POWER OF HEARING IN INSKOTS. 75 



It would be, on the other hand, most unsafe to 

 conclude that spiders are incapable of hearing. Dahl * 

 has given reasons for believing that some of their hairs 

 serve as auditory organs. Westring has discovered, 

 in certain species of Theridium (T. serratipes, oculatum, 

 castaneum, etc.), a stridulating organ, consisting of a 

 sort of raised bow attached to the upper part of the 

 abdomen, which rubs against the under and hinder 

 part of the cephalothorax, producing a whirring sound. 

 Lebert f naturally observes that this appears to indicate 

 a power of hearing on their part. 



As regards inseots, it would be easy to multiply such 

 evidence almost indefinitely ; I have given more illus- 

 trations than I should probably have otherwise thought 

 necessary, because so excellent an observer as Forel, 

 whose opinion I should value on such a point as much as 

 that of any authority, expresses doubt whether insects 

 really hear at all. "Ce qu'on semble," he says, in his 

 last memoir on the subject, "considerer comme preuxe 

 de I'ouie me parait comme a Duges reposer a pen d'excep- 

 tions pres sur des ebranlements mecaniques de I'air ou 

 du sol qui sont simplement pergus comme tels par les 

 organes tactiles des insectes. Cela correspond a pen 

 pres a la derniere opinion de Graber sur" I'ouie "de 

 la Periplaneta. Mais on n'a pas le droit de nommer 

 ouie de pareilles sensations." J 



Graber, however, has endeavoured to meet this 

 objection by an ingenious experiment.§ He placed 

 some water-boatmen (Corixa) in a deep jar full of 



* "Das Gehor-und Geruclisorgane dtr Spinuen," Arch, fur Mlc. 

 Anat, 1885. 



■f " Die Spianen der Schweiz." 



i A. Forel, " Sensations des Insectes," Uccueil Zuol. Suisse, t. iv. 1887. 



§ Arch.fiir Mia. Anat., 1882. 



