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The chemical integration strategies of facultative social parasites of social insects have not received the scientific attention they deserve, even though there is considerable research being done on the strategies of obligate social parasites. We simulated intraspecific nest usurpations in the social paper wasp, Polistes biglumis, by dividing each nest into two parts and putting one half in the care of the original foundress and the other half in the care of a usurper. After 8days, we removed and killed foundresses and usurpers, and later tested the responses of naïve, sister-offspring to them. In each half-colony, the offspring were more tolerant to the female that was last on the nest, regardless of whether she was the foundress or a usurper. This suggested that usurpers had the chemical means to be tolerated by the host offspring. Comparisons between the epicuticular hydrocarbon profiles of foundresses and usurpers showed that usurpers were neither chemically insignificant nor transparent, nor were they mimetic, as obligate parasites often are. Instead, usurpers had chemical profiles richer in methyl-branched hydrocarbons than those of the foundresses. Analyses of the hydrocarbon profiles of nest paper revealed that usurpers supplemented host nests with their own hydrocarbons, a sort of nest marking. As a result, the chemical profiles of the host nests became qualitatively more similar to those of the usurpers. These chemical strategies illustrate that branched hydrocarbons play a role as semiochemicals and that facultative parasites may not all be on the main pathway to obligate parasitism. [ABSTRACT FROM AUTHOR]

1. Like avian brood parasites, obligate insect social parasites exploit the parental care of a host species to rear their brood, causing an evident loss of host reproductive success. This fitness cost imposes selective pressure on the host to reduce the parasite effect. A possible outcome of an evolutionary arms race is the selection of host morphological counter-adaptations to resist parasite attacks. 2. We studied host–parasite pairs of Polistes wasps in which the fighting equipment of the parasite's body allows it to enter the host colony. 3. We searched for host morphological traits related to fighting ability that could be considered counter-adaptations. As a host–parasite co-evolutionary arms race can only occur where the two lineages co-exist, we compared morphological traits of hosts belonging to populations with or without parasite pressure. We report that host foundresses belonging to populations under strong parasite pressure have a larger body size than those belonging to populations without parasite pressure. 4. Behavioural experiments carried out to test if an increase in host body size is useful to oppose parasite usurpation show that large body size foundresses exhibit a greater ability of nest defence. [ABSTRACT FROM AUTHOR]

Coevolutionary theories applied in the study of host–parasite systems indicate that lineages exhibit progressive trends in response to reciprocal selective pressures. Avian brood parasites have generated intense interest as models for coevolutionary processes. Similar to avian cuckoos, Polistes wasp social parasites usurp a nest and exploit the parental care of a congeneric species to rear their own brood. In the present study, we show a coevolutionary arms race in the daily activity pattern in a Polistes host–parasite pair. We measured the daily activity rate, in constant laboratory conditions, of both host and parasite females during the period in which nest usurpations occur. The parasites showed a hyperkinesis in the middle of the day. As the field observations suggested, this mid-day activity is used to perform host nest usurpation attempts. Timing the usurpations allows the parasite to maximize its usurpation attempts during daytime when the host defence is lower. A field comparison of host presence on the nest in two populations with different parasitism rates showed that populations under strong parasitic pressure exhibit timing counteradaptations to optimize nest defence. This study provides the first example of a mutual coadaptation in timing activity in a parasite–host system. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 399–405. [ABSTRACT FROM AUTHOR]

Foundresses and workers of Polistes paper wasps show slight morphological and physiological differences. However, after the emergence of the workers, the castes can be readily discriminated by their behaviour: the dominant foundress is the principal egg-layer, whereas workers perform different tasks linked to colony development. Previous studies have demonstrated in this genus that defence of the colony by the workers is more effectively carried out by a collective response elicited by venom volatiles used as alarm pheromones. In the present study, gas chromatography-mass spectrometry analyses of the venom volatiles of foundresses and workers of Polistes dominulus (Christ) show predominantly quantitative differences. Spiroacetals, mainly (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, are significantly higher in the venom volatiles fraction of workers, whereas the amount of N-(3-methylbutyl)acetamide is almost double in foundresses. On the basis of the chemical results, behavioural assays were performed on fifteen field colonies to test the alarm response of the resident wasps to venom extracts from foundresses and workers. Our behavioural results suggest that worker venom has a stronger alarm effect on the colonies than that of the foundresses, which seems unable to elicit the complete alarm response ending with a final attack and sting. The venom volatiles of P. dominulus workers serve mainly to alarm the colony whilst those of foundresses may also be linked to additional functions related to conspecific interactions. [ABSTRACT FROM AUTHOR]

The active and coordinating capacity of defending the nest is a key feature of social insects. The present study investigates the presence of alarm pheromones in the venom of workers of the social wasp, Polistes dominulus. Laboratory experiments were performed with caged colonies of P. dominulus using a wind tunnel apparatus to test the behavioural response of workers to venom released by other workers and to venom extracts. Contrary to that previously reported for European paper wasps, the present results show that the venom is the source of alarm pheromones. Field experiments combining a visual (black target) and a chemical stimulus (venom extract) were performed to test the effect of the venom on the reaction of colonies. Wasps leave the nest, land on the visual target and attack the target significantly more once exposed to venom extract plus target than to solvent plus target. This work shows that the venom of P. dominulus workers elicits an alarm response, reduces the threshold for attack and acts as an attractant on targets. These results using P. dominulus indicate that, in both American and European species, colony defence is based on the same features, suggesting that chemical alarm is a widespread trait in the genus Polistes. [ABSTRACT FROM AUTHOR]

