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Exocrine glands are important mediators of communication in eusocial insects and the description of novel glands reflects the complex context in which these animals live. Here we revisit the head-associated glands in workers of the Neotropical termite Cornitermes cumulans through histological analysis and describe a novel gland for this caste, the intramandibular glands. This structure is located underneath the cuticle of the dorsodistal part of each mandible. The glands showed an epithelial arrangement, but the cytological morphology is complex, comprising classes I and III of secretory cells. The present data highlight the importance of the intramandibular glands in the worker caste and demonstrate different morphology of these glands in Isoptera, probably related to the specialized function of the castes. Features of active glandular activity were also observed in the mandibular, labral, and salivary glands of these workers. Despite the intramandibular glands being also found in workers of other social insects, their occurrence in termites was restricted to the soldier caste of Machadotermes. Even so, their cytological structure differs from those of C. cumulans workers. The likely function of the worker intramandibular glands is discussed considering the separate-nest life type present by C. cumulans and tasks performed by workers. The chemical nature of the secretion and the occurrence of the glands in other termite taxa still require further investigation., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Social insects have developed a broad diversity of nesting and foraging strategies. One of these, inquilinism, occurs when one species (the inquiline) inhabits the nest built and occupied by another species (the host). Obligatory inquilines must overcome strong constraints upon colony foundation and development, due to limited availability of host colonies. To reveal how inquilinism shapes reproductive strategies in a termite host-inquiline dyad, we carried out a microsatellite marker study on Inquilinitermes inquilinus and its host Constrictotermes cavifrons. The proportion of simple, extended and mixed families was recorded in both species, as well as the presence of neotenics, parthenogenesis and multiple foundations. Most host colonies (95%) were simple families and all were monodomous. By contrast, the inquiline showed a higher proportion of extended (30%) and mixed (5%) families, and frequent neotenics (in 25% of the nests). This results from the simultaneous foundation in host nests of numerous incipient colonies, which, as they grow, may compete, fight, or merge. We also documented the use of parthenogenesis by female-female pairs. In conclusion, the classical monogamous colony pattern of the host species suggests uneventful development of simple foundations dispersed in the environment, in accordance with the wide distribution of their resources. By contrast, the multiple reproductive patterns displayed by the inquiline species reveal strong constraints on foundation sites: founders first concentrate into host nests, then must attempt to outcompete or absorb the neighbouring foundations to gain full control of the resources provided by the host nest., (© 2024 John Wiley & Sons Ltd.)

The family Termitidae is renowned for its diverse nesting behaviors, with the evolution of epigeal and arboreal nests hypothesized to increase desiccation stress due to greater exposure to air. However, these nests may also alleviate desiccation stress through humidity regulation. To explore the implications of acquiring epigeal and arboreal nests, we investigated desiccation tolerance traits in 16 Termitidae termite species with varying nest types and analyzed trait correlations. Principal component analysis revealed that termites constructing epigeal and arboreal nests exhibited reduced water loss rates and enhanced survival under desiccated conditions. Furthermore, termites building arboreal nests displayed a notably higher water content. Redundancy analysis demonstrated that nest types accounted for a substantial portion (57.2%) of the observed variation in desiccation tolerance. These findings support the hypothesis that epigeal and arboreal nests in termites are associated with increased desiccation stress and increased desiccation tolerance. These findings highlight the role of nest type in influencing desiccation tolerance mechanisms and water regulation strategies in termites., (© The Author(s) 2023. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Termites consume substantial amounts of plant material across tropical and subtropical ecosystems. During the process of lignocellulose digestion, the symbiotic methanogenesis within termites' guts produces the potent greenhouse gas methane (CH 4 ). Termites contribute an estimated 1%-5% of global CH 4 emissions, with these estimates derived from the product of termite biomass and termite CH 4 production rate per unit of termite biomass. However, termite CH 4 production rates vary significantly across species, genus, family, and feeding group, yet our understanding of this variation remains poor. Here, we reviewed papers published from 1975 to 2021 to create a single consistently derived list of species-level termite CH 4 production rates. We searched the Google Scholar using two key words: termite and methane. We only included studies that had measured termite CH 4 production rates using the incubation method. For each eligible study, we extracted and tabulated termite CH 4 production rates and other relevant variables (e.g., feeding groups). We used μg CH 4 g -1 (termite) h -1 as the standardized unit, and if other units were presented, we converted them into this standardized unit. Overall, these data include 134 termite species from 65 genera and 5 families. Termite CH 4 production rates ranged from 0 to 25.26 μg CH 4 g -1 (termite) h -1 , with an average rate of 3.74 (standard deviation = 4.08, n = 251). Reported CH 4 production rates were largely concentrated in the family Termitidae. Across feeding groups, soil feeders tended to have higher CH 4 production rates than wood feeders. However, published data represent fewer than 5% of described termite species, and therefore we hope that our study will initiate a community-wide effort to fill data gaps and advance our understanding of the role of termites in critical biogeochemical cycles and other ecosystem processes. The data set is in the public domain under a Creative Commons Zero (CC0) license waiver., (© 2022 The Ecological Society of America.)

