Groups Of Social Insects Research Articles

Phylogenetic analyses of the proteins involved in encapsulation signaling pathways in ants

"One of the major evolutionary transitions is the shift from solitary to social lifestyle, which involved a plethora of behavioral and physiological changes in social entities. Group living has several advantages as the evolution of collective defense mechanisms. It may also affect the individual immune system either due to the efficiency of social immune defenses or because of the high transmission frequency of pathogens. Individual defense consists of the innate and acquired immune components. In insects, there are two signaling pathways (Toll and Jak/Stat) that result in the expression of specific immune genes, which, in their turn, encode peptides, proteins and activate innate immune responses like encapsulation. The main aim of our study was to verify whether transition to eusocial lifestyle is reflected in proteins involved in immune responses. We carried out phylogenetic analyses of 15 proteins involved in encapsulation signaling pathways in ants. We also included four other social insect groups, bees, sweat bees, social wasps, and termites, and three solitary insect groups, as fruit flies, braconid wasps, and megachilid bees. Ants grouped separately from other insect groups in most cases, however, there were some notable exceptions mostly in the case of pattern recognition proteins, probably correlating with differences in potential pathogens. No major differences were revealed though between solitary and social insects with respect to proteins involved in encapsulation. Keywords: eusociality, evolution, immune response, innate immunity, insects, social immunity"

Meta-Analysis of Public RNA Sequencing Data Revealed Potential Key Genes Associated with Reproductive Division of Labor in Social Hymenoptera and Termites.

Eusociality in insects has evolved independently many times. One of the most notable characteristics of eusociality is the reproductive division of labor. In social insects, the reproductive division of labor is accomplished by queens and workers. Transcriptome analyses of queens and workers have been conducted for various eusocial species. However, the genes that regulate the reproductive division of labor across all or multiple eusocial species have not yet been fully elucidated. Therefore, we conducted a meta-analysis using publicly available RNA-sequencing data from four major groups of social insects. In this meta-analysis, we collected 258 pairs (queen vs. worker) of RNA-sequencing data from 34 eusocial species. The meta-analysis identified a total of 20 genes that were differentially expressed in queens or workers. Out of these, 12 genes have not previously been reported to be involved in the reproductive division of labor. Functional annotation of these 20 genes in other organisms revealed that they could be regulators of behaviors and physiological states related to the reproductive division of labor. These 20 genes, revealed using massive datasets of numerous eusocial insects, may be key regulators of the reproductive division of labor.

From inter-group conflict to inter-group cooperation: insights from social insects.

The conflict between social groups is widespread, often imposing significant costs across multiple groups. The social insects make an ideal system for investigating inter-group relationships, because their interaction types span the full harming-helping continuum, from aggressive conflict, to mutual tolerance, to cooperation between spatially separate groups. Here we review inter-group conflict in the social insects and the various means by which they reduce the costs of conflict, including individual or colony-level avoidance, ritualistic behaviours and even group fusion. At the opposite extreme of the harming-helping continuum, social insect groups may peacefully exchange resources and thus cooperate between groups in a manner rare outside human societies. We discuss the role of population viscosity in favouring inter-group cooperation. We present a model encompassing intra- and inter-group interactions, and local and long-distance dispersal. We show that in this multi-level population structure, the increased likelihood of cooperative partners being kin is balanced by increased kin competition, such that neither cooperation (helping) nor conflict (harming) is favoured. This model provides a baseline context in which other intra- and inter-group processes act, tipping the balance toward or away from conflict. We discuss future directions for research into the ecological factors shaping the evolution of inter-group interactions. This article is part of the theme issue 'Intergroup conflict across taxa'.

