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Mimicry, the superficial resemblance between organisms of two or more species, is considered a textbook example for natural selection, for which it is assumed that predators are important selective agents. Ant mimicking spiders have received considerable attention in studies on mimicry because they include examples with remarkable, species‐specific morphological adaptations. Ant‐like behaviours such as erratic locomotory patterns, abdomen bobbing and vertical movements of the first or second pair of legs to imitate antennal movements, are assumed to have evolved before morphological mimicry and may be considered adaptations to general ant resemblance. Species‐specific behavioural ant mimicry (behaviour that is only observed in specific ants and imitated by their mimics) was very rarely documented and ant resembling behaviour that repels predator attacks has not been confirmed yet. In this study we report and discuss such species‐specific behaviour, a spray display (SD), in the castianeirine spiders Myrmecotypus iguazu (a morphologically accurate mimic of the carpenter ant Camponotus sericeiventris), and M. tahyinandu (a morphologically accurate mimic of C. crassus). The SD consisted of the raising of the cephalothorax and moving of the abdomen ventrally under the cephalothorax, pointing the apex forward, and holding the antennae (ant) or first pair of legs (spiders) at an angle of about 45°–120°. The morphological adaptations that are required to perform the SD and the lack of an alternative explanation for the purpose of this display suggest that the SD has evolved to enhance both general behavioural and morphologically accurate ant resemblance. The two observed Myrmecotypus species may be considered the behaviorally most accurate ant‐resembling spiders known to date, as the SD may provide protection against spider‐ and ant‐eating predators at a point in predator interactions where other myrmecomorph spiders may abandon their ant‐resembling behaviour. [ABSTRACT FROM AUTHOR]

Camponotus floridanus ants show altered behaviors followed by a fatal summiting phenotype when infected with manipulating Ophiocordyceps camponoti-floridani fungi. Host summiting as a strategy to increase transmission is also observed with parasite taxa beyond fungi, including aquatic and terrestrial helminths and baculoviruses. The drastic phenotypic changes can sometimes reflect significant molecular changes in gene expression and metabolite concentrations measured in manipulated hosts. Nevertheless, the underlying mechanisms still need to be fully characterized. To investigate the small molecules producing summiting behavior, we infected C. floridanus ants with O. camponoti-floridani and sampled their heads for LC–MS/MS when we observed the characteristic summiting phenotype. We link this metabolomic data with our previous genomic and transcriptomic data to propose mechanisms that underlie manipulated summiting behavior in "zombie ants." This "multiomic" evidence points toward the dysregulation of neurotransmitter levels and neuronal signaling. We propose that these processes are altered during infection and manipulation based on (1) differential expression of neurotransmitter synthesis and receptor genes, (2) altered abundance of metabolites and neurotransmitters (or their precursors) with known behavioral effects in ants and other insects, and (3) possible suppression of a connected immunity pathway. We additionally report signals for metabolic activity during manipulation related to primary metabolism, detoxification, and anti-stress protectants. Taken together, these findings suggest that host manipulation is likely a multi-faceted phenomenon, with key processes changing at multiple levels of molecular organization. [ABSTRACT FROM AUTHOR]

Simple Summary: Florida carpenter ants (Camponotus floridanus) live in colonies comprised of thousands of workers. The smallest workers, known as minors, engage in routine tasks such as nursing and foraging while the largest workers, known as majors, are thought to be soldiers specialized for defending the nest. How ant colonies allocate their workforce to address the dynamic and ever-changing needs of the colonies remains an open question in the field, but current evidence suggests that ant social behavior likely results from a combination of genetic/epigenetic, physiological, and systems-level processes. Here, we extend these studies by investigating the role of olfactory sensitivity in regulating ant behavior. Minor workers exhibited significant shifts in olfactory sensitivity and odor coding as they aged and switched tasks. The olfactory sensitivity of majors, however, remained relatively stable as they aged. From these studies, we also identified a single compound, 3-methylindole, which elicited significantly higher olfactory responses and aversive behavior in nurses compared to foragers, suggesting that this chemical may have a role in brood care. Overall, these studies support the hypothesis that changes in olfactory sensitivity play an important role in regulating social behavior in ants. Age-related changes in behavior and sensory perception have been observed in a wide variety of animal species. In ants and other eusocial insects, workers often progress through an ordered sequence of olfactory-driven behavioral tasks. Notably, these behaviors are plastic, and workers adapt and rapidly switch tasks in response to changing environmental conditions. In the Florida carpenter ant, smaller minors typically perform most of the work needed to maintain the colony, while the larger majors are specialized for nest defense and rarely engage in these routine tasks. Here, we investigate the effects of age and task group on olfactory responses to a series of odorant blends in minor and major worker castes. Consistent with their respective roles within the colony, we observed significant age-associated shifts in the olfactory responses of minors as they transitioned between behavioral states, whereas the responses of majors remained consistently low regardless of age. Furthermore, we have identified a unitary compound, 3-methylindole, which elicited significantly higher responses and behavioral aversion in minor nurses than in similarly aged foragers suggesting that this compound may play an important role in brood care. Taken together, our results suggest that age- and task-associated shifts in olfactory physiology may play a critical role in the social organization of ant colonies. [ABSTRACT FROM AUTHOR]

The physiology and behavior of social organisms correlate with their social environments. However, because social environments are typically confounded by age and physical environments (i.e., spatial location and associated abiotic factors), these correlations are usually difficult to interpret. For example, associations between an individual's social environment and its gene expression patterns may result from both factors being driven by age or behavior. Simultaneous measurement of pertinent variables and quantification of the correlations between these variables can indicate whether relationships are direct (and possibly causal) or indirect. Here, we combine demographic and automated behavioral tracking with a multiomic approach to dissect the correlation structure among the social and physical environment, age, behavior, brain gene expression, and microbiota composition in the carpenter ant Camponotus fellah. Variations in physiology and behavior were most strongly correlated with the social environment. Moreover, seemingly strong correlations between brain gene expression and microbiota composition, physical environment, age, and behavior became weak when controlling for the social environment. Consistent with this, a machine learning analysis revealed that from brain gene expression data, an individual's social environment can be more accurately predicted than any other behavioral metric. These results indicate that social environment is a key regulator of behavior and physiology. This study combines automated behavioral tracking of ants with multi-omics, revealing that individual behavior, brain gene expression, and gut microbiota composition are all more strongly correlated with social network position than they are with one another, indicating that social interactions likely regulate social behavior and underlying physiology. [ABSTRACT FROM AUTHOR]

