FOOD OP INSECTS. 413 



Lastly, she runs to the centre and bites away the small 

 cotton-like tuft that united all the radii, which being now 

 held together by the circular threads have thus probably 

 their elasticity increased ; and in the circular opening 

 resulting from this procedure she takes her station and 

 watches for her prey. 



In the above description, which is from my own ob- 

 servations, I have supposed the spider to fix the first 

 and main line of her net to points from one of which she 

 could readily climb to the other, dragging it after her ; 

 and many of these nets are placed in situations where 

 this is very practicable. They are frequently, however, 

 stretched in places where it is quite impossible for the 

 spider thus to convey her main line — between the branches 

 of lofty trees having no connexion 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 

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



