PERCEPTION OF SEX IN SILKWORM MOTHS 291 



according to physical and physiological laws, could be so diffused 

 as to be perceptible at a distance of many kilometers; and just 

 as extraordinary must be the sense which serves to discover it. 

 Fabre is right in observing that the world of sensations is much 

 wider than our imperfect and obtuse organs of sense reveal to 

 us. It is now certain that animals, for instance, hear sounds 

 that escape our ears; see ultra-violet rays which our eyes do 

 not see. It is easy to believe that these lower organisms, espe- 

 cially the insects, are endowed with organs of sense quite special 

 and so complicated that they differ absolutely from ours. They 

 may serve purposes as different from any of ours as sound, for 

 instance, differs from light. It is only by indirect methods, 

 that is, by the study of ethology, of the intelligence of animals, 

 of their relation to the forces of nature, of the appearance which 

 the external world has for them, that we can arrive at the dis- 

 covery of the senses and sensations which are now only an 

 hypothesis. 



Another characteristic of the Bombyx mori which I studied, 

 and also of other moths, is the buzzing made by the wings. In 

 the males of Bombyx, this is more intense than in the females, 

 and the movements of the wings are more rapid. The movements 

 are more rapid also when the male is resting upon a cocoon which 

 contains a female moth about to emerge, than when it rests upon 

 any other object. In this case, the male may hear the move- 

 ments of the female inside the cocoon, and having thele-percep- 

 tion of the sex, augments the vibrations of his wings. 



In performing my experiments, I took two hundred cocoons 

 of Bombyx mori and kept them in a big pasteboard box at a 

 constant temperature of 15° C. As the moths emerged, I re- 

 corded whether they attached themselves at once to another 

 cocoon, whether they remained there constantly until the en- 

 closed moth came out, and whether the latter was of the same 

 or different sex. I reckoned also the uncertain results, that is, 

 the cases where the moth did not remain constantly on one 

 cocoon, but went to another from which afterwards came a 

 moth of the same or different sex. 



