90 THE CANADIAN ENTOMOLOGIST. 



bv imported insects, have not had time to acquire that degree of immunity 

 which nature has enabled them gradually to acquire against older and 

 familiar foes ; consequently they become an easier jirey to these new 

 enemies. In the last place, the parasites and other predaceous insects 

 that kept these pests in control in their native land very often fail to be 

 introduced along with their hosts. 



We shall pass on now to the last put of our subject, namely, the 

 intentional introduction by man of beneficial insects to help him in his 

 struggle against the injurious ones. The subject of parasitic insects is 

 attracting a great deal of attention to-day, but is by no means a new sub- 

 ject. We find that for a good many years efforts have been made by 

 entomologists to discover what were the particular parasites that con- 

 trolled destructive insects in their native countries, and to introduce such 

 parasites to keep in check these same insects when' imported. In this 

 way ever year new species of parasites are brought from Australia, New 

 Zealand, Europe, Asia and Africa, to the United States, and vice versa. 

 Though most of these have disappointed the too sanguine expectations of 

 their importers, yet several have proved of great service. Of these, two 

 stand out pre-eminently, namely, Vedalia cardinalis and Scutellista cyanea. 

 The former is a species of ladybird beetle introduced from Australia to 

 combat the white scale that was destroying the orange trees of California, 

 the latter is an insect from South Africa meant to combat the black scale. 

 Both have worked wonders in controlling the ravages of these respective 

 pests. We have, of course, in our own country, many native species of 

 parasites or predaceous insects, such as several kinds of ladybird beetles, 

 Ichneumon flies, Aphis lions, etc. These are distributed throughout the 

 country, either along with their host insects, or in similar ways to those 

 mentioned above. 



Though this subject of insect distribution is far from being exhausted 

 by what has been said, it is yet hoped that the different points dwelt upon 

 may awaken a new interest in insects and the insect world among those 

 who, though not trained entomologists, are yet lovers of nature in her 

 different phases. It may interest such to mention that with the marvellous 

 increase of commerce between all countries of the globe, and the bring- 

 ing of continent into close contact with continent, by the ever-increasing 

 speed of ocean vessels, the time appears to be rapidly approaching when 

 practically all insects will, so far as climate will permit, become cos- 

 mopolitan. 



