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Abstract: The use of pathogens as biological control agents has long been considered a promising technology for termite control. Over the past five decades, there has been a large accumulation of scientific literature on the development of control methods using various pathogens. However, despite the evidence that biological control has essentially failed, or failed to be developed, as a method for commercial termite control, this field of research remains very active. In this study, we examined 50years of research on the microbial control of termites in order to understand why commercial products have failed to be developed and why this field of research remains so active. All (to the extent of our knowledge) of the literature published between 1960 and 2011 was evaluated to investigate any publication bias and to detect false positives in the form of overly optimistic conclusions. This re-interpretation supports the idea that the conclusions frequently expressed have been misleading to some extent, or at least overly optimistic, about the potential for application of biological control to termites. Many results obtained from bioassays with poor biological relevancy have been interpreted as promising, while few results actually support practical application. We also suggest that the failure of termite biological control and the continued research emphasis in this area resulted in part from unrealistic optimism about the potential for development of environmentally friendly methods to control termites, publication bias, and poor understanding of termite biology. [Copyright &y& Elsevier]

Subterranean termites forage through a network of tunnels. The topology of the networks can be characterized in terms of branch angles and branching rate. When termites encounter depressions in the walls of tunnels, they may excavate the soil from the depression, which could result in the formation of new branches, or they may deposit previously excavated soil from elsewhere, which could fill in the depression. Thus, the likelihood of a branch forming is determined by the balance between soil arriving and filling the void and soil being excavated to enlarge it. We examined the tunneling behaviour of Coptotermes formosanus Shiraki in experimental arenas and found that excavation and deposition do not take place evenly across the face of tunnel wall depressions: excavation (by unloaded termites moving towards the digging face at the tunnel tip) is more likely at the proximal face (relative to the tunnel tip), while deposition (by loaded termites returning from the tunnel tip) is more likely at the distal face. This differential focus of labour within depressions facilitated branch formation by reducing localized competition between loaded and unloaded termites. Once a branch was established, biased excavation and deposition led to a shift in branch heading from about 90° relative to the main tunnel to about 50–60°, close to the theoretical optimum for the efficient flow of termites through tunnels. The basic elements of the excavation/deposition system and feedback between the two may be selected in evolution to optimize the tunnel network and thus the cost/benefit balance of feeding. [Copyright &y& Elsevier]

Abstract: Reticulitermes flavipes workers were topically inoculated with ≈10,000 conidia of the entomopathogenic fungus Metarhizium anisopliae. After being kept in groups of 20 individuals for 1–9 d, histopathological examination showed that termites had an individual immune reaction. The nodule formation at the point of entrance of the fungal hyphae was identified as a cellular encapsulation and the different steps in the nodule formation are described. The relative number of hemocytes per termite increased 24h after fungal exposure and remained high in the hemolymph for at least 3 d before decreasing back to pre-exposure levels. The role of an individual immune cellular reaction in social insects is discussed. [Copyright &y& Elsevier]

Abstract: Reticulitermes flavipes workers were individually inoculated with 10,000conidia of the entomopathogenic fungus Metarhizium anisopliae. After being kept in groups of 20 individuals for 1–6d, histopathological approach showed that most of the inoculated conidia were groomed from the surface of the cuticle by nestmates within 24h, and that a large number of conidia was subsequently found in different parts of the gut of the groomers. Our observations showed that, among thousands of conidia found in the termite’s gut, conidial germination never occurred in all inspected specimens, even when the conidia had the chance to bind to the surface of the cuticular lining of the gut. In addition, when termites were left for decomposition several days after death caused by an external infection of M. anisopliae, the hyphal growth was generalized in the body cavity of the cadaver, but was never observed in the lumen of the gut even 2d post-mortem. Our observation suggests that the putative biochemicals involved in the termite’s gut defense against fungal pathogens are from multiple origins. [Copyright &y& Elsevier]

Abstract: Antifungal activity of norharmane, a β-carboline alkaloid found in termites (Isoptera, Rhinotermitidae) was tested against two entomopathogenic fungi, Metarhizium anisopliae and Aspergillus nomius. It was determined that, at physiological concentration (10μgml−1), norharmane had no significant effect on A. nomius mycelial growth rate but reduced M. anisopliae growth rate by 11.9%. Contrary to previous findings, we suggest that norharmane has a limited role in disease resistance against fungal pathogens in individual subterranean termites, and we discuss the potential role of this chemical at a colony level. [Copyright &y& Elsevier]