Studies on avian cuckoos have demonstrated that parasite chicks compete with host fledglings to monopolize food or manipulate the foster parents to increase their provisioning rate. This topic has never been explicitly investigated in insect social parasites, which use the social system of another species to raise their brood. Here we show that the immature brood of the cuckoo wasp Polistes sulcifer grows more rapidly than the host immature brood. Host workers perform more parental care to parasite larvae than to conspecific ones. Thus, the rapid growth of the parasite larvae is evidently due to increased host care, which prolongs the development of host larvae reared in the same colony. We suggest that parasite larvae play an active role in host exploitation through manipulation of host workers, as occurs in parasitic birds. [ABSTRACT FROM AUTHOR]

Reproduction in cooperative animal groups is often dominated by one or a few individuals, with the remaining group members relegated to nonreproductive helping roles. This reproductive skew can evolve if helpers receive fitness benefits such as potential future inheritance of the breeding position, but the mechanisms by which inheritance is determined are not well resolved. Polistes paper wasps form highly reproductively skewed groups and inheritance of the breeding position is likely to play a key role in the maintenance of this social structure, making them excellent models for the processes by which simple societies are maintained. Reproductive succession is thought to be determined via an age-based convention in some Polistes species, but there is also evidence for contest-based succession systems in which the replacement queen uses physical aggression to overpower and thereby subordinate her nestmates. Here, we provide evidence that queen succession in colonies of the European paper wasp Polistes dominula is determined via convention rather than contest, with little disruption to the colony's social functioning. We use queen removal experiments and fine-scale behavioral analyses to confirm that age is a strong predictor of succession, and that behavioral responses to queen removal are restricted to the oldest individuals rather than being experienced equally across the group. We provide the most comprehensive and detailed experimental analysis on the dynamics of breeder succession in a cooperatively breeding invertebrate to date, thereby shedding light on the mechanisms by which animal societies are able to maintain cohesion in the face of within-group conflict. [ABSTRACT FROM AUTHOR]

Differences in male and female phenotypes are often the results of sexual selection. Over the years, a vast number of studies investigated how and why the 2 sexes differ in their physical appearance, reaching the conclusion that peculiar visual traits, signals, or ornaments usually evolve under the pressure of sexual selection to mediate intrasexual competition and mate choice. In social contexts, however, males and females can hold different roles and social interactions may depend on the individual gender. The female-dominated hymenopteran societies represent a fascinating scenario to investigate recognition and communication among individuals of different genders outside a common sexual selection framework because sterile female workers typically do not mate and are not attracted to males. Here, we used laboratory bioassays (lure presentation experiments) to evaluate the ability of Polistes dominula workers to discriminate between individuals of the 2 genders, investigating the relevance of the chemical and visual cues potentially involved in such process. Our results showed that P. dominula workers are able to discriminate between the sexes and visual cues rather than chemical ones are responsible for such discrimination. [ABSTRACT FROM AUTHOR]

Males are under different selective pressures than females, which results in differences in the physiology of the two sexes to maximize their fitness. In terms of immunity, males are typically considered as the 'sicker sex', where immunocompetence is reduced to favour increased reproductive output. However, male social Hymenoptera are also haploid and therefore lack allelic variation at the individual level, which can also lead to reduced immunocompetence. Over the last decade, several studies have provided evidence for a higher susceptibility to disease in males of social Hymenoptera, without clarifying whether this susceptibility was a direct consequence of their haploid condition or the result of a 'live hard, die young' overall evolutionary strategy. In the present study, we used an experimental approach of bacterial challenge to test the immune response of males and females in two species of social Hymenoptera (honey bees, Apis mellifera; paper wasps, Polistes dominula), where males show very different life-history traits. Drones benefit from colony protection for most of their life, whereas P. dominula males leave their colonies and have to survive for weeks at leks. If the haploid condition is responsible for a higher susceptibility in males, we should expect a lower immune response in males of both species compared to females. Conversely, if the immunocompetence depends on the life-history traits of males, an opposite trend is expected in males of the two species. Our results do not support the 'haploid susceptibility hypothesis' but are in accordance with the different life history of males from the two species. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 274-278. [ABSTRACT FROM AUTHOR]

Invasive alien pest insect species represent a major threat for agriculture and biodiversity. Because chemical treatments employed to contrast such pests elicit serious environmental and human health problems, a great effort is currently directed to develop long term and environmentally friendly biological control strategies. However, the successful application of some promising techniques, such as the Sterile Insect Technique (SIT), requires a deep knowledge of the pest basic biology. Here, we argue that understanding pest sexual biology using a social network approach can significantly improve the performance of control strategies. For example, SIT may benefit from understanding how individuals interact and how males accede to reproduction, in order to target the most reproductively active and polygamic males. In this paper we studied the socio-sexual networks of the Asian red palm weevil (RPW) Rhynchophorus ferrugineus, a worldwide invader which is causing heavy economic impacts on several palm species. We found that the RPW has a highly promiscuous mating system, characterized by forced interruptions of pair copulations by additional males. The social network is highly non-random nor regular: few males almost monopolize reproduction, behaving as key-players in the network of matings. Additionally, males have a stable pattern of sexual behaviour over time. We use RPW social network as a case study to direct the development of management techniques such as SIT strategy. [ABSTRACT FROM AUTHOR]

