DISEASES AND ACCIDENTS. 35 



noxious insects devastating whole forests, there are also many useful 

 little animals which, by their operations, may be said to act as 

 the good genii of all trees, and chiefly of the Coniferous tribe." 

 Among the latter may be mentioned the Ichneumon flies, which 

 destroy myriads of caterpillars that infest Fir and Pine trees, 

 and also a little insect to which Linnaeus gave the name of 

 Thanasinus formicarius, "whose destructive abilities are truly mar- 

 vellous, depositing its eggs not unfreque^ntly in the wood boring 

 larvae themselves, as well as in the bodies of many other 

 destructive insects." * 



Observations made on the habits of the insects destructive to 

 Coniferous trees, tend to show, that much of the mischief caused 

 by them, may be prevented by forethought and judicious management. 

 Mr. Robert Hutchison in the excellent paper above quoted, points out 

 that " trees of the Pine tribe most frequently affected in their young 

 stage by the attacks of insects, are those which are planted in soil 

 previously cropped by the same description of tree. This will also be 

 the case even although the previous crop may not have been affected 

 in the least degree by such ravages, thus clearly showing that the cause 

 of the destruction to the second crop does not lie in any sort of 

 infection or transmission of the disease (if so it may be called), but 

 rather from the growth and establishment of larvae in the ground itself, 

 engendered probably by the dry condition of the soil, caused by the 

 previous cropping and absorption of the moisture by the numerous roots 

 left in the ground after felling. 



" Another fact worthy of notice is, that these marauders of Coniferous 

 plantations seem greatly enamoured of the cut and drying twigs and 

 branches from early prunings or thinnings. It has been frequently 

 observed that they prefer locating themselves among these cut branches 

 to any other shelter or cover, so long as they find them in a fresh 

 although drying condition, and they will invariably settle on them 

 rather than on any part of the growing trees themselves. This 

 predilection for shoots in a semi-dry or half withered state is further 

 attested by the circumstance that insects which attack the Fir tribe, 

 invariably commence on a subject already evincing indications of 

 sickness or decay." 



" The modes of insect attacks upon Coniferous trees may be directed 

 towards the root, the bark, or the tender young shoots; but in any 

 case their preference for the apparently weaker growths and constitutions 

 holds good, whatever may be the mode of attack, and whether their 

 victim be a recently planted seedling or a mature tree. They probably, 



* Mr. Robert Hutchison in Proceedings of the Scotch Arloricultural Society, 1874. 



