Queenright Colonies Research Articles

Expression and function of the vitellogenin receptor in the hypopharyngeal glands of the honey bee Apis mellifera (Hymenoptera: Apidae) workers.

The vitellogenin receptor (VgR) is essential for the uptake and transport of the yolk precursor, vitellogenin (Vg). Vg is synthesized in the fat body, released in the hemolymph, and absorbed in the ovaries, via receptor-mediated endocytosis. Besides its important role in the reproductive pathway, Vg occurs in nonreproductive worker honey bee, suggesting its participation in other pathways. The objective was to verify if the VgR occurs in the hypopharyngeal glands of Apis mellifera workers and how Vg is internalized by these cells. VgR occurrence in the hypopharyngeal glands was evaluated by qPCR analyses of VgR and immunohistochemistry in workers with different tasks. The VgR gene is expressed in the hypopharyngeal glands of workers with higher transcript levels in nurse honey bees. VgR is more expressed in 11-day-old workers from queenright colonies, compared to orphan ones. Nurse workers with developed hypopharyngeal glands present higher VgR transcripts than those with poorly developed glands. The immunohistochemistry results showed the co-localization of Vg, VgR and clathrin (protein that plays a major role in the formation of coated vesicles in endocytosis) in the hypopharyngeal glands, suggesting receptor-mediated endocytosis. The results demonstrate that VgR performs the transport of Vg to the hypopharyngeal glands, supporting the Ovary Ground Plan Hypothesis and contributing to the understanding of the role of this gland in the social context of honey bees.

Requeening queenright honey bee colonies with queen cells in honey supers.

Many Canadian beekeepers replace a subset of their honey bee queens annually. However, introducing a new queen to a honey bee colony is a management practice with a high degree of uncertainty. Despite the consensus that it is most effective to introduce queens to queenless colonies, some commercial beekeepers claim success with introducing queen cells into the honey super of queenright colonies. We tested the success rate of this practice by introducing queen cells to 100 queenright colonies in southern Alberta during a honey flow. The genotypes of the resultant offspring drones were determined using the microsatellite marker A76 to identify their laying queen mothers. Our results show that new queens successfully supersede original queens in 6% of queenright colonies, suggesting that the practice does not result in the new queen taking over leadership in most colonies. Additionally, supersedure by daughter queens is more common (13%) than new queen supersedure when introducing queen cells to queenright colonies during a honey flow. However, there could be a benefit to the practice of requeening queenright colonies with queen cells in honey supers if the colonies that accepted a new queen (whether a daughter of or unrelated to the old queen) were colonies with a failing queen.

Re‐evaluation of a method used to study nutritional effects on bumble bees

Abstract Bee declines are an increasingly recognised problem globally. Nutritional stress due to agricultural intensification is one of the drivers of bee declines. Therefore, understanding the nutritional requirements of bees is crucial to mitigate the effects of food scarcity on bee populations. Laboratory studies evaluating nutritional effects on bumble bees often use microcolonies as a model system for effects on queenright colonies. Microcolonies consist of workers, whereby one worker will lay male‐destined unfertilized eggs. Consequently, microcolonies exclusively produce males, while queenright colonies produce (female) workers and reproductives (males and queens). A comparison between Bombus terrestris (L.) microcolonies and queenright colonies was made by feeding three diets of varying nutritional quality. The experimental diets affected most fitness parameters of microcolonies differently than those of queenright colonies. Low‐protein, largely monofloral, pollen affected queenright colony fitness by reducing colony size and increasing larval mortality, while these fitness parameters were not affected in microcolonies. High‐protein polyfloral pollen reduced larval mortality in queenright colonies but did not affect larval mortality in microcolonies. For both colony types, a similar result was obtained when assessing offspring body mass, which was reduced by the low‐quality diet and increased by the high‐quality diet. In conclusion, our results demonstrate that microcolonies are inaccurate model systems and their use can lead to erroneous conclusions in terms of effects of nutritional stress or pollen quality on bumble bees. Our results further highlight the importance of high‐quality (here high‐protein polyfloral) pollen for sustaining colony development of bumble bees.

