1912] Evolution of the Webs of Spiders 7 
frets. In the webs of this species, the larger part of the web is 
made of dry silk. While the hackled band is doubtless the most 
efficient factor in the capture of insects, it is still a subordinate 
part of the web. 
In the webs of Dictyna sublata the utilization of the hackled 
band is carried much farther. Here only so much dry silk is 
used as is necessary to support an elaborate lace-like sheet of 
viscid silk. This represents the quantitative extreme in the 
use of viscid silk. 
A somewhat similar condition exists in the webs of a species 
of Amaurobius which spins its webs on cliffs. 
In the webs of Hypochilus thorellit is found the same type 
of hackled band as in the webs of the Dictynide. I have been 
able to find no differences between the hackled bands of this 
spider and that of Amaurobius. But the web of Hypochilus is 
of regular form being lamp-shade shaped. 
It is a remarkable fact that this spider which has retained 
the most generalized condition of its respiratory organs of all 
true spiders, being four lunged like the Tarantulas, should 
have attained the making of a regular web. 
While the hackled bands of Amaurobius and Hypochilus 
are remarkable structures they lack much of representing the 
extreme of specialization in this direction. To see this we must 
examine the web of Fulistata, a very common house spider in the 
South. Here the hackled band is composed of four distinct 
kinds of silk. But the web itself is more simple than that of 
Hypochilus. 
Let us turn our attention now to the second of the principal 
lines of specialization of webs, that in which the attention of the 
spiders, to speak figuratively, has been devoted to perfecting 
the foundation of the web, while the viscid silk has remained 
comparatively simple. The culmination of this line is reached 
in the webs of the orb-weaving spiders. 
There are two families of orb-weaving spiders, the Uloboridz 
and the Argiopide. In the more typical webs of each of these 
families the most striking feature is the presence of a central, 
more or less orbicular part in which the frame-work of the web 
consists of radiating lines, which in the completed web support 
the viscid silk. The regular spacing of these radii gives the 
maximum of stability to the web with the minimum use of 
material. Most of the webs already described are built against 
