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ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1923 



As to organs of hearing, everyone knows that insects do not have 

 ears such as ours on the sides of their heads, yet it is surprising 

 to most people to learn that some of them may have auditory organs 

 on the sides of the body or in the legs. The grasshopper, for example, 



Fig. 32. — The Carolina locust, a grasshopper (Dissosteira Carolina), with front wing 

 elevated to show the large "ear" (e) oa side of first abdominal segment. (1% times 

 natural size) 



has a large cavity on each side of its first abdominal segment which 

 has a tense eardrumlike membrane or tympanum stretched over its 

 inner surface (fig. 32, e). Air sacs lie against the inside face of the 



EW. 



Tm 



Tm 



Fig. 33. — Details of the "car" of the Carolina locust (greatly enlarged). A, external 

 view of the ear in surrounding part of first abdominal segment (IT), d, upper sup- 

 porting arm of internal peg (B, Pg) of tympanum; EW, wall of external ear cavity; 

 P, pear-shaped thickening of tympanum ; Pt, external pit of tympanum forming the 

 internal peg (B, Pg) ; Sp, first abdominal spiracle ;* Tm, tympanum; v, lower support- 

 ing arm of the tympanal peg. B, inner view of the wall of the ear cavity (EW), the 

 tympanum (Tm) and other parts shown in A. The external pit (A, Pt) forms a large 

 internal peg (Pg) to which is attached the sense body or Miiller's organ (SB) which 

 receives the auditory nerve (.Yi - ). J/i'J, the tensor muscle of the tympanum 



membrane, which would seem to furnish the proper statical condi- 

 tion to allow it to vibrate freely with sound waves of the air. At- 

 tached to the inner surface of the tympanum, moreover, there is a 

 complicated sensory apparatus (fig. 33, B). This consists of a 

 cellular body (SB) known as Miiller's organ, which is continuous 



