282 ANIMAL SKETCHES. CHAP. 



In repeating and extending these interesting experi- 

 ments, the American observers found that spiders which 

 form a web gradually become callous to the sound of the 

 fork vibrating near them, letting themselves down to a 

 less distance when they fall, and after a varying number 

 of trials, ceasing to take any notice of the noise. On one 

 spider a series of trials were made on successive days. 

 After a fortnight's experience she ceased to take any 

 notice of the vibrating fork, but on one or two subsequent 

 occasions seemed seized with a renewal of nervousness, 

 and dropped two or three times. Other spiders than 

 those which weave webs, the leaping spiders for instance, 

 did not seem to take the slightest heed of the sound 

 produced by the vibrating tuning-fork. But Astia vittata, 

 one of the Attidse, jumped to one side when "'bang" was 

 shouted in a loud voice with the head turned away ; and 

 whe x n Mr. Peckham whistled, it stood on the tip of its 

 abdomen with the head held high, apparently in an 

 attitude of attention. 



We have seen that some of the above experiments show 

 incidentally that the spider is sensitive to the vibrations 

 which reach her along the strands of her web. One of 

 the triangle spiders described by another American ob- 

 server, Professor Burt Wilder, weaves a triangular net of 

 four radii. At the apex there is a slack rope which she 

 draws tight by furling up some of the line between her 

 front and back legs. Then she remains motionless, like 

 a compact brown mass about the size of a raisin seed, and 

 much resembling the projections on the dried hemlock 

 twigs to which her nest is attached. No sooner did a fly 

 touch the net than the line was let go and the web, flying 

 forward, flapped from side to side, thus entangling the 

 insect. Subsequently the radii were cut and the web 



