12 

 PARASITIC INSECTS IN THE CONTROL OF INJURIOUS FORMS 



By Professor W. Lochhead, Macdonald College. 



During the last ten years much effort has been expended in the United 

 States in attempts to control certain noxious insects, nota'bly the Gypsy 

 and the Brown Tail Moths, by the introduction of parasitic 

 forms from Europe and Japan. The scientific world is interested in this 

 work on account of the magnitude of the operations and the difficulties 

 to be overcome, and of the probable far-reaching influence in the control 

 of other noxious insects. 



It seems to me, therefore, that not only the members of this Society 

 but also the people of Quebec shoulu be informed as to the progress that 

 has been made by entomologists in ihe control of injurious insects 

 through the introduction of parasitic forms. The following account is 

 based largely on a report prepared by Howard and Fiske of the TJ. S. 

 Bureau of Entomology ( Bulletin 911)1, and on a report by Dr. F. Silvestri 

 of Italy, entitled "A Survey of the Actual state of Agricultural Entomo- 

 logy in the United States of America." 



A SHORT HISTORY OF INSECT PARASITISM, 



From early times students of insect life have observed that some- 

 times from caterpillars and their chrysalids there emerge insects that 

 are different from them and that often cause their death. According to 

 Silvestri, Aldrovandi ( 1602 ) w^as the first to observe the exit of the 

 larvae of Apanteles glomeratus, w^liich he thought were eggs, from 

 the common cabbage caterpillar. Later, Redi ( 1668 ) recorded the same 

 observation, and another on insects of different species. 



Valisnieri (1661-1730) was probably the first to discover the real 

 nature of parasitism Reaumur (about 1735, and De Geer about 1760) 

 published records of many parasitic forms. About the beginning of the 

 19th century considerable attention was given to the study of insect 

 parasites by several Zoologists, and many records ^vere published. Ratze- 

 burg's great work on "The Ichneumons of Forest Insects," published 

 about 1850, was for a long time t[he great classic on the subject. During 

 the last part of the 19th century Entomologists of many countries made 

 important contributions so that by the end of the century the literature 

 on the subject was quite voluminous. 



The economic use of parasitic insects naturally sho\vs three phases: — 

 ( I ) The utilization of the native parasites of the district; 



( 2 ) The transportation of t(he parasites from one district to anoth- 

 er: and 



