506 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 84 



and has given comments relative to their success or faikire. I rather 

 wish that it were possible here to follow out this plan to date. 

 Trouvelot's list was by no means complete for the period it covered, 

 and since the date of its publication many new efforts have been made 

 by many nations, and, as in the case of Aphelinus mali, the same para- 

 site has been taken with success to many different countries and to 

 many distinct life zones. Further, experience has shown that reports of 

 success are frequently premature, while reports of failure are very 

 often premature ; and there are recorded already cases where parasites 

 have recovered 20 and even 23 or 24 years after introduction, all hope 

 of success having in the meanwhile been abandoned. 



Many articles discussing various aspects of natural control have 

 been published in recent years. Some of them look at the subject from 

 an ecological standpoint, as in fact is very necessary, while W. R. 

 Thompson actually goes into the mathematics of the subject. The 

 simple, broad idea that the writer had when he began to bring parasites 

 of the gipsy moth from Europe to America, that to reproduce in this 

 country so far as possible the parasite complex that exists in Europe 

 would be the desirable thing to do, and that to do it was simply to 

 bring over in number the parasitized stages of the host insect, is now 

 referred to condescendingly by recent workers as " the old method," 

 but it is still being followed in the main in much of the big importation 

 work that is going on. 



I think it will be well to publish here the chronological list as 

 printed by Trouvelot. It is, put into English, as follows : 



Trouvki.ot's List (19.^5) 



1873 Introduction into France of Tyroglyphus phylloxerae Riley. American 



parasite of Phylloxera. — No appreciable results. 



1874 Introduction of Coccinella ii-punctata from England into New Zealand. — 



Acclimatized, but no results. 

 1883 Introduction of Apantcles glomcralns from Europe to America to fight 



cabbage worm. — Good result. 

 1889 Importation of Noz'ius into California from Australia. — Splendid result. 



Afterwards constantly successful in Italy, Portugal,. Florida, Cape 



Colony, Hawaii, Egypt, France, etc. 



1891 Importation into America of European parasites of the Hessian fly. — 



One species recovered. 



1892 Attempted introduction to California of Thalpocharcs cocclphaga, an 



Australian Lepidopterous parasite of wax scales. — No result. 

 1892 to 1902 Trials of the same nature with the European Erastria scifula. — 



No result. 

 1892 Attempted introduction into tlic United States of a Clcrid (Tluiitasiiiiiis 



fonuicaritis), European predator on the larvae of bark-beetles. — The 



species not recovered. 



