae; however, evidence for viral transgenerational immune priming is lacking across insects in general. Here we test for the presence of transgenerational immune priming in honey bees with Deformed wing virus (DWV) by injecting pupae from DWV-exposed queens and measuring virus titer and immune gene expression. Our data suggest that there is evidence for viral transgenerational immune priming in honey bees, but it is highly context-dependent based on route of maternal exposure and potentially host genetics or epigenetic factors.

Social Apoptosis in Varroa Mite Resistant Western Honey Bees (Apis mellifera).

Honey bees are eusocial animals that exhibit both individual and social immune responses, which influence colony health. This is especially well-studied regarding the mite Varroa destructor Anderson and Trueman (Parasitiformes: Varroidae), a parasite of honey bee brood and disease vector. Varroa was introduced relatively recently to Apis mellifera L. (Hymenoptera: Apidae) and is a major driver of the catastrophic die-off of honey bee colonies in the last decade. In contrast, the original host species, Apis cerana Fabricius (Hymenoptera: Apidae) is able to survive mite infestations with little effect on colony health and survival. This resilience is due in part to a newly identified social immune response expressed by developing worker brood. Varroa infested female A. cerana brood experience delayed development and eventually die in a process called 'social apoptosis'. Here, an individual's susceptibility to Varroa results in colony level resistance. We tested for the presence of the social apoptosis trait in two Varroa resistant stocks of A. mellifera (Pol-line and Russian) with different selection histories and compared them to a known Varroa-susceptible stock (Italian). We assessed the survival and development of worker brood reared in either highly or lightly infested host colonies, then receiving one of three treatments: uninfested, experimentally inoculated with a Varroa mite, or wounded to simulate Varroa damage. We found that response to treatment was only differentiated in brood reared in lightly infested host colonies, where experimentally infested Russian honey bees had decreased survival relative to the mite-susceptible Italian stock. This is the first evidence that social apoptosis can exist in Western honey bee populations.

Honey Bees (Apis mellifera Hymenoptera: Apidae) Preferentially Avoid Sugar Solutions Supplemented with Field-Relevant Concentrations of Hydrogen Peroxide Despite High Tolerance Limits.

Honey bees (Apis mellifera L. Hymeoptera: Apidae) use hydrogen peroxide (synthesized by excreted glucose oxidase) as an important component of social immunity. However, both tolerance of hydrogen peroxide and the production of glucose oxidase in honey is costly. Hydrogen peroxide may also be encountered by honey bees at high concentrations in nectar while foraging, however despite its presence both in their foraged and stored foods, it is unclear if and how bees monitor concentrations of, and their behavioral responses to, hydrogen peroxide. The costs of glucose oxidase production and the presence of hydrogen peroxide in both nectar and honey suggest hypotheses that honey bees preferentially forage on hydrogen peroxide supplemented feed syrups at certain concentrations, and avoid feed syrups supplemented with hydrogen peroxide at concentrations above some tolerance threshold. We test these hypotheses and find that, counter to expectation, honey bees avoid glucose solutions supplemented with field-relevant hydrogen peroxide concentrations and either avoid or don't differentiate supplemented sucrose solutions when given choice assays. This is despite honey bees showing high tolerance for hydrogen peroxide in feed solutions, with no elevated mortality until concentrations of hydrogen peroxide exceed 1% (v/v) in solution, with survival apparent even at concentrations up to 10%. The behavioral interaction of honey bees with hydrogen peroxide during both within-colony synthesis in honey and when foraging on nectar therefore likely relies on interactions with other indicator molecules, and maybe constrained evolutionarily in its plasticity, representing a constitutive immune mechanism.

Proteomic profiling of royal jelly produced by Apis mellifera L. exposed to food containing herbicide-based glyphosate.

Royal jelly (RJ) is rich in protective elements associated with collective immune defenses in the hive of Apis mellifera. Exposure of bees to glyphosate-based herbicides causes ultrastructural changes in the hypopharyngeal glands and a reduction in the production of RJ. However, the effects of glyphosate-based herbicides on the protein composition of RJ and consequences for the hive are unknown. Thus, we performed proteomic profiling of royal jelly produced in hives of A. mellifera exposed to food containing 1,5 µL of Roundup® (2.16 mg. g-1 of glyphosate). The production of RJ was carried out in six hives, following the method of artificial production of queens. The combs containing 80 grafting cells were introduced into the hives, and the collection of royal jelly was performed after 72 h. Two treatments were determined based on hive feeding and the hive as the experimental unit: Control and "Roundup®". Royal jelly from the Roundup® treatment hives was compared to the Control hives. Proteins with differences in expression were identified by mass spectrometry. Only the proteins present in all three biological replicates were considered in the differential abundance analysis, using Student's t-test (p-value < 0.05, two-tailed). Hives that received food containing Roundup®, analysis showed alterations in protein profile in the RJ produced therein. In total, 24 proteins were identified, and the accumulation of Major royal jelly protein 3 (MRJP3) was downregulated, showing a significant reduction in hives exposed to food containing Roundup® in relation to control hives (t = 0.0017). MRJP3 acts analogously to polyclonal antigen-antibody reactions, performing functions related to immunity in bees of different ages and castes. To the best of our knowledge, this is the first study to demonstrate changes in the proteomic profile of RJ caused by glyphosate-based herbicides, indicating its negative effects on the nutrition and social immunity of bees.

