PREFACE. 



In the ijreseiit work I have attempted to give a systematic descrip- 

 tion of the species of the Hymenopterous family Proctotrypidce, found 

 in Korth America, north of Mexico, at the same time systematizing 

 and describing the genera of the worhl, as an aid to fntni^ students. 



It represents several years study of the family, and although sen- 

 sible of its incompleteness and many imperfections I shall be fully 

 repaid for the labor involved if I have paved the way for a more 

 thorough study of the family or stimulated others to collect these 

 curious insects and study their remarkable habits. 



In the preparation of this work my tliauks are especially due to the 

 following friends: 



To Mr. W. Hague Harrington, of Ottawa, Canada, I am indebted 

 for valuable contributions to my cabinet during many years and for 

 types of some of the species described by the Abbe Provancher; to my 

 friends and colleagues, E. A. Schwarz, Theo. Pergande, and Otto 

 Heidemann, who have contributed by donating, from time to time, 

 specimens taken during our entomological excursions in and around 

 Washington and elsewhere; to Prof. E. A. Popenoe, for a few species 

 collected in Kansas; to Dr. C. V. Kiley, for the free use of his valuable 

 notes on the reariugs and habits of the species, and for other courte- 

 sies shown me during the progress of the work; to Mr. L. O. Howard, 

 my friend and colaborer in the Microhymenoptera for like courtesies; 

 to Dr. Gustav Mayr, of Vienna, Austria, for some typical European 

 genera, and to Dr. C. W. Stiles, for making a microscopical section of 

 the ovipositor. 



Finally, to Prof. Dr. K. Mobius, director of the Royal Berlin Museum, 

 and to Dr. F. Karsch, custodian of said museum, my warmest thanks 

 are due for allowing me to study and describe the North American 

 species contained therein, 



I have also had the privilege of studying and describing the many 

 new and interesting forms in the National collection and in the collec- 

 tion of the American Entomological Society, kindly sent by Mr. E. T. 

 Cresson to the Museum for study and exchange, and which contains 

 the types of Cresson, Patton, and Haldeman. 



Dr. Eiley has also permitted me to include from his maiuiscript, a 

 few descriptions of species in which he has been particularly interested. 



W. H. A. 



Washington, D. C, March 4, 1893. 