Determination of total protein, trans- 10-Hydroxy-2-Decenoic Acid (10-HDA) and major royal jelly proteins in royal jelly produced at different harvest times in queenless and queenright colonies

Two of the most important ingredients to add functional properties to royal jelly are 10-HDA and major royal jelly proteins (MRJPs). The effect of royal jelly (RJ) production and the effect of royal jelly harvest time (24, 48 and 72 hours) on 10-HDA, the total protein content of RJ, and molecular weights of major proteins in RJ were investigated in queenright and queenless colonies. RJ production colonies were divided into 2 groups as queenless and queenright where the queen was confined with frames. Subgroups were formed within each group (queenless and queenright) according to harvest time (24, 48 and 72 hours). 80 larvae were transferred to each colony. In this study, as the harvest time increased, total protein (TP) ratio decreased (p<0.05); TP ratio in RJs harvested at 24, 48 and 72 hours was determined as 18.4±1.24%, 15.2±0.80%, 10.6±0.27%, respectively. As the harvest time increased, 10-HDA decreased. It was determined 10-HDA rates in RJ harvested at 24, 48 and 72 hours respectively; 2.52±0.109%, 2.20±0.110%, 2.00±0.112%. MRJP1, MRJP2, MRJP3 and MRJP5 were found from the MRJP family, and their molecular weights were determined as 53 kDa, 46.5 kDa, 66.8 kDa, 80.9 kDa, respectively. As a result, the early harvested (24 and 48 hours) RJ had higher values in terms of TP and trans 10-HDA than the royal jelly harvested at 72 hours.

Ovary activation correlates with the reproductive potential of honeybee (Apis mellifera) workers if they are in a foreign colony

In eusocial Hymenoptera, the laying of male-determined eggs by workers in an unrelated colony can be a powerful strategy for increasing direct fitness benefits. A recent study showed that honeybee rebels, which are workers that develop under queenless conditions and have high reproductive potential, drift to foreign colonies, with a preference for hopelessly queenless colonies, and act as reproductive parasites. In our experiment, by introducing 5-day-old rebels and normal workers into foreign queenright colonies, we discovered that only rebels developed a reproductive phenotype by activating their ovaries. In a similar experiment with 1-day-old workers, neither rebels nor normal workers displayed such a tendency. We suggest that workers’ reproductive potential could thus be a key parameter activating the ovaries in not only drifting workers but also workers acting as reproductive parasites. Our results also support the hypothesis that the colony recognition cue probably has an environmental, rather than a genetic, origin.

Histone acetylation regulates the expression of genes involved in worker reproduction in the ant Temnothorax rugatulus

BackgroundIn insect societies, queens monopolize reproduction while workers perform tasks such as brood care or foraging. Queen loss leads to ovary development and lifespan extension in workers of many ant species. However, the underlying molecular mechanisms of this phenotypic plasticity remain unclear. Recent studies highlight the importance of epigenetics in regulating plastic traits in social insects. Thus, we investigated the role of histone acetylation in regulating worker reproduction in the ant Temnothorax rugatulus. We removed queens from their colonies to induce worker fecundity, and either fed workers with chemical inhibitors of histone acetylation (C646), deacetylation (TSA), or the solvent (DMSO) as control. We monitored worker number for six weeks after which we assessed ovary development and sequenced fat body mRNA.ResultsWorkers survived better in queenless colonies. They also developed their ovaries after queen removal in control colonies as expected, but not in colonies treated with the chemical inhibitors. Both inhibitors affected gene expression, although the inhibition of histone acetylation using C646 altered the expression of more genes with immunity, fecundity, and longevity functionalities. Interestingly, these C646-treated workers shared many upregulated genes with infertile workers from queenright colonies. We also identified one gene with antioxidant properties commonly downregulated in infertile workers from queenright colonies and both C646 and TSA-treated workers from queenless colonies.ConclusionOur results suggest that histone acetylation is involved in the molecular regulation of worker reproduction, and thus point to an important role of histone modifications in modulating phenotypic plasticity of life history traits in social insects.

Pollen Source Richness May Be a Poor Predictor of Bumblebee (Bombus terrestris) Colony Growth.

