POOD OF INSECTS. 413 



now held together by the circular threads have thus 

 probably their elasticity increased ; and in the circular 

 openinfij 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, how- 

 ever, 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; between two distinct and elevated build- 

 ings ; and even between 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 inaccessible openings of this de- 

 scription ? 



With the view of deciding this question, to which I 

 could find no very satisfactory solution in books, I 

 majde an experiment, for the idea of which I am in- 

 debted to a similar one recorded by Mr. Knight % 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 nu- 

 merous fine threads so light as to float in the air, some 

 one of which attaching 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 diffi- 



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