Obligate insect social parasites evolve traits to effectively locate and then exploit their hosts, whereas hosts have complex social behavioral repertoires, which include sensory recognition to reject potential conspecific intruders and heterospecific parasites. While social parasites and host behaviors have been studied extensively, less is known about how their sensory systems function to meet their specific selective pressures. Here, we compare investment in visual and olfactory brain regions in the paper wasp Polistes dominula, and its obligate social parasite P. sulcifer, to explore the links among sensory systems,brain and behavior. Our results show significant relative volumetric differences between these two closely related species, consistent with their very different life histories. Social parasites show proportionally larger optic lobes and central complex to likely navigate long‐distance migrations and unfamiliar landscapes to locate the specific species of hosts they usurp. Contrastingly, hosts have larger antennal lobes and calyces of the mushroom bodies compared with social parasites, as predicted by their sensory means to maintain social cohesion via olfactory signals, allocate colony tasks, forage, and recognize conspecific and heterospecific intruders. Our work suggests how this tradeoff between visual and olfactory brain regions may facilitate different sensory adaptations needed to perform social and foraging tasks by the host, including recognition of parasites, or to fly long distances and successful host localizing by the social parasite. [ABSTRACT FROM AUTHOR]

Understanding the major mechanisms that allow an alien species to become invasive is crucial for limiting the impact of such species, and individual immunity seems to be a crucial trait for their large range colonization when introduced to a new area. Indeed, a high resistance to pathogens and parasites could favour the establishment and proliferation of an alien species in a newly colonized region. A striking example of recent successful invasion is represented by the Asian hornet, Vespa velutina nigrithorax, which has invaded Western Europe threatening bees and beekeeping activities. Investigating the biology of this species is fundamental to understand how V. velutina nigrithorax has become invasive in Europe and this knowledge could be crucial for limiting its impact. Here, by performing bacterial challenge bioassays, we compare the immune competence of different castes and sex of a population of the invasive Asian hornet, V. velutina nigrithorax, and of the native European hornet, V. crabro. Our results demonstrate that the two species differ in their immunocompetence with respect to caste: a higher level of immunocompetence was found in the reproductive females of the Asian hornet which were resistant to bacterial challenge when compared to workers and males of both species and to reproductive females of the native European hornet. The high pathogen resistance in reproductive females of the Asian hornet, might therefore represent a key factor contributing to the ecological success and spread of this invader. [ABSTRACT FROM AUTHOR]

In order to understand how the apparent freedom of individual movements can concur with social order in a colony, we investigated spatial relationships between foundresses, workers and immature brood in a paper wasp. This is the first time an ecological analytical approach (home range analysis) has been employed to describe small scale spatial use in a social context. In this study, home range was not used in its strictly ecological sense, but rather applied to the comb. Our results show that the positions individual wasps assumed on Polistes dominulus combs are spatially structured. Workers and foundresses do not occupy the comb in random distribution, but rather follow predictable spatial patterns. Each active wasp has its own spatial fidelity area, at least over a 1 d observation period, spending the majority of its time within a very small area averaging approx. 12% of the comb but occasionally it may cover an area of up to 50% of the comb surface. Dominant females occupied a significantly smaller area that either subordinate foundresses or workers. Areas patrolled by workers varied in shape and size, with no relation to time spent on the comb, wasp density or position of immature brood. All the wasps clumped around the dominant female, who proved to be the only individual affected by cell content. Nevertheless, although the wasps tended to clump together, average superimposition rates among nest-mates was very low (higher in workers than foundresses), suggesting that the wasps limit each other’s individual spaces. [ABSTRACT FROM AUTHOR]

During reproductive phase, larvae of male and female are intermingled in nest of social wasps. Workers care for and feed larvae that gives them an opportunity to bias investment with respect to sex, or even to kill some larvae, if they can distinguish between immature males and females. Cuticular hydrocarbon (CHC) mixtures are the most studied cues for species, nestmate, and caste recognition in social Hymenoptera. In this study, we investigate the paper wasp Polistes dominulus to see if male and female larvae show different patterns of CHCs and if workers are able to discriminate between male and female larvae on this basis. We performed gas chromatography-mass spectrometry analysis on cuticular extracts of larvae, and then we genotyped them to assign sex. We found sex-based variation in CHC-profiles sufficient for discrimination. However, our behavioral assays do not support the view that adults discriminate between male and female larvae within nests. [ABSTRACT FROM PUBLISHER]

Simple Summary: Social insects use cuticular hydrocarbons for chemical recognition and communication. Cuticular hydrocarbons can also be exploited by parasites to their advantage for undermining host recognition systems. The small hive beetle (SHB) is a parasite of honey bee colonies but can also infest nests of other bee species. However, its chemical profile is still not known. For the first time, the present study investigated the SHB chemical profile and compared it with that of its honey bee host. The results show that the SHB has a low chemical profile that is similar to its honey bee host's. However, while honey bees had a clear colony-specific chemical profile, SHBs did not. The generic chemical profile of the SHB is most likely linked to its free-flying behaviour in the field as these parasites are known to switch between host colonies, possibly limiting the acquisition of a colony specific chemical profile. Our findings also suggest that SHBs do not exploit any finely tuned chemical strategy to conceal their presence inside host colonies and probably rely on behavioural adaptations. Cuticular hydrocarbons (CHCs) cover insects' bodies and play important roles in chemical communication, including nestmate recognition, for social insects. To enter colonies of a social host species, parasites may acquire host-specific CHCs or covertly maintain their own CHC profile by lowering its quantity. However, the chemical profile of small hive beetles (SHBs), Aethina tumida, which are parasites of honey bee, Apis mellifera, colonies, and other bee nests, is currently unknown. Here, adults of SHB and honey bee host workers were collected from the same field colonies and their CHC profiles were analysed using GC-MS. The chemical profiles of field-sampled SHBs were also compared with those of host-naive beetles reared in the laboratory. Laboratory-reared SHBs differed in their CHC profiles from field-sampled ones, which showed a more similar, but ten-fold lower, generic host CHC profile compared to host workers. While the data confirm colony-specific CHCs of honey bee workers, the profile of field-collected SHBs was not colony-specific. Adult SHBs often commute between different host colonies, thereby possibly preventing the acquisition of a colony-specific CHC profiles. An ester was exclusive to both groups of SHBs and might constitute an intraspecific recognition cue. Our data suggest that SHBs do not use any finely tuned chemical strategy to conceal their presence inside host colonies and instead probably rely on their hard exoskeleton and defence behaviours. [ABSTRACT FROM AUTHOR]

