a survey of beetles damaging commercially impotrtant ... - Icrisat.ac.in

IIIRESULTS AND DISCUSSIONPART A - INSECT BORERS OF MAJOR TIMBER SPECIESThe coleopterous borers can be generally grouped into two categoriesviz., the large borers belonging to the family Cerambycidae and the smallborers belonging mainly to the families, Bostrychidae, Lyctidae, Scolytidae,Platypodidae, Curculionidae and Anthribidae.The Cerambycidae, commonly called longicorn or long-horned beetles,generally attack freshly felled timber. Their eggs are laid in crevices in thebark and the newly hatched larvae feed underneath the bark initially. Thenthey tunnel into the sapwood boring out large excavations filled with frassand excreta. Prior to pupation most species bore into the heartwood causingconsiderable damage to timber.The small borers have been variously called powder-post beetles,pin-hole borers, ambrosia beetles, shot-hole borers etc. Although the termpowder-post beetle is generally applied to the Bostrychidae and Lyctidae,pin-hole borers to Platypodidae, shot-hole borers and ambrosia beetles toScolytidae, much confusion exists in the literature due to such usage becauseno clear distinction can be made between the various categories. In thepresent report, the term small borers will be used to refer to all the abovefamilies and the family name will be used wherever further distinction isnecessary.The small borers generally start their attack immediately after the treeis cut and stacked. They also attack converted and sawn timber, commercialproducts like veneers, packing-case boards, bobbins, tool handles etc. andhence are of great economic significance. The damage caused by severalspecies is confined to the outer sapwood which in the case of hard timbersis not very significant since the sapwood portion is often discarded when thetimber is processed. However, in the case of soft timbers with low heart-wood content, the tunnels extend as far as the centre of the logs. This isespecially so in the case of boles of small dimensions.Timber thus heavilyattacked is practically of no use where planks are desired. Planks of evenhard timber used in furniture, buildings, machineries, etc . are also susceptibleto this group of borers.