Linoleic acid as corpse recognition signal in a social aphid

Social insect colonies constantly produce dead insects, which cause sanitary problems and potentially foster deadly pathogens and parasites. Hence, many social insects have evolved a variety of hygienic behaviors to remove cadavers from the colonies. To that end, they have to discriminate dead insects from live ones, where chemical cues should play important roles. In ants, bees and termites, such corpse recognition signals, also referred to as “death pheromones” or “necromones”, have been identified as fatty acids, specifically oleic acid and/or linoleic acid. Meanwhile, there has been no such report on social aphids. Here we attempted to identify the “death pheromone” of a gall-forming social aphid with second instar soldiers, Tuberaphis styraci, by making use of an artificial diet rearing system developed for this species. On the artificial diet plates, soldiers exhibited the typical cleaning behavior, pushing colony wastes with their heads continuously, against dead aphids but not against live aphids. GC-MS and GC-FID analyses revealed a remarkable increase of linoleic acid on the body surface of the dead aphids in comparison with the live aphids. When glass beads coated with either linoleic acid or body surface extract of the dead aphids were placed on the artificial diet plates, soldiers exhibited the cleaning behavior against the glass beads. A series of behavioral assays showed that (i) soldiers exhibit the cleaning behavior more frequently than non-soldiers, (ii) young soldiers perform the cleaning behavior more frequently than old soldiers, and (iii) the higher the concentration of linoleic acid is, the more active cleaning behavior is induced. Analysis of the lipids extracted from the aphids revealed that linoleic acid is mainly derived from phospholipids that constitute the cell membranes. In conclusion, we identified linoleic acid as the corpse recognition factor of the social aphid T. styraci. The commonality of the death pheromones across the divergent social insect groups (Hymenoptera, Blattodea and Hemiptera) highlights that these unsaturated fatty acids are generally produced by enzymatic autolysis of cell membranes after death and therefore amenable to utilization as a reliable signal of dead insects.

Colonization by the Red Imported Fire Ant, Solenopsis invicta, Modifies Soil Bacterial Communities.

The long-standing association between insects and microorganisms has been especially crucial to the evolutionary and ecological success of social insect groups. Notably, research on the interaction of the two social forms (monogyne and polygyne) of the red imported fire ant (RIFA), Solenopsis invicta Buren, with microbes in its soil habitat is presently limited. In this study, we characterized bacterial microbiomes associated with RIFA nest soils and native (RIFA-negative) soils to better understand the effects of colonization of RIFA on soil microbial communities. Bacterial community fingerprints of 16S rRNA amplicons using denaturing gradient gel electrophoresis revealed significant differences in the structure of the bacterial communities between RIFA-positive and RIFA-negative soils at 0 and 10 cm depths. Illumina sequencing of 16S rRNA amplicons provided fine-scale analysis to test for effects of RIFA colonization, RIFA social form, and soil depth on the composition of the bacterial microbiomes of the soil and RIFA workers. Our results showed the bacterial community structure of RIFA-colonized soils to be significantly different from native soil communities and to evidence elevated abundances of several taxa, including Actinobacteria. Colony social form was not found to be a significant factor in nest or RIFA worker microbiome compositions. RIFA workers and nest soils were determined to have markedly different bacterial communities, with RIFA worker microbiomes being characterized by high abundances of a Bartonella-like endosymbiont and Entomoplasmataceae. Cloning and sequencing of the 16S rRNA gene revealed the Bartonella sp. to be a novel bacterium.

Wolbachia Across Social Insects: Patterns and Implications

Abstract Wolbachia is one of the most common intracellular symbionts among insects, but the function of this infection and its effects on the host still remain largely unknown for many taxa. In the case of many social insects, living in colonies results in close interactions, facilitating the dispersion of the symbiont. However, having only one caste responsible for reproduction (queens) could restrict infections. Several groups of social insects have been reported to be highly infected with these symbionts. However, Wolbachia associations across social and closely related non-social insects in a comparative framework has not been examined to date, which may help us understand the role social behavior, geography, and ecology plays in structuring this association. Since 2006 the Multi-Locus Sequencing Type (MLST) approach has been shown to be appropriate for diversity studies, which consists of sequencing five genes spread across the Wolbachia genome. Over the past 15 yr, studies using this approach have been conducted worldwide and have generated large volumes of data. In this review article, we intend to produce a meta-analysis by combining MLST data from across social insects (ants, bees, termites, wasps) and beyond, together with their closest relatives to better elucidate the patterns behind the diversity of this symbiotic interaction. Our main findings reveal that the diversity of Wolbachia (supergroups) is correlated with the host insect taxonomy, biogeography, and social/solitary behavior. In addition, solitary insects such as bees and wasps can interact with a greater diversity of Wolbachia supergroup compared to their social representatives.

Chemical Ecology in Insect-microbe Interactions in the Neotropics.

