4 Annals Entomological Society of America [Vol. V, 
least seven different kinds of silk, each adapted to a special 
purpose, are spun by spiders. 
The step from a drag-line to a web is not a great one. A 
spider spinning a thread wherever it goes would make a web if 
by chance it moved about in a limited space as in some nook in 
which it had taken up its abode. In such a web insects would 
be trapped, and thus might arise the habit of building webs for 
the purpose of trapping insects. The simpler webs made by 
spiders are irregular nets formed of the same kind of silk as that 
of which the drag-line is made. Such a web is made by Pholcus. 
It consists of a comparatively few threads spun without any 
regularity of arrangement. 
A marked step in advance of the irregular nets of Pholcus is 
illustrated by the regular webs of the sheet-web-weavers, the 
Linyphiide. These are constructed of dry silk, the kind used 
for the drag-line, but they are of more or less definite form. 
That of Linyphia phrygiana is a flat sheet spun between the 
twigs of ashrub oratree. Linyphia pusilla makes a horizontal 
platform between stems of grass and spins an irregular net 
above it to impede the flight of insects and cause them to fall 
upon the platform where they can be caught by the waiting 
spider. Linyphia marginata makes a filmy dome beneath 
which it waits to capture the insects that fall upon it after 
striking in their flight the irregular net spun above the dome, 
and Linyphia communis spins a bowl-shaped web with an 
irregular net above and a sheet below it. 
A type of web resembling those of the Linyphude in con- 
sisting largely of a sheet of silk, but differing in having a funnel- 
shaped retreat is made by certain members of the Agelenide of 
which the grass-spider, Agelena nevia is our most familiar 
example. A similar web is made in the basement of buildings 
and in other secluded places by Tegenaria. 
All of these webs of which illustrations have been shown 
so far are made of the same kind of silk as that used for the 
drag-line. Their function is to impede the flight of insects 
giving the waiting spider time to capture them. 
In the course of the evolution of the web- Bidens habit 
there has been developed in many families of spiders organs for 
producing a second kind of silk, which being of a viscid nature 
is fitted to hold fast the entangled insect. The nature of this 
