A number of arthropod taxa contain metals in their mandibles (jaws), such as zinc, manganese, iron, and calcium. The occurrence of zinc and its co-located halogen chlorine have been studied in relation to the mechanical properties and shown to be linked in a direct fashion with increasing concentration. Hardness along with elastic modulus (stiffness) has also been linked to zinc and halogen concentration in some marine polychaete worms. The metal appears to be incorporated within the biological matrix, possibly bonding with proteins. However, the comparative advantage of metal inclusion has not been tested. It is possible that without metals, alternative mechanisms are used to achieve hardness of equal value in similar 'tools' such as mandibles. This question has direct bearing on the significance of metal hardening. In the present article, we compare across mandibles from six termite species, including samples with major zinc concentration, minor manganese, and no metals. Nanoindentation, electron microscopy, and electron microanalysis are used to assess metal concentration, form, and mechanical properties. The data demonstrate that termite mandibles lacking metals when fully developed have lower values for hardness and elastic modulus. Zinc is linked to a relative 20% increase in hardness when compared with mandibles devoid of metals. The similar transition metal, manganese, found in minor concentrations, is not linked to any significant increase in these mechanical properties. This raises the question of the function of manganese, which is as commonly found in insect mandibles as zinc and often located in the same mandibles.

Previously, the presence of metals in arthropod mandibles has been linked with harder cuticle, and in termites, a 20% increase in hardness has been found for mandibles containing major quantities of zinc. The current study utilises electron microscopy and energy-dispersive X-ray microanalysis to assess incidence and abundance of metals in all extant subfamilies of the Isoptera. The basal clades contain no zinc and little to no manganese in the cutting edge of the mandible cuticle, suggesting that these states are ancestral for termites. However, experimentation with mandibles in vitro indicates the presence of some elements of the cuticular biochemistry necessary to enable uptake of zinc. The Termopsidae, Serritermitidae, Rhinotermitidae and Termitidae all contain minor quantities of manganese, while trace to minor quantities of zinc occur in all except the Serritermitidae. In contrast, all Kalotermitidae or drywood termites contain major levels of zinc in the mandible edge. Diet and life type are explored as links to metal profiles across the termites. The presence of harder mandibles in the drywood termites may be related to lack of access to free water with which to moisten wood. Scratch tests were applied to a set of mandibles. The coefficient of friction for Cryptotermes primus (Kalotermitidae) mandibles, when compared with species from other subfamilies, indicates that zinc-containing mandibles are likely to be more scratch resistant.

The aim of this study was to determine specific distribution of metals in the termite Tumulitermes tumuli (Froggatt) and identify specific organs within the termite that host elevated metals and therefore play an important role in the regulation and transfer of these back into the environment. Like other insects, termites bio-accumulate essential metals to reinforce cuticular structures and utilize storage detoxification for other metals including Ca, P, Mg and K. Previously, Mn and Zn have been found concentrated in mandible tips and are associated with increased hardness whereas Ca, P, Mg and K are accumulated in Malpighian tubules. Using high resolution Particle Induced X-Ray Emission (PIXE) mapping of whole termites and Scanning Electron Microscope (SEM) Energy Dispersive X-ray (EDX) spot analysis, localised accumulations of metals in the termite T. tumuli were identified. Tumulitermes tumuli was found to have proportionally high Mn concentrations in mandible tips. Malpighian tubules had significant enrichment of Zn (1.6%), Mg (4.9%), P (6.8%), Ca (2.7%) and K (2.4%). Synchrotron scanning X-ray Fluorescence Microprobe (XFM) mapping demonstrated two different concretion types defined by the mutually exclusive presence of Ca and Zn. In-situ SEM EDX realisation of these concretions is problematic due to the excitation volume caused by operating conditions required to detect minor amounts of Zn in the presence of significant amounts of Na. For this reason, previous researchers have not demonstrated this surprising finding.

No abstract

The Moolart Well gold deposit lies in the Duketon Greenstone Belt in the Western Australian Goldfields in an area that has seen nearly 150 years of Au exploration with limited success due to the transported cover masking deposits. Here, the site displays no anomaly indicative of underlying mineralization within surface soils. Termites have the ability to burrow to the subsoil and contribute to the development of soil profiles through bioturbation. This study discusses the use of mounds formed by the termite Tumulitermes tumuli from a site where shallow ferruginised palaeochannel sediments with secondary Au enrichment overlays deeper primary mineralization. A series of samples from termite nests and surrounding soil were sampled along a transect from background areas to over mineralization. Various fractions of these samples were analysed with ICP-MS/AES. Tumulitermes tumuli is able to bring sub-surface mineralized material to the surface from 1 to 4 m depth. Termite mounds over mineralization and soil immediately adjacent to the mounds display an Au anomaly in both <250 and >250 µm fractions. Very high concentrations (>5000 ppb) were found in >2000 µm fractions in nests over mineralization as a result of vertical transport of anomalous pisolitic gravels by termites. These results suggest termite-driven local soil heterogeneity and termite mounds being a consistent geochemical and mineralogical sample medium for the discovery of ore deposits beneath weathered cover and shallow sediments.

No abstract

This study investigates the characteristics of leaching into a solvent of an active used as termiticide, Bifenthrin 1 (a synthetic pyrethroid) entrapped in polymer, and the effect of layered silicates on this diffusion. Two contrasting solvents, water and acetone, were used to understand this phenomenon; the active is soluble in acetone but has very low solubility in water. The data are used to understand the migration characteristics of Bifenthrin when encapsulated in polyurethane to form a termite barrier. The absorption characteristics of Bifenthrin in polyethylene were also studied for comparison. Bifenthrinpolyurethane blends containing 0, 0.5, and 5% of layered silicates were prepared and monitored for the release of Bifenthrin. Using the time-concentration dependence of the active in polymer, diffusion coefficients of Bifenthrin from the polymer were inferred assuming Fickian diffusion. The presence of silicates had no significant effect on the diffusion behavior.

An ether based polyurethane (EPU) was blended with a synthetic pyrethroid, Bifenthrin V R , to produce a material for potential use as a termite barrier for timber structures. FTIR was used to investigate the interaction between the active component and the polymer, whereas distribution of the active was probed using X-ray photoelectron spectroscopy. The aromatic end of the Bifenthrin molecule was found to interact with the hard segments of the EPU, whereas the active end of the Bifenthrin V R molecule was found to be concentrated at the surface of the blend. The efficacy of the blends was demonstrated to induce high mortality rates when the blend was directly tested against termites.