Search

The sequencing of the honeybee genome in 2006 was an important technological and logistic achievement experience. But what benefits have flown from the honeybee genome project? What does the annotated genomic assembly mean for the study of behavioural complexity and organismal function in honeybees? Here, I discuss several lines of research that have arisen from this project and highlight the rapidly expanding studies on insect epigenomics, emergent properties of royal jelly, the mechanism of nutritional control of development and the contribution of epigenomic regulation to the evolution of sociality. I also argue that the term 'insect epigenetics' needs to be carefully redefined to reflect the diversity of epigenomic toolkits in insects and the impact of lineage‐specific innovations on organismal outcomes. The honeybee genome project helped pioneer advances in social insect molecular biology, and fuelled breakthrough research into the role of flexible epigenomic control systems in linking genotype to phenotype. [ABSTRACT FROM AUTHOR]

In Indonesia, the control of Coptotermes curvignathus populations as living tree termite pests has been carried out since the early 20th century. Recently, C. curvignathus has been considered the main termite pest and designated as the only species model for wood and wood products resistance tests against subterranean termite attack testing protocol in the Indonesian National Standard (SNI). However, the species distribution range of C. curvignathus has been long questioned as Coptotermes gestroi is commonly reported as a species found in urban areas of Southeast Asian region, particularly in Indonesia. One of the reasons for the species distribution discrepancies is the lack of morphological markers to distinguish both species in the field. Thus, limiting the field inspection effectiveness in termite pest management in Indonesia. This study reexamined and clarified the morphological differences between C. curvignathus and C. gestroi , based on soldier caste. The head shape, mandible shape, and distribution of genal setae on the ventro-anterior head part and pronotum marked the difference between the 2 species. These current results support previous findings of C. curvignathus as the forest dweller while clarifying C. gestroi as the common urban dweller in Indonesia. The putative benefit of morphological features related to the head, mandible, and setae distribution to the defensive adaptation in their common habitat was discussed. Ultimately, the inclusion of C. gestroi into the Indonesian National Standard (SNI) as an alternative species for efficacy tests against subterranean termites is highly recommended. [ABSTRACT FROM AUTHOR]

This article discusses a new defensive behavior called "wing-slapping" exhibited by Japanese honey bees against invading ants. The study observed Japanese honey bee colonies being invaded by Japanese pavement ants and recorded the bees' defensive behaviors using a high-speed camera. The results showed that the bees slap the ants with their wings through direct contact. The study also found that the effectiveness of wing-slapping varied among different ant species. The article suggests that wing-slapping may have evolved as a low-energy defense against ant incursion, but further research is needed to understand the evolution of defensive behaviors in honey bees. The study highlights the potential risks posed by invasive ants to honey bee populations and calls for more attention to the defensive behaviors of bees against ants. [Extracted from the article]

The fitness effects of overt parasites, and host resistance to them, are well documented. Most symbionts, however, are more covert and their interactions with their hosts are less well understood. Wolbachia, an intracellular symbiont of insects, is particularly interesting because it is thought to be unaffected by the host immune response and to have fitness effects mostly focussed on sex ratio manipulation. Here, we use quantitative PCR to investigate whether host genotype affects Wolbachia infection density in the leaf-cutting ant Acromyrmex echinatior, and whether Wolbachia infection density may affect host morphology or caste determination. We found significant differences between host colonies in the density of Wolbachia infections, and also smaller intracolonial differences in infection density between host patrilines. However, the density of Wolbachia infections did not appear to affect the morphology of adult queens or likelihood of ants developing as queens. The results suggest that both host genotype and environment influence the host-Wolbachia relationship, but that Wolbachia infections carry little or no physiological effect on the development of larvae in this system. [ABSTRACT FROM AUTHOR]

In social insect colonies, selfish behaviour due to intracolonial conflict among members can result in colony-level costs despite close relatedness. In certain termite species, queens use asexual reproduction for within-colony queen succession but rely on sexual reproduction for worker and alate production, resulting in multiple half-clones of a single primary queen competing for personal reproduction. Our study demonstrates that competition over asexual queen succession among different clone types leads to the overproduction of parthenogenetic offspring, resulting in the production of dysfunctional parthenogenetic alates. By genotyping the queens of 23 field colonies of Reticulitermes speratus, we found that clone variation in the queen population reduces as colonies develop. Field sampling of alates and primary reproductives of incipient colonies showed that overproduced parthenogenetic offspring develop into alates that have significantly smaller body sizes and much lower survivorship than sexually produced alates. Our results indicate that while the production of earlier and more parthenogenetic eggs is advantageous for winning the competition for personal reproduction, it comes at a great cost to the colony. Thus, this study highlights the evolutionary interplay between individual-level and colony-level selection on parthenogenesis by queens. [ABSTRACT FROM AUTHOR]

In insects and other animals, nutrition-mediated behaviors are modulated by communication between the brain and peripheral systems, a process that relies heavily on the insulin/insulin-like growth factor signaling pathway (IIS). Previous studies have focused on the mechanistic and physiological functions of insulinlike peptides (ILPs) in critical developmental and adult milestones like pupation or vitellogenesis. Less work has detailed the mechanisms connecting ILPs to adult nutrient-mediated behaviors related to survival and reproductive success. Here we briefly review the range of behaviors linked to IIS in insects, from conserved regulation of feeding behavior to evolutionarily derived polyphenisms. Where possible, we incorporate information from Drosophila melanogaster and other model species to describe molecular and neural mechanisms that connect nutritional status to behavioral expression via IIS. We identify knowledge gaps which include the diverse functional roles of peripheral ILPs, how ILPs modulate neural function and behavior across the lifespan, and the lack of detailed mechanistic research in a broad range of taxa. Addressing these gaps would enable a better understanding of the evolution of this conserved and widely deployed tool kit pathway. [ABSTRACT FROM AUTHOR]

Workers' task specialization and division of labor are critical features of social insects' ecological success. It has been proposed that the division of labor relies on response threshold models: individuals varying their sensitivity (and responsiveness) to biologically relevant stimuli and performing a specific task when a stimulus exceeds an internal threshold. In this work, we study carbohydrate and protein responsiveness and their relation to worker task specialization in Vespula germanica, an invasive social wasp. The sucrose and peptone responsiveness of two different subcastes, preforagers and foragers, was determined by stimulating the antenna of the wasps with increasing concentrations of the solution and quantifying whether each concentration elicited a licking response. We studied responsiveness in five different ways: (1) response threshold, (2) concentration 50 (concentration to which at least 50% of wasps responded), (3) maximum response, (4) mean scores and (5) median scores. Our results suggest that V. germanica foragers are more sensitive to sucrose (lower thresholds) than preforager workers. However, we found no differences for peptone thresholds (i.e., a protein resource). Nonetheless, this is the first study to investigate response thresholds for protein resources. The intercaste variation in sucrose responsiveness shown in our work contributes to the existing knowledge about response threshold theory as a mechanism for task specialization observed in V. germanica. [ABSTRACT FROM AUTHOR]

The fitness effects of overt parasites, and host resistance to them, are well documented. Most symbionts, however, are more covert and their interactions with their hosts are less well understood. Wolbachia, an intracellular symbiont of insects, is particularly interesting because it is thought to be unaffected by the host immune response and to have fitness effects mostly focussed on sex ratio manipulation. Here, we use quantitative PCR to investigate whether host genotype affects Wolbachia infection density in the leaf-cutting ant Acromyrmex echinatior, and whether Wolbachia infection density may affect host morphology or caste determination. We found significant differences between host colonies in the density of Wolbachia infections, and also smaller intracolonial differences in infection density between host patrilines. However, the density of Wolbachia infections did not appear to affect the morphology of adult queens or likelihood of ants developing as queens. The results suggest that both host genotype and environment influence the host-Wolbachia relationship, but that Wolbachia infections carry little or no physiological effect on the development of larvae in this system.

