1971] 
Robinson & Mirick — Nephila clavipes 
1 33 
Table 2. Acridiids 
weighted and 
unweighted all lengthened 
Prey A 
to 70 mm. 
Prey 
Behaviors. 
yes 
8 
2 
1. Bite and back off 
no 
4 
10 
yes 
11 
4 
2. Bite, legs raised 
no 
1 
8 
yes 
12 
11 
3. Wrap in web 
no 
0 
1 
yes 
4 
8 
4. Quit the web 
no 
8 
4 
Prey A weights 1700-1800 mg. Prey B weights 400-550 mg. 
Statistical analysis — Fisher’s exact probability: Difference between A 
& B for bite and back off, level of probability 0.025; difference between 
A & B for bite, legs raised, level of probability 0.01 ; difference between 
A & B for wrap in web not significant; difference between A & B for quit 
the web not significant. 
All levels one-tailed 
with the prey, by tapping weighted and control dummies from behind 
the web. (We did this when the spider was in tarsal contact with 
the prey and before it had attacked). This led to a numerical, but 
non statistically significant, increase in the number of bite & back 
off attacks. It is very difficult to standardize simulated prey move- 
ments. 
A by-product of these experiments was the suggestion that the 
wrapping of prey in situ might be a response to the failure of the 
spider to pull out the prey. The number of wrap in situ responses 
was significantly greater in the case of the artificially lengthened 
prey used in the first experiment. These were, to the observer, 
obviously a much greater problem to the spider at the pull out 
stage. We therefore decided to carry out some experiments to see 
if increasing the adhesion of the prey to the web, or its ‘apparent* 
adhesion, would affect the spider’s behavior at this stage in the 
predatory process. 
( b ) Pulling out and wrapping behavior 
As a first simple experiment we used domestic crickets as prey. 
We simply presented 20 dead unmodified crickets and scored the 
