1971] 
Robinson & Mirick — Nephila clavipcs 
135 
Table 4. Wrap in situ behavior (ii). Experiment with stringed crickets. 
Wrap in web Pull out alone Reject 
Experimentals 19 0 1 
Controls 2 18 0 
Experimentals were held by string from behind the web. 
it free. In this experiment the spiders made extended and persistent 
efforts to pull the prey before initiating the wrapping behavior. 
The process of free wrap proved to be much more difficult to 
elicit under experimental conditions. We had observed that this 
behavior occurred most frequently in the treatment of butterflies and 
moths. These could be freed from the web by pulling but were, 
nonetheless, bulky and cumbersome insects. Other cumbersome in- 
sects such as dragonflies adhered strongly to the web, were wrapped 
and then cut free of the web, and were thus largely trussed and 
packaged at this stage. They were not therefore suitable for experi- 
ments on free wrap behavior. We reasoned that free wrapping was 
a response to insects that could be removed from the web by pulling 
but were too bulky to be transported without becoming entangled 
in the web. The spider makes movements during the pulling out 
process that could enable it to gauge the bulk of the prey as it is 
removed from the web. These movements involve legs I & II. The 
tarsi are passed along the adhering margins of the prey and ease them 
away from the viscid elements of the web. Our observations on the 
removal of butterflies and moths from the web suggested that the 
cumbersomeness of detached prey was, to a large extent, a function 
of apparently chance factors. Thus it was partially dependent on 
the point on the prey body at which the spider exerted the pull out 
movements (i.e. the point at which the prey was held in the jaws), 
and partially a result of the orientation of the wing and body sur- 
faces in relation to the sticky elements of the web. (Some idea of 
the complexity of these factors can be gained by visualizing the 
process of picking up a randomly cast down book, by the spine, 
from a sticky surface. A winged insect, like the book, may open 
in a variety of ways, depending on where it is seized and where it 
is stuck down.) 
Starting from this point we tried to present a series of moths to 
the spiders with the entire dorsal surface of their wings adhering 
to the web but at differing orientations to the radii (and therefore 
the hub and the spider). We hoped that these would be seized at 
different points on the body and that our sole experimental variable 
