408 
Psyche 
[December 
habitat. I have to thank Dr. and Mrs. Jeremiah Blatt for permission 
to use the site, and Dr. and Mrs. Carl Chapman for their hospitality. 
Mr. David Bard helped with the photography. 
Structure of the web 
Hypochilus gertschi is usually found under overhanging rock ledges. 
While fairly moist localities, such as stream banks, cliffs with seepage 
flow, etc., usually harbor a few specimens, PI. gertschi seems to be 
more common in drier, sunnier locations than H. thorelli farther 
south. Hoffman (1963) commented on this, and I have observed 
individuals on very dry, south-facing cliffs. On two occasions, 1 
have seen populations fully exposed to sunlight much of the day. 
The web of PI. gertschi is usually described and pictured (Hoffman, 
1963; Kraus, 1965) as a “lampshade-shaped” mesh, broadly flared 
beneath, and attached by its smaller end to the under surface of a 
rock ledge. At the upper (or inner) attached end of the lampshade, 
a fine sheet of silk is spun over the substrate. Of all previous pub- 
lished references to the web, only Kraus (1965) mentioned the ex- 
tensive tangle of threads extending, when the web is under a ledge, 
to the ground beneath, or to nearby plants. 
The webs of H. gertschi I observed incorporated these previously 
described features. The size of the web is proportional to the size 
of the individual. Webs of large (probably penultimate instar) speci- 
mens were about 8 cm in diameter at the open end of the lampshade, 
and usually about 1 cm less in diameter at the closed end. The main 
portion of the shade consists of a close, irregular mesh (Fig. 1). The 
flared end of the lampshade ( A , Fig. 2) is held taut by 10-15 double 
support lines (i?, Fig. 2), attached in pairs to a roughly polygonal 
frame line (C, Fig. 2). The frame line is in turn guyed to the sur- 
rounding rock surface and to the extensive tangle below. The tangle 
(D ( Fig. 2) is always cone-shaped, with the apex attached below, 
and the base at the frame line, when the web is placed under a ledge, 
or so that the plane of the lampshade walls is nearly vertical. When 
the webs are attached to an almost vertical surface, and the plane of 
the lampshade walls is nearly horizontal, the spider faces a number 
of problems in guying the frame line in such a way that the lamp- 
shade is held tautly flared. If a reasonably narrow crevice is used, 
the web can be attached to the opposite wall (Fig. 3). In cases where 
no such directly opposing surface is available, guy lines are run from 
the frame line nearly parallel to the surface to which the lampshade 
is attached until a protrusion in the rock, the surface of a gently 
sloping rock face, or some other support is reached (Fig. 4). This 
