17S Leland O. Howard 



In the majority of the subfamihes, however, there is a much 

 greater subdivision of the correlation of structure and habit, 

 frequently descending to genera, and often apparently to 

 species. 



A lengthy series of interesting though occasionally appar- 

 ently conflicting facts could be gained by the careful study of 

 the host-relations of the species of any one of these subfamilies, 

 but in undertaking such a study it is prerequisite that the 

 group shall have been well classified from morphological de- 

 tails and that verj^ extensive rearings shall have been made. 

 These two prerequisites debar us at the present time from any 

 but initial attempts at generalizations with most of the groups 

 where the general trend of habit is not at once evident. It is 

 even too soon to secure the best view of the conditions in the 

 subfamily which I have chosen, but sufficient facts are avail- 

 able to render study and arrangement of interest and perhaps 

 of importance. 



The Encyrtinae of Europe have been carefully monographed 

 bj? that learned and able entomologist, Dr. G. Mayr, of Vienna, 

 (Verh. d. K. K. Zool-Bot. Ges. Wien, 1876). Nearly all of 

 the European forms have passed beneath his analytical ej^e 

 and a model systematic paper has resulted. He has also col- 

 lated and displayed in an instructive table all biologic facts 

 known concerning the species of that fauna. 



Originally drawn to the study of the group through its econ- 

 omic importance as containing so man}' parasites of injurious 

 Coccidae, the writer has, at unfortunately rare intervals, since 

 18S0 studied the structure of the North American forms with 

 the unrivalled advantages offered by the collection of the U. 

 S. National Museum. The European species accepted by 

 Mayr in 1876 numbered 102, distributed in 25 genera. The 

 North American species contained in the National Museum, 

 number about 150. Twenty of the 25 European genera have 

 been found to have representatives in our fauna while repre- 

 sentatives of 14 new genera have been found. The 150 species 

 of the Museum collection have all been carefully studied ge- 

 nerically and have been generically placed, although only about 

 50 have received specific description and name. This is our 



