FAMILY SCOLYTIDAE 505 



GENERATION III. 



2nd week in August Eggs 



3rd week in August to 3rd week in September . . . Grubs 



3rd week in September to 2nd week in October . . Nymphs 



ist week in October to 3rd week in October . . . Beetles 



GENERATION IV (a complete generation). 



Beginning of October ....... Eggs 



ist week of October to ist week in November . . . Grubs 



ist week in November to 3rd week in November . . Nymphs 



2nd week in November to 2nd and 3rd week in April . Beetles 



The November beetles will hibernate in the trees and lay the eggs of the first generation 

 of the following year. 



The exact time of the appearance of the various stages of the insect in 

 these generations, and the number of life-cycles passed through, depend, of 

 course, to a considerable extent on elevation, aspect, and climatic condi- 

 tions, south and east aspects and a dry warm spring and summer following 

 an open winter being most favourable. The generations will also be found 

 to overlap to some extent. 



This insect confines its attacks to young growth and poles only, infest- 

 ing trees which have not as yet acquired an outer layer 



m th p" 1 " 1 * ^ ^ dead bark. Owing to its polygamous habits it is 



capable of an even greater rapidity in increase than 



the deodar Scolytus, once conditions are favourable to it. For egg-laying 

 purposes it undoubtedly has a preference for the blue pine, and next to the 

 blue pine the spruce. It has been shown, however, that when these trees 

 are scarce in a forest and the beetle is abundant it will oviposit in deodar, 

 and this characteristic of the insect renders it a much more dangerous pest 

 than would otherwise be the case at present. 



It is of course possible that both blue pine and spruce may become more 

 valuable commercially in the future should paper mills be established in the 

 outer Himalaya. In such an event the capabilities of this insect of attacking 

 and killing off young trees will have to be borne in mind. For the moment 

 it is in areas of young deodar in which a few blue pine trees are present th;it 

 the insect is a pest to be dreaded. 



It is a more active beetle than the Scolytus, and flies by day and tunnels 

 into trees in broad daylight and even in sunlight. It is not so sensitive to 

 sunlight as its companion, and will tunnel into a tree or branch on almost 

 any side. Poles, saplings, and quite young growth are alike infested, and it 

 will tunnel into healthy green standing trees in the forest. The beetle 

 appears endowed with a strong vitality, for it will almost invariably be 

 found in some stage of its existence in felled green trees and grcc-n branch- 

 wood of the trees it affects, and is not so susceptible to their rapid drying 

 as is the Scolytus. It spreads in a forest in a manner similar to that of the 

 Scolytus beetles. 



