66 R. Bigalke 



The Production of Sound in a South African Locustid 

 Acanthoplus bechuanus Per. 



By R. Bigalke, M.A. 



In South Africa there occurs a number of species of large, 

 almost wingless locustids known as korenkrieks; such a korenkriek 

 (A. bechuanus Per.) is common at Glen, O.F.S., during the 

 months of April and May, and can be found in long grass, on 

 acacia bushes, or on cypress trees. During June these insects 

 were observed to become less conmion, and later to disappear 

 altogether. From the dead and benumbed specimens obtained at 

 this time it was concluded that they were killed off by the frosty 

 weather. 



Both male and female are stoutly built, and each has a large 

 spiny shield-like pronotum which projects backwards and extends 

 over the mesonotum and metanotum. In the adult male the 

 metathoracic wings are absent, and the tegmina are very much 

 reduced in size. In other locustids, such as for example Microcen- 

 irum, the tegmina are well developed and veined, and, in addition 

 to being provided with a stridulating apparatus, they protect the 

 hind wings, the organs of flight. In A. bechuanus the sole function 

 of the much reduced tegmina is that of producing a shrill sound; 

 this can be kept up for a long time, and may be heard during 

 the greater part of the day when these insects are common; it 

 has also been noticed on moonlight and other evenings. Since these 

 tegmina are very much reduced in size and subserve one function 

 only in the male, that of stridulation, it seems justifiable to de- 

 signate them with a special name, and the term ionotegmen (L. 

 tonus = sound or tone) is suggested. 



The adult female has vestiges of tegmina much smaller than 

 those of the male; there is one in the form of a very small flap 

 along each side of the mesonotum, and they are separated by a 

 considerable space, neither shoving any trace of a stridulating 