Antibiotic resistance is one of the most important global healthcare challenges and is responsible for the mortality of millions of people worldwide every year. It is a crisis attributed to misuse of antibiotics and a lack of new drug development. Actinomycetes constitute a group of Gram-positive bacteria known for their distinctive high guanine-cytosine (G+C) content in their genomic DNA. These microorganisms are widely recognized for their capability to generate a wide range of secondary metabolites with diverse biological activities. These versatile microorganisms are ubiquitous in diverse ecosystems, including soil, freshwater, marine sediments, and within the bodies of insects. A recent study has demonstrated that social insects, such as ants, host a diverse array of these bacteria. In this study, we involved the isolation and characterization of a total of 72 actinomycete strains obtained from 18 distinct ant species collected from various regions across Thailand. Utilizing 16S rRNA gene analysis, these isolated actinomycetes were classified into four distinct genera: Amycolatopsis (2 isolates), Micromonospora (1 isolate), Nocardia (8 isolates), and Streptomyces (61 isolates). Among the Streptomyces strains, 23 isolates exhibited antimicrobial activity against a panel of Gram-positive bacteria, including Bacillus subtilis ATCC 6633, Staphylococcus epidermidis ATCC 12228, Staphylococcus aureus ATCC 25923, Kocuria rhizophila ATCC 9341, and Methicillin-resistant Staphylococcus aureus (MRSA) DMST 20646. Additionally, two isolates displayed antifungal activity against Candida albicans TISTR 5554. Based on 16S rRNA gene sequence similarity studies, these two isolates, ODS25 and ODS28, were demonstrated to be closely related to Streptomyces lusitanus NBRC 13464T (98.07%) and Streptomyces haliclonae DSM 41970T (97.28%), respectively. The level of 16S rRNA gene sequence similarity below 98.65% cutoff indicates its potential as a novel actinomycete species. These findings underscore the potential of actinomycetes sourced from ants as a valuable reservoir of novel antimicrobials.

Camponotus japonicus (Hymenoptera: Formicidae) is an omnivorous social insect which builds sizable colonies in sparse woodlands or cropland and spreads across multiple climatic zones in the Chinese mainland. This study aims to reveal the role of climate changes and geological events in driving the genetic structure of social insect populations by investigating the phylogenetics and historical demography of C. japonicus in the Chinese mainland. Phylogenetic analyses were conducted based on the mitochondria DNA dataset using MrBayes and IQ‐TREE. We constructed a haplotype network, calculated analyses of molecular variance, estimated the divergence time, and reconstructed the maximum clade credibility tree. Mismatch distribution and Bayesian skyline plots were used to infer historical population fluctuations. Additionally, ecological niche modeling was employed to predict the potential distribution of the species during the present, mid‐holocene, and last glacial maximum periods in the Chinese mainland. The phylogenetic tree and median‐joining network analyses support the presence of four distinct lineages in C. japonicus. These lineages exhibit significant genetic differentiation and limited gene flow. The divergence among the four lineages began in the early Pleistocene, approximately 1.41 million years ago (Ma). Subsequently, the central lineage diverged from both the northern and southern lineages around 1.16 Ma, while the northern and southern lineages diverged from each other at approximately 1.07 Ma. Population expansion was observed in the southern, central, and northern lineages prior to the last glacial maximum, while the Yunnan‐Sichuan lineage experienced a slight increase in population size in more recent times. The predicted distribution of the species corresponds well with the actual distribution. Furthermore, the current suitable habitat areas in northern Xinjiang, southern Tibet, and the southeast coastal regions have significantly decreased compared to the last glacial maximum and the mid‐holocene periods. Our results suggest that climate oscillations and geological events play an important role in driving genetic patterns and differentiation of C. japonicus. Mountain barriers isolate populations from each other, hinder the flow of genes, and effectively prevent the spread of this species. But at the same time, it also formed refugia at low altitudes areas such as Qinling‐Bashan Mountains and Yanshan‐Taihang Mountains and provide suitable habitats during glaciation. This study provides a good model for understanding how complex climate changes and geological events affect population genetic differentiation of social insects in the Chinese mainland. [ABSTRACT FROM AUTHOR]

Honey bees (Apis spp.) are important pollinators in many natural and agro-ecosystems across the world. Effective means of surveying wild populations are therefore key to their conservation and management. One available survey method infers honey bee colony density from the genotype of drones (males) sampled from sites known as Drone Congregation Areas (DCAs). While this approach has been commonly used for the Western honey bee (A. mellifera), its feasibility for other Apis species is unknown. Here, we investigate drone congregation behaviour in the Asian honey bee Apis cerana in north-east Australia and its suitability for inferring colony density. As this A. cerana population is invasive, surveys in this case can aid in monitoring the population’s growth and spread. Over 5 years, we identified 30 DCAs, many of which were stable across time. DCAs were sheltered areas beside tree-lines or openings in the forest canopy. A. cerana drones joined DCAs during 1–2-h afternoon intervals and could be sampled at heights of 2–24 m via adhesive lines attached to helium balloons carrying lures coated in queen pheromone. Drones were more likely to be present at a DCA as temperature increased, though abiotic factors did not predict overall drone abundance. Drones could be sampled in low numbers even where colony density was extremely low. Based on the genotyping and inferred sibship of drones sampled at DCAs between 2016 and 2021, we estimate population density in Australia’s A. cerana to be in the range 1.1–8.1 colonies/km2. This extrapolates to a total population size in the range 11,000–83,000 colonies, with more refined estimates requiring better knowledge of drone flight distance and the effect of habitat on colony density. We conclude that population surveys based on drones from DCAs are possible for A. cerana and propose that this approach be part of a toolkit of methods used to monitor Asian honey bee populations in both their native and invasive ranges. [ABSTRACT FROM AUTHOR]

Abstract Camponotus japonicus (Hymenoptera: Formicidae) is an omnivorous social insect which builds sizable colonies in sparse woodlands or cropland and spreads across multiple climatic zones in the Chinese mainland. This study aims to reveal the role of climate changes and geological events in driving the genetic structure of social insect populations by investigating the phylogenetics and historical demography of C. japonicus in the Chinese mainland. Phylogenetic analyses were conducted based on the mitochondria DNA dataset using MrBayes and IQ‐TREE. We constructed a haplotype network, calculated analyses of molecular variance, estimated the divergence time, and reconstructed the maximum clade credibility tree. Mismatch distribution and Bayesian skyline plots were used to infer historical population fluctuations. Additionally, ecological niche modeling was employed to predict the potential distribution of the species during the present, mid‐holocene, and last glacial maximum periods in the Chinese mainland. The phylogenetic tree and median‐joining network analyses support the presence of four distinct lineages in C. japonicus. These lineages exhibit significant genetic differentiation and limited gene flow. The divergence among the four lineages began in the early Pleistocene, approximately 1.41 million years ago (Ma). Subsequently, the central lineage diverged from both the northern and southern lineages around 1.16 Ma, while the northern and southern lineages diverged from each other at approximately 1.07 Ma. Population expansion was observed in the southern, central, and northern lineages prior to the last glacial maximum, while the Yunnan‐Sichuan lineage experienced a slight increase in population size in more recent times. The predicted distribution of the species corresponds well with the actual distribution. Furthermore, the current suitable habitat areas in northern Xinjiang, southern Tibet, and the southeast coastal regions have significantly decreased compared to the last glacial maximum and the mid‐holocene periods. Our results suggest that climate oscillations and geological events play an important role in driving genetic patterns and differentiation of C. japonicus. Mountain barriers isolate populations from each other, hinder the flow of genes, and effectively prevent the spread of this species. But at the same time, it also formed refugia at low altitudes areas such as Qinling‐Bashan Mountains and Yanshan‐Taihang Mountains and provide suitable habitats during glaciation. This study provides a good model for understanding how complex climate changes and geological events affect population genetic differentiation of social insects in the Chinese mainland.

