———————S SS = ee lh hr 
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 
Dysdera’s : ‘ : : 
Skill, a paper box in which I had 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 into the corner of a room, 
for example, in such a cylindrical shape that it would stand out stark 
and smooth, my admiration for the cunning skill of my aranead 
friend was much increased. At all events, the art that can build 
and stay such a work out of such flimsy material as the silken 
lines emitted from a spider’s spin ning spools, is entitled to a 
high place, at least in animal engineering. 
The snare of Theridium is a mass of intersecting lines 
suspended at all points of the outer margins by con- 
verging threads attached } to the surrounding site. The 
spider takes her posi tion within the centre of this 
mass, and in the. course of time there is a 
very strong tenden' — cy in the spinningwork 
to assume the shape _ of a nest. The lines 
become thickened ~ in the centre, and 
may occasionally be found so approxi- 
mated that they pre sent the appearance 
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 
Fic. 211, Trestlework snare of a young Theridium, 
Therid- screen, or within a box, or other like situations which will allow 
ium’s : : : ‘ 
Trestles. ‘ese supporting lines to be formed with some degree of regu- 
arity, 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, Pholeus 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. 
