1969] 
Robinson — Predatory Behavior 
493 
of a katydid during a close quarters attack. In fact, Nephila attacks 
large prey with legs I and II raised off the web and flexed back, 
and often darts forward to make a short bite and then backs off 
before attacking again. A succession of short bites and retreats may 
thus occur. 
Wrapping attacks may be initiated while the spider is actually 
standing on the prey. These may still protect the spider from injury 
since it can maintain a greater distance between itself and the prey 
than is possible during the more intimate bite. We feel, however, 
that immobilization wrapping may confer a further and very impor- 
tant advantage. It may help to achieve an economy of time spent 
away from the hub while attacking and immobilizing prey, as Rob- 
inson (1969) suggested. Any reduction in the time spent in capturing 
prey must enable the spider to be in a better position to respond to 
further prey before they can escape from the web. Additionally, if 
the spider is more vulnerable to predators when it is attacking prey, 
it would be advantageous to reduce time spent out on the web. 
There is a statistically significant difference between the duration 
of the bite given before wrapping (in the long bite/wrap sequence) 
and the duration of the bite given after wrapping (in the wrap/short 
bite sequence). The long bite may be long simply because the spider 
has to wait for it to take effect before it can safely release the prey 
and commence wrapping. In the case of immobilization wrapping, 
the prey is secured before the bite is given, and the spider gives a 
short bite and retires to the hub to resume “monitoring” the web. 
The short bite may inject a smaller venom dose, or one which is 
slower acting. However, since the prey is wrapped, it can safely be 
left while the venom takes effect. The effects on living prey of the 
two types of bite are under investigation. There is certainly a differ- 
ence in the time spent at the capture site when the spider uses the 
two types of attack against the same type of prey (Robinson, 1969, 
p. 170). 
The above conclusions about function can be summarized as fol- 
lows : 
1. Post immobilization wrapping at the feeding site results in 
the prey being safely anchored to the web by silk. It functions to 
permit the spider to make further attacks without losing the prey 
“in hand”. In effect, the spider does not have to lose time securing 
the prey to the web at the moment when a new prey strikes the web 
(i.e., when it needs to be able to make an immediate attack). That 
this is a correct interpretation is suggested by the fact that those 
prey which are carried suspended on a silk thread are not wrapped 
