Feeding behaviour of termites (Insecta: Isoptera) on tropical timbers and treated materials

The feeding behaviour of five species of dry-wood termite (Kalotermitidae) and six species of subterranean termite (fthinoter<nitidae and Termitidae) was studied experimentally. Small samples of 28 tropical timbers were tested with the dry-coed termite Cryptotermes cynocephalus and the subterranean termites Coptotermes curvignathus and Reticulitermes lucifugus. A resistance classification of the 28 tropical timbers to the three species of termites was derived on the basis of cluster analysis. The effects of naturally-occurring chemicals and termite soldier defence secretions on termite feeding behaviour were also included in these studies.The results revealed that four among 28 species of wood studied were completely resistant and repellent to the three species of termite: The four species of wood are Dalbergia latifolia, T,eideroxylon zwageri Intsia bijuga and Tpctona grandi.s. The presence of secondary substances, which apparently cause rejection of the woods, is believed to be the main reason of their resistance to termites. Extracts of selected resistant woods and synthetic samples of known secondary substances were shown to be repellent to the termites Agathis alba, Dipterocarpus species and Mangifera species are classified as most preferred wood species to termites. The feeding activity of termites was also associated with side hardness of the timbers, but not with ash content, basic density or lignin content. The wood extracts have stronger repellent effect than the solid wood. Extracts of resistant wood species were toxic to the dry-wood termite C. cynocephalus and repellent to the subterranean termites. Naturally-occurring chemicals inhibited the feeding behaviour of termites. The monoterpenes were repellent to termites although they were non-toxic at the concentrations used. Qiinones and anthraquinones were both repellent and toxic. The chemicals were more toxic and repellent to termites when they were used on filter pads than when they were presented on wood chips. Soldier extracts (major and minor) of Schedorhinotermes malaccensis (Rhinotermitidae) may be of value in protecting timbers and treated materials against termite attack, although relatively high concentrations may be required. Soldier extracts of this species of termite were toxic and repellent to the dry-wood termite C. cynocephalus. The extracts were also repellent to C. dudleyi and to the subterranean termite R. lucifugus. Ketones similar to those putorius and S. lamanianus were found inextracts of major and minor soldiers of S. malaccensis.