Agricultural intensification has drastically altered foraging landscapes for bees, with large-scale crop monocultures associated with floral diversity loss. Research on bumblebees and honeybees has shown individuals feeding on pollen from a low richness of floral sources can experience negative impacts on health and longevity relative to higher pollen source richness of similar protein concentrations. Florally rich landscapes are thus generally assumed to better support social bees. Yet, little is known about whether the effects of reduced pollen source richness can be mitigated by feeding on pollen with higher crude protein concentration, and importantly how variation in diet affects whole colony growth, rearing decisions and sexual production. Studying queen-right bumblebee (Bombus terrestris) colonies, we monitored colony development under a polyfloral pollen diet or a monofloral pollen diet with 1.5-1.8 times higher crude protein concentration. Over 6 weeks, we found monofloral colonies performed better for all measures, with no apparent long-term effects on colony mass or worker production, and a higher number of pupae in monofloral colonies at the end of the experiment. Unexpectedly, polyfloral colonies showed higher mortality, and little evidence of any strategy to counteract the effects of reduced protein; with fewer and lower mass workers being reared, and males showing a similar trend. Our findings (i) provide well-needed daily growth dynamics of queenright colonies under varied diets, and (ii) support the view that pollen protein content in the foraging landscape rather than floral species richness per se is likely a key driver of colony health and success.

Reproductive Potential Accelerates Preimaginal Development of Rebel Workers in Apis mellifera.

Simple SummaryAll female honeybee larvae may develop into workers or queens, depending on the food they receive. During this period, queen mandibular pheromones (QMP) perform a regulatory function in inhibiting ovarian development in adult workers. These pheromones are transmitted (via trophallaxis) by workers to pass information to larvae on the presence or absence of the queen. Queen-less conditions are conducive to the emergence of rebel workers that are set to reproduce, and do not participate in the rearing of successive bee generations in contrast to the sterile, normal workers. We posited that rebels are not only similar to queens in some anatomical features, but also develop in a shorter time in comparison to normal workers. Therefore, the aim of this study was to compare the duration of preimaginal development in rebel and normal workers. Our results confirmed that the workers who develop in a queen-less colony undergo a shorter preimaginal development than those in a queen-right colony.Rebel workers develop from eggs laid by the previous queen, before it went swarming and left the colony orphaned, until the emergence of a new queen. In contrast to normal workers developing in the queen’s presence, rebels are set to reproduce and avoid rearing of successive bee generations. They have more ovarioles in their ovaries, as well as more developed mandibular glands and underdeveloped hypopharyngeal glands, just like the queen. We posited that rebels are not only similar to queens in some anatomical features, but also develop in a shorter time in comparison to normal workers. Therefore, the aim of this study was to compare preimaginal development duration in rebel and normal workers. The results show that rebels, i.e., workers with a higher reproductive potential, had a significantly shorter preimaginal development period (mean ± SD, 19.24 ± 0.07 days) than normal workers (22.29 ± 0.32 days). Our result confirmed that workers who develop in a queen-less colony undergo a shorter preimaginal development than those in a queen-right colony.

Worker-Born Males Are Smaller but Have Similar Reproduction Ability to Queen-Born Males in Bumblebees.

