Dominant Work Research Articles

The effect of diet on the development of pheromone signals in Apis mellifera scutellata workers

The social organization of honey bee colonies is predominantly controlled by the pheromonal cues produced by the queen, workers and brood. Pheromone composition is dependent on the social environment, context, audience and physiological status of the individual. In the absence of the queen, ontogenic changes and reproductive status modulate pheromone production and composition in workers. In these queenless workers, pheromonal status influences diet with dominant workers consuming less pollen than subordinates as they are fed protein jelly through trophallaxis, which positively correlates with their ovarian activation. However, it is not known to what extent diet affects pheromonal status in queenless workers. To investigate whether diet affects the production of glandular signals, Apis mellifera scutellata workers were fed carbohydrate-only or protein-rich diets for twenty-five days. The mandibular and tergal gland secretions were analyzed using gas chromatography and the ovarian activation statuses were evaluated. A clear link between diet and pheromone profiles was observed with workers fed a protein-rich diet producing mandibular gland chemical profiles more typical of queens. The effect of diet on tergal gland chemical profiles was less distinct, but a shift from fatty acid to n-alkane components was seen in the older workers irrespective of diet, most likely due to ontogeny. Though mandibular gland profiles were queen-like with high proportions of 9-HDA, the levels of 9-ODA remained in the range of non-reproductive workers and the ovaries were not fully activated. This suggests that diet could prime queenless workers to become false queens, but do not trigger the transformation into false queens.

Delayed maturation of the exoskeleton and muscle fibres in the ant Platythyrea punctata

Abstract In many species of eusocial Hymenoptera, workers exhibit a division of labour based on age, wherein young workers remain protected within the nest before transitioning to foraging activities. These changes in tasks and in external stress exposure are accompanied by physiological and anatomical modifications. Although pigmentation changes in the exoskeleton are well documented in ants, limited information is available on muscle morphology and developmental changes in the adult cuticle. Here, we investigated the alterations in the exoskeleton and thoracic muscles across different age groups of the clonal ant Platythyrea punctata, in which reproduction is monopolized by one or a few dominant workers. Our findings revealed a significant thickening of the cuticle and muscle fibres in young workers during the intranidal period, reaching a final stage in forager individuals. We further tested the influence of reproductive status on body development and found variations only in muscle fibres between reproductive and nonreproductive individuals. This suggests that dominant individuals allocate resources in egg-laying by minimizing other metabolic costs. These findings shed light on how eusociality profoundly alters selection pressures and results in temporal shifts in individual development. This strategy probably provides advantages to colonies by minimizing nutritional waste and optimizing resource allocation.

The Biology of the Cape Honey Bee, Apis mellifera capensis (Hymenoptera: Apidae): A Review of Thelytoky and Its Influence on Social Parasitism and Worker Reproduction

Abstract Cohesion in social insect colonies is maintained by use of chemical signals produced by the queen, workers, and brood. In honey bees in particular, signals from the queen and brood are crucial for the regulation of reproductive division of labor, ensuring that the only reproductive female individual in the colony is the queen, whereas the workers remain reproductively sterile. However, even given this strict level of control, workers can, in principle, activate their ovaries and lay eggs. Although much is known about the behavioral and physiological traits that accompany the switch from worker sterility to being reproductively active, much less is known regarding the molecular changes that accompany this switch. This review will explore what is known about the genes and molecular pathways involved in the making of laying workers/false queens in the Cape honey bee, Apis mellifera capensis Eschscholtz, through an analysis of the basis for thelytoky in this subspecies, the exocrine glandular chemistry of reproductively dominant workers and what is known about the biosynthesis of their pheromone components. This review will contribute to our understanding of the genetic regulation of thelytoky and the molecular mechanisms that govern reproductive division of labor in honey bees and provide generalizations that may be applicable to other social hymenoptera using this evolutionary fascinating example of worker reproduction.

