ICHNEUMONID FINAL INSTAR LARVAE SHORT 393 



mounted in Canada balsam. Balsam was used to ensure a satis- 

 factory permanent mount, but for more rapid work larvae may be 

 transferred from distilled water to Faure's fluid. Where larval mate- 

 rial was available in the host pupa, as in the Ichneumoninae and 

 Pimplini, the entire pupa was softened by boiling in caustic potash 

 and the pupa was cut open when soft to extract the ichneumonid 

 larval skin. This method ensured that the brittle pupa was not 

 not damaged. Fresh larvae were opened by a midventral cut and 

 then boiled in a 5 percent solution of caustic potash. They were 

 then washed, dehydrated, and mounted. 



Nomenclature 



The taxonomy of the Ichneumonidae is in a confused state, and the 

 nomenclature of European and American authors differs to some 

 extent. Since much of the material used in this study is North 

 American in origin, the nomenclature of Walkley (1958) is used. The 

 names of larvae described in the literature have been altered, when 

 necessary, to conform with this nomenclature. When genera were 

 not listed by Miss Walldey, her advice was sought on nomenclature, 

 or, if the genera were listed in Kloet and Hincks (1945), the nomen- 

 clature of these authors was followed. 



Description and Classification 



Since the relationships indicated by the larval characters support 

 a classification similar to that given by Townes and Townes (1951) 

 in the U.S. Department of Agriculture's synoptic catalog and by 

 Walkley (1958) in the supplement to that catalog, the classification 

 of these- authors has been followed. Although a somewhat different 

 classification could have been constructed on the basis of larval 

 structure alone, every effort was made to avoid this because informa- 

 tion on both larvae and adults is essential for an understanding of 

 the taxonomy of the group. A classification based solely on the 

 characters of the larvae would be as unsatisfactory as a classification 

 based solely on the characters of the adults. 



It was necessary to depart from the classification in the above- 

 mentioned synoptic catalog in one case: The Anomalinae are here 

 considered as a separate subfamily rather than as a tribe of the 

 Ophioninae. Such differences are to be expected since the inde- 

 pendence of larval and adult forms makes a separate evolution possible 

 (Wiggles worth, 1954). Selective factors acting on the legless larvae 

 are different from those acting on the mobile adults. 



Studies on larval systematics are of interest from two standpoints; 

 they enable workers to identify larvae and they help in understanding 

 the classification of the adults (see van Emden, 1957). It is hoped 