Simple SummaryIn bumblebee colonies, the authority of male reproduction is not entirely controlled by the queen. Workers who lose mating ability could also produce haploidy males. The conflict over the reproduction of males in bumblebee colonies becomes more evident compared to the higher eusocial honeybees. However, the reproductive characteristics of worker-born males in bumblebees remain unclear. Here, we evaluated the body size and reproductive ability of males produced by worker and queen in Bombus terrestris. Smaller size and slighter individuals’ weight but equally high sperm viability was found in worker-born males compared to that of queen-born males. Moreover, worker-born males performed as excellently as queen-born males in copulation and colony development of the mated queens, such as queen egg laying, colony foundation, and colony size. This study contributes the new knowledge of the reproductive biology of eusocial bees.Queen-worker conflict over the reproduction of males exists in the majority of haplodiplioidy hymenpteran species such as bees, wasps, and ants, whose workers lose mating ability but can produce haploid males in colony. Bumblebee is one of the representatives of primitively eusocial insects with plastic division labor and belongs to monandrous and facultative low polyandry species that have reproductive totipotent workers, which are capable of competing with mother queen to produce haploid males in the queenright colony compared to higher eusocial species, e.g., honeybees. So, bumblebees should be a better material to study worker reproduction, but the reproductive characteristics of worker-born males (WMs) remain unclear. Here, we choose the best-studied bumblebee Bombus terrestris to evaluate the morphological characteristics and reproductive ability of WMs from the queenless micro-colonies. The sexually matured WMs showed smaller in forewing length and weight, relatively less sperm counts but equally high sperm viability in comparison with the queen-born males (QMs) of the queenright colony. Despite with smaller size, the WMs are able to successfully mate with the virgin queens in competition with the QMs under laboratory conditions, which is quite different from the honeybees reported. In addition, there was no difference in the colony development, including the traits such as egg-laying rate, colony establishment rate, and populations of offspring, between the WM- and the QM-mated queens. Our study highlights the equivalent reproductive ability of worker-born males compared to that of queens, which might exhibit a positive application or special use of bumblebee rearing, especially for species whose males are not enough for copulation. Further, our finding contributes new evidence to the kin selection theory and suggests worker reproduction might relate to the evolution of sociality in bees.

Low Virulence of the Fungi Escovopsis and Escovopsioides to a Leaf-Cutting Ant-Fungus Symbiosis.

Eusocial insects interact with a diversity of parasites that can threaten their survival and reproduction. The amount of harm these parasites cause to their hosts (i.e., their virulence) can be influenced by numerous factors, such as the ecological context in which the parasite and its host are inserted. Leaf-cutting ants (genera Atta, Acromyrmex and Amoimyrmex, Attini: Formicidae) are an example of a eusocial insect whose colonies are constantly threatened by parasites. The fungi Escovopsis and Escovopsioides (Ascomycota: Hypocreales) are considered a highly virulent parasite and an antagonist, respectively, to the leaf-cutting ants’ fungal cultivar, Leucoagaricus gongylophorus (Basidiomycota: Agaricales). Since Escovopsis and Escovopsioides are common inhabitants of healthy colonies that can live for years, we expect them to have low levels of virulence. However, this virulence could vary depending on ecological context. We therefore tested two hypotheses: (i) Escovopsis and Escovopsioides are of low virulence to colonies; (ii) virulence increases as colony complexity decreases. For this, we used three levels of complexity: queenright colonies (fungus garden with queen and workers), queenless colonies (fungus garden and workers, without queen) and fungus gardens (without any ants). Each was inoculated with extremely high concentrations of conidia of Escovopsis moelleri, Escovopsioides nivea, the mycoparasitic fungus Trichoderma longibrachiatum or a blank control. We found that these fungi were of low virulence to queenright colonies. The survival of queenless colonies was decreased by E. moelleri and fungus gardens were suppressed by all treatments. Moreover, E. nivea and T. longibrachiatum seemed to be less aggressive than E. moelleri, observed both in vivo and in vitro. The results highlight the importance of each element (queen, workers and fungus garden) in the leaf-cutting ant-fungus symbiosis. Most importantly, we showed that Escovopsis may not be virulent to healthy colonies, despite commonly being described as such, with the reported virulence of Escovopsis being due to poor colony conditions in the field or in laboratory experiments.

The Effects of Queenright and Queenless Colonies and Nutrition on the Stress Protein (HSP70) in Royal Jelly Production 'A Preliminary Study'

The Effects of Queenright and Queenless Colonies and Nutrition on the Stress Protein (HSP70) in Royal Jelly Production 'A Preliminary Study'