Some Ophiocordyceps species infecting ants are able to manipulate the host behavior. The hosts are manipulated in order to move to location that are advantageous for fungal spore transmission. Ophiocordyceps species that are able to manipulate the ant's behavior are called "zombie-ant fungi". They are widespread within tropical forests worldwide, with relatively few reports from subtropical monsoon evergreen broad-leaf forest. Zombie-ant fungi have been described and reported in different countries worldwide. However, there were a few reports from China. This study proposed six new species of zombie-ant fungi from China based on multi-gene (SSU, LSU, TEF, RPB1 and RPB2) phylogenetic analyses and morphological characteristics. Six novel species of Ophiocordyceps from China were identified as the Ophiocordyceps unilateralis core clade, forming a separate lineage with other species. Six novel species of Ophiocordyceps with hirsutella-like asexual morphs exclusively infecting ants were presented herein, namely, Ophiocordyceps acroasca, Ophiocordyceps bifertilis, Ophiocordyceps subtiliphialida, Ophiocordyceps basiasca, Ophiocordyceps nuozhaduensis and Ophiocordyceps contiispora. Descriptions and illustrations for six taxon were provided. Five of these species were collected from the subtropical monsoon evergreen broad-leaf forest, and one was collected from the rainforest and subtropical monsoon evergreen broad-leaf forest. This work proposes that the same host of Camponotus can be infected by multiple ant pathogenic fungi, while multiple ants of Polyrhachis can be infected by the same pathogenic fungi at the same time. This study contributes towards a better understanding of the evolutionary relationship between hosts and fungi, and provides novel insights into the morphology, distribution, parasitism, and ecology of Ophiocordyceps unilateralis sensu lato. We have provided a method for obtaining living cultures of Ophiocordyceps unilateralis complex species and their asexual morphs based on the living cultures, which is of significant value for further studies of Ophiocordyceps unilateralis complex species in the future. [ABSTRACT FROM AUTHOR]

Ophiocordyceps fungi manipulate the behaviour of their ant hosts to produce a summit disease phenotype, thereby establishing infected ant cadavers onto vegetation at elevated positions suitable for fungal growth and transmission. Multiple environmental and ecological factors have been proposed to shape the timing, positioning and outcome of these manipulations.We conducted a long‐term field study of Ophiocordyceps camponoti‐floridani infections of Camponotus floridanus ants—the Florida zombie ants. We propose and refine hypotheses on the factors that shape infection outcomes by tracking the occurrence of and fungal growth from hundreds of ant cadavers. We modelled and report these data in relation to weather, light, vegetation and attack by hyperparasites.We investigated environmental factors that could affect the occurrence and location of newly manipulated ant cadavers. New cadaver occurrence was preferentially biased towards epiphytic Tillandsia bromeliads, canopy openness and summer weather conditions (an interactive effect of temperature, humidity and precipitation). Furthermore, we suggest that incident light at the individual cadaver level reflects microhabitat choice by manipulated ants or selective pressure on cadaver maintenance for conditions that improve fungal survival.We also asked which environmental conditions affect fungal fitness. Continued fungal development of reproductive structures and putative transmission increased with moist weather conditions (interaction of humidity and precipitation) and canopy openness, while being reduced by hyperparasitic mycoparasite infections. Moreover, under the most open canopy conditions, we found an atypical Ophiocordyceps growth morphology that could represent a plastic response to conditions influenced by high light levels.Taken together, we explore general trends and the effects of various ecological conditions on host and parasite disease outcomes in the Florida zombie ant system. These insights from the field can be used to inform experimental laboratory setups that directly test the effects of biotic and abiotic factors on fungus–ant interactions or aim to uncover underlying molecular mechanisms. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Simple Summary: Adhesive tapes are as effective as baits and pitfall traps in monitoring Solenopsis invicta and Tapinoma melanocephalum in urban areas in southern China. However, adhesive tapes detected less ants and fewer species of non-target ants than baits and pitfall traps. Our study demonstrated that tape-paving behavior can potentially be used in developing more specific monitoring methods for S. invicta and T. melanocephalum in urban areas in southern China. Our previous study discovered that two urban pest ants, red imported fire ants, Solenopsis invicta Buren (Formicidae: Myrmicinae), and ghost ants, Tapinoma melanocephalum (Fabricius) (Formicidae: Dolichoderinae), can pave viscose surfaces with particles to facilitate food search and transport. We hypothesize that this paving behavior can be applied to monitor S. invicta and T. melanocephalum. In the present study, 3998 adhesive tapes, each with a food source (sausage), were placed in 20 locations around Guangzhou, China (181–224 tapes per location), and their efficiency to detect S. invicta and T. melanocephalum was compared with two traditional ant-monitoring methods, baiting and pitfall trapping. Overall, S. invicta was detected by 45.6% and 46.4% of baits and adhesive tapes, respectively. In each location, the percentage of adhesive tapes detecting S. invicta and T. melanocephalum was similar when compared to baits and pitfall traps. However, significantly more non-target ant species showed up on bait and pitfall traps. Seven non-target ant species—Pheidole parva Mayr (Formicidae: Myrmicinae), Pheidole nodus Smith (Formicidae: Myrmicinae), Pheidole sinica Wu & Wang (Formicidae: Myrmicinae), Pheidole yeensis Forel (Formicidae: Myrmicinae), Carebara affinis (Jerdon) (Formicidae: Myrmicinae), Camponotus nicobarensis Mayr (Formicidae: Formicinae), and Odontoponera transversa (Smith) (Formicidae: Ponerinae)—also showed tape paving behavior, but they can be easily distinguished morphologically from S. invicta and T. melanocephalum. Our study showed that the paving behavior occurs in different subfamilies of ants (i.e., myrmicinae, dolichoderinae, formicinae, and ponerinae). In addition, paving behavior can potentially be used to develop more specific monitoring methods for S. invicta and T. melanocephalum in urban areas in southern China. [ABSTRACT FROM AUTHOR]

Background: Camponotus floridanus ant colonies are comprised of a single reproductive queen and thousands of sterile female offspring that consist of two morphologically distinct castes: smaller minors and larger majors. Minors perform most of the tasks within the colony, including brood care and food collection, whereas majors have fewer clear roles and have been hypothesized to act as a specialized solider caste associated with colony defense. The allocation of workers to these different tasks depends, in part, on the detection and processing of local information including pheromones and other chemical blends such as cuticular hydrocarbons. However, the role peripheral olfactory sensitivity plays in establishing and maintaining morphologically distinct worker castes and their associated behaviors remains largely unexplored. Results: We examined the electrophysiological responses to general odorants, cuticular extracts, and a trail pheromone in adult minor and major C. floridanus workers, revealing that the repertoire of social behaviors is positively correlated with olfactory sensitivity. Minors in particular display primarily excitatory responses to olfactory stimuli, whereas major workers primarily manifest suppressed, sub-solvent responses. The notable exception to this paradigm is that both minors and majors display robust, dose-dependent excitatory responses to conspecific, non-nestmate cuticular extracts. Moreover, while both minors and majors actively aggress non-nestmate foes, the larger and physiologically distinct majors display significantly enhanced capabilities to rapidly subdue and kill their adversaries. Conclusions: Our studies reveal the behavioral repertoire of minors and majors aligns with profound shifts in peripheral olfactory sensitivity and odor coding. The data reported here support the hypothesis that minors are multipotential workers with broad excitatory sensitivity, and majors are dedicated soldiers with a highly specialized olfactory system for distinguishing non-nestmate foes. Overall, we conclude that C. floridanus majors do indeed represent a physiologically and behaviorally specialized soldier caste in which caste-specific olfactory sensitivity plays an important role in task allocation and the regulation of social behavior in ant colonies. [ABSTRACT FROM AUTHOR]

