XII 



EARS 



285 



modified hairs, and he states that in certain females the stages 

 intermediate between hair and peg can be found. There is 

 apparently much variety in the structure of these instruments in 

 different species, and even in individuals of the same species. 

 In Stenohothrus lineatus, instead of pegs, the instrument consists 

 of raised folds. 



In some of tlie aberrant forms of Acridiidae certain Eremo- 

 biides and Pneumorides the males are provided with sound- 

 producing instruments different to those we have described, both 

 as regards situation and structure. 



If the dorsal aspect of the first segment of the hind body of 

 an Acridian Insect be carefully examined there may be seen in 

 the majority of species an organ which has 

 somewhat the appearance of an ear (Fig. 172), 

 and wiiich there is- great reason for believing to 

 be really an organ of that nature. It is situate 

 a little over the articulation of the hind leg, 



very close to the 

 spot where . the 

 sound is, as above 

 described, produced. 

 There are three 

 forms of these Acri- 

 dian ears as described by Brunner:^ 

 (1) a membrane surrounded by a 

 rim ; (2) the membrane somewdiat 

 depressed, a portion of the segment 

 projecting a little over it ; (3) the 

 depression very strongly marked, 

 and the sides projecting over it so 

 much that all that is seen externally 

 is a sort of broad slit with a cavity 

 beneath it. This last is the con- 

 dition in which the ear exists in 

 the genera Mecostethus (Fig. 173) 

 and Stenohothrus, which are among 

 our few native grasshoppers. On 

 minute examination this ear proves to consist of a tympanum 

 supplied internally wdth nerve and ganglion in addition to 

 1 Verh. zooL-boL Ges. Wien, xxiv. 1874, p. 286. 



Fig. 172. Middle 

 oihody oiPachy- 

 tylus nigrofasci- 

 atus, to show 

 tympanum, e. 

 (After Brunner.) 



Fig. 173. Mecostethus grossus : A, 

 Insect with wings expanded ; B, 

 profile of head and iirothorux, 

 (After Brunner.) 



