174 
Psyche 
[June 
(Marx) (Uloboridae, all ages, both sexes), Diguetia canities (Mc- 
Cook) (Diguetidae, mature females), and Linyphia marginata 
(Koch) ( Linyphiidae, various ages, both sexes). While the behavior 
of spiders is often regarded as quite stereotyped, there was great 
variation in the details of attack sequences, even those exhibited by 
a single individual. However, the basic outlines of an attack were 
quite constant for the species observed, and, at least in one case, 
appear to be for an entire family (Uloboridae) (Marples, 1962, 
1966). I have attempted to describe only these relatively fixed as- 
pects of their behavior. Unless otherwise noted, the descriptions 
apply to attacks in well-lit situations on live prey at least 1/3 the 
size of the spider. Simpler attacks on smaller prey sometimes occur 
(especially in Araneidae). 
Kaston (1966) surmises that the earliest spiders had no silk, and 
relied on speed and agility to capture their prey. The webless thera- 
phosids, in the Mygalomorpha which is morphologically a primitive 
sub-order of spiders, used little more than this in their attacks. As 
also observed by Baerg (1959) and Gertsch (1949), they attacked 
by holding the prey with the tarsi of the legs and pulling it close to 
the mouth where it was bitten with the powerful chelicerae. The 
prey was overcome and held by the spider’s chelicerae until their 
crushing action and poison immobilized it. Very little if any silk 
was used in the attacks. Occasionally, however, with the partially 
subdued prey held in the chelicerae, the spider arched its cephalo- 
thorax away from the ground and turned slowly in a circle, dabbing 
its spinnerets to the ground periodically. Possibly the silk laid during 
these actions served to give the spider a better grip on the substrate. 
The attack behavior of the araneids and uloborids differed from 
that of the theraphosids. They spun orb webs and responded to the 
struggles of prey trapped in the web by running to it and quickly 
swathing it in silk. Araneids generally held the radius (or radii) on 
which the prey was resting with both legs II, straddling the prey 
as they wrapped it. Legs IV alternated in pulling swathing silk 
from the spinnerets and looping it over the prey. The spiral strands 
in which the prey was entangled were broken, and the band of 
swathing silk was wrapped onto the prey as it was spun rotisserie 
fashion by the palps and legs III and I. The spider bit the prey 
briefly with its chelicerae soon after the swathing began, and then 
delivered a longer bite after the prey was more completely wrapped. 
After the prey was completely covered with silk, the spider freed 
it from the web and attached a short line to it. Holding this line 
