Queen and king recognition in the subterranean termite, Reticulitermes flavipes: Evidence for royal recognition pheromones

Royal recognition is a central feature of insect societies, allowing them to maintain the reproductive division of labor and regulate colony demography. Queen recognition has been broadly demonstrated and queen recognition pheromones have been identified in social hymenopterans, but not in termites. Here we describe behaviors that are elicited in workers and soldiers by neotenic queens and kings of the subterranean termite, Reticulitermes flavipes, and demonstrate the chemical basis for the behavior. Workers and soldiers readily perform a lateral or longitudinal shaking behavior upon antennal contact with queens and kings. When royal cuticular chemicals are transferred to live workers or inert glass dummies, they elicit antennation and shaking in a dose-dependent manner. The striking response to reproductives and their cuticular extracts suggests that royal-specific cuticular compounds act as recognition pheromones and that shaking behavior is a clear and measurable queen and king recognition response in this termite species.

Social enforcement depending on the stage of colony growth in an ant

Altruism is a paradox in Darwinian evolution. Policing is an important mechanism of the evolution and maintenance of altruism. A recently developed dynamic game model incorporating colony demography and inclusive fitness predicts that, in hymenopteran social insects, policing behaviour enforcing reproductive altruism in group members depends strongly on the colony growth stage, with strong policing as the colony develops and a relaxation of policing during the reproductive phase. Here, we report clear evidence supporting this prediction. In the ant Diacamma sp., reproduction by workers was suppressed by worker policing when the colony was small, whereas in large, mature colonies worker policing was relaxed and worker-produced males emerged. Conditional expression of traits can provide strong empirical evidence for natural selection theory if the expression pattern is precisely predicted by the theory, and our results illustrate the importance of intracolony population dynamics in the evolution of social systems.

Pharaoh ant colonies dynamically regulate colony demography by culling young queen and male-destined larvae

The success of social insect colonies is dependent upon efficient and dynamic allocation of resources to alternate queen and worker castes. The developmental and molecular mechanisms regulating the caste fate of individual larvae in response to environmental cues have been the focus of intense study. However, the mechanisms regulating colony-level resource allocation into alternate castes (i.e. caste allocation ratios) are less well studied. Here, we systematically manipulate colony demography to elucidate the social regulatory mechanisms of caste allocation in the antMonomorium pharaonis. We find that differences in caste allocation result from differences in timing and efficiency of culling of very young reproductive-destined larvae, which are always present in colonies. Based on our results, we develop a conceptual model depicting how colonies integrate numerous individual-level caste determination decisions to regulate colony-level caste allocation. We propose that adult workers make decisions about culling larvae based on the ratio of the number of workers to the number of eggs contained in colonies, likely signalled by pheromone present on eggs. This strategy is a bet-hedging strategy which enables the dynamic alteration of colony demography in response to internal and external conditions. The strategy is likely key to the ability ofM. pharaonisand similar ants to thrive in disturbed habitats and to become widespread invasive species.Significance StatementThe defining feature of social insect societies is the presence of alternate queen (reproductive) and worker (non-reproductive) castes of individuals. The fitness of social insect colonies is dependent upon efficient allocation of resources to alternate castes, particularly in the case of highly polygynous (multi-queen) societies. However, the mechanisms by which such societies regulate caste allocation are largely unknown. In this study, we show that colonies manipulate their production of queens (and also males) versus workers according to the present density of eggs in the colony, which serves as a reliable indicator of queens’ fertility. Provided egg density is high, colonies kill queen-and male-destined larvae; when egg density falls, colonies begin to rear queens and males. This flexible resource allocation strategy is key to the ability of highly polygynous species to thrive in marginal (often human-associated) habitats.

A taxonomic revision of the Cardiocondyla nuda group (Hymenoptera: Formicidae)

