74 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 
The trapezoidal foundation lines, x—x, are woyen within the basilar 
part of the triangle thus formed. We have here the usual Foundation 
Space, FS, and indeed might aptly apply that term to the entire Founda- 
tion system. But it will be convenient, in webs of this form, to name 
the inner side of the trapezoid, IFL, the Inner Foundation Lines, and the 
large exterior cords, ab, ed, the Outer oun- 
dation Lines, and the intermediate space, 
OFS, the Outer Foundation Space. 
The inner foundation lines are of course 
necessary to the construction of the orb 
under such circumstances, but 
they are plainly so adjusted as 
not only to allow the nicest bal- 
ance of the beautiful snare, but also to 
afford the greatest power of resistance by 
Fic. 69. Spinning the initial radit. distributing the disturbing forces of wind 
and struggling entangled insects along the 
elastic inner foundation lines. Webs of this character have less rigidity 
and would seem to be better designed to endure, than those which are 
directly attached to limbs and foliage. 
A foundation having been secured, the spider proceeds to place in 
the radii. ‘To this end a position is taken at or near the centre of 
_, the orb, usually by dropping down from a top line, dragging 
a after her a thread which becomes the initial radius, Fig. 69, a. 
At the central terminus of this radius a little ball of floss (1H) 
is formed by emitting a thick ray of silk or by gathering together into a 
wad the many tentative lines with which the space within the frame is 
frequently matted. This ball evidently serves as an 
anchorage for the radii and perhaps also as a guidon 
for the animal herself. Sometimes as the work pro- 
ceeds and the strain of the new laid radii is felt 
upon the centre, the bit of floss is pulled out into 
an irregular frayed mass with interlacing filaments, 
as at Fig. 70, which shows a hub of a snare of 
Epeira vertebrata arrested when nine radii had been 
spun. The spider hung at the centre, and the posi- 
tions of the feet in their order (first, second, etc.) are indicated by the 
numerals. 
The spider may now proceed in two ways: first to drop downward 
from H along c¢, to the foundation line, and attach thereto the thread, 
which is done by touching the spinnerets to the point of attachment, the 
natural viscidity of the exuded silk causing it to adhere. This gives the 
second radius. ‘Thence the spider returns along ¢ to the centre H, and 
ascends a, to form the third radius Hk or Hi, If, however, the tentative 
Use of In- 
ner Lines. 
Fic. 70. Pulled out guidon. 
