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Context plays an important role in a discriminator's ability to make appropriate recognition decisions, such as accepting what is acceptable and rejecting what is not acceptable. Previously it was shown that in both honey bees and stingless bees, discriminating workers (guards) make more errors towards conspecific non-nestmates when the guards are removed from the natural hive entrance. However, it may be that guards, in addition to making incorrect recognition decisions, also may adopt non-guarding behaviours. Here, we tested honey bee guards in two contexts (natural versus unnatural) against five types of introduced arthropods (conspecific nestmates and non-nestmates; allospecific wasps, beetles and woodlice), which should be rejected without error. We scored a guard's response as accept, reject, avoid and ignore. Total errors significantly increased from natural to unnatural contexts. Specifically, guards were significantly more likely to make an acceptance error, guarding and accepting both conspecific and allospecific non-nestmates, in the unnatural context. Importantly, guards were significantly more likely to adopt a non-guarding behaviour in the unnatural context, which usually involved ignoring or avoiding, where a guard makes contact but then immediately retreats, the introduced arthropod. Overall, these data demonstrate the context is important. Removing a guard from the home that it protects elicits either incorrect discrimination or, additionally, a complete lack of discriminator behaviour altogether. [ABSTRACT FROM AUTHOR]

Social insects often respond to signals and cues from nest-mates, and these responses may include changes in the information they, in turn, transmit. During foraging, Lasius niger deposits a pheromone trail to recruit nestmates, and ants that experience trail crowding deposit pheromone less often. Less studied, however, is the time taken for signalling to revert to baseline levels after conditions have returned to baseline levels. In this paper we study the behaviour of L. niger foragers on a trail in which crowding is simulated by using dummy ants -- black glass beads coated in nestmate cuticular hydrocarbons. Ants were allowed to make four repeat visits to a feeder with dummy ants, and thus crowding, being present on the trail on all visits (CCCC), none (UUUU) or only the first two (CCUU). If dummy ants were always present (CCCC), pheromone deposition probability was low in the first two visits (54% of ants deposited pheromone) and remained low in visits 3 and 4 (51 %). If dummy ants were never present (UUUU) pheromone deposition probability was high in the first two visits (93%) and remained high in visits 3 and 4 (83%). If dummy ants were present on the first two visits but removed on the second two visits (CCUU) pheromone deposition probability was low in the first two visits (61%) but rose in the second two visits (69%). This demonstrates that even after pheromone deposition has been down-regulated due to crowding in the first two visits, it is rapidly up-regulated when crowding is reduced, although it does not immediately return to the base line level. [ABSTRACT FROM AUTHOR]

Inclusive fitness benefits depend on recognizing the right individuals to interact with. Social insect nests protect themselves from non-kin intruders through nestmate recognition based on chemical cues. The recognition cues on adult individuals are from a mixture of genetic and environmental sources, but the ontogeny and use of recognition cues on eggs has not been previously assessed. We studied recognition by workers of eggs that were either nestmates or non-nestmates. and the ontogeny of recognition cues on eggs in the ant Formica fusca, a species with precise egg recognition abilities. Workers were able to discriminate among freshly laid eggs with no nest derived cues on them, and the egg surface chemicals varied among nests in these eggs, suggesting that queen derived cues are used in nestmate recognition. The results are discussed in the light of their implications on deceptive social parasite strategies and within colony conflicts. [ABSTRACT FROM AUTHOR]

Division of labor among workers is common in insect societies and is thought to be important in their ecological success. In most species, division of labor is based on age (temporal castes), but workers in some ants and termites show morphological specialization for particular tasks (physical castes). Large-headed soldier ants and termites are well-known examples of this specialization. However, until now there has been no equivalent example of physical worker subcastes in social bees or wasps. Here we provide evidence for a physical soldier subcaste in a bee. In the neotropical stingless bee Tetragonisca angustula, nest defense is performed by two groups of guards, one hovering near the nest entrance and the other standing on the wax entrance tube. We show that both types of guards are 30% heavier than foragers and of different shape; foragers have relatively larger heads, whereas guards have larger legs. Low variation within each subcaste results in negligible size overlap between guards and foragers, further indicating that they are distinct physical castes. In addition, workers that remove garbage from the nest are of intermediate size, suggesting that they might represent another unrecognized caste. Guards or soldiers are reared in low but sufficient numbers (1-2% of emerging workers), considering that <1% usually perform this task. When challenged by the obligate robber bee Lestrimelitta limao, an important natural enemy, larger workers were able to fight for longer before being defeated by the much larger robber. This discovery opens up opportunities for the comparative study of physical castes in social insects, including the question of why soldiers appear to be so much rarer in bees than in ants or termites. [ABSTRACT FROM AUTHOR]

The authors give opinion on a study on sex allocation conflict in colonies of eusocial Hymenoptera. A framework for examination of the outcome of the conflict between the queen and the workers through power and the costs of manipulation is presented. Factors that determine power are discussed, one of which is queen-worker dimorphism. Power in sex allocation conflicts between mating partners are also tackled.