Ergatandromorphs are examples of genetic chimeras found in ants, in which they exhibit features of both minor workers and males. In this study, we report a lateral ergatandromorph of Camponotus yamaokai Terayama & Satoh, 1990. The right side of this specimen was characterized as a male and the left side as a minor worker, although some body parts did not show a clear division. The specimen had partially atrophied genitalia on the right side of the metasoma while the genital structures on the left side were absent. The individual engaged in frequent self‐grooming and received trophallaxis and allogrooming from the nestmates. This is the first report of the lateral ergatandromorph in the genus Camponotus, which has few documented cases of gynandromorphism. [ABSTRACT FROM AUTHOR]

The spatial distribution of flowers has important impacts on pollinator movement and foraging decisions. For example, it is well established that bumble bees typically visit larger plants at a higher rate per plant, but the visit rate per flower typically declines as the number of flowers increases. However, much less is known about how honey bee foraging patterns are influenced by plant size and flower number, despite honey bees' importance as agricultural pollinators and their strong competitive impact on other bees. Using a combination of field observations and manipulative experiments with two different wild plant species, we confirmed that honey bees visit larger plants at a higher rate, not only per plant but also per inflorescence. This foraging pattern seems surprising, because it means that there is greater forager density and thus competition for resources on larger plants. We examine three hypotheses to explain why honey bees might nevertheless preferentially visit floral resources on larger plants: (1) larger plants are more salient, making them easier to find and advertise; (2) larger plants offer greater nectar rewards, making visits to them more worthwhile; (3) larger plants have more densely packed flowers, so they are less costly to navigate. We found that honey bee visit rates were indeed influenced by the costs and rewards of their local foraging experience, but the total number of flowers on the plant still positively affected visit rate even when controlling for those local factors. We suggest several ways that the collective foraging strategy of honey bees could lead to an aggregation of foragers on plants with more flowers and discuss the potential implications for agricultural pollination and wild bee conservation as well as foraging theory. • Honey bee visits/inflorescence were higher for large plants than for small plants. • Honey bees' focus on larger plants may stem from their collective foraging strategy. • Prior work has shown that bumble bee visits/flower typically decrease with plant size. • Variation in plant size may reduce competition between honey bees and native bees. [ABSTRACT FROM AUTHOR]

British Columbia beekeepers, like many beekeepers around the world, are currently facing declines in honey bee health and high overwinter colony losses. To better understand the economics and the cycle of yearly colony loss and replacement of this critical agricultural industry, we collected and analyzed survey data on beekeeping costs and returns. Forty British Columbia beekeepers provided details about revenue sources, variable costs, capital costs, and investments. Ten surveyed beekeepers managed between 1 and 9 colonies, 10 managed between 10 and 39 colonies, 9 managed between 40 and 100 colonies, 5 managed between 101 and 299 colonies, 3 managed between 300 and 699 colonies, and 3 managed 700 colonies or more. The data was used to calculate beekeeping profit and to parameterize a model that explores the economic impact of colony loss rates and replacement strategies. Survey results show that when the data is aggregated, revenues exceed costs for beekeeping operations in British Columbia with a per colony profit of $56.92 or $0.87 per pound of honey produced. Surveyed operations with fewer than 100 colonies have negative profits, while operations with 100–299 colonies have positive profits. Surveyed operations in the Cariboo, North Coast, and Okanagan regions have the highest profits while surveyed operations in the Peace region have the lowest profits. Profit modeling shows that replacing losses with packages generates lower profit than replacing losses with split colonies. Our modeling shows that operations that diversify their revenue to include bee sales and commercial pollination accrue higher profits and can withstand higher winter loss rates. [ABSTRACT FROM AUTHOR]

Native bees play a vital role in the pollination of different flora in an ecosystem. But the natural history of most native bee species is unknown, and knowledge about natural history helps in understanding their social evolution, and further protecting and conserving the bee species. Braunsapis mixta (Smith) is a common stem-nesting bee and a widespread endemic species of Southern Asia. This study aimed to record the nesting biology, development and natural enemies of B. mixta, which is an important pollinator of cashew. Nests of B. mixta were found in the dried sticks and pruned cut ends of cashew stems. A total of 442 nests were collected, of which 64% of the active nests were single-adult nests and 20% were of two adults. Eggs were found at the interior end, followed by larvae at varied developmental stages and pupae. The maximum number of nest occupants in a nest was 41, in which four were adults and a maximum of 11 adults were recorded in a single nest. The maximum number of females found in a nest was nine. A significant positive correlation was obtained between the number of adults and their immature stages. Egg production and brood maturation occurred throughout the year. The mean incubation period of eggs was 5.32 days. Rearing of larvae could not be achieved in the laboratory. The pupal period lasted for 11–14 days. The parasitoids recorded on B. mixta include Neochalcis breviceps and Diomorus nr. indicus. [ABSTRACT FROM AUTHOR]

Abstract Background Theory predicts that the level of escalation in animal contests is associated with the value of the contested resource. This fundamental prediction has been empirically confirmed by studies of dyadic contests but has not been tested experimentally in the collective context of group-living animals. Here, we used the Australian meat ant Iridomyrmex purpureus as a model and employed a novel field experimental manipulation of the value of food that removes the potentially confounding effects of nutritional status of the competing individual workers. We draw on insights from the Geometric Framework for nutrition to investigate whether group contests between neighbouring colonies escalate according to the value to the colony of a contested food resource. Results First, we show that colonies of I. purpureus value protein according to their past nutritional intake, deploying more foragers to collect protein if their previous diet had been supplemented with carbohydrate rather than with protein. Using this insight, we show that colonies contesting more highly valued food escalated the contest, by deploying more workers and engaging in lethal ‘grappling’ behaviour. Conclusion Our data confirm that a key prediction of contest theory, initially intended for dyadic contests, is similarly applicable to group contests. Specifically, we demonstrate, through a novel experimental procedure, that the contest behaviour of individual workers reflects the nutritional requirements of the colony, rather than that of individual workers.

