To produce each of the photographs shown here, a 35mm camera was mounted on a tripod in front of a plant or plant-like structure, and a series of photographs were taken as the spider moved in pursuit of its intended prey (a fly suspended from a long hair). In each case, the fly was immediately removed after the first photograph was taken, so that subsequent orientation by the spider to the prey position was based solely on memory of the original position of the prey. The separate photographs for each pursuit sequence were overlaid in a montage to illustrate each successive position of the spider in a single image.
Figure 13.1 Pursuit of prey by adult male
Phidippus pulcherrimus. Pursuit began when the spider (1)
sighted the target overhead (x). The target was immediately removed
as the spider turned and ran toward the stem (2). The spider continued
up the stem and then stopped to reorient to the target position (3).
The spider then continued up to a leaf near the target (4 and 5) and looked
around. Note how this spider moved further away from the target position
(2) in order to ultimately attain it.
Figure 13.2 A second pursuit of prey by adult male Phidippus
pulcherrimus, presented with the same problem of access. After
the spider (1) sighted the target (x), the target was immediately removed.
Again, the spider immediately moved down to the main stem of the plant
(2), but this time did not stop to reorient until it had climbed all the
way up to the leaf near the target position (3). The spider then
proceeded to a position on top of the leaf (4) from which it looked around
in various directions.
Figure 13.3 Pursuit of prey by an adult female Phidippus pulcherrimus
on a horizontal bar, viewed from above. This controlled configuration,
inside of a white cylinder, was used to study the ability of these spiders
to compensate for both the initial distance of the prey, the direction
of that prey relative to the bar or direction of pursuit, and the
length of pursuit (2) prior to the reorientation turn (3), in determining
the direction of that reorientation turn. Pursuit began when the
spider (1) sighted the target (x), which was immediately removed after
the spider turned to run along the back side of the bar (2) in pursuit.
Finally, the spider reoriented in the expected prey direction from a new
position (3). Many, but not all, individual spiders routinely ran
along the side of the bar away from the prey, as shown here. The
advantage of this concealed approach is obvious. Units of 1.0 cm
in length are marked off on the bar for reference.
Figure 13.4 Pursuit of prey by an adult male Phidippus pulcherrimus.
viewed from the side. The spider (1) sighted the prey (x) as it was
held in a horizontal direction. The prey was removed as the spider
immediately turned left to run toward and climb up the "stem" (2), and
then climbed out onto a "leaf" (3) in a single, uninterrupted run.
Only when this spider had attained the top of the "leaf" (4), did it reorient
to the expected prey position. This, and similar, demonstrations
have been completed in a controlled environment hundreds of times.
This demonstrates clearly how these spiders will move toward sighted secondary
objectives (the "stem" and "leaf: in turn), even when this leads
them further away from the prey position. As shown here, a segment
of pursuit prior to reorientation (position 1 to position 4) does not need
to be linear. This and related experiments have shown clearly that
these spiders can orient visually (e.g., to the "leaf" at postion 3)
when they are moving, and do not need to stop to compete this orientation.
Notice also that when this spider reoriented to the prey position (4),
it looked back to the right in a horizontal projection to compensate for
its turn away from the prey at (1), and it also looked down to compensate
for its movement above the prey position (2 to 3), as part of the same
turning movement.
Phidippus pulcherrimus, like many other Phidippus, frequent the upper layers of herbaceous plants in an open field or prairie habitat. The spiders shown here were captured when immature in Ocala National Forest, east of Ocala, Florida, and reared to maturity in the laboratory. They were maintained in a healthy but "less than satiated" condition so that they would readily engage in the pursuit of prey.
Several features of the detours depicted here are important to recognize. First, these spiders routinely run "detoured" or indirect routes in order to obtain positional objectives. This may occur in the context of predatory pursuit, as shown here. It may also occur in during pursuit of a mate, or during pursuit of a sighted position in the foliage. Second, as these spiders move, they frequently stop to look back at the target ("reorientation"), compensating for their own movement in determining the relative direction of the prey from a new position. Third, as shown here, Phidippus readily move further away from the primary objective (e.g., prey) during the course of these pursuits, if the prey cannot be approached directly. In doing so, however, they move directly toward an immediate or "secondary" objective, such as a connecting branch or stem, which will ultimately allow them to attain the primary objective. These secondary objectives are identified visually during the course of the pursuit.
Earlier studies have shown that Phidippus spiders utilize a combination of visual cues, a memory of the extent and relative direction of body movement along the path of pursuit, a memory of direction with respect to gravity, and an initial estimate of the distance of the prey, in order to determine the relative position of that prey from a new position. Spiders that jump and miss prey can even reorient accurately in the original prey direction, once they have climbed back up the drag-line to their starting position.
If you wish to engage in laboratory experiments related to the behavior of salticid spiders, it is important to realize that every species is different, and may behave quite differently when presented with the same situation. I have found that Phidippus pulcherrimus, P. princeps, and P. clarus are excellent subjects for the study of these indirect pursuits. All of these spiders live in the upper herbaceous layer in open field or prairie habitats.