SPIDERS 1015 



trap-line of silk carried to her den, she can, by a veritable telegraphy, 

 discover instantly, not only the fact that there is prey upon her 

 snare, but the exact spot in the web of the snare in which that 

 prey is entangled. In the same way, by seizing certain tightly 

 stretched threads communicating with the main lines of the snare, 

 she can discover in an instant the presence and position of her prey, 

 though far beyond the reach of vision. 



The most characteristic and interesting part in the special 

 organisation of the spider is the ' spinning apparatus/ by means of 

 which its often elaborately > 



constructed webs arc pro- 

 duced. These consist of 

 ' spinnerets ' on the ex- 

 terior of the body and 

 glandular organs lying 

 within the abdomen ; it is 

 by them that the silk from 

 which all the elements of 

 the snare are produced is 

 secreted. 



Of these glands there 

 are two pairs which are 

 sac-like in form, with a FlG - 749. Foot, with comb-like claws, of the 

 coiled tube opening 'di- common spider (^dra). 



rectly on the spinnerets : 



there are three pairs, of a convoluted appearance, opening on the 

 hinder spinnerets ; and there are three of a sinuous tubular form 

 opening on the hinder and middle spinnerets. Beyond these there 

 are respectively 200 and 400 smaller glands, which open on the 

 front, middle, and hinder spinnerets. They all terminate in tubes 

 of great delicacy, through which the silk is drawn at the will of the 

 spinster ; and, while the scaffolding or framework of the web of 

 Epeira is double and hardens rapidly in air (fig. 750, A), those which 

 lie across the polygons of 



the scaffolding are stud- A 



ded at regular intervals 



with viscid globules, as ^ 



seen in fig. 750, B ; and B ~ ' O 



it is to these viscid glo- 

 bules that the peculiarly FlG - 750. Ordinary thread (A) and viscid 

 adhesive character of the thread (B) of the common 8plder " 

 web is due. 



The usual number of the spinnerets is six. They are little teat- 

 like processes crowned with silk tubes. They are movable at the 

 will of the spider, and can be erected or depressed, and one, many, 

 or all of the tubes crowning a spinneret may be caused to exude 

 and have drawn from it or them the silk as the spider determines. 

 There can be no doubt that there is a difference in the silk secreted 

 by different glands, and its appropriate employment is a part of 

 the skill of the spider. 



It is certain that the silken threads of a snare are of two kinds ; 



