ANTS AND SOME OTHER INSECTS. 49 



He tried in vain (which was to have been foreseen) to conceal the female by odors 

 which are strong even to our olfactories. The males came notwithstanding. He 

 established the following facts: (i) Even an adverse wind does not prevent the 

 males from finding their way ; (2) if the box containing the female is loosely closed, 

 the males come nevertheless ; (3) if it is hermetically closed (e. g., with wadding or 

 soldered) they no longer come ; (4) the female must have settled for some time on 

 a particular spot before the males come ; (5) if the female is then suddenly placed 

 under a wire netting or a bell-jar, though still clearly visible, the males neverthe- 

 less do not fly to her, but pass on to the spot where she had previously rested 

 and left her odor ; (6) the experiment of cutting off the antennae proves very little. 

 The males without antennae do not, of course, come again ; but even the other 

 males usually come only once : their lives are too short and too soon exhausted. 



At first Fabre did not wish to believe in smell, but he was compelled finally, 

 as a result of his own experiments, to eliminate sight and hearing. Now he makes 

 a bold hypothesis : the olfactory sense of insects has two energies, one (ours), 

 which reacts to dissolved chemical particles, and another which receives "physical 

 odor-waves," similar to the waves of light and sound. He already foresees how 

 science will provide us with a "radiography of odors" (after the pattern of the 

 Roentgen rays). But his own results, enumerated above under (4) and (5) contra- 

 dict this view. The great distances from which the Bombyx males can discern 

 their females is a proof to him that this cannot be due to dissolved chemical par- 

 ticles. And these same animals smell the female only after a certain time and 

 smell the spot where she had rested, instead of the female when she is taken away! 

 This, however, would be inconceivable on the theory of a physical wave-sense, 

 while it agrees very well with that of an extremely delicate, chemical olfactory 

 sense. 



It is a fact that insects very frequently fail to notice odors which we perceive 

 as intense, and even while these are present, detect odors which are imperceptible 

 to our olfactories. We must explain this as due to the fact that the olfactory pa- 

 pillae of different species of animals are especially adapted to perceiving very differ- 

 ent substances. All biological observations favor this view, and our psycho-chem- 

 ical theories will have to make due allowance for the fact.] 



