28 INDIAN FOREST INSECTS 



had got down into the wood the barking would be too late to prevent 

 its subsequent tunnelling operations into the heart-wood, and that all 

 timber containing these grubs would be rendered unfit for sale purposes. 



We come then to the next point that a knowledge of the life histories 

 of the more dangerous of the tree pests of his locality is essential to the 

 Forest Officer if he is to be in a position to 



(1) Prevent serious attacks to the standing crop resulting in the 

 loss of many individual trees or of whole blocks of forest, with the 

 consequent upsetting of his working plan. The tremendous damage 

 Scolytidae are capable of committing in coniferous areas is a well-known 

 example. 



(2) Prevent his timber being destroyed by insects after the trees 

 have been felled in the forest for sale purposes. That this is possible 

 the Hoplocerambyx example already quoted renders evident. 



How are the life histories of tree pests to be ascertained ? 



Some insects only attack young seedlings. Close observation by 

 officers in charge of nurseries, assisted by careful inspection of areas of 

 sowings in the forest, will enable the life histories of these pests to 

 be ascertained. There is urgent need that such observations should be 

 carried out. For some years it has been an acknowledged fact that 

 deodar seed sown in lines or patches in the forest has completely failed. 

 The young seedlings may have come up only to gradually die off and 

 disappear. 



Observations have shown that a melolonthid or cockchafer grub 

 (p. 82), a wireworm (E later, p. 230), and a cut-worm caterpillar (A gratis), 

 are responsible for a great deal of this mysterious disappearance of 



sowings. 



Other insects only attack the leaves, buds, or flowers and fruits and 

 seeds of the trees. The working out of the life histories of such pests 

 requires close observation and investigation to be undertaken in the forest 

 at the times when such attacks are being experienced. 



Another class whose attacks are often only too visible in the tree, 

 although it is extremely difficult to track down and secure the identifi- 

 cation of the mature insect, is that of the bark-eating and wood-boring 

 caterpillars. The caterpillars themselves can be secured, but the identi- 

 fication of the particular pest cannot be undertaken from the caterpillar. 

 The grub only feeds upon the juicy bast layer and the sap-filled sapwood, 

 subsequent "weathering" often setting up at the place attacked (cf. fig. 18). 

 The grub may sometimes, as in the case of the bee-hole borer of teak 

 (Duomitus cerauiicits), tunnel down into the hard dry wood to pupate, but 

 only when full-fed, and for pupating purposes alone. How to secure the 

 mature stage or moth of these bark-eating and wood-eating caterpillars is 

 a difficult problem. If one cuts the stem down and keeps a section in 

 which the caterpillar is known to be, as soon as the latter finds the bast 

 or wood beginning to lose its sap and dry up it comes to the outside and 



