Introduction

A large variety of insects attack timber during various stages of its utilization from trees felled in the forest to manufactured articles in use. The resulting waste of this valuable raw material is enormous although no reliable estimate of the loss is available. An indication of the potential for damage can be obtained from the fact that about 130 species of insect borers have been recorded from sal (Shorea robusta) timber alone in India (Beeson, 1941). The species of insects found vary depending on the geographical region, species of timber, season and stage of processing of the timber. However, unlike many pests of living trees which attack only a single or a narrow range of hosts, the timber borers in general attack a large number of timber species; that is, they are less host-specific.

Insects attack wood mainly for food although the wood serves as a place of shelter also. The insect's basic food requirements are surprisingly similar to that of humans, with minor exceptions – they require proteins, carbohydrates, fat and vitamins, although there are variations in the specific requirements of different insect species. Sapwood generally contains more nutrients like carbohydrates and proteins and for this reason most insects feed on the sapwood, and bore into the heartwood only for shelter. Like us, most insects are unable to digest the cellulose and lignin of wood, but some insects like termites accomplish this with the help of their intestinal symbionts, that is, some kinds of protozoa and bacteria.