702 teoceedings of the third entomological meeting 



3. Bark-beetles. 



I have already mentioned that the forests of India have not suffered 

 appreciably from the epidemic attacks of bark-beetles. We have not 

 been faced with the Dendroctonus problem of the coniferous forests in 

 the United States and Canada, or with the bdrkenMferfmge of the country 

 that used to be Germany. Nevertheless it is inevitable. 



The changes in the management of the coniferous forests of the 

 Himalayas, which are accompanying the revision of working plans, 

 will produce fundamental alterations in the composition and aspect of 

 these forests. The existing irregular uneven aged stock is being con- 

 verted into uniform forests ; that is to say, into forests of one or very 

 few species arranged in regular blocks in which all the trees are nearly 

 of the same age. These blocks are produced on areas cleared by one 

 felling or by two or three fellings at intervals of a few years. In the 

 first case the area is planted up artificially ; in the second, reliance is 

 placed to a great extent on the natural regeneration by seed-bearers 

 left on the area for that purpose. 



Bark-beetles breed in the slash and felling refuse ; and, since most 

 Himalayan species have three or four broods a year, rapid increase is 

 possible. 



Ips longifolia, Steb., the large pine bark-beetle, is a species which is 

 beginning to give trouble in chir pine forests. Normally it is a secondary 

 species breeding in dead trees ; but, on felling areas of rhe uniform 

 system, a succession of generations develops in the bark of the felled 

 trees, and in the refuse on the coupe area after the logs have been 

 extracted ; and then in the following season, finding no more dead 

 breeding-material, it is forced to attack living trees or migrate. By a 

 series of massed attacks the bark-beetles break down the resistance of 

 the young growth on the regenerated area, and overwhelm it. To 

 adopt a familiar simile, they now consolidate their ground. The broods 

 emerging from the killed pine saplings adopt the same tactics with 

 equal success against the young growth in the vicinity. But mass 

 attacks on any field of battle are costly and the amount of territory 

 gained in each successive onslaught decreases, until the zone of action 

 is reduced to a few centres of resistance, which eventually disappear. 

 The attack is spent, and the trees now have the situation well in hand. 



Before this stage is reached the Forest Officer intervenes and nulli- 

 fies the success of his plant allies by making another felling. This act 

 supphes the bark-beetles with powerful reinforcements. The mass 

 attacks are repeated and each year with each annual coupe a fresh 

 batch of beetle reinforcements is called up and a corresponding number 

 of chir trees is killed, These are the tactics now being developed by the 