Juvenile hormone regulates brain-reproduction tradeoff in bumble bees but not in honey bees

Gonadotropic hormones coordinate processes in diverse tissues regulating animal reproductive physiology and behavior. Juvenile hormone (JH) is the ancient and most common gonadotropin in insects, but not in advanced eusocial honey bees and some ants. To start probing the evolutionary basis of this change, we combined endocrine manipulations, transcriptomics, and behavioral analyses to study JH regulated processes in a bumble bee showing a relatively simple level of eusociality. We found that in worker fat body, more JH-regulated genes were up- rather than down-regulated, and enriched for metabolic and biosynthetic pathways. This transcriptomic pattern is consistent with earlier evidence that JH is the major gonadotropin in bumble bees. In the brain, more JH-regulated genes were down- rather than up-regulated and enriched for protein turnover pathways. Brain ribosomal protein gene expression shows a similar trend of downregulation in dominant workers, which naturally have high JH titers. In other species, similar downregulation of protein turnover is found in aging brains or under stress, associated with compromised long-term memory and health. These findings suggest a previously unknown gonadotropin-mediated tradeoff. Analysis of published data reveals no such downregulation of protein turnover pathways in the brain of honey bee workers, which exhibit more complex eusociality and in which JH is not a gonadotropin but rather regulates division of labor. These results suggest that the evolution of complex eusociality in honey bees was associated with modifications in hormonal signalling supporting extended and extremely high fertility while reducing the ancient costs of high gonadotropin titers to the brain.

Testing trade‐offs and the dominance–impoverishment rule among ant communities

AbstractAimAnt communities are believed to be structured by competition, with dominant species competitively excluding subordinates (the dominance–impoverishment rule). However, a high number of seemingly similar species coexist, possibly due to interspecific trade‐offs. Here, we examine the evidence for the dominance–impoverishment rule across a broad latitudinal gradient and explore whether trade‐offs explain coexistence within and among ant communities.Location40 sites in 19 countries across Europe, western North America and northern South America.TaxonFormicidae.MethodsWe conducted 2‐hr baiting experiments at each site. Three dominance scores were calculated for each species at each site where it occurred. We then examined the relationship between ant dominance and diversity and tested for the generality of three trade‐offs (dominance–discovery, dominance–thermal tolerance and dominance–generalism) within and among ant communities along with the possible effects of environmental variables on these trade‐offs.ResultsWe found no support for the dominance–impoverishment rule. Instead, overall species richness at baits was positively correlated with the number of dominant species and exhibited a unimodal relationship with the relative abundance of dominant ants. Moreover, we found little consistent evidence for the three interspecific trade‐offs.Main conclusionAlthough total species richness at baits is positively correlated with species richness of dominant species and, to a point, increasing worker numbers of dominants, trade‐offs among species do not appear to shape broad‐scale patterns of coexistence among ants. Species richness declines only when the numbers of dominant workers are very high. Together, these results suggest that while trade‐offs and the dominance–impoverishment rule might promote coexistence or shape ant communities in some locations, the evidence for their being general across communities is scant.

State-sponsored trade unions after democratic transitions

ABSTRACT New democracies inherit a variety of institutions from prior authoritarian regimes, including political parties, militaries and entrenched oligarchies. While these authoritarian legacies have generally been well-researched, one set of institutions has received relatively little attention: state-backed trade unions that lose official sponsorship after democratizing transitions. In most new democracies and competitive authoritarian regimes, these “legacy unions” have remained the dominant workers’ organizations despite few internal reforms. Previous research on the causes and consequences of legacy union dominance has rested on case studies of post-transition countries and small-N comparisons. In this article, we offer a global perspective on the fates of legacy unions by introducing new data about the relative importance of legacy unions in post-Third Wave democracies. We show that most legacy unions survive democratic transitions and remain dominant in new democracies, although with significant regional variation. Our data and analyses suggest that these trade unions are authoritarian legacies which continue to influence labour politics in new democracies. Dominant legacy unions are associated with lower labour movement fragmentation and better-protected labour rights in new democracies.

