Proceedings of the South African Philosophical Society. iii 



Eugaster and Hetrodes, known here under the name of ''Corn- 

 crakes," in which the upper wings are almost rudimentary and 

 hidden under the pronotum, the noise produced is certainly sharper 

 or more sharply rasping than in any other South African species of 

 Locus tinm which I have been able to observe. These rudimentary 

 tegmina, for the lower wing is quite obliterated, are very strong and 

 quite hidden under the elongated pronotum. By the raising or 

 lowering of the prothorax, the latter acting as a resounding board, 

 I have made the live animal produce notes pitched in a different key. 



If, under favourable circumstances, you carefully observe the 

 male of Gryllus capensis at work, you will find that the modulation 

 of the ear-splitting noise is due also to the raising or lowering of the 

 upper wings, the surface of the chitinous abdomen acting also as 

 a resounding board. 



Stridulating or sound-producing organs imply of necessity 

 specialised ears both in the male and in the female : in the male 

 to enable him to redouble his efforts against the singing power of his 

 rival or rivals, or perhaps to enable him to acknowledge his defeat ; 

 in the female to enable her to appreciate perhaps the superiority in 

 that line of one of her numerous suitors, perhaps also for her to 

 repeat sotto voce the challenge or love-song of the suitor. These 

 organs of audition are situated on the front legs in the Locmtincc, 

 and are in the shape of an oblong or ovate exposed tympanum, or of 

 a slit at the bottom of which is a tympanic membrane. It sometimes 

 happens even, that in some species in which the wings are totally 

 obliterated, and are therefore incapable of producing sound in the 

 orthodox manner {Stenopclmatince), these organs of audition are 

 occasionally retained. 



I have already alluded, in treating of the protective colouration in 

 insects, to some of the wonderfully well-protected leaf-like Locustids. 

 In their case it is easy to conceive that this phonation should have 

 developed in the way it has, owing to the possible inability on their 

 part to discover their mates on account of their protective resem- 

 blance to their surroundings. In the Gryllinoi which are not so 

 well protected, and are more of troglodyctic disposition, and mostly 

 nocturnal, the great adaptation to sound-producing is probably due 

 to their being dwellers in caves. You can at any time obtain here 

 in summer nights a singing contest by inducing a Cricket kept in 

 captivity to commence its chirping. 



AcridiincB. — In the Acridiince, of which the peregrine locust is 

 a type, the organs for the production of sound are of a greatly 

 modified type. Instead of the basal part of the wings, it is the hind 

 thigh (femur) which serves that purpose. These thighs, which are 



