34 
Psyche 
[Vol. 89 
Radii and non-sticky spiral were laid as in U. diversus (Eberhard, 
1972) and their construction lasted 5 and 1.5 minutes, respectively. 
Radii were laid by walking out from the hub on an existing radius 
with a dragline, attaching the dragline to a frame thread, and then 
doubling it by walking back to the hub with another dragline. At the 
hub the dragline was attached to a succession of adjacent radii 
(forming the closed hub spiral) before the next radius was laid. 
When most of the radii were completed, the spider continued the 
hub spiral outward to form the non-sticky spiral, laying occasional 
“tertiary radii” (Le Guelte, 1966) during the process. This non-sticky 
spiral did not reach the frame threads. 
At the start of the sticky spiral even very faint light falling on the 
spider caused her to cease spinning and bounce up and down on the 
web. Consequently, observations of sticky spiral construction were 
made only sporadically, using indirect lighting. The first (outer- 
most) loop of non-sticky spiral was completed in 13 min. During 
sticky spiral construction the spider reversed directions five times in 
the larger part of the web. The sticky spiral was attached to each 
radius that it crossed, and the spider broke non-sticky spiral loops as 
she laid the sticky spiral. One immature female was observed laying 
a zigzag outer loop of sticky spiral. The sequence of attachments of 
the cribellar silk to produce the zigzag loop (Fig. 5a) was distinct 
from that involved in laying the normal sticky spiral loops (Fig. 5b). 
After meticulous, slow sticky spiral construction, which in one 
case lasted 3 hrs. 6 min., the spider suddenly began spinning out 
cribellar silk in a rapid and seemingly reckless fashion while moving 
inward toward the hub at an angle of about 25° to the last turn of 
the regular sticky spiral (Figs. 2, 4). After completing half a loop, 
the spider reversed direction and continued spiralling toward the 
hub, laying a jagged and irregularly spaced sticky spiral. The jagged 
spiral was attached to only a few radii, crossing 3-7 radii and, in 
some cases, several non-sticky spiral loops between attachments. 
The non-sticky spiral was left intact. This entire phase was very 
rapid and in one case the four jagged loops were completed in just 6 
min. This jagged spiral was to become the sticky spiral of the future 
cone. 
After completing the cone sticky spiral, the spider moved to the 
hub and slowly turned in a circle, pulling on successive radii with the 
first legs. After 2 min. she went out to the end of a radius and 