Small molecules frequently mediate symbiotic interactions between microorganisms and their hosts. Brazil harbors the highest diversity of insects in the world; however, just recently, efforts have been directed to deciphering the chemical signals involved in the symbioses of microorganisms and social insects. The current scenario of natural products research guided by chemical ecology is discussed in this review. Two groups of social insects have been prioritized in the studies, fungus-farming ants and stingless bees, leading to the identification of natural products involved in defensive and nutritional symbioses. Some of the compounds also present potential pharmaceutical applications as antimicrobials, and this is likely related to their ecological roles. Microbial symbioses in termites and wasps are suggested promising sources of biologically active small molecules. Aspects related to public policies for insect biodiversity preservation are also highlighted.

Evolution of cooperation on temporal networks

Population structure is a key determinant in fostering cooperation among naturally self-interested individuals in microbial populations, social insect groups, and human societies. Traditional research has focused on static structures, and yet most real interactions are finite in duration and changing in time, forming a temporal network. This raises the question of whether cooperation can emerge and persist despite an intrinsically fragmented population structure. Here we develop a framework to study the evolution of cooperation on temporal networks. Surprisingly, we find that network temporality actually enhances the evolution of cooperation relative to comparable static networks, despite the fact that bursty interaction patterns generally impede cooperation. We resolve this tension by proposing a measure to quantify the amount of temporality in a network, revealing an intermediate level that maximally boosts cooperation. Our results open a new avenue for investigating the evolution of cooperation and other emergent behaviours in more realistic structured populations.

Physico-Chemical Aspects and Complete Bacterial Community Composition Analysis of Wasp Nests

Wasps are a group of social insects that build a house, known as a nest, from locally available building materials cemented by their saliva and secretions. Similar to termite nests, there could be many beneficiary bacteria present in their house that can play an important part in maintaining sustainability in soil ecosystems. Thus, the present study was initiated with a physico-chemical characterization of wasp nests collected from residential and forest zones, followed by unconfined compressive strength (UCS) and X-ray diffraction (XRD) analysis to identify major associated minerals. Further, MiSeq Illumina sequencing of the 16S rRNA gene (V3–V4 regions) was carried out to analyze complete bacterial community composition of wasp nests. The resulting data showed a dominance of Actinobacteria followed by Proteobacteria in both nests. Kaistobacter and Phycicoccus were the dominant genera in each type of wasp nest. It was concluded that wasp nests are an abundant source to isolate bacteria that can potentially be helpful in soil biogeochemical cycling and fertility, antibiotics production and bioremediation.

Synergies Between Division of Labor and Gut Microbiomes of Social Insects

Social insects maximize resource acquisition and allocation through division of labor and associations with microbial symbionts. Colonies divide labor among castes and subcastes, where the plasticity of caste roles decreases in clades with higher social grades. Recent studies indicate that specific castes may also foster distinct gut microbiomes, suggesting synergies between division of labor and symbiosis. The social organization of a colony potentially partitions evolutionary persistent microbial partners to optimize symbioses and complement division of labor. However, research in this area has received limited attention. To elucidate if a structured microbiota is adaptive, we present three testable predictions to address consistent community structure, beneficial functions, and selection for microbiota that support caste roles. First, we posit that social insect groups spanning lower to higher social grades exhibit increasingly distinct caste microbiomes, suggesting that structured microbiomes may have evolved in parallel to social complexity. Second, we contend that the development of these microbiomes during colony maturation may clarify the extent to which they support division of labor. Third, we predict that mature social insect colonies with the most extreme division of labor demonstrate the strongest distinctions between caste microbiomes, carrying the greatest promise of insight into microbiome composition and function. Ultimately, we hypothesize that caste-specific microbiomes may enhance symbiotic benefits and the efficiency of division of labor, consequently maximizing fitness.

Honeybees possess a structurally diverse and functionally redundant set of queen pheromones.

Queen pheromones, which signal the presence of a fertile queen and induce workers to remain sterile, play a key role in regulating reproductive division of labour in insect societies. In the honeybee, volatiles produced by the queen's mandibular glands have been argued to act as the primary sterility-inducing pheromones. This contrasts with evidence from other groups of social insects, where specific queen-characteristic hydrocarbons present on the cuticle act as conserved queen signals. This led us to hypothesize that honeybee queens might also employ cuticular pheromones to stop workers from reproducing. Here, we support this hypothesis with the results of bioassays with synthetic blends of queen-characteristic alkenes, esters and carboxylic acids. We show that all these compound classes suppress worker ovary development, and that one of the blends of esters that we used was as effective as the queen mandibular pheromone (QMP) mix. Furthermore, we demonstrate that the two main QMP compounds 9-ODA and 9-HDA tested individually were as effective as the blend of all four major QMP compounds, suggesting considerable signal redundancy. Possible adaptive reasons for the observed complexity of the honeybee queen signal mix are discussed.