The Queen of the Paper Wasp Polistes jokahamae (Vespidae: Polistinae) Is Not Aggressive but Maintains Her Reproductive Priority

The behaviors performed on the nest by the foundress queen and workers of the paper wasp Polistes jokahamae were observed in three colonies in the field and one colony in a cage set in the field. Each queen was rarely ranked top in the dominance hierarchy determined by the pairwise dominance–subordinate interactions and did not display more frequent direct aggression toward the top-ranked worker than toward other workers. Furthermore, the queen exhibited aggression less frequently than did the most aggressive workers in all four colonies. The dominance order among the workers was positively correlated with the emergence order, with older workers being more dominant. The queen laid eggs in a dominant or monopolized way; some dominant workers laid eggs in three colonies. These observations suggest that the queen maintained her queen status, including her reproductive priority, using signals rather than aggression. Lateral vibrations (rapidly laterally vibrating the abdomen) and abdominal rubbing (rubbing the abdomen onto the comb) appeared to be candidate signals of the fertility or reproductive potential of the performer. Lateral vibrations were performed only by the queen, and their frequency was positively correlated with the frequency of ovipositing. The queen and some dominant workers performed abdominal rubbing; the frequency was higher for the queen than for any of the dominant workers early in the colony’s development, but not later. Although performers of abdominal rubbing were more likely to lay eggs than non-performers, the frequency of abdominal rubbing was not a predictor of the frequency of ovipositing.

Glandular sources of pheromones used to control host workers (Apis mellifera scutellata) by socially parasitic workers of Apis mellifera capensis

Pheromonal control by the honey bee queen is achieved through the use of secretions from diverse glandular sources, but the use of pheromones from a variety of glandular sources by reproductively dominant workers, has not previously been explored. Using the social parasite, Apis mellifera capensis clonal worker we studied the diversity of glandular sources used for pheromonal control of reproductively subordinate A. m. scutellata workers. To determine whether pheromones from different glandular sources are used by reproductively active workers to achieve dominance and evaluate the degree of pheromonal competition between workers of the two sub-species, we housed groups of workers of the two sub-species together in cages and analysed mandibular and tergal gland secretions as well as, ovarian activation status of each worker after 21days. The results showed that A. m. capensis invasive clones used both mandibular and tergal gland secretions to achieve reproductive dominance and suppress ovarian activation in their A. m. scutellata host workers. The reproductively dominant workers (false queens) produced more queen-like pheromones and inhibited ovarian activation in subordinate A. m. scutellata workers. These results show that tergal gland pheromones working in synergy with pheromones from other glands allow individual workers (false queens) to establish reproductive dominance within these social groups and to act in a manner similar to that of queens. Thus suggesting that, the evolution of reproductively dominant individuals (queens or false queens) and subordinate individuals (workers) in social insects like the honey bee is the result of a complex interplay of pheromonal signals from different exocrine glands.

Intrinsic worker mortality depends on behavioral caste and the queens' presence in a social insect.

According to the classic life history theory, selection for longevity depends on age-dependant extrinsic mortality and fecundity. In social insects, the common life history trade-off between fecundity and longevity appears to be reversed, as the most fecund individual, the queen, often exceeds workers in lifespan several fold. But does fecundity directly affect intrinsic mortality also in social insect workers? And what is the effect of task on worker mortality? Here, we studied how social environment and behavioral caste affect intrinsic mortality of ant workers. We compared worker survival between queenless and queenright Temnothorax longispinosus nests and demonstrate that workers survive longer under the queens' absence. Temnothorax ant workers fight over reproduction when the queen is absent and dominant workers lay eggs. Worker fertility might therefore increase lifespan, possibly due to a positive physiological link between fecundity and longevity, or better care for fertile workers. In social insects, division of labor among workers is age-dependant with young workers caring for the brood and old ones going out to forage. We therefore expected nurses to survive longer than foragers, which is what we found. Surprisingly, inactive inside workers showed a lower survival than nurses but comparable to that of foragers. The reduced longevity of inactive workers could be due to them being older than the nurses, or due to a positive effect of activity on lifespan. Overall, our study points to behavioral caste-dependent intrinsic mortality rates and a positive association between fertility and longevity not only in queens but also in ant workers.

