OHAPTEE lY. 



CONSTRUCTION OF AN ORBWEB. 



A DESCRIPTION of the remaining })art of the orb will be better reached 

 by a detailed account of the maimer in which an orbweb is constructed. 

 There are some variations in methods among different species, 

 Laying- r^^ might be expected from the varieties of w^ebs, but the process 

 p^ is substantially the same in all species observed. The first ste^) 



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

 which is known as the Foundation or Frame, and the several 

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

 accomplisliing this. 



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

 along the objects over and upon which slie purposes to spin her snare, 



drawing after her a 

 A Frame ^^^^ which at various 

 Down points she fastens to 

 the surface in this 

 wise : the spinnerets, which are 

 grouped in a little rosette at the 



Fi.;.58. Epeira moving with dragline and anchorage. q^^(1 of the abdomeu, haVC 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 

 si)iniierets 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 si)inning 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 spider 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. H.S. An ordinary pocket lens, if a|)plied 

 to one of the little white dots wliich mark the point of adhesion, 

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

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



m 



Drag- 

 lines. 