Split sex ratios and genetic relatedness in a primitively eusocial sweat bee

In eusocial Hymenoptera, queens and their helper offspring should favour different sex investment ratios. Queens should prefer a 1:1 investment ratio, as they are equally related to offspring of both sexes (r = 0.5). In contrast, helpers should favour an investment ratio of 3:1 towards the production of female brood. This conflict arises because helpers are more closely related to full sisters (r = 0.75) than brothers (r = 0.25). However, helpers should invest relatively more in male brood if relatedness asymmetry within their colony is reduced. This can occur due to queen replacement after colony orphaning, multiple paternity and the presence of unrelated alien helpers. We analysed an unprecedentedly large number of colonies (n = 109) from a UK population of Lasioglossum malachurum, an obligate eusocial sweat bee, to tease apart the effects of these factors on colony-level investment ratios. We found that multiple paternity, unrelated alien helpers and colony orphaning were all common. Queen-right colonies invested relatively more in females than did orphaned colonies, producing a split sex ratio. However, investment ratios did not change due to multiple paternity or the presence of alien helpers, reducing inclusive fitness pay-offs for helpers. Queen control may also have been important: helpers rarely laid male eggs, and investment in female brood was lower when queens were large relative to their helpers. Genetic relatedness between helpers and the brood that they rear was 0.43 in one year and 0.37 in another year, suggesting that ecological benefits, as well as relatedness benefits, are necessary for the maintenance of helping behaviour.Significance statementHow helping behaviour is maintained in eusocial species is a key topic in evolutionary biology. Colony-level sex investment ratio changes in response to relatedness asymmetries can dramatically influence inclusive fitness benefits for helpers in eusocial Hymenoptera. The extent to which helpers in primitively eusocial colonies can respond adaptively to different sources of variation in relatedness asymmetry is unclear. Using data from 109 colonies of the sweat bee Lasioglossum malachurum, we found that queen loss, but not multiple paternity or the presence of alien helpers, was correlated with colony sex investment ratios. Moreover, we quantified average helper-brood genetic relatedness to test whether it is higher than that predicted under solitary reproduction (r = 0.5). Values equal to and below r = 0.5 suggest that relatedness benefits alone cannot explain the maintenance of helping behaviour. Ecological benefits of group living and/or coercion must also contribute.

Effects of the Neonicotinoid Acetamiprid in Pollen on Bombus impatiens Microcolony Development.

Honey bees and other wild bee species including bumble bees have experienced population declines in recent decades. Although many stressors are implicated in bee population declines, much attention has focused on neonicotinoid pesticides, which are widely used and known to be toxic to pollinators. One neonicotinoid, acetamiprid, has been studied very little in bumble bees, despite its use on bumble bee-pollinated crops. We assessed the impacts of acetamiprid to the North American bumble bee Bombus impatiens using the microcolony model. We examined nest growth, development, and subsequent nest productivity as measured by drone production. We found that high concentrations of acetamiprid in pollen (4520 µg/kg) significantly impacted nest growth, development, and, ultimately, reproduction (drone production). We found the no-observable-adverse effect level to be 45.2 µg/kg. Overall, acetamiprid has the potential to negatively impact reproductive endpoints for B. impatiens. However, effects occurred at concentrations substantially higher than expected environmental concentrations that would be achieved when following label rates. Further work is required to assess the effects of this pesticide on B. impatiens via alternate routes of exposure and on queenright colonies. Environ Toxicol Chem 2020;39:2560-2569. © 2020 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Short-term lab assessments and microcolonies are insufficient for the risk assessment of insecticides for bees

Risk assessment studies addressing effects of agrochemicals on bumblebees frequently use microcolonies. These are queenless colonies consisting of workers only in which typically one worker will lay unfertilized male-destined eggs. In the first tier of risk assessment for bees, short-term laboratory experiments (e.g. microcolonies) are used, the results of which will determine whether higher tier (semi-)field experiments are needed. To evaluate the suitability of microcolonies for risk assessment, a direct comparison between different assessment methods for the neonicotinoid pesticides acetamiprid and thiacloprid was made: microcolonies and queenright colonies under short-term laboratory conditions, queenright colonies under long-term laboratory conditions, and queenright colonies under field conditions. Here, we demonstrate that results from microcolonies contradict results from queenright colonies. While thiacloprid negatively impacted gyne production in queenright colonies, it had a positive effect on microcolony size. By contrast, thiacloprid had no significant effect on fitness parameters of queenright colonies under short-term laboratory conditions when mostly workers are produced. These results thus highlight both the need for long term assessments, allowing evaluation of gyne production, and the risk of reaching erroneous conclusions when using microcolonies. The negative effect of thiacloprid on colony fitness was confirmed under field conditions, where thiacloprid affected the production of reproductives, colony weight gain, worker weight, and foraging behaviour. For acetamiprid, a negative trend on colony fitness could only be shown in a field setup. Therefore, field-realistic setups, which allow colonies to forage freely, are most appropriate to assess sublethal effects of pesticides affecting behaviour and learning.