Queen contact and among-worker interactions dually suppress worker brain dopamine as a potential regulator of reproduction in an ant

How individual organisms whose behavior is potentially driven by selfish interests cooperate to form a society is a central question in evolutionary biology. Worker reproduction and its suppression in eusocial insects provide an illuminating model of such a conflict resolution. Although many theoretical and empirical studies focus on the nature and evolutionary consequences of this reproductive conflict, little is known about its physiological underpinnings. Here, we hypothesized that the dopaminergic system, which has a gonadotropic function in eusocial Hymenoptera, is controlled by social suppression via the queen presence signal and the worker-worker dominance interactions. In Diacamma sp. from Japan, the queen presence signal is transferred to workers by direct contact, and worker-worker dominance interaction occurs commonly in large colonies, even when a queen is present. Using the ant Diacamma sp., we showed that the aggressive interactions among workers suppressed brain dopamine levels of the workers. Moreover, our data suggest that the queen presence signal transmitted by direct contact suppresses the brain dopamine level and the transcription of dopamine synthetic enzyme (ddc) of workers. Our data provide clear empirical evidence that worker brain dopamine is suppressed by both social stimuli directed from dominant workers and the queen. In eusocial Hymenoptera, worker reproduction is suppressed by social interactions such as queen presence information and dominance interaction. Dopamine, one of the biogenic amines, is a well-known gonadotropic neurohormone in eusocial Hymenoptera. Honeybee studies revealed that the queen presence information regulated dopamine levels in worker brains. In an ant, the dominance interaction also controlled dopamine levels of workers. In a queenless ant Diacamma sp., queen presence information and dominance interaction are known to dually suppress worker reproduction. Given the above examples, dopaminergic signaling is predicted to be a general mechanism that can suppress worker reproduction in multiple ways. We here test whether both the queen- and worker-originated signals (i.e., queen presence information and dominance interaction) affect the worker dopamine level. We show that dopaminergic signaling is affected by dual social factors, suggesting the general role of dopaminergic signaling in mediating social interaction and reproductive suppression.

Plights of Migrant Construction Workers

This study attempts to examine the conditions of construction workers and problems faced by them in Gandhinagar city. From the analysis, it is clear that economic condition of the workers has slightly improved, but demographic–social and working–living situations of the workers are extremely pathetic and vulnerable till now. The demand and supply of migrant workers is managed through the contract system. Contractors and sub-contractors play a crucial role in providing facilities and obtaining desired employment within a short time span. From the employment point of view, the industry is totally male dominant and preponderant and female workers are unskilled and remain unskilled during their entire life. Of the many theories of migration, the Harris–Todaro model of migration is partially applicable in the rural-to-urban migration process. Unlike government employees, a construction worker has no social security, no earned leave, no sick leave and no pension or gratuity. Finally, it is clear that the objective of decent work for migrant workers will remain a major challenge for years to come.

Regulation of host workers' oviposition by the social parasite ant Polyergus samurai.