Bumble bee queens initiate nests solitarily and transition to living socially once they successfully rear their first cohort of offspring. Bumble bees are disproportionately important for early season pollination, and many populations are experiencing dramatic declines. In this system, the onset of the social stage is critical for nest survival, yet the mechanisms that facilitate this transition remain understudied. Further, the majority of conservation efforts target the social stage of the bumble bee life cycle and do not address the solitary founding stage. We experimentally manipulated the timing of worker emergence in young nests of bumble bee (Bombus impatiens) queens to determine whether and how queen fecundity and survival are impacted by the emergence of workers in the nest. We found that queens with workers added to the nest exhibit increased ovary activation, accelerated egg laying, elevated juvenile hormone (JH) titres and also lower mortality relative to solitary queens. We also show that JH is more strongly impacted by the social environment than associated with queen reproductive state, suggesting that this key regulator of insect reproduction has expanded its function in bumble bees to also influence social organization. We further demonstrate that these effects are independent of queen social history, suggesting that this underlying mechanism promoting queen fecundity is reversible and short lived. Synchronization between queen reproductive status and emergence of workers in the nest may ultimately increase the likelihood of early nesting success in social systems with solitary nest founding. Given that bumble bee workers regulate queen physiology as we have demonstrated, the timing of early worker emergence in the nest likely impacts queen fitness, colony developmental trajectories and ultimately nesting success. Collectively, our findings underline the importance of conservation interventions for bumble bees that support the early nesting period and facilitate the production and maintenance of workers in young nests.

Solenopsis invicta Buren (Hymenoptera: Formicidae), a red imported fire ant that originated from South America, is a worldwide invasive pest. This study investigated the efficacy of the newly designed baited trap to detect red imported fire ants, Solenopsis invicta Buren, under field conditions in China. Among the five food lures tested for red imported fire ants, the ants preferred ham sausage and fish powder, followed by mixed powder (50% fish powder + 50% black soldier fly powder) and black soldier fly powder. These lures were compared to sugar water (control) to determine their efficacy in trapping red imported fire ants. Field data revealed that the ham sausage powder trap was more efficient than the fish powder trap based on its ability to trap more red imported fire ants under field conditions and ease of use. Thus, it was concluded that the baited traps are efficient for longterm red imported fire ants monitoring.

Insects and fungi are abundant in many environments and often interact. However, little information exists on the fungal infestation of insect eggs. Here, we report an entomogenous fungus similar to Hormiscioideus filamentosus (Blackweel & Kimbrough, 1978) infesting eggs of the termite Nasutitermes corniger (Motschulsky, 1855). The fungus arises from egg chorion and has long and simple filaments. The small haustorial cells infiltrate the egg chorion and the fungal thalli number varies from two to ten. Future studies will elucidate the infestation levels of termite eggs by this entomogenous fungus in the Neotropical region and its effects on termite colonies.

Vigilant animals detect and respond to threats in the environment, often changing posture and movement patterns. Vigilance is modulated not only by predators but also by conspecific threats. In social animals, precisely how conspecific threats alter vigilance behavior over time is relevant to long‐standing hypotheses about social plasticity. We report persistent effects of a simulated conspecific challenge on behavior of wild northern paper wasp foundresses, Polistes fuscatus. During the founding phase of the colony cycle, conspecific wasps can usurp nests from the resident foundress, representing a severe threat. We used automated tracking to monitor the movement and posture of P. fuscatus foundresses in response to simulated intrusions. Wasps displayed increased movement, greater bilateral wing extension, and reduced antennal separation after the threat was removed. These changes were not observed after presentation with a wooden dowel. By rapidly adjusting individual behavior after fending off an intruder, paper wasp foundresses might invest in surveillance of potential threats, even when such threats are no longer immediately present. The prolonged vigilance‐like behavioral state observed here is relevant to plasticity of social recognition processes in paper wasps. [ABSTRACT FROM AUTHOR]

Copyright of Revista Chapingo Serie Ciencias Forestales is the property of Universidad Autonoma Chapingo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Honey bees (Apis mellifera) express remarkable social interactions and cognitive capabilities that have been studied extensively. In many cases, behavioral studies were accompanied by neurophysiological and neuroanatomical investigations. While most studies have focused on primary sensory neuropils, such as the optic lobes or antennal lobes, and major integration centers, such as the mushroom bodies or the central complex, many regions of the cerebrum (the central brain without the optic lobes) of the honey bee are only poorly explored so far, both anatomically and physiologically. To promote studies of these brain regions, we used anti‐synapsin immunolabeling and neuronal tract tracings followed by confocal imaging and 3D reconstructions to demarcate all neuropils in the honey bee cerebrum and close this gap at the anatomical level. We demarcated 35 neuropils and 25 fiber tracts in the honey bee cerebrum, most of which have counterparts in the fly (Drosophila melanogaster) and other insect species that have been investigated so far at this level of detail. We discuss the role of cerebral neuropils in multisensory integration in the insect brain, emphasize the importance of this brain atlas for comparative studies, and highlight specific architectural features of the honey bee cerebrum. [ABSTRACT FROM AUTHOR]

Diversification of sperm design is a common feature in animals. Considerable intra-individual variation has been detected even in species whose males produce a monomorphic sperm. The evolutionary forces that shape the variation in the gross morphology of these gametic cells are still not completely understood. Previous studies suggest that the intra-individual variation in sperm size reduces as a result of post-copulatory sexual selection. To our knowledge, for the first time, we provide evidence here that pre-copulatory sexual selection can also play a role. By studying the Neotropical paper wasp, Polistes simillimus, a monandrous species, we found reduced variation in sperm length in males bearing sexual ornamentation preferred by females. Besides, the female spermatheca contains a less variable sperm compared to that in the male seminal vesicles. Thus, the scope of selection, acting on this sperm trait, seems broader than previously acknowledged. [ABSTRACT FROM AUTHOR]

Juvenile hormone (JH) in insects plays a key role in regulating reproduction, but in some social insects it has also acquired secondary functions in regulating the age-related division of labour among the workers. Previous work has shown that JH regulates division of labour in honey bees, in several primitively eusocial paper wasps and in leafcutter ants, which comprise three independent origins of sociality. It remains unclear, however, to what degree JH could have a conserved role in regulating division of labour within these clades. To this end, we investigated whether JH also regulates division of labour in the highly eusocial Vespine wasp Vespula vulgaris , in which JH had previously been shown only to regulate reproduction and affect queen pheromone signalling. In line with JH having a conserved role in regulating division of labour in social wasps, we show that JH in this species indeed affected behavioural maturation and division of labour in the worker caste. In particular, topical application of the JH analogue methoprene onto workers accelerated behavioural maturation and hastened the onset of foraging, thereby significantly decreasing the time they spent conducting activities inside the nest. We discuss how this conserved role of JH in regulating division of labour could indicate the same conserved genetic toolkits being used to regulate division of labour across several independent origins of sociality. In addition, we examine the implications of JH having several pleiotropic effects in this species and discuss whether this could constrain the expression of reproductive conflicts in their societies. • JH regulates the temporal polyethism in the common wasp, V. vulgaris. • JH analogue methoprene sped up the transition from intranidal to foraging tasks. • JH has a conserved role in regulating polyethism in several social Hymenoptera. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Solenopsis invicta is an invasive ant introduced into the United States in the early 1900s. Control efforts and damage caused by this ant exceed $8 billion annually. Solenopsis invicta virus 3 (SINV-3) is a positive-sense, single-stranded RNA virus (Solinviviridae) that is being used as a classical natural control agent for S. invicta. S. invicta colonies were exposed to purified preparations of SINV-3 to investigate the impact of the virus on the ant. Food retrieval behavior (i.e., foraging) by worker ants was significantly decreased, which led to mortality among all life stages. Queen fecundity and weight were also significantly decreased. The change in food retrieval was associated with the exhibition of an unusual behavior, whereby the remaining live ant workers wedged dead ant worker corpses into and on top of cricket carcasses (the laboratory colony food source). SINV-3 infection alters foraging behavior in S. invicta , which adversely impacts colony nutrition. [Display omitted] • SINV-3 infection decreased worker ant foraging in its host Solenopsis invicta. • SINV-3 infection caused larval and pupal mortality. • SINV-3 infection resulted in decreased fecundity and queen weight. • SINV-3 infected worker ants exhibited an unusual behavior. [ABSTRACT FROM AUTHOR]

