412 FOOD OF INSECTS. 



of lofty trees having no connection with each other ; be- 

 tween two distinct and elevated buildings ; and even be- 

 tween plants growing in water. Here then a difficulty 

 occurs. How does the spider contrive to extend her 

 main line, which is often many feet in length, across in- 

 accessible openings of this description ? 



With the view of deciding this question, to which I 

 could find no very satisfactory answer in books, I made 

 an experiment, for the idea of which I am indebted to a 

 similar one recorded by Mr. Knight a , who informs us 

 that if a spider be placed upon an upright stick having 

 its bottom immersed in water, it will, after trying in vain 

 all other modes of escape, dart out numerous fine threads 

 so light as to float in the air, some one of which attach- 

 ing itself to a neighbouring object furnishes a bridge for 

 its escape. It was clear that if this mode is pursued by 

 the geometric spiders, it would go considerably towards 

 furnishing a solution of the difficulty in question. I ac- 

 cordingly placed the large field spider (Epeira Diadema] 

 upon a stick about a foot long, set upright in a vessel 

 containing water. After fastening its thread (as all spi- 

 ders do before they move) at the top of the stick, it 

 crept down the side until it felt the water with its fore 

 feet, which seem to serve as antenna? : it then immedi- 

 ately swung itself from the stick (which was slightly bent) 

 and climbed up by the thread to the top. This it re- 

 peated perhaps a score times, sometimes creeping down 

 a different part of the stick, but more frequently down 

 the very side it had so often traversed in vain. Wearied 

 with this sameness in its operations, I left the room for 

 some hours. On my return I was surprised to find my 

 8 Treatise on the Apple and Pear, p. 97- 



