PREY CAPTURE IN MANTIDS 



53 



The sternocervical plate was found by Pringle (1938), the tergocervical 

 plate by the author (Mittelstaedt, 1952). There is another very small 

 group of hairs at the pro-episternal wall of the prothorax which I shall not 

 mention further, because its functional influence can be neglected. 



Fig. 1. Proprioceptors of the neck 

 region (left side). K = sternocervi- 

 cal hair plate, situated on the an- 

 terior end of the laterocervical scler- 

 ite (L). N = tergocervical plate. 

 The common afferent nerve of both 

 organs is cut at the ventral border of 

 the laterocervical sclerite. (O). 



The external physical mechanism of these hair plates is easily under- 

 stood. In the normal position of the head some of the hair sensillae are 

 bent down by the posterior wall of the head. If the head is turned hori- 

 zontally, say to the left, some more hairs on the left-side plates are bent 

 down, while on the right side a correlated nimiber are set free and erected 

 elastically. 



As Pringle (1938) has demonstrated in Periplaneta, bending down a 

 hair causes an increase in the impulse frequency of the afferent nerve, 

 which, after an initial peak rising and falling within a few seconds, remains 

 constant in time. Thus each position of the head causes a correlated pattern 

 of nervous activity, and the system is indeed able to take up information 

 about the position of the head as has been demonstrated by the author in 

 dragonflies (Mittelstaedt, 1950). 



The first experimental series consists of four sets. The performance of the 

 animal in hitting prey has been examined, ( 1 ) after cutting ofif the sensory 

 nerves of the hair plates, (2) after giving the head a fixed position relative 

 to the prothorax, (3) after a combination of (1) and (2), (4) after having 

 loaded the head of the otherwise undisturbed animal by an extraneous 

 mechanical force. 



In all four cases a statistical method was used to get quantitative results 

 about the hitting performance. The animals (I have worked mainly with 

 Parastagmatoptera imipunctata from Argentina) were sitting free on the 

 gauze ceiling of the cage in which they were normally kept. Then as many 

 files (I have used Calliphora and Lucilia) were brought in as the experi- 

 menter and his assistant could easily observe while they wrote down what 