Polyergus samurai, an obligatory social parasite ant, lacks the ability to perform usual colony tasks. It depends completely on host Formica japonica workers. In the mixed colony, arrhenotokous reproduction by host workers must be detrimental to the parasites. This study, conducted under artificial rearing conditions, investigated the behavioral influence by P. samurai worker on the production of host workers' male eggs. Host workers started laying eggs when the P. samurai queen was removed, but most eggs were destroyed by P. samurai workers. In a queenless condition, P. samurai workers showed frequent intraspecific dominance interactions, but few interspecific ones. After a short while the P. samurai worker started laying eggs, the F. japonica worker stopped laying eggs. The ovary had no mature oocyte. These results suggest that both the P. samurai queen and dominant workers can inhibit host workers' oviposition. A mesh experiment revealed that the dominant P. samurai workers were able to inhibit host workers' oviposition without contacts. The dominant workers and queens of P. samurai frequently received grooming and trophallaxis from host workers just as a host queen does, suggesting that the parasites secreted similar products to those of the host queen to inhibit the host workers' oviposition.

Orphaning does not affect the colony productivity of the primitive eusocial wasp Polistes snelleni

In colonies of primitively eusocial wasps, some dominant workers become successive queens and inherit queenship after the death of the foundress queens. Although workers in many species do not mate, workers of Polistes snelleni are capable of mating and female production. In this study, we removed foundress queens from colonies of P. snelleni to evaluate the effects of queen loss on the dominant–subordinate relationships among the remaining workers and the productivity of colonies in the species. The foundress queens were the sole egg layers in almost all of the queenright colonies. The frequency of dominance behaviour among the wasps in the queenright colonies was significantly less than in the orphan colonies. The frequency of dominance behaviour in the successive queens after queen removal was significantly more than in the foundress queens. Multiple workers had developed ovaries, including the successive queens in 66.7 % (10/15) of the orphan colonies after queen removal. The orphan colonies produced significantly more cells and eggs than the queenright colonies. Our results suggest that the reproductive potential of the successive queens in the orphan colonies is not lower than that of the foundress queens, and that the productivity of the orphan colonies is maintained rather than causing potential conflict over direct reproduction among workers.

Polistes japonicus (Hymenoptera, Vespidae) queens monopolize ovipositing but are not the most active aggressor in dominant-subordinate interactions

In order to elucidate the dominant–subordinate relationship between the foundress and workers, five colonies of the paper wasp Polistes japonicus were observed in a netted and covered cage located outdoors. The number of workers in each colony ranged from four to eight. Workers were divided into first and second broods. Abdominal wagging and ovipositing were performed almost exclusively by the foundress throughout colony development. However, an analysis of aggressive encounters indicated that although the foundress hardly received dominance behaviors (aggression) from workers, it lacked either partially or completely the following characteristics of the queen that are usually seen in paper-wasp colonies with independent-founding queens (except in one colony that produced no second brood): the queen being socially dominant over any worker (the queen had more wins than losses in one-on-one dominance contests with any worker), exhibiting the highest frequency of dominance behaviors, and directing dominance behaviors primarily toward the socially most-dominant worker. In particular, during the mixed-brood period (when all first- and second-brood workers were present on the nest) the foundress hardly exhibited dominance behaviors toward socially dominant workers (mainly second brood) but frequently directed dominance behaviors toward socially subordinate workers (mainly first brood). The foundress disappeared in two colonies before the reproductives emerged; in these colonies the socially most-dominant worker inherited the colony and laid many eggs. The frequency of abdominal wagging by these two foundresses decreased during colony development, while it did not in the other colonies. This suggests that abdominal wagging provides information about the vigor of the performer. The superseder was socially dominant over all other workers, but spent little time wagging its abdomen and allowed some workers to lay eggs.

The appeasement effect of sterility signaling in dominance contests among Bombus terrestris workers