Disputes over resources are initially resolved by signals, which reveal the resource-holding potential (RHP) of the contestants. Contests in social animals can simultaneously involve numerous individuals, raising the question of what determines group RHP. We employed a series of novel field experiments to investigate the outcome of individual and group contests over food resources between neighbouring colonies of meat ants, Iridomyrmex purpureus. Body size, a taxonomically widespread proxy of fighting ability, did not influence the outcome of individual contests. The outcome of colony level contests was instead determined by colony size, with the numerically larger colony usually gaining exclusive access to the food, but neither colony obtaining exclusive access if matched in colony size. These results help explain why numerous workers are deployed to display grounds, where they apparently signal colony size and thus group RHP to their neighbour. • The outcome of worker level contests in ants is not influenced by worker size. • The outcome of colony level contests in ants is determined by colony size. • Realistic models are needed to evaluate group RHP in nonhuman animals. [ABSTRACT FROM AUTHOR]

Abstract Vigilant animals detect and respond to threats in the environment, often changing posture and movement patterns. Vigilance is modulated not only by predators but also by conspecific threats. In social animals, precisely how conspecific threats alter vigilance behavior over time is relevant to long‐standing hypotheses about social plasticity. We report persistent effects of a simulated conspecific challenge on behavior of wild northern paper wasp foundresses, Polistes fuscatus. During the founding phase of the colony cycle, conspecific wasps can usurp nests from the resident foundress, representing a severe threat. We used automated tracking to monitor the movement and posture of P. fuscatus foundresses in response to simulated intrusions. Wasps displayed increased movement, greater bilateral wing extension, and reduced antennal separation after the threat was removed. These changes were not observed after presentation with a wooden dowel. By rapidly adjusting individual behavior after fending off an intruder, paper wasp foundresses might invest in surveillance of potential threats, even when such threats are no longer immediately present. The prolonged vigilance‐like behavioral state observed here is relevant to plasticity of social recognition processes in paper wasps.

Studies have identified that mating induces a series of physiological changes in animals. In this period, males tending to invest more energy, immune peptides, and other substances to reduce the cost of living for females. This results in lower survival rates in later life than females. Meanwhile, both males and females shorten lifespans due to reproduction. However, the reasons why termites' queens and kings are both extremely long-lived and highly fecund are unclear. Therefore, this study aimed to examine the effects of mating on the expression of immune and DNA repair genes for lifespan extension in termite queens and kings. Here, we reported that mated queens show relatively higher expression of immune genes (phenoloxidase, denfensin, termicin, transferrin), antioxidant genes (CAT, SOD), detoxification genes (GST, CYP450) than virgin queens in the Reticulitermes chinensis. In addition, mated kings also highly expressed these genes, except for termicin, transferrin, GST, and CYP450. After mating, both queens and kings significantly upregulated the expression of DNA repair genes (MLH1, BRCA1, XRCC3, RAD54-like). Mismatch repair genes (MMR) MSH2, MSH4, MSH6 were considerably increased in mated queens, while MSH4, MSH5, MSH6 were upregulated in mated kings. Our results suggest that mating increases the expression of immune and DNA repair genes in the termite queens and kings, and thus possibly improving their survival during reproductive span due to the omnipresent pathogens.

Eusocial insects display caste structures in which reproductive ability is possessed by a single or a few queens while all other colony members act as workers. In social insects like ants, bees, and termites, vital physiological processes are regulated at the colony scale. Females in social insects have at least one reproductive caste and one nonreproductive caste; many termites have at least two male castes. The castes have considerable anatomical, physiological, and behavioural differences in higher social insects. Organismal systems, such as pheromone sensing, hormone signaling, and brain signaling pathways, are deployed in novel circumstances to impact nestmate and colony behaviours due to physiological decentralization over evolutionary time. Significant morphogenesis with region-specific cellular proliferation and degradation occurs during soldier development through two moulting via a presoldier stage in termite. JH action has been developed, in which a high JH titer causes soldier differentiation and a low JH titer causes alate differentiation. A monogamous pair of primary reproductives (one king and one queen) generated from alates normally establishes termite colonies (winged adults). The nymph-alate pathway (sexual pathway) or the worker pathway differentiates larvae in Reticulitermes termites (neuter pathway). Haplo-diploid sex determination controls the first developmental transition, in which unfertilized (haploid) embryos become males and fertilized (diploid) embryos become females in the case of Cataglyphis ant genus. The queen’s mandibular gland secretion, a mix of fatty acids and aromatic chemicals, is critical for maintaining the reproductive division of labour in honeybees (Apis mellifera), suppressing ovary growth in workers. Besides this, the brood produced by the queen also inhibits ovary development in workers by emitting two pheromones: the brood pheromone (BP), mainly composed of esters, and the highly volatile E-b-ocimene.

Ironwood trees (Casuarina equisetifolia) in Guam have been suffering from Ironwood Tree Decline (IWTD) since 2002. Putative plant pathogenic bacteria such as Ralstonia solanacearum and Klebsiella species were identified in the ooze of declining trees and considered to be linked to IWTD. In addition, termites were found to be significantly associated with IWTD. Microcerotermes crassus Snyder (Blattodea: Termitidae) was identified as a termite species that attacks ironwood trees in Guam. Since termites harbor a diverse community of symbiotic and environmental bacteria, we sequenced the microbiome of M. crassus workers attacking ironwood trees in Guam to assess the presence of IWTD-associated pathogens in termite bodies. This dataset contains 652,571 raw sequencing reads present in M. crassus worker samples collected from six ironwood trees in Guam obtained via sequencing the V4 region of the16S rRNA gene on the Illumina NovaSeq (2 × 250bp) platform. Sequences were taxonomically assigned in QIIME2 using SILVA 132 and NCBI GenBank as reference databases. Spirochaetes and Fibrobacteres were the most dominant phyla in M. crassus workers. No putative plant pathogens of the genera Ralstonia or Klebsiella were found in the M. crassus samples. The dataset has been made publicly available through NCBI GenBank under BioProject ID PRJNA883256. This dataset can be used to compare the bacterial taxa present in M. crassus workers in Guam to bacteria communities of related termite species from other geographical locations. In addition, this dataset can also be used to investigate the relationship between termite microbiomes and the microbiomes of ironwood trees they attack and of the surrounding soil.