In animals, restlessness is a strategy to fulfil a goal within a narrow seasonal window when ecological and physiological constraints require the performance of certain fundamental events. Although restlessness can be expected in parasitic species that have their biological cycle similar to that of the host, no ‘urge to parasitize’ has thus far been demonstrated in any host-parasite pair. The paper wasp, Polistes sulcifer, is a social parasite that has lost the nest-building ability and marked by the absence of the worker caste; it depends on a congeneric host species to reproduce. Host colony usurpation is successful when it occurs in a well-defined seasonal window. The short time available for host-nest usurpation might lead to parasite restlessness that overlaps this period. Under controlled laboratory conditions, we demonstrated that the parasite females exhibit ‘usurpation restlessness’ during the period in which field usurpations occur. Additional experiments showed that both this period and laboratory temperature influence the parasite’s ‘urge to usurp’. [ABSTRACT FROM AUTHOR]

Abstract: Social insects use cuticular hydrocarbons (CHCs) as recognition cues in a variety of social contexts, such as species and nestmate recognition. Discrimination of nestmates is an important requisite to avoid exploitation by unrelated individuals. In social wasps, use of CHCs in nestmate recognition has been demonstrated only among adults, whereas very little is known regarding brood recognition. We performed gas chromatography–mass spectrometry analyses of the CHCs of adults and larvae of the social wasp Polistes dominulus and found that larvae possess a characteristic chemical colony-specific pattern distinct from that of adults. Behavioural assays confirmed that these are recognized and discriminated by adults. Larval epicuticular substances are therefore sufficient for recognition of nestmate larvae by adults and demonstrate that wasps are able to discriminate between alien and nestmate larval odours. [Copyright &y& Elsevier]

Polistes foundresses can behave as facultative social parasites when, instead of founding their own nest, they usurp colonies of the same or a different species and temporary use the host workforce to raise their own brood. Conspecific usurpation appears to be common among Polistes wasps, but nothing is known about the mechanisms that these facultative social parasites use to have themselves accepted within usurped colonies. Using behavioural tests, we studied the chemical strategies employed by females of Polistes nimphus when they behave as facultative social parasites in colonies of the same or of a different species. We hypothesized that usurpers would mark host nests with their own odours and/or acquire host nest odours in order to camouflage their real identity from host workers. Our results indicated that P. nimphus usurpers used different chemical strategies depending on host nest species: they acquired conspecific host odours but marked heterospecific host combs with their own odours. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 505–512. [ABSTRACT FROM AUTHOR]

Reports on a study that focuses on the social wasp, Polistes dominulus, and the purpose of kin selection in wasp life spans. Details on the wasp and its environment; How social wasp societies are functionally unlike other social insects, but similar to certain vertebrate societies; Methods of study; Diagrams; Results and conclusions.

The assessment of species composition in a certain area may become outdated over time due to community dynamics including species range expansion, but also to local extinctions, species introductions and taxonomic redefinition. Therefore, updated checklists are required for animal conservation and management. Exhaustive checklists of invertebrate species may be challenging, as species determination often requires the analysis by specialists, but they are fundamental for local conservation practices. In this work, we provided an annotated preliminary checklist of invertebrates of the Special Conservation Area "Poggi di Prata" (province of Grosseto, southern Tuscany), detected through field samplings with experts, and a permanent Bioblitz set out on an online citizenscience platform (iNaturalist.org). The final dataset (1898-2020) included 329 records of 282 species (217 insects, 34 gastropods, 30 arachnids and 1 chilopod). Most records were uploaded on iNaturalist (about 56.5%), others came from observations or sampling collections (37%) and were determined by specialists. Only the remaining 6.5% of records came from published studies. Three species were protected by the Habitat Directive, 15 by the Tuscan Regional Law. We also detected two endemic or near-endemic taxa of this area: the beetle Paramaurops diecki massetanus and the land snail Marmorana saxetana. The unexpected (Italian southernmost) record of Gaurotes virginea needs to be deepened. Furthermore, 12 alien species, including insects affecting human economy and wellness (e.g., Rhinchophorous ferrugineus, Aedes albopictus, Halyomorpha halys, Dryocosmus kuriphilus and Cydalima perspectalis), were also detected. With our work, we confirmed that citizen-science platforms (e.g. iNaturalist) are valuable tools, complementary to field-work by specialists, to map local biodiversity and they may help to improve biogeographical knowledge. [ABSTRACT FROM AUTHOR]

