344 ARACHNIDA ARANEAE CHAP. 



The silk is utilised in many ways, serving for the construc- 

 tion of snares, nests, and- cocoons, as well as for enwrapping the 

 captured prey, and for anchoring the spider to a spot to which 

 it may wish to return. 



Spiders may be roughly distinguished as sedentary or vagabond, 

 the former constructing snares, and the latter chasing their prey 

 in the open. We will first consider the various forms of snare, 

 beginning with that characteristic of the Epeiridae. 



The Circular Snare. This familiar object, sometimes spoken 

 of as the orb-web or wheel-web, is always the work of some 

 spider of the Family Epeiridae. 



The accuracy and regularity of form exhibited by these snares 

 has caused their architects to be sometimes called the geometric 

 spiders. The ingenuity displayed by them has always excited 

 the admiration of the naturalist, and this is increased on closer 

 observation, for the snares are in reality even more complex than 

 they appear at first sight. 



The first care of the spider is to lay down the foundation 

 threads which are to form the boundary lines of its net. If the 

 animal can reach the necessary points of attachment by walking 

 along intervening surfaces the matter is comparatively simple. 

 The spinnerets are separated and rubbed against one of the points 

 selected, and the spider walks away, trailing behind it a thread 

 which it keeps free from neighbouring objects by the action of 

 one of its hind legs. On reaching another desirable point of 

 attachment the line is made taut and fixed by again rubbing 

 the spinnerets against it. By a repetition of this proceeding a 

 framework is presently constructed, within which the wheel or 

 orb will ultimately be formed. 



The process of fixing and drawing out a line can be con- 

 veniently watched in the case of a Spider imprisoned in a glass 

 vessel, and it will be seen, by the aid of a lens, that a large 

 number of very fine lines starting from the point of attachment 

 seem to merge into a single line as the Spider moves away. This 

 has given rise to the prevalent and very natural idea that the 

 ordinary spider's line is formed or " woven " of many strands. 

 This, however, is not the case, 1 for the fine attachment-lines are 

 not continued into the main thread, but only serve to anchor it 

 to the starting-point. 



1 \Varburton, Q. J. Micr. Sei. xxi., 1890, p. 29. 



