INSECTS. 347 



ported by the fact that death-ticks (Anolium 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 ob- 

 served a female ticking,* and in an hour or two afterward 

 has found her united with a male, and on one occasion sur- 

 rounded 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. 



* According to Mr. Doubleday, "the noise is produced by the 

 insect raising itself on its legs as high as it can, and then striking its 

 thorax five or six times in rapid succession against the substance 

 upon which it is sitting." For references on this subject see Landois, 

 " Zeitschrift fur wissen. Zoolog.," B. xvii, s. 131. Olivier 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, obedi- 

 ent to this call, soon attends her, and they pair." 



