72 THE PHYSIOLOGY OF INSECT SENSES 



and Crisp maintained that there is communication. They performed a 

 series of extirpation experiments that are in agreement with 

 Baunacke's hypothesis (Fig. 52). In the control (A) bugs on a seesaw 

 gave sixty-eight correct performances out of ninety- two. B did not 



Fig. 52. A. Diagram illustrating the various operations performed on the 

 three pairs of pressure organs in Nepa. (Redrawn from Thorpe and 

 Crisp, 1947.) B. Diagram to illustrate the principle of action, when 

 tilted in water, of a system of distensible membranes enclosing an air 

 space and connected by an air-filled tube, of three pressure receptors 

 of one side of Nepa. (Redrawn from Thorpe and Crisp, 1947.) 



differ statistically from A, C and D were generally negative; E res- 

 ponded fairly well and F less well. It was concluded that the three pair 

 of organs in Nepa were indeed co-ordinated as a differential mano- 

 meter system. 



A less-compHcated organ occurs in adults of the predatory water 

 bug Aphelocheirus (Fig. 53). There is a pair of oval sensory plates on 



