1965] 
Gardner — Phidippus 
145 
of silk to the substratum, and jumps at the prey. Somewhat more 
elaborate tracking occurs when a small P . coccineus pursues a much 
larger prey, such as a blue-bottle fly: the spider may take a curved 
course so that the final jump is from behind the prey. 
It is possible to vary the frequency and duration of each hunting 
response by withholding the stimuli for the succeeding response 
(Drees, 1952; Precht, 1952; Gardner, 1964). For example, if the 
model is kept about 10 cm from the spider by moving it at the same 
speed as the pursuing predator, pursuit is prolonged far beyond its 
normal duration as the next response, crouching, requires a very 
small distance between prey and predator. Again, a model moving 
slowly within a transparent tube 2.5 cm in diameter seldom evokes 
jumping for the crouched spider cannot get close enough, while with 
a narrower tube jumping occurs readily. 
Having captured the prey, the spider settles in one spot and does 
not move again until it has discarded the undigestible hard remains 
of the prey — a small mass in the case of the Drosophila, or the 
perfect empty shell of a large prey such as Calliphora . The time 
required to consume the prey reflects the relative size of the spider 
and its prey. For example, a group of small (4-6 mm) immature 
P. coccineus, tested at 7 days food deprivation, required a median 
time of 29.O min. to consume a Drosophila, while larger individuals 
(8-10 mm) required only 8.6 min. Even the large adult females 
required almost one hour to consume large prey such as Musca 
domestica. For P. coccineus (and P. clarus as well), consuming time 
increases reliably with days of food deprivation. Thus, the same 
group of small spiders required only 21.8 min. to consume a Droso- 
phila when tested at 1 day food deprivation. 
Hungry P. coccineus will readily capture more than one prey at a 
time, provided the second prey comes very near (the spider will not 
move away from the place at which it has settled with the first prey). 
This situation was explored with the pole technique and perhaps it is 
common in the natural counterpart of the pole — the branch tips 
where hunting Phidippus can be found. The spiders accepted several 
pairs of prey on the pole, but as they became satiated, it was much 
less likely that they would accept the second prey. Instead, the spiders 
responded by extending the forelegs toward the Drosophila — once 
again using the ubiquitous display that occurs in courtship, intra- 
specific encounters, etc. 
Given the choice between two prey that differ in size, such as 
Musca and Drosophila or Calliphora and Drosophila, P. coccineus 
chooses the large prey less consistently than does P. opifex and P. 
