176 
Psyche 
[June 
line as the spider rushed off to attack. This description agrees in all 
major points with those of Savory (1950) and Peters (1931, 1933). 
The attacks by uloborids that I observed and that Marples re- 
ported (1962) were similar to those of the araneids with three 
major differences. 
1. The prey was never bitten (Uloboridae have no poison glands). 
Immobilization was accomplished entirely by use of silk. This total 
reliance on silk represents the farthest departure of any spider from 
the primitive attack formula of “grasp and poison”. 
2. The prey was always carried in the palps and was never at- 
tached to the web. If another prey landed on the web the first was 
carried to the attack site, and often the two were wrapped into a 
single bundle. The presence of the first prey did not seem to hinder 
the movements of the second attack in any way. 
3. Rather than straddling the prey at the start of an attack, the 
spider often turned to face away from it and pulled silk from the 
spinnerets, guiding it toward the prey with legs IV. In general, the 
larger the prey was, the farther the spider stayed from it as it com- 
menced wrapping. The uloborids were thus farther from the strug- 
gling prey than the araneids in the initial stages of attack when the 
prey was least subdued. 
The observations reported so far suggest this situation: 
primitive — capturing prey with legs and chelicerae, holding it with 
the chelicerae and using poison to subdue it, not applying silk to it; 
advanced — capturing and subduing prey from a distance by apply- 
ing silk to it, holding it with appendages other than the chelittrtk. 
A clue to the origin of the use of silk in the evolution of attack 
behavior comes from the behavior of spiders in the poorly known 
family Diguetidae. These spiders spun relatively organized webs 
that were somewhat similar to those spun by linyphiids. The web 
was a roughly circular mesh platform suspended in a network of more 
widely spaced supporting strands. A nearly cylindrical “retreat” 
hung in the mesh just above the center of the platform (Fig. 1). 
The undersurface of the platform was continuous with the inside 
of the retreat. The spider remained inside the retreat during the 
day, and hung under the platform near the retreat at night. 
When a prey fell onto the platform, the spider rushed out from 
