254 ABOUT SPIDEES AOTD THEIR WEBS. 



Spider's webs are in this country proverbially fragile 

 and delicate. "We speak metaphorically of brushing 

 away difficulties like spiders' webs; and the almost 

 invisible fibres spun by very small spiders, such as we 

 call "money-spinners," are used for the cross "wires" 

 of astronomical and other optical instruments on account 

 of their exceeding fineness. 



All the Trap-door spiders are remarkable for the 

 great strength of their webs, which are used, not for the 

 capture of prey, but for the strengthening of their 

 earthen homes. The silk is mostly yellow, and so tough 

 that a nest can be removed without any danger of 

 damaging it ; and the silk is so strong that even when 

 the earth has been dried and wholly removed, it will 

 bear a considerable strain without breaking, and can be 

 drawn over the finger like a glove. 



Up to this point the burrow possesses no advantage 

 over that of the Bird spider, being a simple silk-lined 

 tube. But the spider now sets to work at the construc- 

 tion of a door, by which the opening may be not only 

 closed but concealed. 



Guided by instinct, it weaves a circular web, rather 

 less than the diameter of the burrow, and works into it 

 a quantity of earth. A second and rather larger web is 

 placed upon it, similarly mixed with earth. This process 

 s repeated until the spider has constructed a circular 

 plate of alternate layers of web and earth, nearly twice 

 the thickness of a penny and slightly conical. Eight or 

 ten layers are employed in the manufacture of the plate. 



