622 THE SENSES 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. 
Fic. 82.—The wing organs on the remigium of the Blow-fly. 4, surface view ; B, 
section through the line 4 in A ; ¢, epidermis; g, ganglion cells ; 4, hypodermal 
cells 5 7, 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. 
