240 Studies in Animal Behavior 



the evolution of the organic world. It is doubt- 

 less futile to conjecture what the organ;ic world 

 would have been like if the institution of sex had 

 never been evolved. Even if the processes of varia- 

 tion and selection had gone on to the same extent — 

 which is scarcely probable — the absence of sex would 

 certainly have given to evolution a very different 

 direction from that which was actually followed. 

 Many of the most complex of the structural ar- 

 rangements of organisms have especial reference 

 to securing the meeting of the germ cells. The color 

 and scent of flowers, and their many and beautiful 

 adaptations to effect cross fertilization would never 

 have appeared if plants were propagated solely by 

 the asexual method. In animals the structural pe- 

 culiarities associated with sex are, as a rule, among 

 the most complex features of the body. Correlated 

 with these structures we find mating instincts which 

 frequently manifest themselves in complex modes of 

 behavior. More acute senses have been evolved in 

 many cases very largely in relation to securing the 

 meeting of the sexes. The large antennas of male 

 moths and several other insects, the larger eyes 

 of the common drone bee, and the auditory appara- 

 tus of the male mosquito are a few of the numerous 

 illustrations of this fact. 



The various kinds of apparatus in insects for mak- 

 ing sounds which are found in crickets, locusts, and 

 cicadas are devices for drawing the sexes together, 

 and the complementary development of auditory or- 



