622 



THE SEXSES AND SENSORY ORGANS. 



of the subcostal nervure, and the surface view is represented 

 in Fig. 82, A. 



Graber states that he has not obtained any satisfactory 

 sections of the wing nervures showing these organs, nor have 

 I been more successful except in the advanced pupa of the 

 Blow-fly. I have represented a section of the integument and 

 underlying structures from the remigium of a pupa, and this 

 shows the partially developed wing organs, and leads me to the 

 view that each nerve terminal is connected with a vesicle 

 enclosing a suspended spherical particle, which Graber mis- 

 took for a pore in the integument. If this is the case, we have 

 in the wing organs the less specialised condition which attains 

 its fuller development in the halter. 



FIG. 82. The wing organs on the remigium of the Blow-fly. A, surface view ; B, 

 section through the line /' in A ; e, epidermis ; g, ganglion cells ; //, hypodermal 

 cells ; n, nerve. 



Such organs are commonly found on both the anterior and 

 posterior wings of insects, but are usually more highly 

 developed on the posterior pair. Thus it will be seen that in 

 the Diptera the halteres not only replace the posterior wings 

 of other insects, but exhibit organs which are usually found on 

 the posterior wings, and which have probably a function similar 

 to that of the organs at the bases of the halteres. 



