1976] 
Jackson — Phidippus johnsoni 
253 
tors not adapted to respond to the nest per se may fail to detect 
the occupant. 
3. The nest may provide the occupant with an early-warning 
device, in effect forming an extension of the spider’s tactile sen- 
sory system. 
4. The nest may put the occupant in a highly defendable posi- 
tion with respect to many predators. Usually there are only two 
nest doors. This may be the only or easiest way for many preda- 
tors to gain access to the occupant. Some of the responses shown 
by females to courting males, such as pulling the door and strik- 
ing, are apparently effective defense against some predators. 
Such behavior was used during the interactions with gnaphosids; 
and in the majority of cases, the P. johnsoni survived the en- 
counter with the predator. 
Summary 
P. johnsoni males may court and mate with females either 
inside or outside their nests, employing a different type of court- 
ship in each circumstance. Although predation probably pre- 
sents a greater risk to pairs courting and mating outside rather 
than inside nests, the difference is evidently relative, not abso- 
lute. Large gnaphosid spiders were found to occupy P. john- 
soni nests containing dead P. johnsoni in the field. Laboratory 
observations implicate the gnaphosid spider Herpyllus hespero- 
lus as a predator of P. johnsoni females while they occupy their 
nests. Other observations implicate H. hesperolus as a predator 
of P. johnsoni males that court at the nests of P. johnsoni females 
occupied by H. hesperolus. P. johnsoni can discriminate be- 
tween empty P. johnsoni nests and empty H. hesperolus nests, 
courting at the former and remaining only briefly at the latter. 
Acknowledgments 
Roy L. Caldwell and Evert I. Schlinger are gratefully acknow- 
ledged for their assistance during all phases of this work. I 
thank Charles Griswold for identifying the gnaphosid spiders 
and for his comments on the manuscript. 1 also wish to thank 
Peter Witt for his comments on the manuscript and Rubenia 
Daniels for typing the manuscript. This work was supported in 
part by a NSF predoctoral fellowship. 