Termites are well recognized by their complex development trajectories, involving dynamic differentiation process between non-reproductive castes, workers and soldiers. These insects are associated with endosymbiotic microorganisms, which help in lignocellulose digestion and nitrogen metabolism. Aiming to identify genes harbouring biotechnological potential, we analyzed workers and soldiers RNA-Seq data of three neotropical termites: Heterotermes tenuis (Isoptera: Rhinotermitidae), Velocitermes heteropterus (Isoptera: Termitidae) and Cornitermes cumulans (Isoptera: Termitidae). We observed differences in the microbiota associated with each termite family, and found protists' genes in both Termitidae species. We found an opposite pattern of caste-biased gene expression between H. tenuis and the termitids studied. Moreover, the two termitids are considerably different concerning the number of differentially expressed genes (DEGs). Functional annotation indicated considerable differences in caste-biased gene content between V. heteropterus and C. cumulans, even though they share similar diet and biological niche. Among the most DEGs, we highlighted those involved in caste differentiation and cellulose digestion, which are attractive targets for studying more efficient technologies for termite control, biomass digestion and other biotechnological applications., (© 2020 The Royal Entomological Society.)

Trail-following behavior is a key to ecological success of termites, allowing them to orient themselves between the nesting and foraging sites. This behavior is controlled by specific trail-following pheromones produced by the abdominal sternal gland occurring in all termite species and developmental stages. Trail-following communication has been studied in a broad spectrum of species, but the "higher" termites (i.e. Termitidae) from the subfamily Syntermitinae remain surprisingly neglected. To fill this gap, we studied the trail-following pheromone in six genera and nine species of Syntermitinae. Our chemical and behavioral experiments showed that (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol is the single component of the pheromone of all the termite species studied, except for Silvestritermes euamignathus. This species produces both (3Z,6Z)-dodeca-3,6-dien-1-ol and neocembrene, but only (3Z,6Z)-dodeca-3,6-dien-1-ol elicits trail-following behavior. Our results indicate the importance of (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol, the most widespread communication compound in termites, but also the repeated switches to other common pheromones as exemplified by S. euamignathus.

Termites are eusocial insects having evolved several feeding, nesting and reproductive strategies. Among them, inquiline termites live in a nest built by other termite species: some of them do not forage outside the nest, but feed on food stored by the host or on the nest material itself. In this study, we characterized some dimensions of the ecological niche of Cavitermes tuberosus (Termitidae: Termitinae), a broad-spectrum inquiline termite with a large neotropical distribution, to explain its ecological success. We used an integrative framework combining ecological measures (physico-chemical parameters, stable isotopic ratios of N and C) and Illumina MiSeq sequencing of 16S rRNA gene to identify bacterial communities and to analyse termites as well as the material from nests constructed by different termite hosts (the builders). Our results show that (1) nests inhabited by C. tuberosus display a different physico-chemical composition when compared to nests inhabited by its builder alone; (2) stable isotopic ratios suggest that C. tuberosus feeds on already processed, more humified, nest organic matter; and (3) the gut microbiomes cluster by termite species, with the one of C. tuberosus being much more diverse and highly similar to the one of its main host, Labiotermes labralis. These results support the hypothesis that C. tuberosus is a generalist nest feeder adapted to colonize nests built by various builders, and explain its ecological success.

