THE CANADIAN ENTOMOLOGIST. 



BOOK NOTICES. 



The Large Larch Sawfly; with an account of its parasites, 

 other natural enemies and means of control. By C. Gordon Hewitt. 

 D. Sc. (Bulletin No. 10. — -Second Series, Entomological Bulletin 

 No. 5. Division of Entomology, Dept. Agriculture, Ottawa.) 



It was a fortunate circumstance that when Dr. Hewitt came 

 to Canada three years ago, he was already intimately acquainted 

 with our most injurious Canadian forest insect, the Larch Sawfly 

 (Nematus erichsonii Hartig), this species being apparently a native 

 of Europe and more or less destructive there also. Dr. Hewitt 

 had already spent three years in the investigation of the life history 

 and economics of this insect in England and having thereby deter- 

 mined the means by which its ravages can be checked in its native 

 country he was particularly well fitted to grapple with the more 

 difficult problem of its control in the vast larch or tamarack dis- 

 tricts of North America. 



Since coming to Canada Dr. Hewitt's studies of the Larch 

 Sawfly have been continued and the results of these and the earlier 

 investigations are embodied in the present report, in which a detailed 

 account is given of the life-history, parasites and other natural 

 enemies of this insect in both Europe and North America and the 

 means by which it can be controlled. 



The artificial means of control which have proved useful in 

 the English larch plantations are, of course, impracticable in the 

 vast forests of Canada and we must therefore rely altogether 

 upon the parasites and other enemies. These are, however, not 

 potent enough in North America to check the extensive out- 

 breaks of the sawfly, which have several times occurred in this 

 country, until most of the trees of the alTected region have 

 been killed by repeated defoliation. Dr. Hewitt has accord- 

 ingly been engaged in the importation of sawfly cocoons from 

 England, where this species is largely controlled by an ichneu- 

 mon fly, Mesoleius tenthredinis Morley, and has succeeded in 

 rearing from the cocoons a considerable number of these useful 

 parasites and liberating them in various parts of Canada where 

 the Larch Sawfly is prevalent. There is thus much reason to 

 hope that the Mesoleius will become established here and in 

 time increase in numbers to such an extent as to materially aid 

 the other natural enemies of the saw-fly, and perhaps entirely 

 prevent the occurrence of such serious outbreaks as that which 

 we have been experiencing in Canada of late years. 