Parasites and pathogens can follow different patterns of infection depending on the host developmental stage or sex. In fact, immune function is energetically costly for hosts and trade‐offs exist between immune defenses and life history traits as growth, development and reproduction and organisms should thus optimize immune defense through their life cycle according to their developmental stage. Identifying the most susceptible target and the most virulent pathogen is particularly important in the case of insect pests, in order to develop effective control strategies targeting the most vulnerable individuals with the most effective control agent. Here, we carried out laboratory tests to identify the most susceptible target of infection by infecting different stages of the red palm weevil Rhynchophorus ferrugineus (larvae, pupae, male, and female adults) with both a generic pathogen, antibiotic‐resistant Gram‐negative bacteria Escherichia coli XL1‐Blue, and two specific strains of entomopathogenic nematodes (EPNs), Steinernema carpocapsae ItS‐CAO1 and Heterorhabditis bacteriophora ItH‐LU1. By evaluating bacterial clearance, host mortality and parasite progeny release, we demonstrate that larvae are more resistant than adults to bacterial challenge and they release less EPNs progeny after infection despite a higher mortality compared to adults. Considering the two EPN strains, S. carpocapsae was more virulent than H. bacteriophora both in terms of host mortality and more abundant progeny released by hosts after death. The outcomes attained with unspecific and specific pathogens provide useful information for a more efficient and sustainable management of this invasive pest. [ABSTRACT FROM AUTHOR]

Social recognition represents the foundation of social living. To what extent social recognition is hard-wired by early-life experience or flexible and influenced by social context of later life stages is a crucial question in animal behaviour studies. Social insects have represented classic models to investigate the subject, and the acknowledged idea is that relevant information to create the referent template for nest-mate recognition (NMR) is usually acquired during an early sensitive period in adult life. Experimental evidence, however, highlighted that other processes may also be at work in creating the template and that such a template may be updated during adult life according to social requirements. However, currently, we lack an ad hoc experiment testing the alternative hypotheses at the basis of NMR ontogeny in social insects. Thus, to investigate the mechanisms underlying the ontogeny of NMR in Polistes wasps, a model genus in recognition studies, and their different role in determining recognition abilities, we subjected Polistes dominula workers to different olfactory experiences in different phases of their life before inserting theminto the social environment of a novel colony and testing them in recognition bioassays. Our results show that workers develop their NMR abilities based on their social context rather than through pre-imaginal and early learning or self-referencing. Our study demonstrates that the social context represents the major component shaping recognition abilities in a social wasp, therefore shedding new light on the ontogeny of recognition in paper wasps and prompting the reader to rethink about the traditional knowledge at the basis of the recognition in social insects. [ABSTRACT FROM AUTHOR]

The significant risk of disease transmission has selected for effective immune-defense strategies in insect societies. Division of labour, with individuals specialized in immunity-related tasks, strongly contributes to prevent the spread of diseases. A trade-off, however, may exist between phenotypic specialization to increase task efficiency and maintenance of plasticity to cope with variable colony demands. We investigated the extent of phenotypic specialization associated with a specific task by using allogrooming in the honeybee, Apis mellifera, where worker behaviour might lower ectoparasites load. We adopted an integrated approach to characterize the behavioural and physiological phenotype of allogroomers, by analyzing their behavior (both at individual and social network level), their immunocompetence (bacterial clearance tests) and their chemosensory specialization (proteomics of olfactory organs). We found that allogroomers have higher immune capacity compared to control bees, while they do not differ in chemosensory proteomic profiles. Behaviourally, they do not show differences in the tasks performed (other than allogrooming), while they clearly differ in connectivity within the colonial social network, having a higher centrality than control bees. This demonstrates the presence of an immune-specific physiological and social behavioural specialization in individuals involved in a social immunity related task, thus linking individual to social immunity, and it shows how phenotypes may be specialized in the task performed while maintaining an overall plasticity. [ABSTRACT FROM AUTHOR]

Eusocial insect colonies represent some of the most extreme examples of specialized division of labor. Ageing in workers is often associated with a temporal polyethism in the tasks performed both inside and outside the colony. Such behavioral transition is sometimes linked to a gradual reduction in individual immunity. Here, we studied the immune ability of Apis mellifera guard bees, which represent an intermediate stage between house bees working inside the nest and foragers collecting resources outside, to assess if their specific task is associated with an immune specialization. Through immune challenge with Gram-negative bacteria Escherichia coli, we compared the guards ability to clear bacterial cells from their haemolymph with respect to house bees and foragers. Our findings demonstrate that guards do not show an immune specialization linked to their task but seem to represent a transition also in terms of immunity, since their anti-bacterial response appears intermediate between house bees and foragers. [ABSTRACT FROM AUTHOR]

In the early stage of the invasion process, alien species may face costs linked to pioneer effect due to genetic bottleneck, drift and the consequential inbreeding depression. Thus, introduced species that show an immediate exponential growth in their invasive population should have some mechanisms to reduce such costs minimising the chance of inbreeding or allowing them to cope with them. The yellow-legged hornet Vespa velutina nigrithorax has been spotted in France in 2004; since then, the species has been invading Europe with a relentless pace. In their native range, males and reproductive females of a Chinese non-invasive sub-species of V. velutina seem to leave their nests to search for unrelated partners. However, previous studies showed a low genetic diversity and a high rate of diploid males in colonies of the invasive population, suggesting that mating could occur inside nests, where males should be able to discriminate between reproductive gynes and sterile workers. Here, we used laboratory behavioural assays to investigate the mating preferences of yellow-legged hornet males from the recent invasive population in Italy. We assessed the importance of nestmateship and female morpho-physiological traits, likely indicators of caste, in determining male attraction towards potential partners. Our results demonstrate that males are more attracted to bigger females with more abundant fat storage, good indicators of female reproductive caste in wasps, regardless of nestmateship. Our findings represent a first step in understanding the reproductive biology of V. velutina nigrithorax in its invasive range, providing a framework for future research in the field to prevent or reduce the species expansion. [ABSTRACT FROM AUTHOR]

