SENSES OF INSECTS. 45 



a sharp flutter with their wings, as if to try and attract the atten- 

 tion of the females. This always reminds me of the " showing 

 off" of many male birds. That these performances are intended 

 for the female is well illustrated by an instance I saw only 

 yesterday. A male cicada was singing on a small branch, and on 

 another parallel branch, about six inches away, was a female. 

 When I first observed him the former was sitting quite still, but 

 he gradually worked himself up, and began walking up and down 

 and all round his branch, occasionally giving a sharp flutter with 

 his wings ; but the female remained quite impassive. He got so 

 excited that on three occasions he even took short flights of a few 

 feet from his branch. T watched with interest to see if he would 

 settle on the other one. But no ; in each case he returned to 

 his own and recommenced his serenading, which seemed to me 

 significant. The female eventually got tired of him and adjourned 

 to a neighbouring tree ; whereupon he became quiescent, though 

 he still continued calling. 



Moreover, there is another fact which throws a very interest- 

 ing side light on the matter. As I have before mentioned, I know 

 of nine different species round here ; and although there is a 

 general similarity in the sounds which they produce, yet the diffe- 

 rences between them are sufficient to enable me, with a little 

 practice, to identify the species merely by hearing its cry. Why, 

 then, should there be such a diversity of sounds if they are to 

 serve no purpose ? If, however, we acknowledge that the male 

 utters his shrill cry for the purpose of attracting the female, the 

 explanation of these distinctions at once becomes evident. For 

 it is manifest that if the female finds the male by his call, and 

 there is a number of different species frequenting the same area, 

 those males which acquire some peculiarly distinctive sound 

 would be likely to attract to themselves more females of their 

 own kind, and thereby would leave more progeny, than those 

 males whose cry more closely resembles that of another species ; 

 for these latter would be apt to attract females of the other 

 species with which they could not interbreed. And, pari passu^ 

 those females which are most adept at distinguishing the notes of 

 their own males from those of other species, are more likely to 

 pair and leave progeny. It is instructive to note, in this con- 

 nection, that the differences in the cries of two species vary 

 in accordance with their relationship ; the more nearly allied 

 species possessing more similar calls. 



Although I have several times imprisoned male cicadas in 

 gauze-covered boxes, to see whether they would attract females by 

 calling, unfortunately my experiments have failed so far, owing 

 to the fact that the male has always refused to utter a sound 

 beyond an occasional indignant squeak, quite distinct from his 

 usual call. One day I came across a most unusual concourse of 

 one species, there being about sixty specimens on a single small 

 b'ish. With one sweep of the net I caught two males and five 