Ironwood trees (Casuarina equisetifolia subsp. equisetifolia L.) are ecologically and economically important trees in tropical and subtropical regions of the Indo-Pacific. Ironwood is one of the dominant tree species in Guam, but since 2002, this tree has been declining dramatically. A previous study showed that numerous sick or dead trees were under termite attack. However, the species of termites were not identified. As a first step to investigate causal relationships between termites and ironwood tree death, we assigned termites collected from ironwood trees to species using a combination of morphological characters and DNA barcoding of the 12S, 16S, COI, COII, and ITS2 regions. Based on morphology and comparisons to reference sequences in NCBI GenBank, the most likely species assignments were Nasutitermes takasagoensis (Nawa) (Blattodea: Termitidae) found to infest 45 trees, followed by Coptotermes gestroi (Wasmann) (Blattodea: Rhinotermitidae) (2 trees), Microcerotermes crassus Snyder (Blattodea: Termitidae) (2 trees), and an additional unidentified Microcerotermes species (1 tree) with no close sequence match to identified species in NCBI GenBank. However, taxonomic revisions and broader representation of DNA markers of well-curated specimen in public databases are clearly needed, especially for the N. takasagoensis species complex., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

In the evolutionarily-derived termite subfamily Nasutitermitinae (family Termitidae), soldiers defend their nestmates by discharging polycyclic diterpenes from a head projection called the "nasus." The diterpenes are synthesised in the frontal gland from the precursor geranylgeranyl diphosphate (GGPP), which is generally used for post-translational modification of proteins in animals. In this study, we constructed a comprehensive gene catalogue to search for genes involved in the diterpene biosynthesis by assembling RNA sequencing reads of Nasutitermes takasagoensis, identifying eight gene copies for GGPP synthase (GGPPS). The number of gene copies is much larger in contrast to other related insects. Gene cloning by reverse transcription-PCR and rapid amplification of cDNA ends confirmed that seven GGPPS genes (NtGGPPS1 to NtGGPPS7) have highly variable untranslated regions. Molecular phylogenetic analysis showed that the NtGGPPS7 gene was grouped with homologs obtained from ancestral termites that have only a single copy of the gene, and the NtGGPPS6 gene was grouped with homologs obtained from a basal lineage of termitids, in which soldiers do not synthesise diterpenes. As the sister group to this clade, furthermore, a monophyletic clade included all the other NtGGPPS genes (NtGGPPS1 to NtGGPPS5). Expression analyses revealed that NtGGPPS7 gene was expressed in all the examined castes and tissues, whereas all the other genes were expressed only in the soldier head. These results suggest that gene duplication followed by subfunctionalisation of the GGPPS genes might have accompanied the evolution of chemical defence in the nasute termite lineage., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The complete mitochondrial genomes (mitogenomes) of two higher termites were reconstructed from the metagenomes of individual gut compartments with more than 2000-fold coverage. The circular mitogenomes of Labiotermes labralis (accession number KY436201) and Embiratermes neotenicus (accession number KY436202) have a length of 15,935 and 15,868 bp and an overall G + C content of 30.7 mol% and 33.7 mol%, respectively, and both have an asymmetric nucleotide composition. Genome structure and orientation are the same as in other termites and in the ancestral insect mitogenome. These data further expand arthropod mitogenome databases, which have become an important resource in ecological, phylogenetic and evolutionary studies., Competing Interests: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper., (© 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)

Termite nests often are referred to as the most elaborate constructions of animals. However, some termite species do not build a nest at all and instead found colonies inside the nests of other termites. Since these so-called inquilines do not need to be in direct contact with the host population, the two colonies usually live in separate parts of the nest. Adaptations of both the inquiline and its host are likely to occur to maintain the spatial exclusion and reduce the costs of potential conflicts. Among them, mutual avoidance, based on chemical cues, is expected. We investigated chemical aspects of cohabitation between Constrictotermes cavifrons (Nasutitermitinae) and its obligatory inquiline Inquilinitermes inquilinus (Termitinae). Inquiline soldiers produce in their frontal glands a blend of wax esters, consisting of the C 12 alcohols (3Z)-dodec enol, (3Z,6Z)-dodecadienol, and dodecanol, esterified with different fatty acids. The C 12 alcohols appear to be cleaved gradually from the wax esters, and they occur in the frontal gland, in soldier headspace, and in the walls of the inquiline part of the nest. Electrophysiological experiments revealed that (3Z)-dodecenol and (3Z,6Z)-dodecadienol are perceived by workers of both species. Bioassays indicated that inquiline soldier heads, as well as the two synthetic compounds, are attractive to conspecific workers and elicit an arresting behavior, while host soldiers and workers avoid these chemicals at biologically relevant amounts. These observations support the hypothesis that chemically mediated spatial separation of the host and the inquiline is an element of a conflict-avoidance strategy in these species.