A taxonomic revision of the Cardiocondyla nuda species group is presented based on methods of Numeric Morphology-Based Alpha-Taxonomy (NUMOBAT) and supplemented by analysis of mtDNA. A total of 258 samples with 571 worker individuals were investigated by the hierarchical and non-hierarchical exploratory data analyses NC-Ward and NC-K-Means clustering considering 16 NUMOBAT characters. Two species are described as new, increasing the number of species in the group to eight. We separate the group into two main clades: the C. mauritanica species complex, which is of Oriental and Indo-Australian origin and contains the cryptic species C. mauritanica Forel 1890, C. strigifrons Viehmeyer 1922, C. kagutsuchi Terayama 1999, and C. itsukii sp. nov. and the Australasian and Polynesian C. nuda species complex with the cryptic species C. nuda (Mayr 1866), C. atalanta Forel 1915, C. paranuda Seifert 2003, and C. compressa sp. nov. The mean error of the two NC-clustering methods relative to the controlling linear discriminant analysis was 0.4% in C. mauritanica, 2.2% in C. itsukii, 0% in C. strigifrons, 0% in C. kagutsuchi, 1.5% in C. nuda, 3.2% in C. atalanta and 3.2% in C. paranuda—all these data are below the 4% threshold recommended by the Pragmatic Species Concept. The morphologically determined species clusters were confirmed by mtDNA data with a rather strong sequence divergence among the cryptic species of the C. nuda complex of 5.6–7.9%. The mean mismatch of two different mtDNA analyses with NUMOBAT clustering was 5.4% in 54 samples of seven species of the C. nuda group for which mtDNA data were available. The mismatch thus is smaller than in many other studies of Eumetazoa in general or ants in particular and is probably explained by low frequencies of ancient hybridization and/or incomplete lineage sorting. Comments on zoogeography, colony demography and behavior are given in the species sections and determination keys are provided. Cardiocondyla ectopia Snelling 1974 and Leptothorax caparica Henin, Paiva & Collingwood 2002 (syn nov.) are synonymized under Cardiocondyla mauritanica. Cardiocondyla nuda sculptinodis is not a member of the C. nuda group and is moved to C. shuckardi sculptinodis, a revived combination.

Pteridine levels and head weights are correlated with age and colony task in the honey bee, Apis mellifera

Background. The age of an insect strongly influences many aspects of behavior and reproduction. This interaction is epitomized in the temporal polyethism of honey bees in which young adult bees perform nurse and maintenance duties within the colony, while older bees forage for nectar and pollen. Task transition is dynamic and is driven by colony needs. However, an abundance of precocious foragers or overage nurses may have detrimental effects on the colony. Additionally, honey bee age affects insecticide sensitivity. Therefore, determining the age of an individual honey bee would be important to provide a measurement of colony health. Pteridines are purine-based pigment molecules found in many insect body parts. Pteridine levels correlate well with age, and wild caught insects may be accurately aged by measuring pteridine levels. The relationship between pteridines and age varies with a number of internal and external factors among many species. Thus far, no studies have investigated the relationship of pteridines with age in honey bees. Methods. We established single-cohort colonies to obtain age-matched nurse and forager bees. Nurses and foragers were collected every 3-5 days for up to 42 days. Heads were removed and weighed before pteridines were purified and analyzed using previously established fluorometric methods. Results. Our analysis showed that pteridine levels were higher in foragers than nurses of the same age, and pteridine levels significantly increased with age in a linear manner. Head weight significantly varied with age increasing until approximately 28 days of age, then declining thereafter for both nurse and forager bees. Discussion. Although the relationship between pteridine levels and age was significant, a large amount of variation in the data yielded an 8-day window in age estimation. This allows an unambiguous method to determine whether a bee may be a young nurse or old forager. Pteridine levels in bees do not correlate with age as well as in other insects. However, most studies used insects reared under tightly controlled laboratory conditions, while we used free-living bees. The dynamics of head weight change with age is likely to be due to growth and atrophy of the hypopharyngeal glands. Taken together, these methods represent a useful tool for assessing colony demography after a colony experiences a stress event. Future studies utilizing these methods will provide a more holistic view of colony health.

Pteridine levels and head weights are correlated with age and colony task in the honey bee, Apis mellifera