Worker insects altruistically sacrifice their own reproduction to rear nondescendant kin. This sacrifice reaches its most spectacular level in suicidal colony defense. Suicidal defense, such as when the sting of a honeybee worker embeds in a predator and then breaks off, is normally a facultative response. Here we describe the first example of preemptive self-sacrifice in nest defense. In the Brazilian ant Forelius pusillus, the nest entrance is closed at sunset. One to eight workers finish the job from the outside and, in doing so, sacrifice their lives. [ABSTRACT FROM AUTHOR]

We studied the effect of prior experience to eggs laid by nestmate and non-nestmate queens on the acceptance of queen-laid eggs by worker wood ants, Formica fusca. We transferred eggs from a non-nestmate queen into colonies during early spring, when their own queen was recommencing egg laying. A few weeks later, workers from these “experienced” colonies accepted eggs of both familiar (44% acceptance) and unfamiliar (40%) non-nestmate queens much more than workers from control colonies (2%) that had only had previous contact with their own queen’s eggs. Thus, prior exposure to eggs laid by a non-nestmate queen induces much greater acceptance of all non-nestmate queen-laid eggs. Mechanistically, we hypothesize that exposure to eggs from several queens may increase acceptance by causing a highly permissive acceptance threshold of non-nestmate queen-laid eggs rather than by widening the template for acceptable queen-laid eggs. These novel results show that egg-discrimination behaviour in F. fusca is flexible and that workers respond to the diversity of eggs experienced in their colony. [ABSTRACT FROM AUTHOR]

1. Atta (Hymenoptera: Formicidae) leafcutter ants display the most polymorphic worker caste system in ants, with different sizes specialising in different tasks. The largest workers (majors) have large, powerful mandibles and are mainly associated with colony defence. 2. Majors were observed cutting fallen fruit and this phenomenon was investigated in the field by placing mango fruit near natural Atta laevigata and Atta sexdens colonies in São Paulo State, Brazil. 3. Ants cutting the fruit were significantly heavier (mean = 49.1 mg, SD = 11.1 mg, n= 90) than the ants carrying the fruit back to the nest (mean = 20.9 mg, SD = 9.2 mg, n= 90). 4. Fruit pieces cut by majors were small (mean = 15.9 mg), approximately half the weight of leaf pieces (mean = 28.5 mg) cut and carried by media foragers. It is hypothesised that it is more difficult to cut large pieces from three-dimensional objects, like fruit, compared to two-dimensional objects, like leaves, and that majors, with their longer mandibles, can cut fruit into larger pieces than medias. 5. The study shows both a new role for Atta majors in foraging and a new example of task partitioning in the organisation of foraging. [ABSTRACT FROM AUTHOR]

In many bees, wasps, and ants, workers police each other in order to prevent individual workers from selfishly producing their own male offspring. Although several factors can selectively favor worker policing, genetic relatedness is considered to be of special importance. In particular, kin selection theory predicts that worker policing should be more common in species where workers are more related to the queen's sons than to other workers' sons. Here we provide strong novel support for this theory based on a comparative analysis of policing and male parentage in 109 species of ants, bees, and wasps. First, an analysis of behavioral data confirms that worker policing occurs more frequently in species where workers are more related to the queen's sons than to other workers' sons. Second, an analysis of male parentage shows that a significantly higher percentage of the males are workers' sons in species where the workers are more related to other workers' sons. Both conclusions also hold if data are analyzed using phylogenetically independent contrasts. Although our analysis provides strong overall support for the theory that relatedness affects kin conflict over male parentage, there is also significant residual variation. Several factors that may explain this variation are discussed. [ABSTRACT FROM AUTHOR]

Although best known for cooperation, insect societies also manifest many potential conflicts among individuals. These conflicts involve both direct reproduction by individuals and manipulation of the reproduction of colony members. Here we review five major areas of reproductive conflict in insect societies: (a) sex allocation, (b) queen rearing, (c) male rearing, (d) queen-worker caste fate, and (e) breeding conflicts among totipotent adults. For each area we discuss the basis for conflict (potential conflict), whether conflict is expressed (actual conflict), whose interests prevail (conflict outcome), and the factors that reduce colony-level costs of conflict (conflict resolution), such as factors that cause workers to work rather than to lay eggs. Reproductive conflicts are widespread, sometimes having dramatic effects on the colony. However, three key factors (kinship, coercion, and constraint) typically combine to limit the effects of reproductive conflict and often lead to complete resolution. [ABSTRACT FROM AUTHOR]

