144 
Psyche 
[June 
In hunting, as in courtship, visual stimuli are the most important, 
and complete hunting behavior can be observed with live prey in 
transparent containers, dead prey dangled by means of an attached 
fine gauge wire (or otherwise made to move), and simple models of 
prey, such as moving dots or spheres. In hunting, the spider is 
essentially tracking a moving target, and full control over the stimuli 
received from the prey is possible with a moving model whose speed, 
distance, and angular displacement can be regulated (Drees, 1952; 
Precht, 1952). The main difficulty in working with actual prey lies 
in the highly variable movements of living animals. To some extent, 
this can be overcome: flightless Drosophila mutants with a uniform 
manner of locomotion have obvious advantages over a prey that can 
fly, and hence sporadically disrupts an ongoing bout of hunting 
behavior by an abrupt change in angle and distance from the spider. 
It is important to arrange a situation in which the prey is not some- 
times moving and sometimes still, as the spider seldom initiates hunt- 
ing behavior to still prey, and interrupts ongoing hunting behavior 
when the prey ceases to move. Curly-type Drosophila melanogaster 
are suitable for this purpose as they crawl upward on a vertical sur- 
face and move continually until they have reached the top. The 
pathway of the prey in relation to the predator can also be made 
uniform. Jumping spiders will readily climb a slender pole, and 
position themselves, facing down, near the top ; the curly-type Droso- 
phila also climb such a pole, moving continually and at a constant 
speed straight toward the spider. With such a technique, the distance 
at which the spider initiates hunting can be measured, and can be 
compared for different species or for different periods of deprivation. 
Results 
Hunting behavior in salticid spiders can be described as a sequence 
of stimuli and responses: the spider performs a given response until 
there is some crucial change in the stimuli received from the prey 
which then evokes the succeeding response. Thus, when introduced 
into a hemispherical testing chamber, the spider generally climbs to 
the top. A few seconds after the prey enters, the spider orients by 
turning so that the large frontal eyes come in line with the prey, and 
this relative position is maintained throughout the remaining hunting 
responses. Once lined up, the spider pursues , moving rapidly at first 
but more slowly as it comes near the prey. When P. coccineus is 
within 5 cm of the prey, the spider presses its body close to the 
ground, and draws the legs in toward the body. At about 1.5 cm, 
the spider becomes still in this crouched position, attaches a thread 
