THE I. \TER.\AL A XATO.UY OF 



L49 



Fit*. 1 66. Side view of a locust with the wings 

 removed; /. tympanum. 



part of these organs, the tympanum, is conspicuous, being a thinned 

 portion of the body-wall (Fig. 166). 



Closely applied to the 

 inner surface of each 

 tympanum (Fig. 167, T), 

 there is a ganglion known 

 as Muller's organ (ga), 

 first described by Muller 

 (1826). This ganglion 

 contains many ganglion- 

 cells and scolopalae and is the termination of a nerve extending 

 from the central nervous system, the auditory nerve (;/). Figure 

 1 68 represents a section of Mulbr's organ, showing the ganglion-cells 

 and scolopalae. 



Intimately associated with the Muller's organ are two horny 

 processes (Fig. 167, o and u) and a pear-shaped vesicle (Fig. 167, bi) 

 and near the margin 

 of the tympanum, 

 there is a spiracle 

 (Fig. 167, ,v/), which 

 admits air to a space 

 inside of the tympa- 

 num, the tympanal 

 air-chamber. 



As the nerve-end- 

 ings in Muller's organ 

 are attached to the 

 tympanum, it is a 

 chordotonal organ 

 of the integumental 

 type; it is attached 

 to a vibratile mem- 

 brane, between two 

 air-spaces. 



I 



Fig. 167. Ear of a locust, Calnplenus italic us, seen from 

 inner side; T, typmanum; TR, its border; o, u, two 

 horn-like processes; bi, pear-shaped vesicle; n, audi- 

 tory nerve; ga, terminal ganglion or Muller's organ; 

 st, spiracle: M, tensor muscle of the tympanum (From 

 Packard after Graber). 



d. THE CHORDOTO- 

 NAL ORGANS OF THE 

 LOCUSTID.-E AND OF 

 THK C.KYLLIDjE 



In the long-horned grasshoppers and in the crickets, there is a pair 

 of tympana near the proximal end of the tibia of each fore leg. In 



