SUMMARY AND CONCLUSIONS. 305 



the brown-tail moth differs from that of the gipsy moth. It further 

 differs in that two small gregarious chalcidids, both of them closely 

 allied or identical with American species of the same respective 

 genera, have occasionally been reared from imported cocoon masses. 

 Neither of these is common. One, Diglochis omnivora Walk, appears 

 to be specifically indistinguishable from the form which goes under 

 the same name in America, where it has occasionally been reared 

 from the gipsy moth and abundantly from the brown-tail moth. 

 The other is a species of Pteromalus, winch, according to Mr. Craw- 

 ford, is hardly to be distinguished from the tussock-moth parasite, 

 Pteromalus cuproideus How. 



Enough of the latter species have been reared to make small 

 colonies possible, but these colonies have been so very small as to 

 make its establishment improbable. It is hoped that a larger 

 number will be imported in 1911, but since it appears to be of very 

 slight importance in Europe no great enthusiasm is felt over the 

 prospect. 



SUMMARY AND CONCLUSIONS. 



The work of introducing into America the parasites and other 

 natural enemies of the gipsy moth and the brown- tail moth has been 

 more arduous than was anticipated when it was begun. It was soon 

 found that the published information concerning these enemies was 

 deficient and unreliable, and that much original research was neces- 

 sary in order that they might be intelligently handled. Later it 

 developed that the rate of dispersion of the introduced species was 

 so very rapid as to necessitate larger and stronger colonies than had 

 been contemplated. 



The policy originally adopted of employing foreign entomologists 

 to collect the eggs, caterpillars, and pupae of these pests abroad for 

 shipment to the Massachusetts laboratory, where the parasites 

 which they contained might be reared, has resulted in the successful 

 importation and colonization of a considerable number of the para- 

 sites which a study of this material, after its receipt at the laboratory, 

 has indicated as being of importance. Numerous others success- 

 fully imported have been colonized, but so recently as to render the 

 success of the experiment uncertain. On account of the rapidity 

 of dispersion, which results in the parasites being very rare over a 

 large territory instead of being common over a restricted territory, 

 as long a period as four years may elapse before it is possible to recover 

 them after colonization. It has been found impossible to secure cer- 

 tain of the parasites in adequate numbers for colonization under satis- 

 factory conditions. The proportion of such is very small, it is true, 

 but at the same time it may easily be that ultimate success or failure 

 95677°— Bull. 91—11 20 