Loss of males from mixed-sex societies in termites

BackgroundSexual reproduction is the norm in almost all animal species, and in many advanced animal societies, both males and females participate in social activities. To date, the complete loss of males from advanced social animal lineages has been reported only in ants and honey bees (Hymenoptera), whose workers are always female and whose males display no helping behaviors even in normal sexual species. Asexuality has not previously been observed in colonies of another major group of social insects, the termites, where the ubiquitous presence of both male and female workers and soldiers indicate that males play a critical role beyond that of reproduction.ResultsHere, we report asexual societies in a lineage of the termite Glyptotermes nakajimai. We investigated the composition of mature colonies from ten distinct populations in Japan, finding six asexual populations characterized by a lack of any males in the reproductive, soldier, and worker castes of their colonies, an absence of sperm in the spermathecae of their queens, and the development of unfertilized eggs at a level comparable to that for the development of fertilized eggs in sexual populations of this species. Phylogenetic analyses indicated a single evolutionary origin of the asexual populations, with divergence from sampled sexual populations occurring about 14 million years ago. Asexual colonies differ from sexual colonies in having a more uniform head size in their all-female soldier caste, and fewer soldiers in proportion to other individuals, suggesting increased defensive efficiencies arising from uniform soldier morphology. Such efficiencies may have contributed to the persistence and spread of the asexual lineage. Cooperative colony foundation by multiple queens, the single-site nesting life history common to both the asexual and sexual lineages, and the occasional development of eggs without fertilization even in the sexual lineage are traits likely to have been present in the ancestors of the asexual lineage that may have facilitated the transition to asexuality.ConclusionsOur findings demonstrate that completely asexual social lineages can evolve from mixed-sex termite societies, providing evidence that males are dispensable for the maintenance of advanced animal societies in which they previously played an active social role.

Colony-founding success of pleometrosis in a fungus-growing termite Odontotermes formosanus

Cooperative colony foundation (pleometrosis) has evolved in independent groups of social insects and enhances the growth rate and survival of a colony, but it is associated with a cost because intracolonial aggression may be higher in pleometrotic than in haplometrotic colonies. We studied 647 colony-founding groups consisting of one to four pairs of reproductives of Odontotermes formosanus (Shiraki) in our laboratory to examine the benefits and costs of pleometrosis by analyzing its effects on nest excavation, degree of aggression, mortality, and colony growth. The results indicate that pleometrosis significantly reduced the time required for searching for a nesting site and increased the tunnel depth. Furthermore, the nest-excavation success rate was increased 35–50% in pleometrotic colonies. Pleometrosis also increased the fecundity and colony-survival rates. However, it increased individual mortality, probably because the reduction in the available space per individual intensified intracolonial aggression, particularly when more than three pairs of reproductives founded the colonies. Overall, the laboratory bioassays revealed that although pleometrosis benefited the colony-founding success of small groups (two pairs), it was costly for large groups (three pairs). The results are consistent with those of a field survey of O. formosanus, which showed that small pleometrotic groups (three or four reproductives) exhibit longevity, whereas large groups (more than four reproductives) are rare in the colony-founding stage. Hence, we conclude that the colony-founding success of pleometrosis depends on group size: pleometrosis benefits a small group but is costly for a large group. The evolution of cooperative colony foundation (pleometrosis) in social insects is believed to have been favored because of its beneficial effects on the survival and growth of colonies. In this study, we demonstrated the costs and benefits of pleometrosis in colonies of O. formosanus, a fungus-growing termite. Pleometrosis benefits survival in the following three ways: improving performance in nest excavation, preventing colony collapse following the death of a single reproductive, and increasing the growth rate. However, colony-founding success depends on group size. Pleometrosis benefits small groups (two reproductive pairs) more than it does large groups (three reproductive pairs). We hypothesize that pleometrosis in termites evolved after eusociality was achieved because it represents a trait that is common in fungus-growing termites.