We hereby report an isolated population of a rare morpho-variant of the ant-mimicking jumping spider Myrmaplata plataleoides (O. Pickard-Cambridge, 1869) from Hazaribagh Wildlife Sanctuary, Hazaribagh, Jharkhand, India, which is also the first record of this species from the state of Jharkhand, India. Descriptions of both male and female spiders, the female's exuviae, its eggs and habitat are presented. We have studied its moulting, feeding and sexual behaviour in detail, and have recorded various behavioural aspects that were never documented before, such as debris-rolling behaviour, photokinetic response, starvation response and oxygen deprivation response. We here report the occurrence of this spider near the colonies of the ground-nesting ant Camponotus compressus (Fabricius, 1787). This spider is known to mimic the Asian weaver ant Oecophylla smaragdina (Fabricius, 1775), which are greenish orange to red in colour. Specimens collected by us are dark brown to black in coloration whereas the commonly reported specimens are often greenish orange to red. We propose that the darker coloration would have been naturally selected in this isolated population of M. plataleoides as an adaptation to coexist with C. compressus , which is also black in coloration and abundant around the spiders. Study of the moulting behaviour of the morpho-variant further reveals the display of a novel mechanism of ant mimicry among these spiders which we have named as temporal myrmecomorphy. Temporal myrmecomorphy has been proposed to be a protective mechanism used by a harmless mimic against the attacks of the aggressive models so that it can co-exist with the models. Present study establishes the usefulness of a morpho-variant as an important model in understanding the evolution and behaviour of a species holistically. [ABSTRACT FROM AUTHOR]

During surveys in central Florida of the zombie-ant fungus Ophiocordyceps camponoti-floridani, which manipulates the behavior of the carpenter ant Camponotus floridanus, two distinct fungal morphotypes were discovered associated with and purportedly parasitic on O. camponoti-floridani. Based on a combination of unique morphology, ecology and phylogenetic placement, we discovered that these morphotypes comprise two novel lineages of fungi. Here, we propose two new genera, Niveomyces and Torrubiellomyces, each including a single species within the families Cordycipitaceae and Ophiocordycipitaceae, respectively. We generated de novo draft genomes for both new species and performed morphological and multi-loci phylogenetic analyses. The macromorphology and incidence of both new species, Niveomyces coronatus and Torrubiellomyces zombiae, suggest that these fungi are mycoparasites since their growth is observed exclusively on O. camponoti-floridani mycelium, stalks and ascomata, causing evident degradation of their fungal hosts. This work provides a starting point for more studies into fungal interactions between mycopathogens and entomopathogens, which have the potential to contribute towards efforts to battle the global rise of plant and animal mycoses. [ABSTRACT FROM AUTHOR]

The invasive Argentine ants (Linepithema humile) and the red imported fire ants (Solenopsis invicta) constitute a worldwide threat, causing severe disruption to ecological systems and harming human welfare. In view of the limited success of current pest control measures, we propose here to employ repellents as means to mitigate the effect of these species. We demonstrate that cuticular hydrocarbons (CHCs) used as nestmate-recognition pheromone in the Japanese carpenter ant (Camponotus japonicus), and particularly its (Z)-9-tricosene component, induced vigorous olfactory response and intense aversion in these invasive species. (Z)-9-Tricosene, when given to their antennae, caused indiscriminate glomerular activation of antennal lobe (AL) regions, creating neural disarray and leading to aversive behavior. Considering the putative massive central neural effect, we suggest that the appropriate use of certain CHCs of native ants can facilitate aversive withdrawal of invasive ants. [ABSTRACT FROM AUTHOR]

In animal societies, individuals may take on different roles to fulfil their own needs and the needs of their group. Ant colonies display high levels of organizational complexity, with ants fulfilling different roles at different timescales (what is known as task allocation). Factors affecting task allocation can be at the individual level (e.g. physiology), or at the group level (e.g. the network of interactions). We focus on group level processes by exploring the relationship between interaction networks, task allocation and task switching using a previously published data set (Mersch et al., 2013, Science, 340 (6136), 1090–1093) tracking the behaviour of six Camponotus fellah colonies over 41 days. In our new analyses, our goal was to better explain the noisy process of task switching beyond simple age polyethism. First, we investigated the architecture of interaction networks using node (individual) level network measures and their relation to the individual's task – foraging, cleaning or nursing – and whether or not the ant switched tasks. We then explored how noisy information propagation was among ants, as a function of the colony composition (how many ants carried out which tasks), through the information-theoretic metric of 'effective information'. Our results show that interaction history is tied to task allocation: ants that switched to a task were more likely to have interacted with other ants carrying out that task. The degree to which interactions related to task allocation, as well as the noise in those interactions, depended on which groups of ants were interacting. Overall, we found that colony cohesion was stable even as ant level network measures varied more for ants when they switched functional groups; thus, ant colonies maintained a high level of information flow as determined by network analysis, and ant functional groups played different roles in maintaining colony cohesion through varied information flows. • We analysed the interaction networks of six C. fellah colonies. • We tested how centrality and information flow are tied to task switching. • Node metrics and effective information explained functional group differences. • Interactions were correlated with task switching. • The strength of this correlation, however, differed across functional groups. [ABSTRACT FROM AUTHOR]

Background: Circadian clocks allow organisms to anticipate daily fluctuations in their environment by driving rhythms in physiology and behavior. Inter-organismal differences in daily rhythms, called chronotypes, exist and can shift with age. In ants, age, caste-related behavior and chronotype appear to be linked. Brood-tending nurse ants are usually younger individuals and show "around-the-clock" activity. With age or in the absence of brood, nurses transition into foraging ants that show daily rhythms in activity. Ants can adaptively shift between these behavioral castes and caste-associated chronotypes depending on social context. We investigated how changes in daily gene expression could be contributing to such behavioral plasticity in Camponotus floridanus carpenter ants by combining time-course behavioral assays and RNA-Sequencing of forager and nurse brains. Results: We found that nurse brains have three times fewer 24 h oscillating genes than foragers. However, several hundred genes that oscillated every 24 h in forager brains showed robust 8 h oscillations in nurses, including the core clock genes Period and Shaggy. These differentially rhythmic genes consisted of several components of the circadian entrainment and output pathway, including genes said to be involved in regulating insect locomotory behavior. We also found that Vitellogenin, known to regulate division of labor in social insects, showed robust 24 h oscillations in nurse brains but not in foragers. Finally, we found significant overlap between genes differentially expressed between the two ant castes and genes that show ultradian rhythms in daily expression. Conclusion: This study provides a first look at the chronobiological differences in gene expression between forager and nurse ant brains. This endeavor allowed us to identify a putative molecular mechanism underlying plastic timekeeping: several components of the ant circadian clock and its output can seemingly oscillate at different harmonics of the circadian rhythm. We propose that such chronobiological plasticity has evolved to allow for distinct regulatory networks that underlie behavioral castes, while supporting swift caste transitions in response to colony demands. Behavioral division of labor is common among social insects. The links between chronobiological and behavioral plasticity that we found in C. floridanus, thus, likely represent a more general phenomenon that warrants further investigation. [ABSTRACT FROM AUTHOR]

