MECHANORECEPTION 37 



Mantids lying in ambush detect tlieir prey visually. The eyes being 

 immovable, the head is turned so that the prey is always faced. 

 Although the mantis may then turn its body to line it up with the prey, 

 it can capture a prey which sits at a considerable lateral deviation 

 from the median plane of the thorax. If the prey is close enough it is 

 seized by a rapid (10-30 milliseconds) stroke of the prothoracic legs. 

 The accuracy of hitting in normal mantids is about 85 per cent. Since 



Fig. 27. A. Proprioceptors of the neck region of the mantis. S, sterno- 

 cervical hair plate; N, tergocervical plate. (Redrawn from Mittel- 

 staedt, 1957.) B. Proprioceptors of the second leg of Periplaneta. 

 C, coxa; I, inner coxal hair plate; O, outer coxal hair plate; T, troch- 

 anteral hair plate. (Redrawn from Pringle, 1 938 c.) 



the speed of the stroke is so great, its direction is not controlled by 

 watching the difference between its direction and that of the prey. Its 

 direction is predetermined by information concerning the position of 

 the prey relative to the plane of the prothorax. Thus, the message 

 steering the stroke must contain information about the direction of the 

 prey relative to the head and of the position of the head relative to the 

 prothorax. The first information is provided by the compound eyes ; 

 the second, by hair plates in the neck region. Two pairs of plates are 

 involved ; the sternocervical plate (Pringle, 1938 c) and the tergocervical 