Background. The age of an insect strongly influences many aspects of behavior and reproduction. This interaction is epitomized in the temporal polyethism of honey bees in which young adult bees perform nurse and maintenance duties within the colony, while older bees forage for nectar and pollen. Task transition is dynamic and is driven by colony needs. However, an abundance of precocious foragers or overage nurses may have detrimental effects on the colony. Additionally, honey bee age affects insecticide sensitivity. Therefore, determining the age of an individual honey bee would be important to provide a measurement of colony health. Pteridines are purine-based pigment molecules found in many insect body parts. Pteridine levels correlate well with age, and wild caught insects may be accurately aged by measuring pteridine levels. The relationship between pteridines and age varies with a number of internal and external factors among many species. Thus far, no studies have investigated the relationship of pteridines with age in honey bees. Methods. We established single-cohort colonies to obtain age-matched nurse and forager bees. Nurses and foragers were collected every 3-5 days for up to 42 days. Heads were removed and weighed before pteridines were purified and analyzed using previously established fluorometric methods. Results. Our analysis showed that pteridine levels were higher in foragers than nurses of the same age, and pteridine levels significantly increased with age in a linear manner. Head weight significantly varied with age increasing until approximately 28 days of age, then declining thereafter for both nurse and forager bees. Discussion. Although the relationship between pteridine levels and age was significant, a large amount of variation in the data yielded an 8-day window in age estimation. This allows an unambiguous method to determine whether a bee may be a young nurse or old forager. Pteridine levels in bees do not correlate with age as well as in other insects. However, most studies used insects reared under tightly controlled laboratory conditions, while we used free-living bees. The dynamics of head weight change with age is likely to be due to growth and atrophy of the hypopharyngeal glands. Taken together, these methods represent a useful tool for assessing colony demography after a colony experiences a stress event. Future studies utilizing these methods will provide a more holistic view of colony health.

Diversity of Species and Behavior of Hymenopteran Parasitoids of Ants: A Review

Reports of hymenopterans associated with ants involve more than 500 species, but only a fraction unambiguously pertain to actual parasitoids. In this paper, we attempt to provide an overview of both the diversity of these parasitoid wasps and the diversity of the types of interactions they have formed with their ant hosts. The reliable list of parasitoid wasps using ants as primary hosts includes at least 138 species, reported between 1852 and 2011, distributed among 9 families from 3 superfamilies. These parasitoids exhibit a wide array of biologies and developmental strategies: ecto- or endoparasitism, solitary or gregarious, and idio- or koinobiosis. All castes of ants and all developmental stages, excepting eggs, are possible targets. Some species parasitize adult worker ants while foraging or performing other activities outside the nest; however, in most cases, parasitoids attack ant larvae either inside or outside their nests. Based on their abundance and success in attacking ants, some parasitoid wasps like diapriids and eucharitids seem excellent potential models to explore how parasitoids impact ant colony demography, population biology, and ant community structure. Despite a significant increase in our knowledge of hymenopteran parasitoids of ants, most of them remain to be discovered.

Edge Effects on Community and Social Structure of Northern Temperate Deciduous Forest Ants

Determining how ant communities are impacted by challenges from habitat fragmentation, such as edge effects, will help us understand how ants may be used as a bioindicator taxon. To assess the impacts of edge effects upon the ant community in a northern temperate deciduous forest, we studied edge and interior sites in Jericho, VT, USA. The edges we focused upon were created by recreational trails. We censused the ants at these sites for two consecutive growing seasons using pitfall traps and litter plot excavations. We also collected nests of the most common ant species at our study sites,Aphaenogaster rudis, for study of colony demography. Significantly greater total numbers of ants and ant nests were found in the edge sites compared to the interior sites but rarefaction analysis showed no significant difference in species richness.Aphaenogaster rudiswas the numerically dominant ant in the habitats sampled but had a greater relative abundance in the interior sites than in the edge sites both in pitfall and litter plot data. Queen number ofA. rudissignificantly differed between the nests collected in the edge versus the interior sites. Habitat-dependent changes in social structure of ants represent another possible indicator of ecosystem health.

Group dynamics and record signals in the ant Temnothorax albipennis

Many purely physical complex systems, in which there are both stochasticity and local interactions between the components, exhibit record dynamics. The temporal statistics of record dynamics is a Poisson process operating on a logarithmic rather than a linear time scale (i.e. a log-Poisson process). Record dynamics often drive substantial changes in complex systems when new high water marks in partially stochastic processes trigger new events. Social insect colonies are exemplary complex biological systems in which many of the local interactions of the components have been moulded by natural selection for the common good. Here, we combine experimental manipulation of ant colony demography with modelling to test the hypothesis that social interactions are the mechanism underlying the record dynamics. We found that compared with the control, log-Poisson statistics were disrupted in colonies in which the pattern of interactions was modified by the removal of the brood, and disappeared completely in ‘callow’ colonies composed entirely of very young workers from the same age cohort. We conclude that a subtle interplay between the demography of the society and the pattern of the interactions between the ants is crucial for the emergence of record dynamics. This could help identify what makes an ant colony a cohesive society.