Many parasites have evolved strategies to exploit host behaviour for successful transmission. Ophiocordyceps manipulations of carpenter ant behaviour represent an evident example. Manipulated ants are coerced to ascend vegetation and clamp down their mandibles in a stereotypical 'death-grip' bite. The fungus then kills the ant, sprouts a stalk and releases infective spores. Research has focused on this final manipulation, leaving the subtler behavioural changes prebiting largely unexplored. Field and transcriptome studies found that the host circadian clock, olfaction and communication may be disrupted, which suggests that the fungus is affecting ant foraging activity and effectivity. To test this hypothesis, we investigated if the foraging behaviour of Camponotus floridanus ants is notably affected during early stage Ophiocordyceps infection. Specifically, we used a maze to quantify foraging patterns and trail optimization. Moreover, by comparing infected individuals to healthy ants and those infected with nonmanipulating Beauveria bassiana , we aimed to distinguish between nonmanipulator-specific and manipulator-specific changes. We found that Ophiocordyceps- infected ants became arrhythmic in their activity patterns, were less likely to participate in effective foraging efforts and seemed less able to communicate with their nestmates compared to healthy ants. We hypothesize that these changes in behaviours are adaptive to Ophiocordyceps transmission since they reduce the chance of aggressive interference by nestmates. Indeed, Beauveria -infected individuals remained rhythmic; however, they also seemed to lose their ability to forage optimally, suggesting that, in part, these changes in behaviour might be mere general behavioural side-effects of infection. Overall, this study informs future work on parasitic strategies underlying host manipulation, other parasite–host interactions and the behavioural ecology of infectious diseases in general. • Ophiocordyceps - and Beauveria -infected ants lost the ability to forage effectively. • Both fungi increased locomotion and affected communication behaviours. • Resulting wandering could favour transmission by minimizing nestmate interference. • Ophiocordyceps caused ant hosts to be arrhythmic while Beauveria did not. • Arrhythmicity causes diurnal host activity that could benefit fungal transmission. [ABSTRACT FROM AUTHOR]

A key question in the rising field of neuroepigenetics is how behavioral plasticity is established and maintained in the developing CNS of multicellular organisms. Behavior is controlled through systemic changes in hormonal signaling, cell-specific regulation of gene expression, and changes in neuronal connections in the nervous system, however the link between these pathways is unclear. In the ant Camponotus floridanus, the epigenetic corepressor CoREST is a central player in experimentally-induced reprogramming of caste-specific behavior, from soldier (Major worker) to forager (Minor worker). Here, we show this pathway is engaged naturally on a large genomic scale during late pupal development targeting multiple genes differentially expressed between castes, and central to this mechanism is the protein tramtrack (ttk), a DNA binding partner of CoREST. Caste-specific differences in DNA binding of ttk co-binding with CoREST correlate with caste-biased gene expression both in the late pupal stage and immediately after eclosion. However, we find a unique set of exclusive Minor-bound genes that show ttk pre-binding in the late pupal stage preceding CoREST binding, followed by caste-specific gene repression on the first day of eclosion. In addition, we show that ttk binding correlates with neurogenic Notch signaling, and that specific ttk binding between castes is enriched for regulatory sites associated with hormonal function. Overall our findings elucidate a pathway of transcription factor binding leading to a repressive epigenetic axis that lies at the crux of development and hormonal signaling to define worker caste identity in C. floridanus. Author summary: The ability to dynamically adapt behavior in response to a variable environment is one of the hallmarks of complex life. Ants provide an excellent system within which to explore the molecular mechanisms governing such behavioral plasticity in the context of complex societies. We find that in the Florida Carpenter Ant C. floridanus two members of a known repressive complex, CoREST and ttk, are predictive of early-life gene expression differences between Major and Minor workers, which display vastly different behaviors. Furthermore, we find that ttk shows a signal of poising genes in the late pupal stage for repression via CoREST upon eclosion, illustrating an order of operations in the establishment of distinct behaviors that distinguish these two worker types. Regions bound by ttk in Minor but not Major workers also show enrichment for sequence motifs associated with hormonal regulation, implying involvement of ttk-mediated repression in attenuating hormonal signaling between castes. Given that differences in hormone signaling between castes have been seen in multiple social insects our results provide evidence of a chromatin bridge between hormones and behavior in a complex social organism. [ABSTRACT FROM AUTHOR]

Aim: Extrafloral nectar, a carbohydrate‐rich liquid, is the main plant‐based resource offered in exchange for ant protection. The positive results of this protection provided by ants are widely studied and supported; however, studies showing the benefits that ants and their colonies have from the resources offered by plants such as extrafloral nectar are scarce. Here, we evaluated how extrafloral nectar and artificial food resources with different nutrient concentration benefit short‐ and long‐term Camponotus crassus colony fitness (number and weight of individuals) and survival. Methods: We conducted two sets of experiments: (1) in the field we attached artificial ant nests to plants with clogged and unclogged extrafloral nectaries; and (2) in the laboratory we offered artificial food resources with different carbohydrate–protein ratios to ant colonies. With these experiments, we evaluated the number and weight of queens, adult workers, pupae, larvae, and eggs, as well as the survival probability of the colonies. Results: In the first experiment, the short‐term provision of extrafloral nectar resulted in a larger number and weight of individuals with access to this resource. In the second experiment, regardless of time, the supply of more concentrated carbohydrate and nitrogen food increased ant colony fitness and survival. Conclusion: We provided new evidence that extrafloral nectar significantly benefits ant colonies. Our results corroborate the assertion that these relationships are reciprocally beneficial. [ABSTRACT FROM AUTHOR]

