THE INSTINCT OF SPIDERS 129 



cross over. It has to perform fully three times as long 

 a journey and pay out three times as much line to 

 complete the spiral in this segment than in any other 

 segment, yet the spider works mechanically on. The 

 journey, the labour, the confusion of the spider have 

 all been increased. A single filament for a bridge 

 and the work might continue as before, but the spider 

 cannot see this. It made many bridges a few minutes 

 before ; it cannot make a single bridge now. The 

 reason is clear ; the time for bridge-making was before 

 the commencement of the viscid spiral. In this snare 

 seven turns of the viscid spiral are complete, and 

 therefore the spider cannot build a bridge now. 



I continue the experiment. In one segment there 

 are no bridges and the spider must continue to the 

 centre of the snare in order to cross over. I now 

 cut carefully across the centre, so that the spider in 

 order to complete the segment will have to pass 

 the centre and cross over by the temporary spiral 

 of the opposite side. Even this does not move the 

 spider to repair. It continues to perform its long 

 journey over the damaged web, cross at every circle 

 to the bridge on the opposite side in order to complete 

 the spiral in that segment. The snare has by now 

 lost almost all trace of its beautiful regularity ; the 

 spokes which bound the divided threads have separated 

 to a hand's breadth, while those on either side have 

 approximated to the width of a finger ; that perfect 

 parallelism in the spiral coils is lost ; threads adhere to 

 one another ; in the narrowed segments they hang down 

 slack ; in the wide segments they are tense to break- 

 ing point ; the radial symmetry has become shapeless ; 

 the snare is held in an uneven strain and it no longer 



