60 INDIAN FOREST INSECTS 



to man, most of the families consisting of pests whose whole sustenance is 

 derived from the tree, or who look to the tree to provide food for their 

 offspring. 



This would be serious enough, having regard to its connection with that 

 portion of the forester's work which deals with the disposal of his produce, 

 if the insects only confined their attentions to the tree after it had died in the 

 forest or been felled for sale purposes. For there are a number of pests who 

 do so restrict their attentions, which are able to destroy very quickly the 

 marketable value of the timber if they are given an opportunity of doing so. 

 A much more serious phase of the life histories of Coleoptera is connected, 

 however, with the large number of beetles who can only derive their 

 sustenance from the green tree, and who require such trees to lay their eggs 

 or oviposit in. Whatever be the attribute, whether due to instinct or some 

 other acquired sense, these insects will never oviposit in dry trees, nor in 

 trees that are in such a condition that they will become dry before the offspring 

 hatching from the eggs laid by them have reached full development as grubs. 



It is often said that beetles, e.g. bark beetles, never attack a green 

 healthy tree standing in the forest. This is a complete fallacy. 



In the ordinary balance of nature, in the primeval forest, the bark 

 beetle, whose offspring depend for their sustenance on the green bast or 

 green timber, will not attack a healthy tree. There is no necessity for it to 

 do so. The balance of power is kept even in nature, and the insect can 

 always find a sufficiency of sickly trees, whose death it hastens, or of 

 green windfalls which provide the necessities of life both for itself and 

 its future offspring. The forester's business is, however, to remove all 

 such blots from his forests and to keep them clean. Also to raise per 

 acre the largest number of trees possible. Given a year favourable to 

 insect life, or a series of favourable years, and the numbers of a particular 

 bark-beetle pest in the forest become so great that they are bound to attack 

 the green standing crop, seeking out, of course, the weaker trees to commence 

 with. Vast numbers of the insects are killed off by the outflow of resin or 



j 



sap with which the healthy trees respond to the attacks. This very output, 

 however, reduces the vitality of the trees, which gradually succumb to the 

 enormous numbers of the foe attacking them, and the trees are in the end 

 killed just as surely as if they had been girdled or felled by the forester. 



The order Coleoptera, to a degree unusual in other orders, contains 

 a "number of pests, to be found principally perhaps in the great families 

 Buprestidae, Cerambycidae, Curculionidae, Scolytidae, and Platypodidae, 

 which demand for their sustenance green bast, green sapwood, or green 

 heart-wood. It is for this reason that the order must be considered as one 

 of the most important, perhaps the most important, to the forester. 



The Coleoptera feed upon the tree in a variety of ways, some infesting 

 the roots, as e.g. species of Melolonthinae, such as S erica (p. 76) and Lach- 

 nosterna on the sal-tree, and Coelosterna on the Acacia arabica. 



Others, again, and perhaps by far the most dangerous, infest the bast 