With recent evidence of hybridization events in the field, the phenotypic traits of F1 hybrid colonies of 2 destructive subterranean termite species, Coptotermes formosanus Shiraki and Coptotermes gestroi (Wasmann) remain to be investigated. In this study, laboratory colonies of 2 conspecific pairings and 2 heterospecific pairings (hybrid F = ♀ C. formosanus  × ♂ C. gestroi , hybrid G = ♀ C. gestroi  × ♂ C. formosanus) were examined in Florida, USA, and in Taiwan. Colony nest architecture for both hybrids displayed disorganized carton materials compared to the defined trabecular carton of both parental species. Soldier head measurements were not a reliable approach for diagnostic purposes, as soldier morphometric traits widely overlapped across all mating combinations, except for hybrid F soldiers displaying abnormally long mandibles. Hybrid F soldiers' mandibles also remained parallel when at rest. However, 4 qualitative morphological differences in soldiers were determined for diagnostic purposes. First, the fontanelle in both hybrids is horizontally ellipsoid whereas subcircular in C. gestroi and trianguliform in C. formosanus. Second, sclerotized striations along the postmental sulcus are present in C. gestroi , absent in C. formosanus , and intermediate in both hybrid soldier types. Third, each lateral margin of the fontanelle is flanked by 2 setae in C. formosanus and both hybrids, while a single seta resides on each side of the fontanelle in C. gestroi. Finally, C. gestroi and hybrid soldiers' heads are characterized by a bulging vertex that is lacking in C. formosanus. Therefore, a combination of these 4 characteristics now allows for soldier identification of hybrid Coptotermes. [ABSTRACT FROM AUTHOR]

Bacteria and fungi in shared environments compete with one another for common substrates, and this competition typically involves microbially-produced small molecules. An investigation of one shared environmental niche, the carton material of the Formosan subterranean termite Coptotermes formosanus, identified the participants on one of these molecular exchanges. Molecular characterization of several termite-associated actinobacteria strains identified eleven known antimicrobial metabolites that may aid in protecting the C. formosanus colony from pathogenic fungal infections. One particular actinobacterial-derived small molecule, bafilomycin C1, elicited a strong chemical response from Trichoderma harzianum, a common soil saprophyte. Upon purification and structure elucidation, three major fungal metabolites were identified, t22-azaphilone, cryptenol, and homodimericin A. Both t22-azaphilone and homodimericin A are strongly upregulated, 123- and 38-fold, respectively, when exposed to bafilomycin C1, suggesting each play a role in defending T. harzianum from the toxic effect of bafilomycin C1. [ABSTRACT FROM AUTHOR]

Coptotermes formosanus Shiraki and Coptotermes gestroi (Wasmann) (Blattoidea: Rhinotermitidae) are invasive subterranean termite pest species with a major global economic impact. However, the descriptions of the mutualistic protist communities harbored in their respective hindguts remain fragmentary. The C. formosanus hindgut has long been considered to harbor three protist species, Pseudotrichonympha grassii (Trichonymphida), Holomastigotoides hartmanni, and Cononympha (Spirotrichonympha) leidyi (Spirotrichonymphida), but molecular data have suggested that the diversity may be higher. Meanwhile, the C. gestroi community remains undescribed except for Pseudotrichonympha leei. To complete the characterization of these communities, hindguts of workers from both termite species were investigated using single‐cell PCR, microscopy, cell counts, and 18S rRNA amplicon sequencing. The two hosts were found to harbor intriguingly parallel protist communities, each consisting of one Pseudotrichonympha species, two Holomastigotoides species, and two Cononympha species. All protist species were unique to their respective hosts, which last shared a common ancestor ~18 MYA. The relative abundances of protist species in each hindgut differed remarkably between cell count data and 18S rRNA profiles, calling for caution in interpreting species abundances from amplicon data. This study will enable future research in C. formosanus and C. gestroi hybrids, which provide a unique opportunity to study protist community inheritance, compatibility, and potential contribution to hybrid vigor. [ABSTRACT FROM AUTHOR]

This study investigated nuclear markers in Coptotermes formosanus Shiraki and Coptotermes gestroi (Wasmann) (Isoptera: Rhinotermitidae) that can be used as a diagnostic tool to detect F1 hybrids from field samples. Six microsatellite markers were compatible for both parental species and hybrid termites and were optimized so that a standard gene library can be built for the south Florida Coptotermes populations. [ABSTRACT FROM AUTHOR]