Substantial direct fitness gains of workers in a highly eusocial ant.

Hamilton's theory of inclusive fitness suggests that helpers in animal societies gain fitness indirectly by increasing the reproductive performance of a related beneficiary. Helpers in cooperatively breeding birds, mammals and primitively eusocial wasps may additionally obtain direct fitness through inheriting the nest or mating partner of the former reproductive. Here, we show that also workers of a highly eusocial ant may achieve considerable direct fitness by producing males in both queenless and queenright colonies. We investigated the reproductive success of workers of the ant Temnothorax crassispinus in nature and the laboratory by dissecting workers and determining the origin of males by microsatellite analysis. We show that workers are capable of activating their ovaries and successfully producing their sons independently of the presence of a queen. Genotypes revealed that at least one fifth of the males in natural queenright colonies were not offspring of the queen. Most worker-produced males could be assigned to workers that were unrelated to the queen, suggesting egg-laying by drifting workers.

Scientific note on small hive beetle infestation of stingless bee (Tetragonula carbonaria) colony following a heat wave

We present the first study of infestation by the small hive beetle, Aethina tumida, in a queenright colony of the stingless bee Tetragonula carbonaria, a species used for pollination services. Nine managed hives were deployed outside the bee’s endemic range. After 2 months, including a heat wave of four consecutive days above 40 °C, one colony was visibly weakened with fewer foragers. This hive was removed from the site for the colony to recover. After a second heat wave, another colony was found weakened and infested with small hive beetle (SHB). Inside the hive, 14 adults and 133 larvae of SHB were discovered. Extreme daily maximum temperatures and low humidity appear to have weakened this colony. Our study highlights the need for careful placement of managed hives, as the SHB has potential to be a significant pest of stingless bees under adverse conditions.

Worker dominance and reproduction in the bumblebee Bombus terrestris: when does it pay to bare one's mandibles?

In bumblebees, dominance behaviour contributes to the regulation of the reproductive division of labour between queens and workers. Towards the end of the colony cycle, at the onset of the competition phase, reproductive workers will establish a dominance hierarchy and challenge the reproductive monopoly of the queen by laying unfertilized, male-destined eggs. However, it has been suggested that the dominance and reproductive hierarchies in bumblebee workers are not completely aligned. By performing manipulative experiments and observing both aggressive behaviour and ovarian activation in Bombus terrestris workers, we aimed to elucidate how these two hierarchies interact and are modulated by the presence of the queen and other reproductive workers. We found that the reintroduction of a queen in a queenless colony not only caused worker ovary regression, but also decreased aggressive interactions between workers, thereby restoring the harmony in the colony. Furthermore, transplanting dominant reproductive workers from queenless colonies into queenright colonies induced the resident workers to activate their ovaries and aggressively compete over reproduction, thereby implying that positive feedback drives the onset of the competition phase. However, we did not see this result when subordinate reproductive workers from queenless colonies were added to queenright colonies, suggesting that ovary activation is mainly initiated in reaction to displays of dominance. Additionally, we observed that workers were attacked irrespective of their reproductive state, questioning the importance of signals that advertise either fertility or sterility in bumblebees. Finally, larger workers were significantly more aggressive and significantly more likely to be attacked, even though smaller workers were equally likely to have activated ovaries. This suggests that large workers resort to aggression to increase their chances of successfully reproducing due to their inherent fighting advantage, whereas small cheater workers could possibly reproduce by staying under the radar to evade nestmate aggression.