Brood is critically important in social insect colonies. It carries the colony's fitness by delivering future reproductive adults as well as workers that will increase the colony's workforce. Adoption of non-nestmate brood can increase the colony workforce but entails the risk of rearing unrelated sexuals or social parasites. Thus, theory would predict that ant workers will evolve the ability to discriminate between nestmate and alien brood using the chemical cues displayed at the brood's surface. This appears especially true for eggs and first-instar (L1) larvae, which require more resources than older brood before becoming adult workers. However, the chemical signature of ant early brood stages and its recognition by workers remains understudied. To fill this gap, we investigated the chemical basis of early brood nestmate and cross-species recognition in six ant species. We also tested the discrimination behaviour of workers in brood retrieval trials. We observed species level cues and discrimination against heterospecific brood. We also found that eggs and most L1 larvae displayed a colony signature. However, only some species discriminated against non-nestmate early brood. Interestingly, these species belong to genera subject to brood parasitism. We hypothesize that non-nestmate brood discrimination could arise from species adaptations against brood parasitism. • Ant larvae appear to acquire their surface hydrocarbons after hatching. • Eggs and first-instar (L1) larvae display a species-specific hydrocarbon signature. • Ant workers discriminate against heterospecific eggs and L1 larvae. • Eggs and most L1 larvae display a colony signature in their surface hydrocarbons. • Brood parasitism might select for discrimination against non-nestmate early brood. [ABSTRACT FROM AUTHOR]

Ants are eusocial insects with a complex adaptive foraging system regulated by trail pheromones. This review summarizes ants' pheromone-producing exocrine glands, the chemical composition of ant trail pheromones, and their function and functional characteristics. Glands that secrete trail pheromones include Dufour's gland, poison glands, Pavan's gland and the pygidial gland. Trail pheromones are mostly volatile substances with complex and diverse structures, including hydrocarbons, alkaloids, organic acids, aldehydes, alcohols, ketones and esters. Their functions include orientation and recruitment. Prospects for the future application of trail pheromones in pest ant management are discussed. [ABSTRACT FROM AUTHOR]

To maintain the eusociality of a colony, ants recognize subtle differences in colony-specific sets of cuticular hydrocarbons (CHCs). The CHCs are received by female-specific antennal basiconic sensilla and processed in specific brain regions. However, it is controversial whether a peripheral or central neural mechanism is mainly responsible for discrimination of CHC blends. In the Japanese carpenter ant, Camponotus japonicus, about 140 sensory neurons (SNs) are co-housed in a single basiconic sensillum and receive colony-specific blends of 18 CHCs. The complexity of this CHC sensory process makes the neural basis of peripheral nestmate recognition difficult to understand. Here, we electrophysiologically recorded responses of single basiconic sensilla to each of 18 synthesized CHCs, and identified CHC responses of each SN co-housed in a single sensillum. Each CHC activated different sets of SNs and each SN was broadly tuned to CHCs. Multiple SNs in a given sensillum fired in synchrony, and the synchronicity of spikes was impaired by treatment with a gap junction inhibitor. These results indicated that SNs in single basiconic sensilla were electrically coupled. Quantitative analysis indicated that the Japanese carpenter ants have the potential to discriminate chemical structures of CHCs based on the combinational patterns of activated SNs. SNs of ants from different colonies exhibited different CHC response spectra. In addition, ants collected from the same colony but bred in separate groups also exhibited different CHC response spectra. These results support the hypothesis that the peripheral sensory mechanism is important for discrimination between nestmate and non-nestmate ants. [ABSTRACT FROM AUTHOR]

Ant societies are primarily composed of females, whereby labor is divided into reproductive, or queen, and non‐reproductive, or worker, castes. Workers and reproductive queens can differ greatly in behavior, longevity, physiology, and morphology, but queen–worker differences are usually modest relative to the differences in males. Males are short‐lived, typically do not provide the colony with labor, often look like a different species, and only occur seasonally. It is these differences that have historically led to their neglect in social insect research, but also why they may facilitate novel phenotypic variation – by increasing the phenotypic variability that is available for selection. In this study, worker variation in multivariate size–shape space paralleled male–queen variation. As worker variation increased within species, so did sexual variation. Across species in two independent genera, using head width as a proxy for body size, sexual size dimorphism correlated with worker polymorphism regardless of whether the ancestral condition was large or small worker/sexual dimorphism. Mounting molecular data support the hypothesis that queen–worker caste determination has co‐opted many genes/pathways from sex determination. The molecular evidence, coupled with the observations from this study, leads to the hypothesis that sexual selection and selection on colony‐level traits are non‐independent, and that sexual dimorphism may even have facilitated the evolution of the distinct worker caste. [ABSTRACT FROM AUTHOR]

Abstract Ant societies are primarily composed of females, whereby labor is divided into reproductive, or queen, and non‐reproductive, or worker, castes. Workers and reproductive queens can differ greatly in behavior, longevity, physiology, and morphology, but queen–worker differences are usually modest relative to the differences in males. Males are short‐lived, typically do not provide the colony with labor, often look like a different species, and only occur seasonally. It is these differences that have historically led to their neglect in social insect research, but also why they may facilitate novel phenotypic variation – by increasing the phenotypic variability that is available for selection. In this study, worker variation in multivariate size–shape space paralleled male–queen variation. As worker variation increased within species, so did sexual variation. Across species in two independent genera, using head width as a proxy for body size, sexual size dimorphism correlated with worker polymorphism regardless of whether the ancestral condition was large or small worker/sexual dimorphism. Mounting molecular data support the hypothesis that queen–worker caste determination has co‐opted many genes/pathways from sex determination. The molecular evidence, coupled with the observations from this study, leads to the hypothesis that sexual selection and selection on colony‐level traits are non‐independent, and that sexual dimorphism may even have facilitated the evolution of the distinct worker caste.

Diel activity of diurnal pollinating insects declines well before the end of day, but a few species, such as bumble bees, can continue foraging in the period before sunset, when light levels decrease. Foraging during this time could be costly for individuals, and key decisions regarding the daily cessation of foraging behaviour have to be made during this period of rapid abiotic change. However, little is known about the behaviour of diurnal bees under these light conditions. We conducted a field experiment in a mixed agricultural landscape to investigate pollen foraging in the hour before sunset in the buff-tailed bumble bee, Bombus terrestris , comparing it to an hour during the afternoon. We monitored activity at the colony entrance and collected pollen sacs from returning foragers. Overall, there were fewer exits and returns in the evening period than in the afternoon period. Evening foragers returned to the colony with partial pollen loads when compared to daytime foragers, and those returning in lower light levels had smaller loads. Additionally, we found that the same flower taxa were being exploited in the evenings as in the daytime. We found no effect of individual size on the likelihood of evening foraging or the size of pollen loads. Our results suggest that B. terrestris are facultative evening foragers that opportunistically exploit profitable flowers they have encountered during the day. Evening foragers decide to return to the colony with partial pollen loads in this period of the foraging day, which results in a largely reduced pollen influx to the colony at the end of the day. Our findings indicate that the gradual decline in light is likely to be an important factor guiding the decisions of bumble bees and other diurnal pollinators of whether to extend or end foraging, and when to return to the colony. • Bumble bees are facultative evening foragers. • Pollen foraging in the evening comes at an acquisition cost. • Light intensity is a key limiting factor for pollen collection. • Evening foragers have the same floral preferences as daytime foragers. • Individual size does not affect pollen foraging in the late evening. [ABSTRACT FROM AUTHOR]

