82 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 



(29—29). The figures given prove better than a long discussion 

 could, that the study of the number of hooks, however promising it 

 may be to the biometrician, is of no use to the systematise 



Although it can only be conceded a very problematic value as an 

 aid in determination, it can still be used, in most cases, as a contribu- 

 tion to the general characterization of the species, genera, and, with 

 certain restrictions, also of the families, among which the Cynipidse, 

 Braconidae, and the greater part the Ichneumonidse show a pretty 

 uniform development of the clasping organ. In so far as a charac- 

 terization of this kind is possible, it is briefly offered below for the 

 families, representatives of which I was able to examine. 



I. Tenthredinid^; 



The distal hooks are slender, slightly curved, typically ribbon- 

 shaped, and very elastic. As a rule, they are arranged in double rows 

 (pi. vii, fig. 4), placed upon the upper branch of the loop formed by 

 the costal and subcostal vein and beginning before it. Single rows are 

 very rare. Subbasal hooks are not always present; when developed 

 they are generally not sharply distinguished (pi. vm, fig. 18), only 

 rarely well differentiated (pi. viii, fig. 15). Marginal bristles are 

 absent or very poorly developed. 



Twenty species were examined, among them Sirex gigas, Ten- 

 thredo mesomchvua L., TentJiredopsis thomsoni in a large number of 

 specimens. 



II. Cynipid.-e 



The distal hooks are slender, very slightly curved, present in small 

 number, and arranged very characteristically on the broadened end 

 of the costal vein, where this reaches the margin (pi. vii, fig. 5). 

 Subbasal hooks and marginal bristles cannot be distinguished from 

 each other. They are present in very small numbers, and not well 

 developed. 



Three species were examined. 



III. Ichneumonid.^ 



The distal hooks are long, slender, moderately curved, and placed 

 upon the costal vein in a single row (as in all following), always 

 beginning behind the junction of the cross-vein (pi. vil, figs. 3, 6). 



Differentiated subbasal hooks, abruptly bent at the point, are 

 always present. They are placed near the base of the wing, upon 

 the upper branch of the forked costal vein, which branch disappears 

 after a short course (pi. viii, fig. 16). When present in greater num- 