The establishment of dominance hierarchies through aggressive interactions is very common in insect societies. In many cases, it is also mediated through pheromone emissions that enable individuals to evaluate the reproductive quality and level of aggressiveness of the dominant individual, thereby reducing the number and intensity of costly fights. Here, we studied these processes in the primitively eusocial bee Bombus terrestris, using a paired bee system. Specifically, we investigated the behavioral, reproductive, and pheromonal correlates of dominance establishment. Workers were shown to establish dominance hierarchies using overt aggression within 3–4 days. Thereafter, the aggression drastically decreased, and dominance was maintained mostly by ritualized agonistic behavior. The behaviorally dominant bee lost the ester compounds that workers produce in their Dufour's gland (the so-called “sterility signal”) concomitantly with the development of her ovaries. The other bee announced as subordinate by continuously producing high amounts of those esters. The hypothesis that sterility signaling serves as an appeasement signal to pacify the dominant bees is supported by the negative correlation found between the proportion of these esters and the level of aggression that the subordinate received from the dominant worker. Physical interactions, and presumably also the ensuing overt aggression between the bees, were essential for the above pheromonal change to take place and enabled the dominant workers to develop their ovaries and to lay eggs. The subordinate bee’s signaling of non-reproductive status may minimize energy expenditure in costly fights and help stabilize the reproductive division of labor among workers.

Worker dominance and policing in the ant Temnothorax unifasciatus

In many species of eusocial Hymenoptera, conflict about the production of males is resolved through “policing.” Recent studies in wasps and the ant Temnothorax unifasciatus suggest that in these species policing workers are dominant themselves and selfishly increase their own chances of later becoming fertile. Policing may therefore to some extent be associated with dominance and selfishness, and dominance and policing behaviour are indeed difficult to distinguish and often not mutually exclusive. Moreover, selfish policing requires that workers form rank orders already in the presence of the queen. Here, we try to allocate aggressiveness by workers towards policing and/or dominance behaviour and investigate whether hierarchies based on subtle, non-aggressive interactions exist in queenright colonies of the ant T. unifasciatus. We either split colonies into a queenright and queenless halve or temporarily removed the queen from complete colonies, which in both cases allows a few dominant workers to lay eggs in the queenless colony. Reunification of colony halves and return of the queen to orphaned colonies led to aggression against those workers that had become fertile during the absence of the queen. Dominant workers in reunited, split colonies were more severely attacked than those in orphaned colonies after return of the queen. Furthermore, we observed that workers, which later became dominant egg layers under queenless conditions, have more contact with the queen than other workers. Both results corroborate the existence of rank relationships among workers in queenright colonies and show that results from policing experiments may be affected by the disturbance of pre-existing hierarchies through colony splitting.

Worker reproductive competition affects division of labor in a primitively social paperwasp (Polistes instabilis)

Social insects are premier models for studying the evolution of self-organization in animal societies. Primitively social species may be informative about the early stages of social evolution and transitions in self-organization. Previous worker removal studies in Polistes instabilis paper wasps suggested that dominant but non-egglaying workers play an important role in regulating rates of task performance by inducing foraging in subordinates. We extend previous worker removal studies by quantifying changes in individuals’ behavior following removals, and by measuring associations between behavioral change and individuals’ reproductive capacity (ovary development). Workers changed their rates of aggressive behaviors more than queens following the dominant worker removals. Increases in worker’s rates of aggressive behaviors were correlated with decreases in their foraging rates. Changes in individual rates of social aggression were associated with their reproductive capacity: worker females with well-developed ovaries increased their rates of aggression. Further changes in rates of aggression after the dominant workers were returned also depended on ovary development. These patterns suggest that task performance and potential fecundity are linked in workers, and that worker interactions play a strong role in regulating task performance. We conclude that worker reproductive competition may have influenced the evolution of colony organization in social insects.

Fertility signals in the bumblebee Bombus terrestris (Hymenoptera: Apidae)