The gonads of honey bee, Apis mellifera, queens and drones are each composed of hundreds of serial units, the ovarioles and testioles, while the ovaries of the adult subfertile workers consist of only few ovarioles. We performed a comparative RNA‐seq analysis on early fifth‐instar (L5F1) larval gonads, which is a critical stage in gonad development of honey bee larvae. A total of 1834 genes were identified as differentially expressed (Padj < 0.01) among the three sex and caste phenotypes. The Gene Ontology analysis showed significant enrichment for metabolism, protein or ion binding, and oxidoreductase activity, and a KEGG analysis revealed metabolic pathways as enriched. In a principal component analysis for the total transcriptomes and hierarchical clustering of the DEGs, we found higher similarity between the queen and worker ovary transcriptomes compared to the drone testis, despite the onset of programmed cell death in the worker ovaries. Four DEGs were selected for RT‐qPCR analyses, including their response to juvenile hormone (JH), which is a critical factor in the caste‐specific development of the ovaries. Among these, DMRT A2 and Hsp83 were found upregulated by JH and, thus, emerged as potential molecular markers for sex‐ and caste‐specific gonad development in honey bees. [ABSTRACT FROM AUTHOR]

Abstract Background Foraging in group living animals such as social insects, is collectively performed by individuals. However, our understanding on foraging behavior of subterranean termites is extremely limited, as the process of foraging in the field is mostly concealed. Because of this limitation, foraging behaviors of subterranean termites were indirectly investigated in the laboratory through tunnel geometry analysis and observations on tunneling behaviors. In this study, we tracked subsets of foraging workers from juvenile colonies of Coptotermes formosanus (2-yr-old) to describe general foraging behavioral sequences and to find how foraging workers allocate time between the foraging site (food acquisition or processing) and non-foraging site (food transportation). Results Once workers entered into the foraging site, they spent, on average, a significantly longer time at the foraging site than the non-foraging site. Our clustering analysis revealed two different types of foraging workers in the subterranean termite based on the duration of time they spent at the foraging site and their foraging frequency. After entering the foraging site, some workers (cluster 1) immediately initiated masticating wood fragments, which they transferred as food boluses to recipient workers at the foraging site. Conversely, the recipient workers (cluster 2) moved around after entering the foraging site and received food from donating workers. Conclusions This study provides evidence of task specialization within foraging cohorts in subterranean termites.

A social insect colony can be seen as a superorganism in which nutrient collection and regulation is achieved through the collective action of workers. Here we investigated how workers of the yellow-legged hornet Vespa velutina, an invasive predator of honeybees and other insects in Europe, distribute the incoming food within their nests. Food transfer among colonies differing in composition of developmental stage and abundance of different castes was compared by feeding workers with protein and carbohydrate solutions labelled with non-radioactive heavy metals (rubidium and caesium) and measuring the heavy metal tracers’ occurrence in adults and larvae in the nests after 24h. Caesium labelled sucrose was more abundant in the adults (workers, males and the queen), while rubidium labelled proteins were more abundant in the larvae. The lightest larvae received more protein than the others. The lightest workers received more carbohydrate, and the largest workers more protein. Even if this work is exploratory, our results considerably improve our knowledge of hornet biology by showing how food distribution patterns may vary throughout the development cycle of colonies. They also provide new perspectives to understand how specific nutrients are distributed in nests, and may help develop Trojan horses biological control strategies based on food distribution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Brain dopamine levels were higher in gynes than in workers during late pupal stage. • Dopamine dynamics were similar between the castes in Bombus ignitus. • Expression levels of dopamine-related genes did not differ between the castes. • Dopamine dynamics in gynes differed between B. ignitus and Apis mellifera. The dopaminergic system is involved in caste-specific behaviors in eusocial bumble bees. However, little is known about how the caste differences in dopaminergic system are formed during pupal stages in the brains of bumble bees. Thus, we investigated the levels of dopamine-related substances and expression of genes encoding enzymes involved in dopamine synthesis and metabolism, dopamine receptors, and a dopamine transporter in the brain of female Bombus ignitus. The levels of dopamine and dopamine-related substances in the brain were significantly higher in gynes than in workers from the late pupal stage to emergence, but the dynamics were similar between the castes. The relative expression levels of genes encoding enzymes involved in dopamine synthesis (BigTh and BigDdc) and dopamine metabolism (BigNat) increased significantly from pupal stage to emergence, but there were no differences in the relative expression levels of these genes between castes. A similar pattern was seen in the relative expression levels of four dopamine receptor genes (BigDop1 , BigDop2 , BigDop3 , and BigDopEcR) and a dopamine transporter gene (BigDat). Compared with the honey bee Apis mellifera , the caste-specific dopaminergic system in the bumble bee is less differentiated, which might reflect the degree of behavioral specialization in these two species. [ABSTRACT FROM AUTHOR]

Insect diversity and biomass have been declining around the world. This might have severe consequences on the environment since insects provide many crucial ecosystem services. One major driver behind the decline is continuous pesticide use which also affects nontarget organisms. Even at low doses, chronic exposure to pesticides may have negative long‐term effects. Ants have not received much attention in this context, despite their importance in terrestrial ecosystems.A full factorial experimental design was used to test how ingestion of two widely used pesticides influence colonies of the ant Cardiocondyla obscurior. Colonies were exposed for 12 weeks to the herbicide glyphosate and the neonicotinoid insecticide thiacloprid, separately and in combination. Brood production and the size of new workers and queens produced in these colonies were measured. In addition, the relative densities of two endosymbionts were quantified and immunocompetence tested by measuring survival after fungal infection.The two pesticides in combination decreased brood production, which was measured as the number of produced eggs and pupae. Workers and queens produced in pesticide‐exposed colonies differed in body size from individuals produced in control colonies. Furthermore, endosymbiont densities decreased after glyphosate exposure. Neither pesticide influenced survival after fungal infection.The results show that chronic exposure to two widely used pesticides causes apparent trade‐offs in reproduction and other physiological traits of ants, potentially decreasing fitness. Even low levels of pesticides in the environment may therefore have negative effects on ant colonies, contributing to the worldwide insect decline. [ABSTRACT FROM AUTHOR]

The gall‐forming aphid Mordwilkoja vagabunda has been an out‐group in molecular studies of the evolution of social behavior in the Pemphigus genus, but Mordwilkoja aphids have not previously been assayed for social behavior, such as altruistic defense. This study reports experiments carried out in July in Ithaca, NY, in which nymphs (immature aphids) of M. vagabunda were video‐recorded under a stereomicroscope while they encountered pyralid moth larvae in a plastic arena. Mordwilkoja vagabunda nymphs of all instars used their legs to claw moth larvae while pressing their rostrums against the larvae, possibly to pierce the cuticle. Many of the attacking aphids were alatoid nymphs, rather than the specialized first‐instar soldiers typically observed in Pemphigus species. Mordwilkoja vagabunda nymphs moved in bursts that sometimes became synchronized among several aphids in the same vicinity. These synchronized, rhythmic movements may be antipredator defense strategies comparable to the collective twitching and kicking response observed in colonies of Aphis nerii and other aphid species. Defensive behaviors by M. vagabunda nymphs may be altruistic fortress defense strategies, which maximize the inclusive fitness of the clone. [ABSTRACT FROM AUTHOR]

