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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]