In eusocial Hymenoptera, queen control over workers is probably inseparable from the mechanism of queen recognition. In primitively eusocial bumblebees (Bombus), worker reproduction is controlled not only by the presence or absence of a dominant queen but also by other dominant workers. Furthermore, it was shown that the queen dominance is maintained by pheromonal cues. We investigated whether there is a similar odor signal released by egg-laying queens and workers that may have a function as a fertility signal. We collected cuticular surface extracts from nest-searching and breeding Bombus terrestris queens and workers that were characterized by their ovarian stages. In chemical analyses, we identified 61 compounds consisting of aldehydes, alkanes, alkenes, and fatty acid esters. Nest-searching queens and all groups of breeding females differed significantly in their odor bouquets. Furthermore, workers before the competition point (time point of colony development where workers start to develop ovaries and lay eggs) differed largely from queens and all other groups of workers. Breeding queens showed a unique bouquet of chemical compounds and certain queen-specific compounds, and the differences toward workers decrease with an increasing development of the workers' ovaries, hinting the presence of a reliable fertility signal. Among the worker groups, the smallest differences were found after the competition point. Egg-laying females contained higher total amounts of chemical compounds and of relative proportions of wax-type esters and aldehydes than nest-searching queens and workers before the competition point. Therefore, these compounds may have a function as a fertility signal present in queens and workers.

Impact of insecticidal proteins expressed in transgenic plants on bumblebee microcolonies

AbstractIn order to assess the risk that insecticidal transgenic plants may pose for bumblebees, we tested whether Bombus terrestris (L.) (Hymenoptera: Apidae) workers are able to detect insecticidal proteins dissolved in sucrose solution and whether consumption of these proteins will affect survival and offspring production. Feeders containing either Bacillus thuringiensis toxin (Cry1Ab), Kunitz soybean trypsin inhibitor (SBTI), or Galanthus nivalis agglutinin (GNA) were offered to bumblebee colonies at low (0.01% wt/vol for SBTI and GNA, 0.001% for Cry1Ab) and high concentrations (0.1% for SBTI and GNA, 0.01% for Cry1Ab) together with a control (pure sucrose solution) in a glasshouse chamber. No difference was found in the number of visits and the duration of visits among the different concentrations for each of the insecticidal proteins, indicating that bumblebees do not discriminate the compounds. To investigate the impact of the different insecticidal proteins on B. terrestris, microcolonies were established by placing three newly emerged bumblebee workers in wooden boxes. Within a few days, a hierarchy in each microcolony was established and the dominant worker developed its ovaries and laid haploid eggs. Bumblebees were fed with Cry1Ab (0.01%), SBTI, or GNA (both at 0.01 and 0.1%) dissolved in sucrose solution and also fed mixed floral pollen for a maximum period of 80 days. Additionally, microcolonies with three drones each were established to measure individual bee longevity. While the Cry1Ab did not affect microcolony performance, the consumption of SBTI and especially GNA affected survival of B. terrestris workers and drones and caused a significant reduction in the number of offspring. The use of microcolonies appears to be well‐suited to measure lethal and sublethal effects of insecticidal proteins expressed in transgenic plants on bumblebees.

REPRODUCTIVE CONFLICTS AFFECT LABOR AND IMMUNE DEFENSE IN THE QUEENLESS ANT DIACAMMA SP. “NILGIRI”

In many species of social Hymenoptera, totipotency of workers induces potential conflicts over reproduction. However, actual conflicts remain rare despite the existence of a high reproductive skew. One of the current hypotheses assumes that conflicts are costly and thus selected against. We studied the costs of conflicts in 20 colonies of the queenless ant Diacamma sp. "nilgiri" by testing the effects of conflicts on labor and worker immunocompetence, two parameters closely linked to the indirect fitness of workers. In this species, the dominant female is the only mated worker (gamergate) and monopolizes reproduction. We experimentally induced conflicts by splitting each colony into two groups, a control group containing the gamergate and an orphaned group displaying aggressions until a new dominant worker arises. Immunocompetence was assessed by the clearance of Escherichia coli bacteria that we injected into the ants. Time budget analysis revealed a lower rate of labor and especially brood care in orphaned groups, supporting the existence of a cost of conflicts on labor. Fifteen days after splitting, a lower immunocompetence was also found in orphaned groups, which concerned workers involved and not involved in conflicts. We propose that this immunosuppression induced by conflicts could stem from stress and not directly from aggression.