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CHAPTER XIII. 



BENEFICIAL INSECTS. 



In the foregoing chapters it will have been noted that all insects con- 

 sidered are injurious to a more or less extent, and the inquiring or 

 philosophic student will naturally ask, Are there no beneficial forest 

 insects'? In a general way an affirmative answer may be given, but 

 in defining "beneficial" insects it is necessary that some qualification 

 should be made. Thus we may divide our subject into three main 

 divisions viz., (1) the question whether insects play any part in the 

 fertilisation of flowers ; (2) the part which insects may play in aiding 

 the rapid destruction of certain refuse in the woods; and (3) the 

 very great part played by parasitic insects i.e., insects living on 

 other insects. 



As regards the first division, it may be said that the majority of 

 our forest trees are wind-fertilised, but there are, of course, probably 

 others which are not so, together with many flowering-shrubs, and it 

 is just possible that this may be to some extent an unworked field. 



With reference to the second division, it is obvious that we can 

 get into closer association with this part of the subject. Thus, much 

 dead wood is often left lying in woods, and the forester desires its 

 early destruction. Many species of insects may be found within 

 rotting wood which doubtless assist in the disintegration of the parts. 

 This, however, may be considered as having a very indirect bearing, 

 inasmuch as many of those insects found in rotting wood may be 

 looked upon as being there purely for shelter or moisture. One not- 

 able exception, however, may be given viz., the case of any insects 

 which may aid in the destruction of roots left in the ground. In Scot- 

 land and the north of England it may be observed that in the roots 

 of Scots pine, after being cut for three or four years, very small, clear- 

 cut, gimlet-like holes can be seen in the solid roots. It will be obvious 



