ENGINEERING SKILL OF SPIDERS. 



223 



and other portions of a shiji, and showed how the right lines seemed al- 

 ways to have been placed in the needed- position. This aranead is so 

 common that anj' one who chooses to test my descriptions and observe 

 independent examples can easily do so for himself. (See Fig. 215.) 



This is not the only Tubeweaver that shows an engineering skill that 

 challenges the admiration of human observers. Fig. 210 represents the 



ordinary tubular snare of Dysdera bicolor, which was spun within 

 <sv1l ^^^ ^ paper box in which I had captured the sjjider, and of course 



in absolute darkness. In the morning I found a circular snare 

 placed against the curved edge of the box, and stayed to the sides and 

 bottom in a way that I have attempted with indifferent success merely to 

 suggest in the figure. As I looked at it, and set to myself the problem of 



how to weave a mass of silken threads 

 for example, in such a cylindrical shape 

 and smooth, my admiration for the 

 friend was much increased. At all 

 and stay such a work out of such 

 lines emitted from a spider's spin 

 high place, at least in animal 



The snare of Theridium 

 suspended at all points of 

 verging threads attached 

 spider takes her posi 

 mass, and in the , 

 very strong tenden' 

 to assume the shape 

 become thickened 

 may occasionally be 

 mated that they pre 



into the corner of a room, 



that it would stand out stark 



cunning skill of my aranead 



events, the art that can build 



flimsy material as the silken 



ning spools, is entitled to a 



engineering. 



is a mass of intersecting lines 

 the outer margins by con- 

 to the surrounding site. The 

 tion within the centre of this 

 course of time there is a 

 cy in the spinningwork 

 of a nest. The lines 

 in the centre, and 

 found so approxi- 

 sent the appearance 



Therid 

 ium's 



Fig. 211. TresUework snare of a youDg Theridium. ,., , « 



of a net, not un like the snare oi 



Linyphia, but not so closely textured as that of Agalena. Beneath this 

 thickened centre a series of lines will often be found stretched downward 

 and attached at the basal extremity. (See Fig. 211.) A web suspended 

 between the joists of an old barn, the slats of a lattice work 

 screen, or within a box, or other like situations which will allow 

 1!;'"^°, these supporting lines to be formed with some degree of regu- 

 larity, presents a striking resemblance to the trestlework of a 

 wooden railroad bridge. I have observed this especially in Theridium 

 tepidariorum, and some very beautiful and remarkable examples in the 

 web of the long legged Cellar spider, Pholcus phalgioides. When such 

 a web is formed, the spider is found suspended to the under part of 

 the thickened portion, which thus becomes to her a sort of nesting place. 

 Fig. 212 was sketched from the snare of a female Theridium differens 

 woven upon a wire frame fastened with staples upon a wooden block. 