Termite colonies are typically founded by a pair of sexually reproducing dispersers, which can sometimes be replaced by some of their offspring. Some Reticulitermes and Embiratermes species routinely practice asexual queen succession (AQS): the queen is replaced by neotenic daughters produced by parthenogenesis, which mate with the primary king. Here, to cast light on the evolution of AQS, we investigated another candidate species, Cavitermes tuberosus (Termitinae). Of 95 nests, 39 contained a primary queen and 28 contained neotenic females (2-667 individuals), usually with the primary king. Microsatellite analyses confirmed that colonies were initiated by single pairs after large dispersal flights. More than 80% of the neotenic females were of exclusively maternal origin and completely homozygous, suggesting automictic parthenogenesis with gamete duplication. Conversely, workers, soldiers, and most alates and primary reproductives were produced sexually. AQS often occurs late, after colonies have reached maturity, whereas early AQS in other species may boost the young colony's growth rate. We suggest additional benefits of AQS in C. tuberosus, related with a smaller size, lesser stability and higher mobility of colonies. Our data add to the phylogenetical dispersion and diversity of modalities of AQS in termites, supporting a multiple evolutionary origin of this process., (© 2016 The Author(s).)

A new species of termite, Macuxitermes colombicus Postle & Scheffrahn is described from soldiers and workers collected from Departamento Magdalena, Colombia. The soldier of Macuxitermes colombicus differs from its lone congener in having no protuberances on the head capsule.

Termitotroxvenus sp. n. is described from Cambodia and represents the second discovery of Termitotrox Reichensperger, 1915 from the Indo-Chinese subregion of the Indomalayan region. Most of the type series was collected from refuse dumps in fungus garden cells of Macrotermescf.gilvus (Hagen, 1858). Macrotermes Holmgren, 1910 was previously an unknown host of Termitotrox species. The new species is easily distinguished from all known congeners by having wing-shaped trichomes on the elytra and the larger body size, at 2.5 mm in length. We also describe the mouthparts to complement the description of the genus Termitotrox.

Asexual queen succession (AQS), in which workers, soldiers and dispersing reproductives are produced sexually while numerous non-dispersing queens arise through thelytokous parthenogenesis, has recently been described in three species of lower termites of the genus Reticulitermes. Here, we show that AQS is not an oddity restricted to a single genus of lower termites, but a more widespread strategy occurring also in the most advanced termite group, the higher termites (Termitidae). We analysed the genetic structure in 10 colonies of the Neotropical higher termite Embiratermes neotenicus (Syntermitinae) using five newly developed polymorphic microsatellite loci. The colonies contained one primary king accompanied either by a single primary queen or by up to almost 200 neotenic queens. While the workers, the soldiers and most future dispersing reproductives were produced sexually, the non-dispersing neotenic queens originated through thelytokous parthenogenesis of the founding primary queen. Surprisingly, the mode of thelytoky observed in E. neotenicus is most probably automixis with central fusion, contrasting with the automixis with terminal fusion documented in Reticulitermes. The occurrence of AQS based on different mechanisms of ploidy restoration raises the hypothesis of an independent evolutionary origin of this unique reproductive strategy in individual lineages of lower and higher termites., (© 2015 The Author(s) Published by the Royal Society. All rights reserved.)

The fauna of termites (Isoptera) preserved in Early Eocene amber from the Cambay Basin (Gujarat, India) are described and figured. Three new genera and four new species are recognized, all of them Neoisoptera - Parastylotermes krishnai Engel & Grimaldi, sp. n. (Stylotermitidae); Prostylotermes kamboja Engel & Grimaldi, gen. et sp. n. (Stylotermitidae?); Zophotermes Engel, gen. n., with Zophotermes ashoki Engel & Singh, sp. n. (Rhinotermitidae: Prorhinotermitinae); and Nanotermes isaacae Engel & Grimaldi, gen. et sp. n. (Termitidae: Termitinae?). Together these species represent the earliest Tertiary records of the Neoisoptera and the oldest definitive record of Termitidae, a family that comprises >75% of the living species of Isoptera. Interestingly, the affinities of the Cambay amber termites are with largely Laurasian lineages, in this regard paralleling relationships seen between the fauna of bees and some flies. Diversity of Neoisoptera in Indian amber may reflect origin of the amber deposit in Dipterocarpaceae forests formed at or near the paleoequator.