Communication through vibrational signals is widespread among social insects and regulates crucial social activities. Females of the social wasp Polistes dominula produce substrate-borne vibrations on the combs by performing a conspicuous abdominal oscillatory behavior, known as abdominal wagging. Several studies have reported correlative evidence in support of its signaling role, but direct evidence is still lacking. Because abdominal wagging is strictly associated with the presence of larvae in the nest and with cell inspection, it has been suggested that it could be involved in adult--larvae communication. According to this hypothesis, abdominal wagging vibrations would have short-term effects related to food and trophallactic exchanges between adults and larvae by modulating salivary secretion (decreasing its amount, to prepare larvae to receive food, or stimulating the release of larval saliva to adults). Here, by using an electro-magnetic shaker, we assessed, for the first time, the short-term effects of abdominal wagging on larval behavior by recording larval responses and by measuring the amount of saliva released immediately after abdominal wagging playback. Our results show that larvae are able to perceive the substrate-borne vibrations produced by abdominal wagging and react by increasing the movement of their body, possibly in order to attract the attention of adult females during feeding nest inspection. Yet, we found that vibrations neither increase nor decrease the release of larval saliva. Our results support the hypothesis of the alleged role of vibrations in adult--larvae communications; however, they do not support the long- lasting hypothesis of salivary release modulation. [ABSTRACT FROM AUTHOR]

Mimicry is one of the most fascinating phenomena in nature 1. Mimicry traits often reflect complex, finely tuned, and sometimes extravagant relationships among species and have evolved to deceive predators or prey. Indeed, mimicry has most often evolved to discourage predation: the 'mimic' exhibits phenotypic convergence towards a non-related 'model' organism which is inedible or harmful, so that a given predator, or 'receiver', will refrain from attacking or ingesting the mimic. Traditionally, mimicry is mainly evident and has been mainly studied in the visual domain. Here, we report experiments that document the first case of interspecific acoustic mimicry in a mammal and demonstrate that the distress calls the greater mouse-eared bat (Myotis myotis) broadcasts when handled imitate sounds of stinging bees or wasps to discourage the bat's avian predators. Ancillotto et al. report a case of interspecific acoustic mimicry in a mammal, and demonstrate that the distress calls of the greater mouse-eared bat imitate sounds of stinging social hymenopterans to discourage the bat's avian predators. [ABSTRACT FROM AUTHOR]

[Display omitted] • Trissolcus japonicus and T. mitsukurii are valid potential biological control agents of H. halys. • Interspecific competition among BCAs can affect pest control success. • Multiparasitism caused a lower reproductive potential offspring production and wasted searching time. The invasive stink bug Halyomorpha halys , native to east Asia, is a severe agricultural pest of worldwide importance and biocontrol is a promising method for its long-term management. The two Asian egg parasitoids Trissolcus japonicus and Trissolcus mitsukurii are considered to be effective candidates as biological control agents. These species can co-occur in the same habitats and interspecific competition for hosts could therefore have an important role in natural control. We assessed the foraging behavior and the progeny production of both species under laboratory conditions with three different interspecific competition scenarios. With indirect competition, H. halys egg masses previously parasitized by the female of one species were offered to the competitor females after 0, 3, 5, or 7 days. With direct extrinsic competition, females of each species were tested in arenas either when introduced simultaneously (synchronous release) or when half of the host egg mass had already been parasitized by the other species (asynchronous release). Both Trissolcus species were able to parasitize host eggs already parasitized by the other species, although the progeny production always favored the species that arrived first on the host egg mass. However, in the synchronous releases scenario, T. mitsukurii displayed more aggressive behavior and spent more time defending the host egg mass than T. japonicus , resulting in a higher progeny production. Our results showed that multiparasitism among T. japonicus and T. mitsukurii , at least under laboratory conditions, resulted in a general waste of searching time, energy, eggs laid, and a lower reproductive potential by the second-arriving species on the host egg mass. [ABSTRACT FROM AUTHOR]

The red palm weevil Rhynchophorus ferrugineus, recently spreading from its native range throughout the world, is one of the most dangerous pests for several palm species. The sterile insect technique (SIT) is a promising environmentally friendly approach for the management of this pest. An essential prerequisite of the SIT is that irradiated males released in nature are as sexually competitive as their wild counterparts. Here we evaluated the potential use of the SIT in red palm weevil males by investigating the sexual competitiveness of gamma-irradiated (Cobalt 60 source, dose 80 Gray) males in the laboratory in a natural-like social context with a balanced sex ratio and by testing their efficacy in impairing female reproduction. Our results showed that irradiation did not affect any of the mating behaviour parameters. However, the male reproductive potential was drastically reduced, as fertility was markedly decreased in females mated with irradiated males. Therefore, an 80 Gray irradiation dose is a promising option for the SIT in the control of the red palm weevil, producing sterile but sexually competitive males when tested in a natural-like mating context. [ABSTRACT FROM AUTHOR]

Insect social parasites have to conquer a host colony by overcoming its defensive barriers. In addition to increased fighting abilities, many social parasites evolved sophisticated sensory deception mechanisms to elude host colonies defenses by exploiting host communication channels. Recently, it has been shown that the conspicuous facial markings of a paper wasp social parasite, Polistes sulcifer , decrease the aggressiveness of host foundresses. Two main hypotheses stand as explanations of this phenomenon: visual sensory deception (i.e. the black patterning reduces host aggression by exploiting the host visual communication system) and visual quality assessment (i.e. facial markings reduce aggressiveness as they signal the increased fighting ability of parasites). Through behavioral assays and morphological measurements we tested three predictions resulting from these hypotheses and found no support either for the visual sensory deception or for the quality assessment to explain the reduction in host aggressiveness towards the parasite. Our results suggest that other discrimination processes may explain the observed phenomenon. [ABSTRACT FROM AUTHOR]

