THE OBGANS OF SPECIAL SENSE. 33 



wings, they are also called balancers, from an idea that they are 

 connected with flight. A very large nerve, terminating in nerve 

 cells fills their cavity, and is connected with a number of 

 sin ill, highly refracting bodies, regularly arranged around the 

 base of the organ, which I am inclined to regard as oto- 

 conia, and if such is the case, the halteres are manifesty 

 organs of hearing. That flies do hear, may be inferred from 

 their possessing the power of emitting special sounds, and also by 

 the manner in which they disappear when one is captured and 

 allowed to make the peculiar plaintive note, which they in- 

 variably emit when distressed. In grasshoppers and other 

 orthoptera, the organs of hearing are situated on the anterior 

 tibiae, so that the position of the halteres cannot be urged as an 

 argument against such a function. A number of minute organs* 

 similar to those, which I believe to be otoconia in the halteres^ 

 are disposed in regular groups in the sub-costal nervure of the 

 wing. These are remarkably constant in insects, and are 

 especially interesting in relation to the halteres of flies, leading 

 us, as it were, gradually up to the complete modification of the 

 second pair of wings into organs of special sense. 



The frontal sac may be connected with the sense of smell. The 

 cephalo-stemum is a most remarkable organ, hitherto undescribed : 

 and the lobes of the proboscis are probably the seat of taste, as 

 they are largely supplied with nerves and have peculiar nipple- 

 shaped organs on their surface. The palpi are probably also con- 

 cerned in taste when the food is regurgitated ; and perhaps they 

 assist the insect in its search for food as they are covered with 

 minute openings with transparent sacs beneath, like those of the 

 antenna?. Many of the hairs which clothe the various parts of the 

 insect may also be endowed with special sense, as their bulbs are 

 supplied largely with nerve filaments. I think it extremely pro- 



* These organs were first pointed out by Dr. Braxton Hicks, but their 

 internal structure has not hitherto been described. 