Colony-Level Viral Load Influences Collective Foraging in Honey Bees.

Nutrition is an important component of social insect colony health especially in the face of stressors such as parasitism and viral infections. Honey bees are known to preferentially select nectar and pollen based on macronutrient and phytochemical contents and in response to pathogen loads. However, given that honey bees live in colonies, collective foraging decisions may be impacted directly by forager infection status but also by colony health. This field experiment was conducted to determine if honey bee viral infections are correlated with pollen and nectar foraging and if these associations are impacted more by colony or forager infection. By comparing regressions with and without forager and colony variables and through structural equation models, we were able to determine the relative contributions of colony and forager virus loads on forager decisions. We found that foragers had higher numbers and levels of BQCV and CBPV but lower levels of DWV viruses than their respective colonies. Overall, individuals appeared to forage based a combination of their own and colony health but with greater weight given to colony metrics. Colony parasitism by Varroa mites, positively correlated with both forager and colony DWV-B levels, was negatively associated with nectar weight. Further, colony DWV-B levels were negatively associated with individually foraged pollen protein: lipid ratios but positively correlated with nectar weight and sugar content. This study shows that both colony and forager health can simultaneously mediate individual foraging decisions and that the importance of viral infections and parasite levels varies with foraging metrics. Overall, this work highlights the continued need to explore the interactions of disease, nutrition, and genetics in social interactions and structures.

Sociality and parasite transmission.

Parasites and their social hosts form many different relationships. But what kind of selection regimes are important? A look at the parameters that determine fitness of the two parties suggests that social hosts differ from solitary ones primarily in the structure of transmission pathways. Because transmission is, both, the physical encounter of a new host and infecting it, several different elements determine parasite transmission success. These include spatial distance, genetic distance, or the temporal and ecological niche overlaps. Combing these elements into a 'generalized transmission distance' that determines parasite fitness aids in the identification of the critical steps. For example, short-distance transmission to genetically similar hosts within the social group is the most frequent process under sociality. Therefore, spatio-genetical distances are the main driver of parasite fitness. Vice versa, the generalized distance identifies the critical host defences. In this case, host defences should be primarily selected to defend against the within-group spread of an infection, especially among closely related group members.

Hygiene-Eliciting Brood Semiochemicals as a Tool for Assaying Honey Bee (Hymenoptera: Apidae) Colony Resistance to Varroa (Mesostigmata: Varroidae).

Despite numerous interventions, the ectoparasitic mite Varroa (Varroa destructor Anderson and Trueman [Mesostigmata: Varroidae]) and the pathogens it vectors remain a primary threat to honey bee (Apis mellifera Linnaeus [Hymenoptera: Apidae]) health. Hygienic behavior, the ability to detect, uncap, and remove unhealthy brood from the colony, has been bred for selectively for over two decades and continues to be a promising avenue for improved Varroa management. Although hygienic behavior is expressed more in Varroa-resistant colonies, hygiene does not always confer resistance to Varroa. Additionally, existing Varroa resistance selection methods trade efficacy for efficiency, because those achieving the highest levels of Varroa resistance can be time-consuming, and thus expensive and impractical for apicultural use. Here, we tested the hypothesis that hygienic response to a mixture of semiochemicals associated with Varroa-infested honey bee brood can serve as an improved tool for predicting colony-level Varroa resistance. In support of our hypothesis, we demonstrated that a mixture of the compounds (Z)-10-tritriacontene, (Z)-8-hentriacontene, (Z)-8-heptadecene, and (Z)-6-pentadecene triggers hygienic behavior in a two-hour assay, and that high-performing colonies (hygienic response to ≥60% of treated cells) have significantly lower Varroa infestations, remove significantly more introduced Varroa, and are significantly more likely to survive the winter compared to low-performing colonies (hygienic response to <60% of treated cells). We discuss the relative efficacy and efficiency of this assay for facilitating apiary management decisions and selection of Varroa-resistant honey bees, as well as the relevance of these findings to honey bee health, pollination services, and social insect communication.

Honey Bee (Apis mellifera) Immunity.

At the individual level, honey bees (Apis mellifera) rely on innate immunity, which operates through cellular and humoral mechanisms, to defend themselves against infectious agents and parasites. At the colony level, honey bees have developed collective defense mechanisms against pathogens and pests, such as hygienic and grooming behaviors. An understanding of the immune responses of honey bees is critical to implement strategies to reduce mortality and increase colony productivity. The major components and mechanisms of individual and social immunity of honey bees are discussed in this review.