Subfamilies Ephialtinae, Xoridinae, and 

 Acaenitinae Denned 



The three subfamilies included in this bulletin were formerly all 

 in one subfamily (Pimplinae) which was defined as having a rather 

 elongate, cylindric body shape; areolet triangular or absent; sternaulus 

 absent or weak and short; tarsal claws not visibly pectinate but often 

 with an accessory tooth (especially in the female); first abdominal 

 segment usually short and broad, with its spiracle at or in front of the 

 midlength, and not strongly curved at the spiracle; and ovipositor 

 almost always more than half as long as abdomen, without a subapical 

 dorsal notch. The above definition will distinguish most of this group 

 of species fiom the majority of other ichneumonids, but is not entirely 

 adequate. No completely workable definition has yet been devised, 

 and the student will need to rely on the habitus figures of the various 

 genera for deciding doubtful cases of whether or not the specimen at 

 hand belongs in the group treated here. 



Studies in the last 20 years have shown the desirability of sub- 

 dividing the subfamily Pimplinae of authors, to arrive at more natural 

 and more easily defined groups of genera. There has been a progres- 

 sive narrowing of the limits of the "Pimplinae" by taking unrelated 

 groups away from it, and in this paper we divide the remainder to 

 make three subfamilies. Two of the resulting subfamilies (Ephial- 

 tinae and Acaenitinae) are probably natural; the third (Xoridinae) 

 may not stand as defined after further critical studies, but represents 

 a plausible synthesis of present knowledge. It is close to the Gelinae. 



Conclusions on relationships which have led to the splitting of the 

 Pimplinae are based on all information available, some of which 

 cannot easily be conveyed in terms of definite characters. Some very 

 important data are in larval morphology. Our information on larvae 

 stems mostly from Beirne's paper on ichneumonid larvae (Trans. Soc. 

 Brit. Ent., vol. 7, pp. 123-190, 1941) and from a larger paper by Dr. 

 J. R. T. Short (Proc. U. S. Nat. Mus., vol. 110, No. 3419, pp. 391-511, 

 64 figs., October 23, 1959). Dr. Short was kind enough to send us 

 a manuscript copy of his paper, which has been extremely helpful in 

 decisions on generic relationships. Such adult characters as can be 

 stated definitely are given in the keys to the three subfamilies and in 

 their descriptions. 



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