REVISION OF THE NEARCTIC ICHNEUMON-FLIES 

 BELONGING TO THE GENUS MACROCENTRUS 



By C. F. W. MuESEBECK 



Senior Entomologist, Bureau of Entomology, United States Department of 



Agriculture 



During the past several years species of the braconid genus 

 Macrocentrus Curtis have been rather abundantly reared from the 

 larvae of certain injurious Lepidoptera, especially from the intro- 

 duced oriental fruit moth {Laspeyresia molesta Busck) and the Euro- 

 pean corn borer {Pyrausta nubilalis Hiibner). The numerous re- 

 quests for identification of specimens of Maci'ocentrus that have come 

 to the taxonomic unit of the Bureau of Entomology, combined with 

 the difficulties in making such identifications owing to the unworked 

 condition of the group, resulted in a demand for a revision of the 

 species occurring in the United States and Canada, Accordingly, I 

 was requested to undertake a study of Macrocentms^ the results of 

 which, presented in this paper, represent a joint contribution from the 

 division of forest insects (gipsy moth and brown-tail moth investiga- 

 tions) and the taxonomic unit of the Bureau of Entomology. 



For the opportunity of examining material in their custody I am 

 indebted to Dr. E. T. Cresson, jr., of the Philadelphia Academy of 

 Natural Sciences; to C. W. Johnson, of the Boston Society of Nat- 

 ural History; and Dr. W. E. Britton, of the Connecticut Agricul- 

 tural Experiment Station. I wish also to acknowledge my appre- 

 ciation of helpful suggestions given by A. B. Gahan and R. A. 

 Cushman, of the taxonomic staff of the Bureau of Entomology. 

 Finally, I am indebted to C. W. Collins, in charge of the gipsy 

 moth and brown-tail moth investigations of the division of forest 

 insects, and to Dr. Harold Morrison, in charge of the taxonomic 

 unit, whose cooperation has made the study possible. 



Although, as noted above, certain material in other institutions 

 has been examined, the present revision is based primarily on the 

 collections of Macrocentrus in the United States National Museum, 

 which consist in large part of specimens reared in the Bureau of 

 Entomology in the course of studies relating to the life history and 



No. 2923.— Proceedings U. S. National Museum. Vol. 80, Art. 23. 



98306—32 1 1 



