394 PROCEEDINGS OF THE NATIONAL MUSEUM vol. no 



that the keys to subfamilies and tribes will require no great modifi- 

 cation as a result of future work, which is expected to take the form 

 of detailed studies within tribes and genera. As a result of such work 

 the keys to genera given here will be greatly modified, for the genera 

 studied were usuall}^ represented b}^ but two or three species. This 

 number of species might be satisfactory if one could assume that the 

 larval characters of all the species of a genus would indicate a close 

 relationship. This is ver}^ far from being the case. In some genera 

 this may be due to species differing more as larvae than as adults. In 

 others, as in the genus Scamhus, it appears to be due to the confused 

 state of the taxonomy of the adults. However, it is hoped that the 

 present keys to genera will serve as a basis for future studies. 



It is generally believed that, since adult insects show a greater 

 degree of differentiation than larvae, their characters are likely to 

 remain more important for species identification (van Emden, 1955). 

 No attempt has been made in the present study to give a key to 

 species. A vast amount of material would be required for such 

 work. But it is significant that species of the braconid genus Apanteles 

 can be arranged into groups corresponding \vith the groups into 

 which the adults are divided (Short, 1953). 



External Structure of Final Instar Larva 



The final instar ichneumonid larva consists of a hemispherical 

 head, three thoracic segments, and ten abdominal segments. The 

 cranium is lightly sclerotized, with the mandibles and certain bands 

 associated with the mouthparts more heavily sclerotized. The body 

 waU of the thorax and abdomen is very lightly sclerotized or un- 

 sclerotized, with the exception of the spiracles and setae. The spi- 

 racles are situated in most species on the prothoracic and first eight 

 abdominal segments. A line of setae is present in most species encir- 

 cling each thoracic and abdominal segment. Small projections are 

 present on the skin and these maj' be lightly sclerotized. 



The structures used in^this classification are the form of the 

 mandibles and head sclerites, and of the antennae, spiracles, and 

 skin. For the basis of the terminology of the head parts, which is 

 outlined below, reference should be made to Short (1952). The 

 head of ichneumonids (fig. 1) is lightly sclerotized except for certain 

 more heavily sclerotized bands strengthening the cranium in the 

 region of the mandibles, maxillae, and labium. The sclerotic arch, 

 which is sometimes present dorsal to the mandibles (md), is called 

 the epistoma (epst). The anterior tentorial pits (at) are situated in 

 the epistoma. Lateral to each mandible is a pleurostoma (plst). 

 The mandible articulates with two processes of the pleurostoma (fig. 

 Ic). The anterior pleurostomal process (app) fits into a cavity of 



