1 88 
Psyche 
[September 
My own observations indicate that Hypochilu? may be placed 
somewhat closer to step 2, since its web, both in placement (on rock 
ledges) and in function (capturing ground and aerial arthropods 
in nearly equal numbers), is neither strictly a ground nor strictly 
an aerial web. Kaston (1964) hypothesized that early snares arose 
from a fringe of drag lines radiating from the mouth of a silk-lined 
retreat. Shear (1970) proposed that “the web of Hypochilus can 
easily be derived” from such a structure, and suggested that the 
lampshade may represent an extension of the original retreat, while 
the paired support lines may represent the capture (originally drag) 
lines in Kaston’s scheme. 
Defensive Behavior 
The defensive behavior of H. thorelli is very similar to that de- 
scribed by Shear (1970) for H. gertschi. There are three major 
components to the defensive behavior: “vibrating,” “running,” and 
“death-feigning” ; and one minor component, “crouching.” The vi- 
brating response is elicited by a mild disturbance of the frame and 
support lines. The spider reacts by oscillating its body rapidly in 
a plane perpendicular to the substrate surface. 
Disturbance of the mesh of the lampshade may trigger one or 
more of the other three responses. The “crouching” response is one 
in which the disturbed spider withdraws to one side of the web base 
and huddles there. Usually, if the disturbance is continued, this is 
followed by the “running” response, in which the spider cuts through 
the lampshade with its chelicerae and runs along the substrate. The 
spider may instead scramble over the mouth of the lampshade, and 
then run along the substrate. Rarely, the spider cannot be provoked 
into any action other than “crouching.” 
Touching the spider or suddenly disturbing the mesh often re- 
sults in the spider’s leaping suddenly out of the web. Leaping (rather 
than simply dropping) enables spiders in webs on vertical rock faces 
to clear the edge of the lampshade. Upon striking the ground, the 
spider assumes the folded position shown in Figure 5. Spiders in 
this position are very difficult to see in the ground cover beneath 
the web. They remain in the “death-feigning” position for 5 to 15 
minutes, then climb back up the substrate until they encounter either 
the tangled portion of the web or the web base. This procedure 
usually presents no particular difficulty, as the spiders are directly 
under the web when they land. No dragline is spun when the spiders 
leave their webs by running or leaping. Probably gravitational cues 
are used in orientation, at least until silk is encountered. 
