620 THE SENSES AND SENSORY ORGANS. 
the semicircular canals and cochlea of a Vertebrate ; and vibra- 
tions of this fluid would be an efficient cause acting upon the 
chordotonal elements of the halter. The vibrations of this 
fluid would necessarily be greatly intensified by the varying 
pressure on the elastic capitellum of the halter. 
I think it probable that some such action occurs as that 
which I have indicated. The halteres appear to me to be 
microphones of a most efficient kind, which probably enable 
these insects to perceive sounds the intensity of which is far 
less than those which affect the human ear. 
12. THE WING ORGANS. 
The wings of most Insects contain organs which are similar 
to the chordotonal organs of the halteres of the Diptera. 
These were discovered by Braxton Hicks [292], and have been 
more fully described by Graber [285]. 
Fic. 81.—The wing organs of Clytus and Chrysopa, after Graber [285]. 4, the 
trachea and nerve of the submarginal nervure of the wing of Clytus, seen as a 
transparent object; 4, surface view of three of the organs from the same; 
C, group of pores on the base of the submarginal nervure of the wing of Chry- 
sopa; a, bands uniting the organs with the integument ; ¢/, chordotonal thread ; 
m, nerve; /, pore or vesicle; /, trachea. 
After investigating these organs in various insects, Graber 
obtained a very satisfactory preparation from the subcostal 
nervure of the wing of Clytus, which he describes in the fol- 
lowing terms: ‘I observed a group of closely-packed and rela- 
tively small pores on that part of the subcostal nervure which 
