SHEET-BUILDING SPIDERS 155 



spiders of this species respond to sound vibrations and 

 to the odour of camphor after the pedipalps have been 

 removed. But I believe they possess a most exquisite 

 sense of touch and that by their means the spider is 

 able to detect the finest vibrations of its snare. This 

 might be expected from their anatomical position, for 

 they do not extend forwards like the antennae of insects, 

 but are bent downwards beneath the spider's body, 

 and not only rest on the snare, but move about on it 

 in a manner resembling limbs. The importance of 

 the pedipalps is shown by the results that follow their 

 amputation. After the pedipalps are removed the 

 Hippasa can still construct a snare, but it resembles 

 the architecture of the Araneus after the amputation 

 of its fore limb ; it is a tangled and a shapeless fabric. 

 The spider, when deprived of its pedipalps, crawls 

 about clumsily ; it has lost much of its skill and pre- 

 cision. It continually catches its feet in the filaments 

 of its web, an act which, in the uninjured spider, never 

 occurs, and I have even seen it tear the snare in the 

 endeavour to free its limbs. Without its pedipalps, 

 the Hippasa can no longer capture flies. It seems to 

 be quite unable to detect the vibrations that follow on 

 the entanglement of its prey. I doubt if its hearing 

 is affected, for I have noticed it extending its fore 

 limbs towards the sound of a buzzing fly as though 

 it were a man deprived of its eyesight and groping 

 in the dark. I believe it had lost a sense as important 

 to a spider as is sight to a human being ; it had lost 

 the sense of touch. 



A little incident illustrating the force of instinct in 

 this species rather amused me. The Hippasa was 

 waiting for visitors at the entrance to its tube and the 



