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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]

For centuries, it has been understood that the final size of adult holometabolous insects is determined by the end of the larval stage, and that once they transform to adults, holometabolous insects do not grow. Despite this, no previous study has directly tested these "old truths" across holometabolous insects. Here, we demonstrate that final adult size is set at the end of the last larval stage in species representing each of the four orders of holometabolous insects: the fruit fly Drosophila melanogaster (Diptera), the tobacco hornworm Manduca sexta (Lepidoptera), the dung beetle Onthophagus taurus (Coleoptera), and the Florida carpenter ant Camponotus floridanus (Hymenoptera). Furthermore, in both D. melanogaster and C. floridanus, we show that the size of adult individuals fluctuates but does not significantly change. Therefore, our study finally confirms these two basic assumptions in the biology of insects, which have for centuries served as the foundation for studies of insect growth, size, and allometry. Research Highlights: Our research confirms an age‐old assumption in holometabolous insects: the body size of terminal larvae highly correlates with the body size of adults.Our research also confirms that, during the adult stage, insects fluctuate in size but do not undergo significant growth. [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]

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]

Ants provide protection to various organisms via myrmecophilous relationships. Most notably, ants and several butterfly species are involved in mainly mutualistic interactions. Previous field studies have shown that butterfly larval survival is increased in the presence of tending ants, suggesting that ants are providing protection against insect predation or parasitism. Here, we conducted a series of timed observational trials under laboratory conditions to assess larval survival and ant protection from insect predators for a myrmecophilous lycaenid butterfly. We focused on a critically endangered butterfly, the Miami blue (Cyclargus thomasi bethunebakeri) (Comstock and Huntington) (Lepidoptera: Lycaenidae), and its most common ant associate, the Florida carpenter ant (Camponotus floridanus) (Buckley) (Hymenoptera: Formicidae), to test this assumption of ant protection. We found that ants provide significant protection to Miami blue larvae, with later instar larvae receiving a higher level of protection due to differences in tending frequencies. These results will aid in informing conservation management and future organism reintroductions for this endangered butterfly. [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]

Camponotus planatus Roger (Hymenoptera: Formicidae) is a broadly distributed New World carpenter ant. Here, I document the geographic distribution of C. planatus and consider evidence concerning where this species may be native, particularly whether it is native to Florida. To evaluate the distribution of C. planatus, I compiled and mapped specimen records from >1500 sites. Although, C. planatus was originally described from Cuba, it remains uncertain whether it is native or exotic there. In addition to scattered records across tropical South America, C. planatus shows a largely continuous continental distribution from Panama through Central America and Mexico to southeastern Texas. Across this continental range, C. planatus shows notable color variation, suggesting that it is native to this region. In Texas, C. planatus records dating to before 1980 are spread across most of its known range. However, eight of the nine northernmost records date to 2014 or later, including all six records from the Houston area in East Texas. This pattern suggests that C. planatus is native to Texas, but populations there appear to have recently expanded, perhaps due to climate change. Camponotus planatus populations in Florida, the Bahamas, and Mississippi are probably non-native. In Florida, C. planatus was first found in Key West in 1887, but populations appear to have greatly expanded, particularly since 1980, and now extend as far north as Jacksonville. Due to continued climate change, C. planatus may soon be able to extend its range all along the Gulf coast from Texas to Florida. [ABSTRACT FROM AUTHOR]

The tawny crazy ant (Nylanderia fulva) is a new invasive pest in the United States. At present, its management mainly relies on the use of synthetic insecticides, which are generally ineffective at producing lasting control of the pest, necessitating alternative environmentally friendly measures. In this study, we evaluated the feasibility of gene silencing to control this ant species. Six housekeeping genes encoding actin (NfActin), coatomer subunit β (NfCOPβ), arginine kinase (NfArgK), and V‐type proton ATPase subunits A (NfvATPaseA), B (NfvATPaseB) and E (NfvATPaseE) were cloned. Phylogenetic analysis revealed high sequence similarity to homologs from other ant species, particularly the Florida carpenter ant (Camponotus floridanus). To silence these genes, vector L4440 was used to generate six specific RNAi constructs for bacterial expression. Heat‐inactivated, dsRNA‐expressing Escherichia coli were incorporated into artificial diet. Worker ants exhibited reduced endogenous gene expression after feeding on such diet for 9 d. However, only ingestion of dsRNAs of NfCOPβ (a gene involved in protein trafficking) and NfArgK (a cellular energy reserve regulatory gene in invertebrates) caused modest but significantly higher ant mortality than the control. These results suggest that bacterially expressed dsRNA can be orally delivered to ant cells as a mean to target its vulnerabilities. Improved efficacy is necessary for the RNAi‐based approach to be useful in tawny crazy ant management. [ABSTRACT FROM AUTHOR]

When resources in a territory have a patchy distribution, intruders may successfully exploit unguarded patches. In such cases, territory owners may use exploitative strategies to reduce the gains of the intruders. The territorial ant Camponotus floridanus attends the leaf nectaries of Urena lobata, which are also visited by the ant Pseudomyrmex mexicanus and other intruders. Residents visited the nectaries at a high rate and in a systematic way, and thereby depressed the mean standing crop per nectary. This reduces the gains of randomly visiting intruders which obtain the mean standing crop per nectary visit. Two or three residents were present on large plants and kept the mean standing crop at the same low level as at small plants with a single ant. This is an ideal free distribution of the ants. The resident ants visited the nectaries at a rate which increased in proportion to the nectar production per nectary. This is the expected systematic visitation when nectar production varies between nectaries. It is suggested that systematic visitation and maximization of the visitation rate are evolutionarily stable strategies in both residents and intruders. However, the intruders are constrained by the residents, so that they visit the nectaries less frequently and in a random manner, and thus have a lower gain rate. When the resident was temporarily absent, the intruders visited the nectaries at a high rate and systematically. [ABSTRACT FROM AUTHOR]

The colony and population structure of the carpenter ant, Camponotus floridanus, were investigated by multilocus DNA fingerprinting using simple repeat motifs as probes [e.g. (GATA)4]. The mating frequency of 15 queens was determined by comparing the fingerprint patterns of the queen and 17-33 of her progeny workers. C. floridanus queens are most probably singly mated, i.e. this species is monandrous and monogynous (one queen per colony). C. floridanus occurs in all counties of mainland Florida and also inhabits most of the Key islands in the southern part of Florida. We tested whether the two mainland populations and the island populations are genetically isolated. Wright's FsT and Nei's D-value of genetic distance were calculated from intercolonial bandsharing-coefficients. The population of C. floridanus is substructured (Fst .0.19 ± 0.09) and the highest degree of genetic distance was found between one of the mainland populations and the island populations (D = 0.35). Our fingerprinting technique could successfully be transferred to 12 other Camponotus species and here also revealed sufficient variability to analyse the genetic structure. In three of these species (C. ligniperdus, C. herculeanus and C. gigas) we could determine the mating frequency of the queen in one or two colonies, respectively. [ABSTRACT FROM AUTHOR]

An established population of a Neotropical carpenter ant, Camponotus novogranadensis Mayr, is reported from Estero, Lee County, Florida. This species is similar in general appearance to C. planatus Roger, differing in color, pilosity, and clypeal shape. Camponotus novogranadensis is known from disturbed sites in Mexico, Central and South America; it has not previously been reported established outside its presumed native range. It is not known to cause economic or ecological problems. [ABSTRACT FROM AUTHOR]