Decisions made by foraging animals conform a complex process based on the integration of information from multiple external environmental stimuli and internal physiological signals, which in turn are modulated by individual experience and a detection threshold of each individual. For social insects in which foraging is limited to given age subcastes, individual foraging decisions may also be affected by ontogenetic shifts and colony requirements. We studied the short‐term changes in foraging preferences of the generalist wasp Vespula germanica, focusing on whether the individual response to different resources could be influenced by the ontogenetic shifts and/or by social interaction with nestmates. We carried both laboratory and field experiments to confront worker wasps to a short‐term resource switch between either protein or carbohydrate‐based foods. We tested the response of (1) Preforager workers (no foraging experience nor interaction with other wasps), (2) Forager workers (experience in foraging and no colony feedback), and (3) Wild forager workers (foraging naturally and exposed to free interactions with nestmates). We evaluated the maxilla‐labium extension response (MaLER) for laboratory assays or the landing response for field assays. We observed that for wasps deprived of colony feedback (either preforagers or foragers), the protein‐rich foods acceptance threshold increased (and thus a lower level of foraging on that item was observed) if they had foraged on carbohydrates previously, whereas carbohydrates were accepted in all assays. However, wasps immersed in a natural foraging context did accept protein foods regardless of their first foraging experience and reduced the carbohydrates collected when trained on protein foods. We provide evidence that short‐term changes in foraging preferences depend on the type of resource foraged and on the social interactions, but not on ontogenetic shifts. [ABSTRACT FROM AUTHOR]

Simple Summary: The membership of social insect colonies is defined by chemical pheromones on the bodies of colony members. In nearly all ant species that have been studied, these pheromones have been shown to be genetically based. In some cases, however, environmentally derived odors have been implicated as colony recognition cues. The widely introduced and invasive Argentine ant is well known for forming massive "supercolonies" in its introduced ranges. Previous studies have implicated both genetic and diet-derived chemicals in the colony recognition systems of introduced populations. Here, we perform feeding experiments, in both realistic field settings and the lab, and show that dietary changes do not cause behavioral changes in the field, as well as under most laboratory conditions. However, one exception was found, in which reduced aggression was recorded in one of the laboratory feeding treatments (with crickets as the dietary item), but, nevertheless, not of sufficient magnitude to explain the unusual colony structure of introduced Argentine ants. We conclude that dietary shifts during introduction to new ranges do not account for the origin of Argentine ant supercolonies. Ants are some of the most abundant and ecologically successful terrestrial organisms, and invasive ants rank among the most damaging invasive species. The Argentine ant is a particularly well-studied invader, in part, because of the extreme social structure, known as unicoloniality, that occurs in introduced populations. Unicoloniality is characterized by the formation of geographically vast supercolonies, within which territorial behavior and intraspecific aggression are absent. Although there is considerable evidence supporting a genetic basis for the odor cues involved in colony recognition, some studies have suggested that diet may also influence colony recognition cues and, thus, colony structure. Here, we test the role for insect-derived recognition cues by performing a diet supplementation experiment in a natural field setting, and a more extreme dietary manipulation experiment in the lab. After one month, in both the field and the lab, we found that aggressive supercolonies remained aggressive toward each other and non-aggressive nests (from the same supercolony) remained non-aggressive, regardless of dietary treatment. In one lab treatment, we did observe a significant decrease in the level of aggression between different supercolonies that were fed the same diet, but aggression was still frequent. We did not see any evidence for cuticular hydrocarbon odor cues being transferred from prey to ants in any of the field treatments. In the more extreme lab treatment, however, several cuticular hydrocarbons were acquired from both roach and cricket insect prey (but not Drosophila). Based on these data, we conclude that dietary changes are unlikely to underlie changes in behavior or colony structure in Argentine ants in real-world settings. However, these results indicate that caution is warranted when interpreting the behaviors of animals that have been reared on diets that are substantially different from natural populations. [ABSTRACT FROM AUTHOR]

While most ant species establish a colony independently, some socially parasitic ants build the foundation of their colony by invading other ant (host) colonies and utilizing their labor forces. Many socially parasitic ants disguise their cuticular hydrocarbon (CHC) profile, which is also known as signature mixture for nestmate discrimination, when invading the host colony. Since the strategy of chemical disguise is widespread in socially parasitic ants, elucidating the mechanism of chemical disguise will promote knowledge on the evolutionary history of social parasitism. However, detailed knowledge is still lacking, as the relevant information has only originated from circumstantial evidence, which was obtained from ecological observations. In this study, we investigated the mechanism of chemical disguise in a new queen of a temporary socially parasitic spiny ant (Polyrhachis lamellidens) by measuring its CHC profile, performing a tracing assay with labeled substances, and analyzing gene expression levels. First, after rubbing behavior was observed against the host workers, the CHC profile in P. lamellidens shifted to pronounced peaks that closely resembling that of the host workers. We also observed a reduction in aggressive behaviors by the host ant against P. lamellidens after rubbing behavior was performed. In addition, P. lamellidens acquired artificially-applied labeling substances from host workers through their rubbing behaviors, while gene expression profiling showed the expression of CHC synthesis-related genes did not change during this behavior. These results suggest that P. lamellidens directly obtains host CHCs through rubbing behavior, and these host CHCs enables P. lamellidens to remain disguised during colony invasion.

Social insect colonies are characterized by an efficient division of labor, allowing high-value individuals (i.e., reproductives and brood) to be sheltered from tasks associated with increased risk of pathogen exposure, such as foraging or corpse disposal. This social organization helps limit the transmission of disease throughout the colony. Further, individuals can actively respond to imminent disease threats by altering their behaviors as a means of social immunity. In subterranean termites, although workers typically avoid detected pathogens, they can be attracted to pathogen cues when a nestmate is infected. Infected termites are usually groomed, but they may instead be cannibalized if the infection has already become lethal. The mechanisms governing these changes in behavior are unclear. We set out to examine immediate changes in individual behaviors, investigating the role that the infected individual plays in communicating its infection status to nestmates. We also assessed gradual changes in social organization after the re-introduction of an infected termite to the colony. Our results reveal that infected termites likely do not signal their infection status to nestmates through shaking behaviors and reduced movements, suggesting the occurrence of other mechanisms used in communicating infection. We also found that infected termites do not self-isolate and may travel to the densest part of the colony, where they can potentially benefit from grooming by large groups of nestmates. These results provide new insights into how individual changes in immune behaviors contribute to overall colony health, highlighting that, at early stages of infection, termites favor a rescuing strategy rather than isolation and/or cannibalization.

Abstract The gall‐forming aphid Mordwilkoja vagabunda has been an out‐group in molecular studies of the evolution of social behavior in the Pemphigus genus, but Mordwilkoja aphids have not previously been assayed for social behavior, such as altruistic defense. This study reports experiments carried out in July in Ithaca, NY, in which nymphs (immature aphids) of M. vagabunda were video‐recorded under a stereomicroscope while they encountered pyralid moth larvae in a plastic arena. Mordwilkoja vagabunda nymphs of all instars used their legs to claw moth larvae while pressing their rostrums against the larvae, possibly to pierce the cuticle. Many of the attacking aphids were alatoid nymphs, rather than the specialized first‐instar soldiers typically observed in Pemphigus species. Mordwilkoja vagabunda nymphs moved in bursts that sometimes became synchronized among several aphids in the same vicinity. These synchronized, rhythmic movements may be antipredator defense strategies comparable to the collective twitching and kicking response observed in colonies of Aphis nerii and other aphid species. Defensive behaviors by M. vagabunda nymphs may be altruistic fortress defense strategies, which maximize the inclusive fitness of the clone.