Carpenter ants (genus Camponotus) are considered to be predominantly omnivorous, mixing several feeding habits that include predation, scavenging of animal matter, and plant-derived resources. Nitrogen acquisition is crucial for the nutritional ecology of ant colonies because growing larvae require sustainable protein provisioning. Here, we investigate the foraging ecology and the spatial nesting structure of the carpenter ant, Camponotus leydigi Forel, in Brazilian cerrado savanna. By marking workers from different nests with distinct colors, we revealed that C. leydigi occupies physically separated but socially connected nests (up to 30 m apart), a phenomenon known as polydomy. Observational data on aboveground internest movements in C. leydigi corroborate cooperative exchanges between nest units and confirm several types of social connections, including internest transfer of liquid and solid food, transport of colony members (brood, workers), movement of solitary workers, and internest recruitment. Polydomous C. leydigi allocate foragers throughout 1,700 m2, feeding mostly on termites and plant-derived exudates. Influx of exudates is threefold higher compared with solid food. Uric acid pellets excreted by lizards comprise 20% of the solid diet in C. leydigi , a rare quantitative assessment of this peculiar type of nitrogen complementation in ants. Based on video recordings, we hypothesize that nest decentralization in C. leydigi may reduce foraging constraints caused by overt interference by the aggressive ant, Ectatomma brunneum Smith, F. (Hymenoptera: Formicidae), which regularly blocks nest entrances. Our field study enhances the importance of natural history data to clarify selective pressures underlying the evolution of particular behavioral patterns (nutritional and nesting habits) in ants. [ABSTRACT FROM AUTHOR]

Ant-infecting Ophiocordyceps fungi are globally distributed, host manipulating, specialist parasites that drive aberrant behaviors in infected ants, at a lethal cost to the host. An apparent increase in activity and wandering behaviors precedes a final summiting and biting behavior onto vegetation, which positions the manipulated ant in a site beneficial for fungal growth and transmission. We investigated the genetic underpinnings of host manipulation by: (i) producing a high-quality hybrid assembly and annotation of the Ophiocordyceps camponoti-floridani genome, (ii) conducting laboratory infections coupled with RNAseq of O. camponoti-floridani and its host, Camponotus floridanus, and (iii) comparing these data to RNAseq data of Ophiocordyceps kimflemingiae and Camponotus castaneus as a powerful method to identify gene expression patterns that suggest shared behavioral manipulation mechanisms across Ophiocordycepsant species interactions. We propose differentially expressed genes tied to ant neurobiology, odor response, circadian rhythms, and foraging behavior may result by activity of putative fungal effectors such as enterotoxins, aflatrem, and mechanisms disrupting feeding behaviors in the ant. [ABSTRACT FROM AUTHOR]

Ant feeding interactions (i.e., trophallaxis events) are thought to regulate the flow of nutrients and disease within a colony. Consequently, there is great interest in learning which environmental and behavioral factors drive ant trophallaxis. In this paper, we analyze ant trophallaxis behavior in a colony of 73 carpenter ants, observed at 1-s intervals over a period of 4 h. The data represent repeated observations from a dynamic contact network; however, traditional statistical analyses of network models are ill-suited for data observed at such high temporal resolution. We present a model for high-resolution longitudinal network data, where the network is assumed to be a time inhomogeneous, continuous-time Markov chain, with transition rates modeled as a function of time-varying individual and pairwise biological covariates. In particular, the high temporal resolution of the data leads to a tractable likelihood function, and likelihood-based inference procedures are utilized to explain which biological factors drive contact. Our results reveal how differences in ant social castes and individual behaviors, such as ant speed and activity levels, influence patterns of ant trophallaxis in the colony. Supplementary materials accompanying this paper appear online. [ABSTRACT FROM AUTHOR]

[Objectives] The sublethal effects of thiamethoxam, a neonicotinoid insecticide, were evaluated on the foraging and discrimination behaviors of the ant Camponotus japonicus, with special attention on the indirect effects through individual communication among ants. [Methods] By simulating the foraging situation, the change of foraging ability of ant in different treated groups was observed. Through the Y-tube test and EAG(electroantennography) test, the ability of different treated groups of ants to the nestmates and non-nestmates was observed. Based on the changes in the discrimination ability, the ability of different treatment groups of ants to discriminate the heterologous ants was observed in the aggressive behavior test. [Results] There was no significant difference in the ability of different treated ants to find food, but there was a difference in foraging efficiency. The control ants performed recruiting behavior, while the indirectly treated ants and the directly treated ants did not. The control ants showed difference to indirectly treated ants and directly treated ants in discriminating the nestmates and non-nestmate, the control ants could discriminate the non-mates well, but the others couldn’t discriminate the non-nestmates well. When discriminating the nestmates, there was no significant difference among different treated ants. In the attack tests, the direct treatment with sublethal thiamethoxam remarkably reduced the aggressive behavior when compared to the control ants. However, the aggressive behavior of indirectly treated ants showed no significant differences from control and directly treated ants. [Conclusions] The sublethal thiamethoxam can directly affect the foraging and discrimination ability of the ants. Through the communications between the ants, the directly treated ants can deliver these negative effects to others which have not been directly exposed to insecticides. The treated ants affect the development of colony of the ants. [ABSTRACT FROM AUTHOR]

Insect societies are often composed of many individuals, achieving collective decisions that depend on environmental and colonial characteristics. For example, ants are able to focus their foraging effort on the most rewarding food source. While this phenomenon is well known, the link between the food source quality and the intranidal food dissemination networks and its dynamics has been neglected. Here, we analysed the global dynamics of food dissemination in Camponotus cruentatus workers, after feeding on a low (0.1 mol l-1) or on a high (1 mol l-1) sucrose concentration food source. We also analysed the trophallaxis activity at the individual level and built the complete network of trophallaxis. The results reveal that the dynamics of food dissemination and the structure of the trophallaxis network are robust and independent of the food concentration. We discuss these results in the light of recent advances in the study of efficiency in food management in ants. [ABSTRACT FROM AUTHOR]

Colony coherence is essential for eusocial insects because it supports the inclusive fitness of colony members. Ants quickly and reliably recognize who belongs to the colony (nestmates) and who is an outsider (non-nestmates) based on chemical recognition cues (cuticular hydrocarbons: CHCs) which as a whole constitute a chemical label. The process of nestmate recognition often is described as matching a neural template with the label. In this study, we tested the prevailing view that ants use commonalities in the colony odor that are present in the CHC profile of all individuals of a colony or whether different CHC profiles are learned independently. We created and manipulated sub-colonies by adding one or two different hydrocarbons that were not present in the original colony odor of our Camponotus floridanus colony and later tested workers of the sub-colonies in one-on-one encounters for aggressive responses. We found that workers adjust their nestmate recognition by learning novel, manipulated CHC profiles, but still accept workers with the previous CHC profile. Workers from a sub-colony with two additional components showed aggression against workers with only one of the two components added to their CHC profile. Thus, additional components as well as the lack of a component can alter a label as “non-nestmate.” Our results suggest that ants have multiple-templates to recognize nestmates carrying distinct labels. This finding is in contrast to what previously has been proposed, i.e., a widening of the acceptance range of one template. We conclude that nestmate recognition in ants is a partitioned (multiple-template) process of the olfactory system that allows discrimination and categorization of nestmates by differences in their CHC profiles. Our findings have strong implications for our understanding of the underlying mechanisms of colony coherence and task allocation because they illustrate the importance of individual experience and task associated differences in the CHC profiles that can be instructive for the organization of insect societies. [ABSTRACT FROM AUTHOR]