In social groups composed of kin, inclusive fitness benefits can favor greater cooperation. Alternatively, cooperation can be enforced through the policing of less cooperative individuals. Here, we show that the effect of policing can be twofold: not only can it directly suppress individual selfishness, it can also entirely remove the incentive for individuals to act selfishly in the first place. We term such individual restraint in response to socially imposed policing "acquiescence" and illustrate the concept using examples drawn from the social Hymenoptera (the ants, bees, and wasps). Inclusive fitness models confirm that when a policing system is in place, individuals should be less tempted to act selfishly. This is shown to have important consequences for the resolution of conflict within their societies. For example, it can explain why in many species very few workers attempt to reproduce and why immature females usually do not attempt to develop as queens rather than workers. Although our analyses are primarily focused on the social insects, our conclusions are likely to be general and to apply to other societies as well. [ABSTRACT FROM AUTHOR]

Dominance interactions determine reproductive status in many animal societies, including many cooperatively breeding vertebrates and eusocial Hymenoptera without queen-worker dimorphism. Typically, the dominant individual monopolises reproduction, and subordinates behave like helpers. In Dinoponera queenless ants, workers are totipotent females and can potentially reproduce, yet only the top-ranking worker actually reproduces. Individual workers ranked immediately below the dominant breeder worker (gamergate) are hopeful reproductives. Whether or not a worker benefits from joining the hierarchy of high-ranking workers depends on the trade-off between the probability of becoming dominant and reproducing directly, and the colony-level cost of an additional lazy high ranker. Inclusive fitness models predict that the length of the dominance hierarchy depends on relatedness, colony size, and the linearity of the hierarchy. Here, we test the effect of colony size by comparing hierarchy length among three species that differ in colony size (Dinoponera australis: median=14 workers, quartiles=10 and 19 workers; D. gigantea: median=41, quartiles=33 and 74; D. quadriceps: median=78, quartiles=55 and 90). Although difficulties in defining where the hierarchy ends hamper comparisons, the results are in broad agreement with the predictions. Hierarchies are close to the predicted lengths and are longer in species with larger colonies (one, three and three workers in the three species in order from smallest to largest colony vs two, three and four predicted). These conclusions are further supported by determining Kokko and Lindström's λ index of skew, which is smaller (i.e. characteristic of a longer hierarchy) in species with larger colonies. [ABSTRACT FROM AUTHOR]

abstract: Mutual policing is thought to be important in conflict suppression at all levels of biological organization. In hymenopteran societies (bees, ants, and wasps), multiple mating by queens favors mutual policing of male production among workers (worker polic-ing). However, worker policing of male production is proving to be more widespread than predicted by relatedness patterns, occurring in societies headed by single-mated queens in which, paradoxically, workers are more related to the workers' sons that they kill than the queen's sons that they spare. Here we develop an inclusive-fitness model to show that a second reproductive conflict, the conflict over sex allocation, can explain the evolution of worker policing contrary to relatedness predictions. Among ants, and probably other social Hymenoptera, workers kill males to favor their more related sisters. Importantly, males are killed at the larval stage, presumably because workers cannot determine the sex of queen-laid eggs. Sex-allocation biasing favors worker policing because policing removes some males (the workers' sons) at low cost at the egg stage rather than at higher cost at the larval stage. Our model reveals an important interaction between two reproductive conflicts in which the presence of one conflict (sex allocation) favors the suppression of the other (male production by workers). [ABSTRACT FROM AUTHOR]

Part II. Focuses on a study of task partitioning in social insect societies in regard to the use of queuing delays between foragers and receivers in recruitment in both honeybees and Polybia wasps. Information content and quality of the delays; Use of a stochastic-simulation model in the study; Results and discussion; Conclusion.

Part I. Focuses on a study of task partitioning in insect societies regarding the effect of colony size on the amount of time lost because of queuing delays in direct transfer from foragers to receivers and on colony ergonomic efficiency. Use of a computer simulation model; Results and discussion; Conclusion.