Rhynchophorus ferrugineus, also known as the red palm weevil, is regarded as the major pest of palm trees. Although studies of the microbiota associated with this species have been performed in recent years, little attention has been dedicated to the influence of the diet in shaping the host bacterial community. Here, we investigated the influence of food sources (i.e. palm tissues vs apple based substrate) on the microbial diversity associated with RPW, which was compared with the microbiota associated with wild individuals of the sister species Rhynchophorus vulneratus. The bacterial characterization was performed using a culture independent approach, i.e. the 16S rRNA pyrotag, and a culture dependent approach for a subset of the samples, in order to obtain bacterial isolates from RPW tissues. The bacterial community appeared significantly influenced by diet. Proteobacteria resulted to be the most abundant clade and was present in all the specimens of the three examined weevil groups. Within Proteobacteria, Enterobacteriaceae were identified in all the organs analysed, including hemolymph and reproductive organs. The apple-fed RPWs and the wild R. vulneratus showed a second dominant taxon within Firmicutes that was scarcely present in the microbiota associated with palm-fed RPWs. A comparative analysis on the bacteria associated with the palm tissues highlighted that 12 bacterial genera out of the 13 identified in the plant tissues were also present in weevils, thus indicating that palm tissues may present a source for bacterial acquisition. [ABSTRACT FROM AUTHOR]

Rhynchophorus palm weevils are large insects belonging to the family Dryophthoridae. All Rhynchophorus species are polyphagous and have a similar life history but some are major pests because of the serious economic damage they cause, in particular to several species of the family Arecaceae. Here we review the natural enemies of Rhynchophorus species in both their native and introduced regions of the world, to assess the possibility of biological control of this taxon. Moreover, particular attention is paid to the well-studied and harmful species Rhynchophorusferrugineus, about which more information is available, and to its natural enemies in the Mediterranean region, because the impact of this pest in this recently colonized area is particularly remarkable and also the recent trend in species management is looking for indigenous natural enemies. More than 50 natural enemies have been reported to attack Rhynchophorus species, even if most of them are associated to R. ferrugineus (Olivier), highlighting the lack of information on the other species of the genus. Pros and cons of all the biological control agents are then discussed: among the considered organisms, fungi are noteworthy to be considered for inclusion in integrated pest management programs. Overall, our overview underlines the need to increase knowledge on natural enemies of all the species of the genus Rhynchophorus, to isolate more virulent strains and to determine the optimum conditions for the actions of the biocontrol agents. [ABSTRACT FROM AUTHOR]

The importance of early experience in animals’ life is unquestionable, and imprinting-like phenomena may shape important aspects of behaviour. Early learning typically occurs during a sensitive period, which restricts crucial processes of information storage to a specific developmental phase. The characteristics of the sensitive period have been largely investigated in vertebrates, because of their complexity and plasticity, both in behaviour and neurophysiology, but early learning occurs also in invertebrates. In social insects, early learning appears to influence important social behaviours such as nestmate recognition. Yet, the mechanisms underlying recognition systems are not fully understood. It is currently believed that Polistes social wasps are able to discriminate nestmates from non-nestmates following the perception of olfactory cues present on the paper of their nest, which are learned during a strict sensitive period, immediately after emergence. Here, through differential odour experience experiments, we show that workers of Polistes dominula develop correct nestmate recognition abilities soon after emergence even in absence of what have been so far considered the necessary cues (the chemicals spread on nest paper). P. dominula workers were exposed for the first four days of adult life to paper fragments from their nest, or from a foreign conspecific nest or to a neutral condition. Wasps were then transferred to their original nests where recognition abilities were tested. Our results show that wasps do not alter their recognition ability if exposed only to nest material, or in absence of nest material, during the early phase of adult life. It thus appears that the nest paper is not used as a source of recognition cues to be learned in a specific time window, although we discuss possible alternative explanations. Our study provides a novel perspective for the study of the ontogeny of nestmate recognition in Polistes wasps and in other social insects. [ABSTRACT FROM AUTHOR]

Simple Summary: Hornets of the genus Vespa and honey bees are the main characters of a coevolutionary arms race that is made evident by the conspicuous number of reciprocal adaptations evolved by both predator and prey. Through this ancient process predatory hornets and honey bees seem to have reached a fragile balance, which is lost when alien hornet species are accidentally introduced into new geographic areas. This is the case of Asian hornet species, such as Vespa velutina and Vespa mandarinia, which have invaded Europe and North America in recent decades, with a heavy impact on Western honey bees and commercial beekeeping. Here, we provide a comprehensive review of the existing studies that have investigated the interactions between hornets and honey bees throughout the world, highlighting the complexity of the specialized strategies adopted by Asian honey bees and their sympatric predators and the relative lack of coevolution and effective defenses of Western honey bees against invasive hornets. Hornets and honey bees have a long history of coevolution resulting in a plethora of captivating adaptations and counteradaptations between predator and prey. From simple physiological mechanisms to complex behavioral strategies, some Vespa hornets have specialized in hunting honey bees, while the latter have put in place effective defenses to counteract their attack. Both hornets and honey bees have evolved the ability to detect the odors and the pheromones emitted by the other to locate the prey or to spot foraging predators. Hornets often rely on their bigger size, heavily armored body and destructive attacks, while honey bees differentiated collective defense responses finely coordinated to deter or kill the hornet menace. However, when new species of hornets and honey bees come into contact, the absence of coevolution can have a heavy impact on the defenseless bees. The evolutionary arms race between hornets and honey bees provides not only compelling examples of adaptations and counteradaptations between predator and prey, but could also represent a starting point for the development of effective and sustainable strategies to protect honey bees and beekeeping activities and to control invasive alien species of hornets. [ABSTRACT FROM AUTHOR]