Many arthropods mimic ants to avoid predation risk from visual predators. Our study of ant-mimicking arthropod diversity revealed 10 sympatric myrmecomorphs including spiders, mantids, bugs and grasshoppers. All, except one, were found predominantly on extrafloral nectary-bearing and homopteran harbouring plants. Of the five plant-visiting ant species, Camponotus compressus, Camponotus paria, Camponotus sericeus, Crematogaster subnuda and Tapinoma melanocephalum, only C. compressus showed significantly high occurrence and abundance on these plants. Except for a small spider morph, the remaining nine myrmecomorphic species resembled C. compressus and apparently use this common and abundant ant species as their model. [ABSTRACT FROM AUTHOR]

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Plants bearing extrafloral nectaries ( EFNs) vary the secretion of nectar between day and night, which creates turnover in the composition of interacting ant species. Daily variation in the composition of ant species foraging on vegetation is commonly observed, but its mechanisms are poorly understood. We evaluated the daily variation in nectar availability and interspecific aggressiveness between ants as possible regulatory mechanisms of the turnover in ant-plant interactions. We hypothesized that (i) plants would interact with more ant species during periods of higher secretion of nectar and that (ii) aggressive ant species would compete for nectar, creating a daily turnover of species collecting nectar. We tested this hypothesis by measuring the production of nectar during the day and night and by experimentally removing EFNs of Bionia coriacea (= Camptosema coriaceum) (Nees & Mart.) Benth. (Fabaceae: Faboideae) plants in a Brazilian savanna (Cerrado). We then compared the abundance and composition of ant species between those treatments and during the day. Our results indicate that more ant workers forage on plants during the day, when nectar was sugary, while more ant species forage at night, when aggressiveness between ant species was lower. We also detected a day/night turnover in ant species composition. Ant species foraging for nectar during the day were not the same at night, and this turnover did not occur on plants without EFNs. Both dominant ant species, diurnal Camponotus crassus (Hymenoptera: Formicidae) and nocturnal Camponotus rufipes (Hymenoptera: Formicidae), were the most aggressive species, attacking other ants in their specific periods of forage while also being very aggressive toward each other. However, this aggressiveness did not occur in the absence of nectar, which allowed non-aggressive nocturnal ant species to forage only during the daytime, disrupting the turnover. We conclude that extrafloral-nectar presence and interspecific aggressiveness between ants, along with other environmental factors, are important mechanisms creating turnovers in ants foraging on plants. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of the distance between two exits on ant evacuation efficiency and the behavior of ants escaping from a two-exit room, we conducted ant egress experiments using Camponotus japonicus in multiple situations. We found that the ants demonstrated the phenomenon of “symmetry breaking” in this stress situation. It was also shown that different locations for the exits obviously affected the ants’ egress efficiency by measuring the time intervals between individual egress and flow rate in eight repeated experiments, each of which contained five different distance between the two exits. In addition, it is demonstrated that there are differences between the predictions of Social Force Model of pedestrians and the behaviors of ants in stress conditions through comparing some important behavioral features, including position, trajectory, velocity, and density map. [ABSTRACT FROM AUTHOR]

The labial gland is a major exocrine gland in the thoracic cavity of ants, which is connected to the mouth area and opens at the base of the labium. The labial gland in the various castes and males of Camponotus japonicus were examined using dissection, light microscopy, scanning and transmission electron microscopy. Our findings reveal clear caste differences in the appearance of the labial gland, and suggest a relationship between gland structure and its behavioral role in queens, males and workers: queens possess the largest reservoir sac; males have the smallest; workers have abundant secretion droplets in the gland cells of the tubules; epithelial thickness of gland cells varies considerably between workers and reproductive ants. The apical cell region has a high density of microvilli and polymorphic mitochondria, whereas the central cell region is rich in rough endoplasmic reticulum (RER) which means its main secretions are proteinaceous compounds. We believe that the labial gland has a different function in the castes of C. japonicus : the gland of workers and queens may be used to feed the larvae; workers participate in trophallaxis in the nest, while the males are not involved in these activities. Calculations of the relative size of the labial gland for each caste and males indicated that minor workers have the relative highest developed labial gland, supporting a role in trophallaxis. In addition, we found a phenomenon of enlarged labial gland in minor workers, which accounted for almost 22%, but the reason for this is unknown. [Display omitted] • Comparative morphology and ultrastructure of the labial gland among castes of Camponotus japonicus. • Found the phenomenon of enlarged labial gland in minor workers, which accounted for almost 22%. • Queens possess the largest reservoir sac and males have the smallest. • Minor workers have the relative highest developed labial gland. [ABSTRACT FROM AUTHOR]

The prepharyngeal gland (prePG) and pharyngeal gland (PG) make up the largest exocrine structures in the head of the ant Camponotus japonicus. We used microscopy to study the histological and ultrastructural features of both glands in different castes. The number of secretory units in the prePG is considerably higher than in other ant species and shows a complex duct system which is made up by duct cells, secondary ducts and a main duct. These lead the secretions of hundreds to thousands of secretory cells into the prepharynx through a modified sieve plate at each side. The glove-shaped PG shows clear caste differences in tubule number. The ultrastructure of both the prePG and PG shows abundant mitochondria and secretion vesicles. Moreover, the prePG is loaded with rough endoplasmic reticulum (RER) which means its main secretions are proteinaceous compounds, while the PG is dominated by smooth endoplasmic reticulum (SER) which means the main secretions are lipids. The morphological differences like cell number of the prePG and tubule number of the PG indicate different secretory abilities of each caste. We for the first time introduce histology-based relative size to indicate secretory activity. The proportionally high development of the prePG in minor workers supports a role in trophallaxis. • Morphology and ultrastructure of the prepharyngeal and pharyngeal glands in the ant Camponotus japonicus. • The first time to report the complex duct system in prepharyngeal gland. • Introduced a precise histology-based gland volume measurement method to study the relative size of class-3 glands. [ABSTRACT FROM AUTHOR]

Myrmecophily is widespread in lycaenid butterflies, in which ants receive food resources and, in turn, protect caterpillars against natural enemies. This interaction ranges from obligate myrmecophily, in which immatures are invariably associated with ants and are dependent on ants for survival, and facultative myrmecophily, in which larvae are not dependent on ants for survival, but the presence of the latter may increase larvae survival. Lycaenids also include non-myrmecophilous butterflies, which do not have positive associations with ants and have developed strategies to avoid being attacked or preyed upon by them. In this study, we examined the relationship between the lycaenid Michaelus ira and two ant species associated with Distictella elongata (Bignoniaceae). This plant has extrafloral nectaries and is patrolled by Camponotus crassus and Ectatomma tuberculatum. Morphological analyses revealed that M. ira larvae have ant organs, such as dorsal nectary organs and perforated cupolas, structures associated with myrmecophily. We performed larval exposure experiments in the field, predicting that, in the absence of myrmecophily, the butterfly larva would present strategies to avoid ant attack. Results showed that larvae were attacked by both ant species. To escape ant molestation, larvae lived and fed inside silk-sealed D. elongata flower buds. We concluded that the M. ira bud-sheltering behavior was a defensive strategy against these ant species, while the dorsal nectary organs were apparently nonfunctional. Nonetheless, myrmecophily, in general, cannot be excluded in M. ira since relationships with other ant species may exist. [ABSTRACT FROM AUTHOR]

