208 ROYAL .SOCIETY OF CANADA 



The general nile wliicli controls tlio amount of insect occurrence 

 is the extent of the foo(l-sui)i)ly ; consequently, those insects which are 

 very exclusive in their diet — and there are many such, — or those which 

 feed ujion rare i)lants or ujjon little grown crops, are corresi)ondingly 

 less abundant than those which have a large range of food plants or 

 which find suitable food in the crops most widely cultivated. 



In a state of nature, we find tlrat there are few insects which are 

 not held back from disproportionate increase by special enemies. These 

 latter are naturally, when only normally abundant, far fewer than the 

 hosts at whose expense they live ; but with the undue increase of their 

 hosts the parasitic species very soon multiply rapidly and restore again 

 the balance of the ratio of occurrence. 



When an insect is introduced accidently into a distant country, 

 the chances are very remote of the special parasites which attack it in 

 its native I'and, being also introduced with it, and, as a result, these 

 foreign species are liable to become serious enemies. In rare instances 

 this has been remedied by the subsequent artificial introduction of 

 parasites. 



During the fifteen years which have elapsed since the publication 

 of Saunders's Insects Injurious lo Fruiis, many species of insects have 

 occuared in Canada as enemies of fruits and other crops, and records 

 have appeared in various publications. 



It has been thought that an annotated list of these might be of 

 interest ; the present paper has therefore been prepared and is sub- 

 mitted he^e^nth. With the mention of each injurious insect will be 

 found notes as to the time of the first recorded appearance of the insect, 

 and the best remedies that the expetience of many workers has enabled 

 us to devise. These notes are grouped under the heads of the different 

 classes of crops attacked. It may further be noticed that some of these 

 insects are not actually new additions to the list of injurions crop pests, 

 but new facts of importance having been discovered concerning them 

 it seems advisable to include them here. 



Cereals. 



The enemies of small grains have received few accessions, but there 

 have been remarkable changes in the amount of injury in various years 

 from the well known pests of these crops. The Hessian Fly, the Joint- 

 worms and the Wheat-stem Maggot have not been for some years, ex- 

 cept in very restricted areas, sources of serious loss to the grain crops. 

 The Wheat ^lidge, "at one time a terrible pest throughout the Dominion, 

 is now restricted to a narrow strip in the Niagara peninsula, where it 



