42 



INDIAN FOREST INSECTS 



(5) Natural Phenomena—Windfalls, Snow-break, Frost, etc. — At 



present the danger from excessive windfalls taking place is only likely to 

 occur either in plantations or in the Himalayan coniferous areas. Damage 

 resulting from devastating cyclones, however, such as the Chittagong cyclone 

 of October 1897, which swept a clear strip several miles in width through 

 the forests of the Chittagong Hill Tracts, the whole of the forest being laid 

 low, is almost certain to be followed by the increase of one or more bad 

 forest pests. One of the results of the above-mentioned cyclone was that 

 the )mili bamboo {Melocanna bamhnsioides) sprang up in thousands on the 

 area cleared of trees by the cyclone, and this sudden increase in its food- 

 plant was foUow^ed b}- the appearance of enormous numbers of the Cyrto- 

 trachclus longipes weevil, which oviposits on this bamboo (p. 440). It is 

 chiefly, however, in coniferous forests that the danger from windfalls, as 

 also from snow-break, is greatest and most to be feared. Thrown deodar, 

 blue pine, spruce, and long-leaved pine are all immediately attacked by 

 scolytid bark-boring pests or by buprestid and longicorn ones within a 

 week or two of their fall, unless this takes place in the winter. In the 

 latter event the first generation of beetles to appear in the spring will 

 oviposit in the fallen trees. The deodar buprestid Sphenoptera and the 

 Scolytiis beetles have been found in large numbers in snow-broken deodar 

 on many occasions. 



The danger from frost is probably greatest in the plains, and especially 

 when abnormally severe frosts are experienced in areas which are usually 

 either entirely free from frost or are only subject to light ones. Severe 

 frosts in such localities leave a large number of trees in a more or less 

 temporarily moribund condition. The trees will not die if they are given 

 time to recover and are not subject to any further strain. Such trees are, 

 however, in the condition in which they are most easily assailable by their 

 bark- and wood-boring enemies, and these kill off many a tree which but for 

 their attacks would have recovered itself in the course of two or three years. 

 The great frosts of February 1905 are a case in point. Great damage was 

 done to the forests over a large tract of country, of which records are to be 

 found in the Indian Forester * I had an opportunity of examining a con- 

 siderable area of the sal forests of the United Provinces Terai and Siwaliks, 

 including Philibhit, also some of the sal areas in the Central Provinces, and my 

 observations tabulated showed that in many places trees weakened by the 

 frosts had been subsequently killed by the bark-borer Sphacrotrypcs and the 

 longicorns JEolesthes and Hoplocerambyx. I made some careful notes in the 

 Siwaliks and United Provinces Terai in 1906, 1907, and 1908 on the after- 

 results of the frosts of 1905. I found that numbers of the younger 

 sal-trees whose upper half had been killed by the frost were attacked below 

 by Sphaerutrypcs siwalikensis, and that both this beetle and the /Eolesthes 

 appeared in many of the older, thicker trees whose vitality had been greatly 



* Indian Forester^ vol. xxxi, pp. 337' 435, 438, 496, 569 ; xxxii, pp. 24, 34: 