In many ant species, sibling larvae follow alternative ontogenetic trajectories that generate striking variation in morphology and behavior among adults. These organism-level outcomes are often determined by environmental rather than genetic factors. Therefore, epigenetic mechanisms may mediate the expression of adult polyphenisms. We produced the first genome-wide maps of chromatin structure in a eusocial insect and found that gene-proximal changes in histone modifications, notably H3K27 acetylation, discriminate two female worker and male castes in Camponotus floridanus ants and partially explain differential gene expression between castes. Genes showing coordinated changes in H3K27ac and RNA implicate muscle development, neuronal regulation, and sensory responses in modulating caste identity. Binding sites of the acetyltransferase CBP harbor the greatest caste variation in H3K27ac, are enriched with motifs for conserved transcription factors, and show evolutionary expansion near developmental and neuronal genes. These results suggest that environmental effects on caste identity may be mediated by differential recruitment of CBP to chromatin. We propose that epigenetic mechanisms that modify chromatin structure may help orchestrate the generation and maintenance of polyphenic caste morphology and social behavior in ants. [ABSTRACT FROM AUTHOR]

Abstract: A virgin ant queen has only one opportunity in her lifetime to realize her reproductive fitness when she leaves her nest for a mating flight. After successful mating she sheds her wings, excavates a nest and starts laying eggs to initiate her own colony. Here we report the results of our study on two related species of Camponotus ants – day active Camponotus paria and night active Camponotus compressus – aimed at investigating (i) if there exist inter-species differences in the activity and phototactic behaviors of males and queens, (ii) whether these behaviors in the queen change after mating, and (iii) whether the activity rhythm of queens changes with age. We find that while activity profiles differ between C. paria and C. compressus virgin males and queens, such differences in queens disappear after mating. Once mated, the activity rhythm of queens shows little change with age; the rhythm in virgin queens, on the other hand, changes considerably. As virgins, C. paria queens are positively phototactic, while C. compressus queens are negatively phototactic. After mating, C. paria queens become less phototactic, particularly during the subjective night, while C. compressus queens remain negatively phototactic. These results indicate that there are considerable differences in the activity and phototactic behaviors of virgin queens of the two related species of Camponotus ants. Most of these differences disappear after mating, which suggests that these behaviors may have evolved primarily for the proper execution of pre-mating events. [Copyright &y& Elsevier]

Abstract: Feeding behaviour is a complex functional system that relies on external signals and the physiological state of the animal. This is also the case in ants as they vary their feeding behaviour according to food characteristics, environmental conditions and – as they are social insects – to the colony’s requirements. The biogenic amine serotonin (5-HT) was shown to be involved in the control and modulation of many actions and processes related to feeding in both vertebrates and invertebrates. In this study, we investigated whether 5-HT affects nectar feeding in ants by analysing its effect on the sucking-pump activity. Furthermore, we studied 5-HT association with tissues and neuronal ganglia involved in feeding regulation. Our results show that 5-HT promotes a dose-dependent depression of sucrose feeding in Camponotus mus ants. Orally administered 5-HT diminished the intake rate by mainly decreasing the volume of solution taken per pump contraction, without modifying the sucrose acceptance threshold. Immunohistochemical studies all along the alimentary canal revealed 5-HT-like immunoreactive processes on the foregut (oesophagus, crop and proventriculus), while the midgut and hindgut lacked 5-HT innervation. Although the frontal and suboesophageal ganglia contained 5-HT immunoreactive cell bodies, serotonergic innervation in the sucking-pump muscles was absent. The results are discussed in the frame of a role of 5-HT in feeding control in ants. [Copyright &y& Elsevier]

The article presents research which assessed the effect of prophylaxis and trophallaxis on the social immunity in the Camponotus pennsylvanicus or the carpenter ant. The researchers examined the various related aspects of the increased antimicrobial activity of the species caused by the enhanced trophallactic behavior. They found that the protein cathepsin D contributes to such activity of the ant.

Recognition of group members is of fundamental importance in social animals, allowing individuals to protect resources against intruders and parasites, as well as ensuring social cohesion within the group. In ants and other social insects, social recognition relies on multicomponent chemical signatures, composed primarily of long-chain cuticular hydrocarbons. These signatures are colony specific and allow discrimination between nestmates and non-nestmates. Nevertheless, the mechanisms underlying detection, perception and information processing of chemical signatures are poorly understood. It has been suggested that associative learning might play a role in nestmate recognition. We investigated whether Camponotus aethiops ants can associate a complete cuticular hydrocarbon profile, consisting of about 40 compounds, with a food reward and whether the new association, developed in an appetitive context, affects aggression against non-nestmates carrying the hydrocarbon profile associated with food. Individual ant workers were able to associate the non-nestmate chemical profile with food. However, conditioned ants were still aggressive when encountering a non-nestmate carrying the odour profile used as training odour in our experiments. This suggests that ants, like some, but not all other insects, show interactions between different modalities (i.e. olfactory and visual), and can treat complex chemical cues differently, according to the context in which they are perceived. This plasticity ensures that learning in an appetitive context does not interfere with the crucial task of colony defence. [ABSTRACT FROM AUTHOR]

Interspecific rivalry among higher animals is not uncommon. However, it is less noticed among invertebrates, which function at micro ecological levels. One such incident was encountered by the authors in an old, neglected mango orchard on the outskirts of Bengaluru, India, between two species of ants, Camponotus compressus Fabricius and Oecophylla smaragdina Fabricius. While these two spatially co-existed and foraged in the orchard, rivalry was found on three trees which harboured arboreal O. smaragdina nests, where C. compressus (a ground nester) also began nesting at the base of the tree. Foragers of O. smaragdina while descending the tree trunks found C. compressus at the base of the tree an intrusion (or vice versa?) and interspecific rivalry ensued for nearly seven weeks leading to mortality in both species. Overall, O. smaragdina suffered six times more loss in terms of number and biomass, but prevailed over C. compressus. The latter was forced to abandon nesting. It is important to record such interspecific processes, in insects at a micro ecological level. [ABSTRACT FROM AUTHOR]

