304 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



The result of this experiment, as in the case above detailed, and indeed 

 in all other cases tried, is the conclusion that the symptoms of hearing, as 

 they have ordinarily been described, seem to appear in the spider 

 Conclu- only when the vibration of the sound instrument is communi- 

 on rom ca j. e( j a i on nr the line of her web to the hairs which form the 

 Experi- e 



ments armature ot her body. 



I can reach no other conclusion from the experiments so ad- 

 mirably portrayed by Mr. Peckham. 1 His experiments upon Orb weavers 

 enabled him to get results which, to his mind, indicated the sense of hear- 

 ing. That the vibrations produced a state of excitement is true, but the 

 question is, what was the mediate cause of that excitement? Did it result 

 from hearing a sound, or was it simply caused by feeling a vibration 

 similar to that made by an insect captured or hovering near? Mr. Peck- 

 ham's experiments indeed seem to me clearly to indicate the conclusion 

 which I myself have reached. 



He used the tuning fork upon a half dozen species taken from different 

 groups of spiders, making ten or twelve trials on each one. No individual 

 gave the least intimation of hearing anything. These unresponsive species 

 belong to the genus Herpyllus among the Tubeweavers, and the genera 

 Pardosa, Piratica, Lycosa, and Dolomedes among the Citigrades. None of 

 these spiders, so far as known, ever capture their prey by means of webs 

 a fact which struck Professor Peckham. It seemed to him " remarkable 

 that while all the Epei'roids responded promptly, being evidently alarmed 

 by the sound of the tuning fork, the spiders that make no web, on the 

 contrary, gave not the slightest heed to the sound. This may perhaps be 

 partially explained by the difference in the feeding habits of the two 

 groups." 



Does this explain anything? The difference here indicated certainly lies 

 in this, that the excitement of the Epei'roids was produced by the agita- 

 tion of the hairs upon their feet, and that agitation was awakened by vibra- 

 tions of the fork along the lines of the web. That the web is affected by 

 these vibrations I thoroughly satisfied myself by experiment. For exam- 

 ple, a vibrating fork, when approximated to the broad, zigzag ribbon upon 

 the orb of Argiope, would cause it to sway back and forth as though 

 agitated by the motion of the air, which, beating upon it, alternately re- 

 pulsed and attracted it. 



It would indeed be a remarkable fact were it to be established that 

 those spiders which, like the Lycosids, are dependent upon keenness of 

 the senses for their success in capturing prey, should prove to be destitute 

 of the valuable sense of hearing ; while the webmaking spiders, who are 

 so little dependent upon the sense of hearing, and are enabled to accom- 

 plish the most important functions of life by the sense of touch alone, 



1 Mental Powers of Spiders, pages 396, 397. 



