ENGINEERING SKILL OF SPIDERS. 



227 



rinthea's 

 Cables. 



by various threads fastened upon the intersecting lines of the maze. From 

 a little corner in the upper part of the leaf a similar line, b, was stretched, 

 braced by two interior lines of a like character (cc and d), which 

 Laby- j^j, e t ^ e s { em cable were also held in place by numerous slighter 

 cords extending through the maze. A careful study of these 

 main supporting cables, and indeed of ah 1 the lines used for 

 upholding the leaf, convinced me that, whether or not the spider was con- 

 scious of any principles of engineering, she had hi her results proved 

 herself an admirable engineer. I kept this leaf under observation for 

 a number of days of varied weather, and it never lost its poise, or was 



FIG. 215. The snare and stay lines of Agalena ncevia in a honeysuckle vine. 



moved from its place within the labyrinth. It endured well the strain of 

 one of the most severe downpours of rain that I ever saw. It thus stood 

 the test of actual use as well as careful observation. 



In accounting for such acts as this, one is compelled to suppose the 

 exercise of reasoning powers of some kind by the spider. Whether the 

 reasoning may have been accomplished by the processes known to man 

 and more highly organized animals, or whether the behavior of the spider 

 was the result of sensations produced by her delicate sense of touch, and a 

 perception of irregularities of weight and tension, which passes human ex- 

 perience, one need not stop to discuss. In point of fact, judging these 



