COMPOSITE SNARES AND SECTORAL ORBS. 139 
three-eighths inch, one-fifth the orb space. These were all webs of young 
spiders. It will thus be seen that there is no fixed rule by which 
Triaranea is guided in this outlay of her web, and that she allows herself 
a wide range of variation, although the greater number of orbs show 
a sector of about one-fifth the orb space. 
Through the open sector passes the free radius or trapline, for such 
Ak. 
Fic. 124. Fic. 125. 
Illustrations of the orientation of the trapline, and width of 
the open sector. 
it is, its use being precisely that of the trapline Fic. 126. Bell shaped tent in which 
in full orb making spiders. Near the point of Oe ee ee 
attachment to the hub this is deltated, diverging into several lines that 
: are fastened at various points to the meshes of the hub. The 
other end of the trapline enters a little bell shaped silken tent 
swung amid a retitelarian maze, where it is held by the spider. (Fig. 126). 
Sometimes several spiral lines will cross the upper part of the open 
sector (Fig. 127); again one may see the variation shown at Fig. 128, where 
two radii (dr dr) detached from the hub (H) are lifted out from the 
plane of the orb, leaving an open space (O) through which the trapline 
(T) passes. Another variation differs from this in having but a single de- 
tached radius (dr) to which cross loops (cl) pass from the marginal radii 
R, R. (Fig. 129.) When weay- 
ing in the spirals this spider does 
not pass entirely around the orb, 
as is the case with the full orb 
makers in the major part of their 
snare, but moves back and forth 
between the radial borders (Fig. 
125, ¢ and d) of the open sector, 
spinning her spirals in successive 
horseshoe loops. This 
is the method observed 
by Zilla, and all sectoral orb makers in fact. The necessity for it 
is at once apparent. Of course, in this case the term “spiral” has only 
a technical application to these lines. (Fig. 130.) 
The number of both spirals and radii varies greatly. The latter are 
more numerous, often far more numerous below than above the hub, 
which frequently is situated” well above the geometric centre of the orb. 
Thus, in an orb six inches wide by seven long the spirals in the upper 
part of the snare numbered nineteen, in the lower thirty-two. The lower 
Trapline. 
Fie. 128. Fig. 129. 
Variations in the open sector; detached radii. 
Spirals in 
Loops. 