Migration control: a distance compensation strategy in ants.

Migratory behaviour forms an intrinsic part of the life histories of many organisms but is often a high-risk process. Consequently, varied strategies have evolved to negate such risks, but empirical data relating to their functioning are limited. In this study, we use the model system of the house-hunting ant Temnothorax albipennis to demonstrate a key strategy that can shorten migration exposure times in a group of social insects. Colonies of these ants frequently migrate to new nest sites, and due to the nature of their habitat, the distances over which they do so are variable, leading to fluctuating potential costs dependent on migration parameters. We show that colonies of this species facultatively alter the dynamics of a migration and so compensate for the distance over which a given migration occurs. Specifically, they achieve this by modulating the rate of ‘tandem running’, in which workers teach each other the route to a new nest site. Using this method, colonies are able to engage a larger number of individuals in the migration process when the distance to be traversed is greater, and furthermore, the system appears to be based on perceived encounter rate at the individual level. This form of decentralised control highlights the adaptive nature of a behaviour of ecological importance, and indicates that the key to its robustness lies in the use of simple rules. Additionally, our results suggest that such coordinated group reactions are central to achieving the high levels of ecological success seen in many eusocial organisms.Electronic supplementary materialThe online version of this article (doi:10.1007/s00114-016-1386-8) contains supplementary material, which is available to authorized users.

Diversity of adipokinetic hormones in termites (Isoptera)

In this study we report on the structural diversity of adipokinetic hormones (AKHs) in the evolutionarily oldest group of social insects, the termites (Isoptera). Using molecular methods combined with in silico bioinformatic analysis, we studied and compared the sequences coding for these neuropeptides in thirteen species of five families of Isoptera. There are three types of AKH octapeptides in termites: Empusa pennata adipokinetic hormone (Emppe-AKH; pQVNFTPNWamide), Microhodotermes viator corpus cardiacum peptide (Micvi-CC; pQINFTPNWamide) and Periplaneta americana cardioaccelerating hormone (Peram-CAH-I; pQVNFSPNWamide). Of these the Peram-CAH-I was the most frequently bioactive form detected in representatives of four out of the six families studied. The complete AKH preprohormones in the termites studied shared at least an 84% amino acid similarity. In agreement with current phylogenetic scenarios of termites as an internal monophyletic clade nested within cockroaches (Blattaria) in the proximity of the family Blattidae, our phylogenetic analysis of the AKH precursor sequences (in the absence of data for the Cryptocercidae) placed the Blattidae (Periplaneta americana) as a sister group of termites and the AKHs of other cockroach families (Blattellidae and Blaberidae) were more divergent from those of termites. Representatives of the basal termite families Mastotermitidae and Archotermopsidae (but also one rhinotermitid genus Prorhinotermes) occurred separately from the phylogenetically advanced lineage (Rhinotermitidae and Termitidae), and Neotermes (Kalotermitidae) was sister to all other termites included.

Rapidly changing environment modulates the thermoregulatory fanning response in honeybee groups

Social insect societies maintain homeostasis through decentralized collective effort. In quickly changing environments, homeostasis can be difficult, as information may promptly become outdated. How do decentralized social insect groups respond to rapid environmental changes? Honeybee (Apis mellifera L.) workers use thermoregulatory fanning behaviour as part of their repertoire to maintain nest temperatures below 36 °C, as larvae can develop malformations and die if temperatures surpass this threshold. Here, we determine whether honeybees alter their fanning behaviour when experiencing different rates of thermal change. We found that honeybee fanners were significantly more likely to fan when experiencing rapidly increasing temperatures, but this response was only seen in larger groups of bees. Additionally, fanners responded at significantly lower temperatures when temperatures were increased quickly, but again, only when they were in larger groups. Our results show a statistically significant interaction between fanning response and group size. These findings illustrate the importance of exploring both response thresholds and probability of response of animals in social groups experiencing changing environments, as both factors affect homeostatic responses. Understanding how self-organized animal societies maintain homeostasis provides insight into decentralized organization across many biological systems.

