Fig. 380. — Sphecius speciosus. 



CHAPTER XXV 

 THE WINGS OF THE HYMENOPTERA 



(a) THE GENERAL FEATURES OF THE WINGS OF THE HYMENOPTERA 



The members of this order have four wings (Fig. 380) ; these are mem- 

 branous, and have the wing-venation more or less reduced. In the more 

 generaHzed famihes the reduction of the wing-venation is shght; in the 



more speciaHzed famihes, it 

 is extreme. The two pairs of 

 wings are similar in texture. 

 The wings of each side are 

 held together by a row of 

 hooks, the hamuli, on the 

 front margin of the hind wing 

 (Fig. 381, h); these hooks 

 fasten to a fold in the hind 

 margin of the front wing, so 

 that the two wings present a 

 continuous surface. The hind 

 wings are smaller than the fore wings, and have a more reduced venation. 

 Some forms are apterous. 



(6) THE VENATION OF THE WINGS OF THE MORE GENERALIZED HYMENOPTERA 



The suborder Chalastogastra has been recognized as the more general- 

 ized of the two suborders of this order independently of any consideration of 

 the characters presented by the wings. This conclusion has been con- 

 firmed by studies of the wings; for within this suborder are to be found the 

 most generalized wings that exist 

 among living representatives of the 

 Hymenoptera. 



In the wings of certain sawflies 

 of the families Xyelidae and Lydidas 

 we find a close approximation in the 

 number of the wing-veins to that of the 

 hypothetical primitive type of wing- 

 venation. But even here the courses 

 of the branches of the forked veins 

 have been greatly modified. These changes have been so great that the 

 determination of the homologies of the wing-veins in this order was one of 

 the most difficult problems of this kind that arose in the course of the study 

 of the wings of insects. 



(362) 



Fig. 381. — Wings of Apis showing 

 hamuli. 