Weaver ants use silk produced by their larvae to build their nests. This behaviour is one of the more notable instances of social cooperation in animals; however, there are few studies of Brazilian species. This study investigated the ecology, natural history and behaviour of the weaver ant Camponotus (Myrmobrachys) senex in Brazil and showed that the weaver larvae have a fundamental function in nest building. The nests were always arboreal (one nest/plant), with a round form, beige in colour, and with leaves and shoots adhered to the silk nest. The average size was 34.24 cm and the average weight was 163.87 g; nests contained up to 50,000 individuals and several queens. Fusion and fission of colony parts were observed for C. senex. Worker ants were frequently observed feeding on honeydew, fruits and insects; and defended their territory. We suggest that C. senex larvae could be considered an effective caste, valuable in nest construction. [ABSTRACT FROM AUTHOR]

Abstract: Modulation of liquid feeding-rate would allow insects to ingest more food in the same time when this was required. Ants can vary nectar intake rate by increasing sucking pump frequency according to colony requirements. We analysed electrical signals generated by sucking pump activity of ants during drinking solutions of different sucrose concentrations and under different carbohydrate-deprivation levels. Our aim was to define parameters that characterize the recordings and analyse their relationship with feeding behaviour. Signals showed that the initial and final frequencies of sucking pump activity, as well as the difference between them were higher in sugar-deprived ants. However, these parameters were not influenced by sucrose solution concentration, which affected the number of pump contractions and the volume per contraction. Unexpectedly, we found two different responses in feeding behaviour of starved and non-starved ants depending on concentration. Starved ants drank dilute solutions for the same length of time as non-starved ants but ingested higher volumes. While drinking the concentrated solutions, starved ants drank the same volume, but did so in a shorter time than the non-starved ones. Despite these differences, for each analysed concentration the total number of pump contractions remained constant independently of sugar-deprivation level. These results are discussed in the frame of feeding regulation and decision making in ant foraging behaviour. [Copyright &y& Elsevier]

We studied olfactory learning in two ant species, Camponotus mus from Argentina and Camponotus fellah from Israel. To this end, we established an experimental laboratory protocol in which individual ants were trained to associate odours with gustatory reinforcers. Ants were trained individually to forage in a Y-maze in which two odours had to be discriminated. One odour was positively reinforced with sucrose solution and the other was negatively reinforced with quinine solution. After a training session of 24 trials, ants of both species learned to differentiate the two odour pairs, the structurally dissimilar limonene and octanal, and the structurally similar heptanal and 2-heptanone. In nonreinforced tests, ants consistently chose the odour previously reinforced with sucrose solution and spent more time searching in the arm of the maze presenting this odour. Learning performances were more robust in the case of limonene versus heptanal. These results thus show for the first time that individual ants perceive and learn odours in controlled laboratory conditions. [Copyright &y& Elsevier]

Comparison of closely related species that differ in their life histories is a powerful method for studying the underlying physiological mechanisms contributing to life-history variation. I investigated whether two closely related members of the Camponotus festinatus species complex of desert carpenter ants, C. nr. festinatus Desert Light and C. nr. festinatus Desert Dark, differed in their life-history tactics with respect to fat storage. Newly mated queens were collected in the field, and colonies were reared under common conditions in the laboratory for 2 yr before sampling. I show that the two species differ in fat storage at the individual level. While the basic scaling relationship between lean mass and fat content did not differ between the two species, Dark workers and soldiers stored significantly more fat per unit lean mass than Light workers or soldiers. There were no significant demographic differences in the proportions of workers or soldiers involved in fat storage between the two species, although there was a trend toward Light colonies having a greater proportion of soldiers storing large amounts of fat. There was also no significant difference in the total amount of fat stored by the two species at the colony level. The detection of strong individual-level effects but no colony-level effects was likely due to the low statistical power of colony-level analyses. Showing that these two closely related species differ in fat storage at the individual level in a common environment demonstrates their utility as a model for understanding the physiological and behavioral mechanisms regulating life-history variation in fat storage in ants. [ABSTRACT FROM AUTHOR]

In social insects, colonies commonly show temporal polyethism in worker behavior, such that a worker follows a predictable pattern of changes between tasks as it ages. This pattern usually leads from workers first doing a safe task like brood care, to ending their lives doing the most dangerous tasks like foraging. Two mechanisms could potentially underlie this pattern: (1) age-based task allocation, where the aging process itself predisposes workers to switch to more dangerous tasks; and (2) foraging for work, where ants switch to tasks that need doing from tasks which have too many associated workers. We tested the relative influence of these mechanisms by establishing nests ofCamponotus floridanuswith predetermined combinations of workers of known age and previous task specialization. The results supported both mechanisms. Nests composed of entirely brood-tending workers had the oldest workers preferentially switching to foraging. However, in nests initially composed entirely of foragers, the final distribution of tenders and foragers was not different from random task-switching and therefore supportive of foraging for work. Thus, it appears that inC. floridanusthere is directionality to the mechanisms of task allocation. Switching to more dangerous tasks is age-influenced, but switching to less dangerous tasks is age-independent. The results also suggest that older workers are more flexible in their task choice behavior. Younger workers are more biased towards choosing within-nest tasks. Finally, there are effects of previous experience that tend to keep ants in familiar tasks. Task allocation based on several mechanisms may balance between: (1) concentrating the most worn workers into the most dangerous tasks; (2) increasing task performance levels; and (3) maintaining behavioral flexibility to respond to demographic perturbations. The degree to which behavior is flexible may correlate to the frequency of such perturbations in a species. [ABSTRACT FROM AUTHOR]

Ants acquire distinct morphological and behavioral phenotypes arising from a common genome, underscoring the importance of epigenetic regulation. In Camponotus floridanus , "Major" workers defend the colony, but can be epigenetically reprogrammed to forage for food analogously to "Minor" workers. Here, we utilize reprogramming to investigate natural behavioral specification. Reprogramming of Majors upregulates Minor-biased genes and downregulates Major-biased genes, engaging molecular pathways fundamental to foraging behavior. We discover the neuronal corepressor for element-1-silencing transcription factor (CoREST) is upregulated upon reprogramming and required for the epigenetic switch to foraging. Genome-wide profiling during reprogramming reveals CoREST represses expression of enzymes that degrade juvenile hormone (JH), a hormone elevated upon reprogramming. High CoREST, low JH-degrader expression, and high JH levels are mirrored in natural Minors, revealing parallel mechanisms of natural and reprogrammed foraging. These results unveil chromatin regulation via CoREST as central to programming of ant social behavior, with potential far-reaching implications for behavioral epigenetics. • Reprogrammed worker ant behavior mirrors natural programming via an epigenetic switch • Neuronal co-repressor CoREST mediates this behavioral programming and reprogramming • CoREST controls genes that then govern levels of foraging-promoting JH Glastad et al. find that epigenetic regulation is pivotal in mediating programming and reprogramming of worker ant behavior. The conserved neuronal co-repressor CoREST, working with histone deacetylation, is vital in establishing foraging behavior via binding to and repressing genes that degrade JH, a behaviorally mportant hormone promoting foraging. [ABSTRACT FROM AUTHOR]