Insect social life is governed by chemicals. A great number of studies have demonstrated that the blend of hydrocarbons present on the cuticle (CHCs) plays a pivotal role in intra- and inter-specific communication. It is not surprising, therefore, that social parasites, specialized in exploiting the costly parental care provided by host workers, exploit the host chemical communication system too. Throughout their life cycle, social parasites intercept and break this CHC-based code. Recently, however, several polar compounds (mainly peptides) have been found in addition to CHCs both on the cuticle and on the comb surface of social insects, and their semiochemical role has been demonstrated in some circumstances. In the present study, we used the paper wasp social parasite-host system Polistes sulcifer (Zimmerman)-Polistes dominulus (Christ) to evaluate the relative importance of the CHC5 and polar compounds in two different steps of the host exploitation process: host nest detection by the pre-usurping parasite and parasite chemical integration into the host colony. After separating the polar and apolar fractions of the host nest as well as those of pre- and post-usurpation parasites, we carried out laboratory assays based on the binary choice model. Our results show that nest polar compounds neither are used by the parasite to detect the host's nest nor play a role in parasite chemical integration into the host colony. In contrast, we demonstrate that CHCs are fundamental in both steps, thus confirming their primary role in social insect life and consequently in social parasite-host interactions. [ABSTRACT FROM AUTHOR]

How work is organized varies in social insect colonies. Some investigators have argued that the queen plays an active role in regulating worker activity in species with small, simple colonies, but that work is self-organized in species with large, complex colonies. Here, we present data that suggest that two species of paper wasps do not fit this pattern. Polistes wasps are traditionally classified as primitively eusocial wasps, showing characteristics of simple insect societies, such as small colony sizes, lack of queen–worker dimorphism, and queen control of both reproduction and worker activity. Colony activity in Polistes is episodic; quiet periods are followed by periods of intense activity when most wasps in the colony are active. We tested whether queens in P. instabilis and P. dominulus controlled work by initiating active periods, goading workers into activity. Instead, we found that colony activity was initiated by the behaviours of workers arriving at the colony, walking across the nest face or, less commonly, antennating, leaving or gaster wagging. Queens initiated no more activity periods than the average worker. Furthermore, activity levels in colonies of P. dominulus in which the queen was removed did not differ significantly from activity levels in colonies with queens. Polistes instabilis and P. dominulus colonies showed characteristics of primitively eusocial insect societies, but also showed worker initiation of colony activity, suggesting that these two species represent examples of an intermediate level of colony organization in which queens control reproduction but do not control the organization of work. [Copyright &y& Elsevier]

Social insects are successful animal invaders. Their survival and success, and in some cases also their impact on invaded ecosystem functioning, is often mediated by symbiosis with microorganisms. Here, we report a comprehensive comparative characterization of the gut microbial communities of different castes and developmental stages of the invasive hornet Vespa velutina nigrithorax. The species recently colonized Europe, becoming a high ecological and economic concern, as it threatens pollinator survival and competes with native hornet species. We used targeted meta-genomics to describe the yeasts and bacteria gut communities of individuals of different reproductive phenotypes (workers and future queens), life stages (larvae, newly emerged individuals and adults) and colony non-living samples (nest paper and larval faeces). Bacilli , Gammaproteobacteria , Actinobacteria , Alphaproteobacteria were the most abundant classes of bacteria, and Saccharomycetes , Dothideomycetes , Tremellomycetes and Eurotiomycetes were the most represented yeast classes. We found that the microbial compositions significantly differ across developmental stages and castes, with yeast and bacterial communities switching in frequency and abundance during ontogeny and according to reproductive phenotype. Moreover, the gut microbial communities poorly mirror those found in the nest, suggesting that hornets possess a specific microbial signature. Our results provide the first metagenomic resource of the microbiome of V. velutina in Europe and suggest the importance of considering life stages, reproductive phenotypes and nest influence in order to obtain a comprehensive picture of social insect microbial communities. Unlabelled Image • Vespa velutina is an alien hornet of high ecological and economic concern in Europe. • Its gut microbiome has been characterized through meta-genomics. • We investigated the effect of ontogeny, phenotype and similarity with environment. • Fungal and bacterial community's abundance depends on ontogeny and phenotype. • Microbiome characterization is a springboard for management strategies. [ABSTRACT FROM AUTHOR]

The entomopathogenic fungus Beauveriabassiana is a widely used biopesticide that is considered as an effective alternative to classical agrochemicals. B. bassiana is thought to be safe for pollinators although little is known about its side-effects on pollinators' behaviour and cognition. Here, we focused on honey bees and used the proboscis extension response (PER) protocol to assess whether B. bassiana affects individual sucrose responsiveness, non-associative and associative olfactory learning and memory. Fungus-treated bees displayed an enhanced sucrose responsiveness, which could not be explained by metabolic alterations. Strikingly, exposed bees were twice as inconsistent as controls in response to sucrose, showing PER to lower but not to higher sucrose concentrations. Exposed bees habituated less to sucrose and had a better acquisition performance in the conditioning phase than controls. Further, neither mid- nor long-term memory were affected by the fungus. As sucrose responsiveness is the main determinant of division of foraging labour, these changes might unsettle the numerical ratio between the sub-castes of foragers leading to suboptimal foraging. Although the use of biocontrol strategies should be preferred over chemical pesticides, careful assessment of their side-effects is crucial before claiming that they are safe for pollinators. [ABSTRACT FROM AUTHOR]