Many animal societies contain few breeders and many helpers. In some species, individuals can become either helpers or breeders, and breeding is often restricted to high rankers in a dominance hierarchy. In social Hymenoptera with no morphological queen caste, all females have the potential to become dominant and reproduce. In our model, females involved in the hierarchy do not work and gain direct fitness if they become alpha following death of the current alpha, while females not in the hierarchy gain indirect fitness by working. Using an inclusive-fitness model combined with models of alpha replacement in slightly different types of near-linear hierarchies, we determined the critical rank (i.e., optimal hierarchy length) for which the gain in fitness by entering the hierarchy as a hopeful reproductive equals the cost caused by a reduced worker force. High relatedness decreases the hierarchy length by lowering the potential benefit of entering the hierarchy. In contrast, large colony size increases the hierarchy length because the cost of each non-working high ranker is relatively lower. The model predicts a hierarchy of five workers in the queenless ant Dinoponera quadriceps, close to empirical data which show that in a colony of about 100 females, the top 5 carry out 72.8% of the aggressive interactions. The model is also used to make several testable predictions about the effect on hierarchy length of (1) variation in colony size and (2) variation in worker reproductive options between species of the queenless ants genus Diacamma. [ABSTRACT FROM AUTHOR]

We argue that caste determination, the process whereby females in the social Hymenoptera develop into either queens or workers, is subject to kin-selected conflict. Potential conflict arises because developing females are more closely related to their would-be offspring than to those of other females. Therefore, they may favour becoming queens contrary to the interests of other developing females and of existing queens and workers. We suggest two contexts leading to potential caste conflict. The first occurs when queens are reared in a reproductive phase following an ergonomic phase of worker production, while the second occurs when queens and workers are reared simultaneously. The first context assumes that workers' per capita contribution to colony survival and productivity falls with rising colony size. A critical feature influencing whether potential conflict is realized is the extent to which developing females can determine their own caste (“self-determination”). Self-determination is facilitated when female larvae control their own food intake and when queen-worker size dimorphism is low. We know of no strong evidence for actual conflict over caste fate arising in the first context. However, stingless bees and polygynous ants with excess queen-potential larvae that are either forced to develop as workers or are culled as adults demonstrate actual caste conflict in the second context. Caste conflict does not preclude caste regulation for “the good of the colony”, but such regulation is contingent on either the absence of potential conflict or on developing females losing control of their caste fate. [ABSTRACT FROM AUTHOR]

The article presents information on insect societies. Insect societies, too, experience internal conflicts, and research increasingly shows that policing is important to resolve these. Within both human and insect societies, conflicts arise because the interests of individuals differ. In insect societies, conflict revolves around reproduction. Reproducing individuals gain by being more closely related to the young males and queens reared in their colony. By reproducing, society members also exploit the colony and this can be costly. First, uncontrolled reproduction upsets the division of labor between queen and workers and results in a less efficient colony. Second, the offspring reared are often genetically less related and so are less valuable to other society members.

Pheromone trails are used by many ants to guide foragers between nest and food. But how does a forager that has become displaced from a trail know which way to go on rejoining the trail? A laden forager, for example, should walk towards the nest. Polarized trails would enable ants to choose the appropriate direction, thereby saving time and reducing predation risk. However, previous research has found no evidence that ants can detect polarity from the pheromone trail alone. Pharaoh's ants (Monomorium pharaonis) produce elaborate trail networks throughout their foraging environment. Here we show that by using information from the geometry of trail bifurcations within this network, foragers joining a trail can adaptively reorientate themselves if they initially walk in the wrong direction. The frequency of correct reorientations is maximized when the trail bifurcation angle is approximately 60 degrees, as found in natural networks. These are the first data to demonstrate how ant trails can themselves provide polarity information. They also demonstrate previously unsuspected sophistication in the organization and information content of networks in insect societies. [ABSTRACT FROM AUTHOR]

Asserts that multiple mating of queens of the wasp species Dolichovespula saxonica results in mutual policing by workers. Correlation between worker relatedness and male production by workers; Conclusion that the kinship caused by single mating of the queen may retard social evolution in this species and others like it.

Cooperation among workers and their seeming altruism result from strict policing by nestmates. [ABSTRACT FROM AUTHOR]

Close relatedness has long been considered crucial to the evolution of eusociality. However, it has recently been suggested that close relatedness may be a consequence, rather than a cause, of eusociality. We tested this idea with a comparative analysis of female mating frequencies in 267 species of eusocial bees, wasps, and ants. We found that mating with a single male, which maximizes relatedness, is ancestral for all eight independent eusocial lineages that we investigated. Mating with multiple males is always derived. Furthermore, we found that high polyandry (>2 effective mates) occurs only in lineages whose workers have lost reproductive totipotency. These results provide the first evidence that monogamy was critical in the evolution of eusociality, strongly supporting the prediction of inclusive fitness theory. [ABSTRACT FROM AUTHOR]