WALTER] CLASPING ORGANS IN HYMENOPTERA 73 



same location, which partly resemble subbasal hooks and partly mar- 

 ginal bristles (pi. vin, fig. 18). The Ichneumonidae and Chrysididae 

 possess well developed, highly differentiated snbbasal hooks. In the 

 first these arise close to the base of the wing from the npper of the 

 two branches into which the costal vein divides at its origin (pi. vm, 

 fig. 3; pi. vin, fig. 16). In the Ichneumonidae there is either only 

 one subbasal hook or a group of hooks standing close together, 

 while in the Chrysididae, where always a considerable number of 

 them is present, the hooks stand at greater and irregular intervals 

 (pi. vin, fig. 17). The subbasal hooks are directed obliquely to- 

 wards the apex and outer side of the wing. With the costal vein 

 they inclose an angle of about 50 to 80 degrees (pi. viii^ figs. 14-18), 

 and with the wing surface, as the accompanying diagrammatic figure 

 of a cross-section shows, an angle of about 140 to nearly 180 degrees. 

 When this angle approaches 180 degrees these 

 hooks lie almost wholly in the plane of the wing 

 surface. 



In their outward appearance the subbasal hooks 

 differ from the costal hooks principally by their 

 being less curved; only just below the distal end 

 they are bent. Like the distal hooks, their trans- 

 verse section is circular at the base, and narrow, 

 elliptical distally. They arise from the upper side 

 of the costal vein ; or, when this is bifurcate, 

 from its anterior branch, in the same manner as the distal hooks 

 (pi. viii, figs. 15, 16, 17, oCA). The anterior branch of the costal 

 vein is, in the Ichneumonidae, short and thickened in the region of 

 the subbasal hooks. It is, as the sections show, often provided with 

 an entirely isolated lumen. Like the distal hooks, the subbasal hooks 

 possess a lumen, in transverse sections circular or punctiform at the 

 base and slit-shaped distally. When the vein from w T hich the hooks 

 arise is hollow the hook cavity openly communicates with the vein 

 cavity. Distally the hook cavity terminates below the pointed apex 

 of the hook ; its end is closed. The manner of insertion is the same 

 as in the distal hooks. The points of insertions do not, however, 

 lie central on the broad side of the costal vein, which is elliptical in 

 cross-section, but greatly approximated to the margin of the wing; 

 at times wholly marginal. (Compare the above diagram, fig. 20, of 

 a cross-section through the wing of an ichneumon-wasp in the region 

 of the subbasal hooks.) 



Besides the distal and subbasal hooks, the anterior margin of the 

 hind wing, as a rule, bears more or less strongly developed marginal 



