Ears — Touch 



47 



when the sound comes from the direction whither the 

 feeler points. Hence a male is able to estimate very 

 exactly the direction in which a female is to be 

 found (25). 



As might be expected, many of the insects which 

 have well-developed ears are able to make audible 

 sounds. The shrill chirping of crickets and grass- 

 hoppers for instance, produced by the rasping of hard 

 teeth over ridges or roughened surfaces, is associated, 

 as we have seen, with ven.- perrect organs of hearing, 

 which 'enable the ^ 



insects to appre- " "" 



date each others' 

 songs. 



Organs of 

 Touch. — An 

 insect, clad for 

 the most part in 

 a firm armour of 

 chitin, receives 

 touch - sensations 

 by means of its 

 hairs. Various 

 parts of the body 

 are more or less 

 covered with 

 hairs, some of 

 which have a special sensory function. At the base 

 of every hair is a generating cell by whose activity it 

 has been built up. A nerve-fibril beneath the skin 

 expands into a nerve-cell, whence a line rilament 

 passes through the generating cell, whose substance 

 forms a protecting sheath, into the cavity of the 

 hair (fig. 29 E). These sensory hairs are specially 

 numerous on the feelers and the palps. No one who 

 has observed an insect exploring the space in front 



' J*: 



Fig. 35 — Section through second antenna! segment 

 ofaMiiige. 1 1. Cuticle of and segment ; 111. 

 base of third segment ; a. drum. .V. Autennal 

 nerve ; ^. c. ganglion cells ; r. t-. rod-shaped 

 cells. MagnineU ;oo times. ' ' -^> . - 

 Zeits. wissen. Zoolog., vol. 5S. 



After Child. 



