1971] 
Robinson & Mirick — Ncphila clavipes 
129 
3. The third attack strategy we call bite & back off. It consists 
of a rapid forward lunge, a short-duration bite and a rapid with- 
drawal to a distance at which the prosoma is well away from the 
prey. We have shown this behavior as a repeatable unit since the 
lunge, bite, retreat sequence may be repeated a large number of 
times (we have records of over 12 repetitions) before a sustained 
long bite ensues. In many cases, when this form of attack is em- 
ployed, the spider can be seen to open the chelicerae until they are 
almost held horizontally, before making the rapid forward lunge 
that terminates in the bite. 
The type of attack strategy that the spider employs seems to be 
largely determined by parameters of weight and/or size of prey; 
our experimental analysis of these factors is described later. We 
have not been able to determine what factor or factors mediate the 
decision to cease repetitions of bite & back-off and commence su- 
stained biting. This process is not dependent on reduction of activity 
by the prey (that might be consequent on a series of bites) since it 
occurs in the spider’s behavior towards large dead prey. 
Behavior following the initial attack phase is somewhat more 
complex than is the case with araneids that are efficient at enswathing 
their prey in silk. Attack is almost always terminated by pull-out 
movements. The body of the spider is lowered, on flexed legs, during 
the biting attack and pulling out consists of strong extensions of 
the leg pairs. These result in the spider pushing down on the web 
and pulling up on the prey. Very small prey, adhering to a small 
area of viscid spiral, are quickly freed, as are lepidopterans which 
do not adhere strongly because of their loose wing scales (see Eisner 
et al 1964). Other prey may be subjected to repeated pull out 
movements before being freed. Prey that are not readily freed by 
pulling movements are wrapped in the web and then cut out by 
the snider. Robinson, Mirick & Turner (1969) called this wrapping 
at the capture site. Type 1. We have been able to show that the 
spider can be induced to wrap prey (in this way) if its pulling out 
attempts are blocked experimentally (see later). It seems possible 
that the pull out movements enable the spider to gauge the degree 
of adhesion of the prey to the web and that the ‘decision’ to continue 
pulling, or to wrap in situ and then cut out, is influenced by this 
information. A further complication arises from the fact that the 
spider may wrap, at the capture site, prey that have already been 
freed from the web by pulling (Post-immobilization wrapping at the 
capture site. Type 2, of Robinson, Mirick & Turner 1969). 
