CHAPTER IV 



CONSTRUCTION OF AN OKBWEB. 

 I. 



A DESCRii'Tiox of the rcnuuiiiiig j)ait of tlie orl) will \h: lii'tter ix'aclu'd 



])}' a dotaik'd account of the manner in wliicli an orliweb is constnu-tcil. 



'J'liere arc some variations in methods among different s[ieeies, 



Laymg- .(^^ miglit be exi)ected from tlie varieties of webs, but the ])rocess 



Out o 1 ) I 



p is substantially the same in all species observed. The tirst step 



of Snare ^^ ^^ secure a suitable framework upon which to hang tlie orb, 

 Mdiich is known as the Foundation or Frame, and the severul 

 parts composing it, as Foundation Lines. The spider has two methods of 

 accomplishing this. 



First, the frame lines are laid down " by hand." The spider crawls 

 along the objects over and upon which she jiurposes to spin her snare, 



drawing after her a 

 A Frame jjj^^, which at various 

 Down points she fastens to 

 the surface in this 

 wise : the spinnerets, which are 

 grouped in a little rosette at the 



Firi. 58. Epeira niosing with dragline and anchorage. p^d of the abdomcn, liaVC a large 



number of minute hollow tubes or spinning spools upon their tips, out 

 of which issues a liquid silk of which all spinningwork is formed. The 

 spinnerets and their hundreds of spools are movable at the will of the 

 spider. When they are held closely together, the numerous threads emitted 

 by them blend into one. When they are held apart, on the contrary, 

 various separate threads are formed. As the spider runs along she stops 

 here and there, expands her spinning organs, and at the same time 

 thrusts them downward and touches the surface. The clustered threads 

 thus issued stick to the surface and at once harden. 



Then the sjjider closes together the spinnerets, as one would close the 

 points of his fingers against his thumb, lifts them, moves on, and the con- 

 tinuous threads dragged behind her again converge into one 

 thread as shown in Fig. 58. An ordinary pocket lens, if applied 

 to one of the little white dots which mark the point of adliesion, 

 will easily resolve it into various parts and show the above construction. 

 At Fig. 59 are magnified drawings of two of these spots. 



(60) 



Drag 

 lines. 



