44 THE PHYSIOLOGY OF INSECT SENSES 



parallel to the length of the leg (similarly in the palps) and when the 

 tarsus is pressed against the ground the compression lines in the cuticle 

 of the upper surface, where these sensilla are located, will also be 

 longitudinal. It must be the compression component which is effective. 

 Electrical recordings have shown clearly that these sensilla are most 

 sensitive to pressure on the cuticle (Pringle, 1938 b). Adaptation is 

 slow and incomplete. 



Stretch Receptors 



Certain of the Type II receptors for which no function had been known 

 have recently been shown by Finlayson and Lowenstein (1955, 1958) 



Fig. 34. Stretch receptor in the right side of the fourth abdominal segment 

 of Periplaneta. The broken lines indicate the posterior ends of the 

 fourth and fifth muscle bands, counting from the dorsal mid-line. 

 (Redrawn from Finlayson and Lowenstein, 1958.) 



to be stretch receptors analogous to the stretch receptors of Crustacea 

 discovered by Alexandrowicz (1951, 1952 a, 1952 b, 1954, 1956) and to 

 the muscle spindles of vertebrates. Firstdescribedby Zawarzin(1912 a) 

 and Rogosina (1928) in dragonfly larvae, they have now been found in 



