ENGINEERING SKILL OF SPIDERS. 



223 



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

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

 common that any 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 

 a P a P er box in wnicn I na d captured the spider, 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 spidec'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 



of a net, not un " " like the snare of 



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 



Trestles tnese 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. 



FIG. 211. Trestlework snare of a young Theridium. 



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 