A comparative analysis of rapid antennation behavior in four species of Odontomachus trap-jaw ants

The exchange of rapid antennal strikes between individuals is a behavior exhibited by many social hymenopterans, largely in dominance contexts within the nest and in aggressive contexts towards non-nestmates. Despite being widely reported, the behavior itself has not been well described or compared between species for the majority of social insect groups. We first document how often rapid antennation is used as an aggressive response to non-nestmates for four species of Odontomachus ants. We then use high-speed videography to measure the rate of rapid antennation behavior for these species. We find that rates are neither conserved nor species-specific and average between 19.5 and 41.5 strikes/s. Next, with O. brunneus, we compare this behavior as it is performed between nestmates and non-nestmates. We find no context-specific differences in rate, bout length, or number of strikes. We conclude by discussing the evolution of this behavior and its potential utility as a model for understanding aggressive behaviors both inside and outside of the nest.

Intraspecific worker parasitism in the common wasp, Vespula vulgaris

Insect societies display a remarkable level of cooperation, but their colonies also represent a valuable resource that can be taken advantage of by genetically unrelated individuals. Indeed, several recent studies have documented cases of intraspecific reproductive parasitism, whereby workers penetrate and lay eggs in unrelated colonies in order to have their brood raised by the host workers. Previously, it has been predicted that queenless colonies should be a prime target of such intraspecific worker parasitism, as in such colonies the parasite workers would be able to reproduce without interference from either the queen or other workers. So far, this prediction has been supported with data from the honeybee, but evidence from other social insect groups is currently lacking. Here we present the first such test in the common wasp, Vespula vulgaris. In particular, workers from queenright colonies left the natal nest at a higher rate than those from queenless colonies. However, contrary to our predictions, drifter workers targeted queenless and queenright colonies equally. Chemical data suggest that this lack of discrimination may be linked to recognition constraints and the lack of volatile signals that reliably indicate the presence or absence of the queen. In addition, in queenright colonies, drifters activated their ovaries at a rate that was ca. five times higher than the natal workers. Overall, our results suggest that also in wasps, workers can gain inclusive fitness by drifting to unrelated nests, even if the chances of successfully reproducing there may be very slim.

Uncovering head gland diversity in neotropical Polistinae wasps (Hymenoptera, Vespidae): Comparative analysis and description of new glands

Exocrine glands are involved in several wasp colony activities; however, the number of known glands in the Vespidae is rather low when compared to other social insect groups. The aim of this study is to survey the head of Neotropical social wasps and to provide a detailed comparative study of the glands found in the Polistinae. A total of 33 species distributed over 13 genera were studied with serial histological sections of the head, excluding the labiomaxillary complex. Additionally, the exoskeleton was explored using scanning electron microscopy looking for associated modifications. A total of eleven exocrine glands were observed, five are structures recorded for the first time for the Hymenoptera, three are new records for the Polistinae and three are previously known organs. The glands studied are: ocellar gland I, ocellar gland II, periocular gland, subantennal gland, hypopharyngeal gland, clypeal gland, posterobasal genal gland, ectal mandibular gland, mesal mandibular gland, intramandibular gland I, and intramandibular gland II. The widespread distribution of most of these glands suggests an origin prior to the evolution of the Polistinae. Our results highlight the importance of detailed morphological studies to unveil the significance of chemical communication in one of the most characteristic groups of social animals.

Dual Effect of Wasp Queen Pheromone in Regulating Insect Sociality

Eusocial insects exhibit a remarkable reproductive division of labor between queens and largely sterile workers [1, 2]. Recently, it was shown that queens of diverse groups of social insects employ specific, evolutionarily conserved cuticular hydrocarbons to signal their presence and inhibit worker reproduction [3]. Workers also recognize and discriminate between eggs laid by the queen and those laid by workers, with the latter being destroyed by workers in a process known as "policing" [4, 5]. Worker policing represents a classic example of a conflict-reducing mechanism, in which the reproductive monopoly of the queen is maintained through the selective destruction of worker-laid eggs [5, 6]. However, the exact signals used in worker policing have thus far remained elusive [5, 7]. Here, we show that in the common wasp, Vespula vulgaris, the pheromone that signals egg maternity and enables the workers to selectively destroy worker-laid eggs is in fact the same as one of the sterility-inducing queen signals that we identified earlier [3]. These results imply that queen pheromones regulate insect sociality in two distinct and complementary ways, i.e., by signaling the queen's presence and inhibiting worker reproduction, and by facilitating the recognition and policing of worker-laid eggs.