SPIDERS: THEIR STRUCTURE AND HABITS. 121 



drawn out and floated on the current, until the delicate filaments 

 attach themselves to some object. Using this temporary line as a 

 bridge, she travels along it, replacing it as she goes by an entire 

 thread. The boundary lines being thus laid down, she now 

 attaches a thread to one of them, and crossing to the opposite side 

 fastens it there, so as to form a diameter. Reascending to the 

 middle of this line, she then attaches a new thread, conveys it 

 back to the margin and along the boundary, (guiding it all the 

 way by her hind feet so that it may not get entangled,) and then 

 fastens it to some point to serve as a first radius. Along this radius 

 she returns to the centre, doubling the thread on her way to 

 strengthen it, and thence proceeds in the same manner to lay 

 down 20 or 30 more radii. These, as well as the boundary lines, 

 are all plain threads. She then returns to the centre, and lays 

 down a spiral line from it to the circumference, intersecting all the 

 radii. These are also plain threads, but finer than the former ; 

 and they serve a temporary purpose only, viz., to afford her a 

 foot-hold while she draws a spiral line of viscid threads from the 

 circumference to the centre, which is to form the most important 

 part of the snare. The plain spiral threads she bites off so soon 

 as she has done with them, just as any other builder removes the 

 scaffolding when it has served its purpose. The viscid spiral is 

 not continued quite up to the centre, but a central space is left, 

 closely covered with plain threads. From this she spins a line of 

 communication with her retreat, near the confines of the web ; 

 and by the vibrations of this line she is promptly informed of the 

 arrival of visitors. 



It will have been noticed that in the process above described 

 the spider has often to walk along two sides of a triangle in laying 

 down the third side, or in order to reach a destined point by a 

 circuitous route. In such cases, one might expect to find a slack 

 line, but it is not so — they are invariably tight. This result she 

 accomplishes by puUing at the non-elastic threads with her 

 pectinated claws, and so tightening them. The elastic threads 

 adjust themselves to any diminution of distance between their 

 extremities : (as may be seen in a piece of ordinary elastic, which 

 after being stretched to perhaps a foot in length, reduces itself to 

 a few inches on being let go). This elasticity of the viscid threads 

 also enables the web to adapt itself to frequent and sudden 

 shocks from the wind, or from the struggles of captured insects. 



Such are the webs of the Epeira diadejna, or " Garden Spider," 

 known by its hunchback and the distinct cross on the upper side 

 of the abdomen. Another species, the Epeira calophylla^ employs 

 a radius of its web for a pathway, and thus gives the snare an 

 unfinished appearance ; as the spaces between this and the two 



