transported alive to the country where it is needed, and again 

 the discovery and successful transportation alike count for noth- 

 ing- economically, unless it can be established at large after its 

 arrival. It is no doubt in many cases decidedly more easy to 

 discover natural enemies of an insect pest than it is to establish 

 them in a new and distant country. We have heard some, who 

 profess to be in favor of the repression of injurious insects by 

 means, of natural enemies, talk of the discovery of a parasite, 

 as though the fact of this discovery were all important, whereas 



we must repeat that unless the parasite can Ije successlull\- in- 

 troduced and established and duly performs its share of work in 

 controlling the pest, the discovery is of insignificant impor- 

 tance. Further, cases where a single natural enenn- is alone 

 sufficient to keep down an injurious insect are rare and excc])- 

 tional, and few pests are to be kept down in this way. .\s a rule, 

 it is a complex of causes that keeps an insect in check, often 

 the joint attack of various parasites and predators, and it may 

 be various diseases and other conditions combined. C )nlv in 

 exceptional cases can the economic entomologist hope to suc- 

 ceed with a single parasite, as any practical field worker nuist 



