304 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



Tlic result of this experiment, as in the ease above detailed, and indeed 



in all other cases tried, is the conclnsion that the symptoms of lu'aring, as 



thoy have oi'dinarily hecn descrilied, seem to appear in the spider 



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



sion lom pjj^j^gd f^iQj^g i\^Q ij„Q Qf jjgj. -^ygij iq ^j^g haii-s which form the 



ments armature of lier liody. 



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

 mirably portrayed by Mr. PeckhamJ His experiments upon Orbweavers 

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

 ing. That the vilirations 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- 

 liam'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 l>rey by means of webs — 

 a fact which struck Professor Peckham. It seemed to liim " 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 Epeiroids was i^roduced 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 welt is affected by 

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

 ple, a vibrating fork, when approximated to the broad, zigzag rilil)on upon 

 the orb of Ai'giope, 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 deiiendent upon keenness of 

 the senses for their success in cai)turing prey, should prove to be destitute 

 of tiie valuable sense of hearing ; while the webmaking spider.s, 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, 



IMental Powers of Siiitlers, pages 396, 397. 



