124 
Psyche 
[September 
the Barro Colorado Island research station of the Smithsonian Trop- 
ical Research Institute. We maintained a minimum of fifteen spiders 
in captivity during the period of study in 1968. The experiments 
carried out in 1969 required a larger number of spiders and 
we used free-living spiders in the Barro Colorado forest as well as 
a number of captive spiders. Even with access to twenty or more 
non-captive spiders it was necessary to use some spiders more than 
once in an experimental series ; details of how these were manipulated 
to obviate the possible effects of experience is given below in the 
appropriate section. Captive spiders were collected from the same 
areas as the non-captives and all were of unknown age and previous 
experience. 
We made repeated presentations of a number of different prey 
items in order to establish the basic patterns of the spider’s behavior. 
This involved fifty presentations of each of seven prey types. These 
were chosen for their relevance to the natural diet of the spider 
(see later) and because they presented large differences in size, 
weight and type of activity after striking the web. We used the data 
obtained from these observations to prepare ethograms of the type 
used by Robinson & Olazarri (1971) and then used these etho- 
grams as a basis for the integrated model. Fifty presentations of 
each prey item meant that a proportion of the spiders received the 
same type of prey more than once. In general we presented but 
one prey per spider each day. In an attempt to avoid any possible 
effects of experience we avoided successive presentations of the same 
type of prey. In all cases at least two days (usually more) inter- 
vened between one presentation and the next presentation of the 
same type. Usually another type of prey, or several other types of 
prey, would be presented between presentations of the same type. 
In addition we made presentations of all the prey types to a large 
number of free-living spiders as a check on the behavior of our 
captive spiders. 
In the course of our initial observational work we presented the 
following prey items: moths (living & dead), grasshoppers (living), 
crickets (living & dead), Tenebrio beetles (living), dragonflies (liv- 
ing), Tfigona sp. (living), pentatomids (living), and blowflies 
(living). Later when we attempted to elucidate the stimuli which 
the spiders were capable of detecting at various stages in the process 
of predation we used a number of experimental techniques involving 
modified insects in the form of ‘dummies’. These techniques are de- 
tailed in the appropriate section below. 
All the insects that we used were weighed and measured before 
being presented to the spiders. Where insects were presented dead 
