306 



The Descent of Man. 



PAliT II. 



apparently serves both sexes as a mutual call. Beetles stridu- 

 late under various emotions, in the same manner as birds use 

 their voices for many jDurposes besides singing to their mates. 

 The great Chiasognathus stridulates in anger or defiance ; many 

 species do the same from distress or fear, if held so that they 

 cannot escape; by striking the hollow stems of trees in the 

 Canary Islands, Messrs. Wollaston and Crotch were able to 

 discover the presence of beetles belonging to the genus Acalles 

 by their stridulation. Lastly, the male Ateuchus stridulates to 

 encourage the female in her work, and from distress when she 

 is removed. 79 Some naturalists believe that beetles make this 

 noise to frighten away their enemies ; but I cannot think that 

 a quadruped or bird, able to devour a large beetle, would 

 be frightened by so slight a sound. The belief that the stridu- 

 lation serves as a sexual call is supported by the fact that death- 

 ticks (Anobium tessellatum) are well known to answer each 

 other s ticking, and, as I have myself observed, a tapping noise 

 artificially made. Mr. Doubleday also informs me that he 

 has sometimes observed a female ticking, 80 and in an hour or 

 two afterwards has found her united with a male, and on one 

 occasion surrounded by several males. Finally, it is probable 

 that the two sexes of many kinds of beetles were at first- 

 enabled to find each other by the slight shuffling noise produced 

 by the rubbing together of the adjoining hard parts of their 

 bodies; and that as those males or females which made the 

 greatest noise succeeded best in finding partners, rugosities on 

 various parts of their bodies were gradually developed by means 

 of sexual selection into true stridulating organs. 



79 M. P. de la Brulerie, as quoted 

 in ' Journal of Travel,' A. Murray, 

 vol. i. 1868, p. 135. 



80 According to Mr. Doubleday, 

 " the noise is produced by the in- 

 " sect raisins: itself on its leo;s as 

 " high as it can, and then striking 

 " its thorax five or six times, in 

 " rapid succession, against the sub- 

 " stance upon which it is sitting." 

 For references on this sao,ect see 



Landois, ' Zeitschrift fur wissen. 

 Zoolog.' B. xvii. s. 131. Oliver 

 says (as quoted by Kirby and 

 Spence, ' Introduct.' vol. ii. p. 395) 

 that the female of Pimelia striata 

 produces a rather loud sound by 

 striking her abdomen against any 

 hard substance, " and that the male, 

 " obedient to this call, soon attends 

 " her, and they pair." 