Behavioural and neurogenomic responses of host workers to social parasite invasion in a social insect

The strong coevolutionary arms race between social parasites and their hosts has dramatically shaped the life-history traits of both parties. One of the main strategies exhibited by hosts in response to parasitism is reproduction by host workers. We lack a mechanistic understanding of how these defence strategies unfold and, specifically, whether hosts exhibit more subtle strategies to reduce the costs of parasitism from the outset. Here we test the hypothesis that there are both behavioural and neurogenomic signatures of worker responses to parasitism, prior to overt expression in the form of egg-laying; we test this using the social parasite—social host system of the paper wasps Polistes sulcifer-Polistes dominula. We characterized individual workers’ position within the social interaction network of queenright and host colonies immediately after parasite usurpation, weeks before the workers’ reproductive rebellion is evident. Parasitism influenced network centrality measures, with workers in parasitized colonies showing increased connectedness and centrality compared to those in unparasitized ones. Next, we quantified brain gene expression levels for five genes related to physiological and behavioural phenotypes in Polistes wasps. The gene Imaginal disc growth factor (Idgf4), thought to be responsive to changes in the social environment, was significantly down-regulated in workers from parasitized colonies; this may be an indication that parasitized workers are anticipating a shift toward a less worker-like phenotype in preparation for their reproductive rebellion. Our results provide the first evidence of early behavioural and neurogenomic responses of host workers toward the presence of an inquiline social parasite in a social insect.

Colony composition, queen behavior, specialized predation on millipedes, and exocrine glands in the ponerine ant Myopias conicara Xu, 1998 (Hymenoptera: Formicidae)

AbstractWe collected a queenright colony of the very rare Myopias conicara Xu in Vietnam (1 dealate queen, 41 workers and 38 larvae). Both the queen and workers fed on xystodesmid millipedes. After paralyzing a millipede, its head was first removed by the workers, and then the larvae were put on the opening of the collum (anteriormost ring of the trunk). After the inner tissue of the collum was consumed, the exoskeleton of the collum was discarded. The feeding sequence was then repeated on the following rings of the trunk, until the entire prey was consumed. The ring‐shaped exoskeletons of the prey were deposited next to the nest entrance. The exocrine system of the workers (excluding the legs) contains 15 glands of which the structural features are similar to these of other ponerine ants. The presence of an oblong plate gland is interesting, as this gland had only been found previously in Myopias hollandi (Forel). However, none of the novel thoracic glands that were recently described in M. hollandi occur in M. conicara, which illustrates the variation within the genus Myopias. A unique characteristic of the class‐3 glands of Myopias ants is the gradual widening of the ducts, which has never been found in other insects, although the functional significance remains unknown.

Queen loss changes behavior and increases longevity in a stingless bee

The death of the queen can lead to behavioral changes in workers of eusocial bees that alter their longevity. Here, we investigated the behavior and longevity of workers in colonies of the neotropical stingless bee Scaptotrigona aff. postica in the absence of a mated queen. Eight colonies, four being queenright, and four with their physogastric queens removed (queenless), were used in experiments. Emerging workers were marked with different colors to obtain age cohorts. We observed external foraging activity, age of workers involved in cell construction and foraging, and worker longevity in all colonies for 100 days. Over time, queenless colonies presented a greater reduction in external activity than queenright colonies; older workers were more frequently observed participating in cell construction and foraging compared with queenright colonies, and worker lifespan in queenless colonies was about a third longer than that observed in queenright colonies. Our study demonstrates that orphaned workers of this species substantially alter their behavior, causing an increase in their overall longevity and workers starting to lay haploid eggs, allowing some direct reproduction by workers in the absence of a queen. For eusocial species, the loss of the reproductive individual is a critical period for colony survival. Our study shows, for the first time, how workers in a neotropical stingless bee species adapt their behavior during periods without a queen. We show that the longevity of workers of Scaptotrigona aff. postica from orphaned colonies on average increased by 33% compared with regular colonies. We also show that many foragers from orphaned colonies spend more time inside the nest building brood cells rather than participating in more risky foraging behaviors. Therefore, workers alter their behavior in the absence of an egg-laying queen; these changes cause a substantial increase of longevity of the labor force (i.e., workers), and consequently, a possibility that the nest survives until a new mated queen resumes oviposition. In case a new queen does not appear in the colony, males produced by egg-laying workers (which gain a direct fitness through direct reproduction) may spread the colonial genome, by mating with queens from other colonies.