PARASITIC AND PREDACEOUS INSECTS. 685 



through, agencies other than its insect enemies, and in this case 

 the facts are particularly interesting, because of the ease with 

 which its disappearance may be attributed to some of the recent 

 introductions from Australia. 



The other law that is worth considering in this connection is 

 that, as a rule, the animals and plants of what is known as the 

 " Old " World i. e., of Europe and Asia when introduced into 

 North America have shown a greater power of multiplication 

 than the indigenoiis species, and in a large number of instances 

 have taken the place of the native forms, which have not been 

 able to compete with them in the struggle for existence. This 

 is still more true of the species introduced from the Old World, 

 as well as from America, into Australia, where the advantage of 

 the introduced forms, as compared with the indigenes, has been 

 in many cases still more marked. 



There are some instances in which there can be no doubt what- 

 ever as to the good which will flow from the introduction of bene- 

 ficial species, and an illustration is afforded in the caprifig insect 

 (Blastophaga psenes). There can be no question as to the good 

 which would result from the introduction of this species from 

 Smyrna into those sections of California where the Smyrna fig is 

 grown without its intervention, and there are other similar in- 

 stances which promise well and involve no risk. But I have said 

 enough to show that the successful utilization of beneficial in- 

 sects is by no means a simple matter, and that discriminating 

 knowledge is required to insure success or prevent disaster, espe- 

 cially in the second category dealt with in this paper. The danger 

 attending introductions of beneficial species by unconsciously ac- 

 companying them with injurious forms, or by failure to appreci- 

 ate the facts here set forth, is well illustrated by the introduction 

 to Europe of our Peronospora viticola, of the English sparrow to 

 America, and of the mongoose to Jamaica. 



Wherever the importance of the matter leads to legislation what 

 are denominated " political " methods are apt either to control or 

 in some way influence the resulting efforts too often with unfor- 

 tunate consequences. We should, as economic entomologists, be 

 on the alert for the special cases where the introduction or dis- 

 semination of beneficial 'species promises good results, and do our 

 best to encourage an intelligent public appreciation of such special 

 cases, while discouraging all that is of unscientific or sensational 

 nature, as likely to mislead and ultimately do our profession more 

 harm than good. 



