136 
Psyche 
[June 
webs are found under stones at the base of the bush. Usually, the 
spider places its nest under one of the few stones that remains shaded 
from the strong desert sun even at mid-day. Occasionally, P. coccineus 
builds nests inside or under cardboard containers dumped in their 
habitat. Phidippus opifex makes frequent use of the insulation pro- 
vided by these cardboard boxes; alternatively, and unlike coccineus , 
opifex builds a large and prominent nest among the branches of a 
bush to souse its egg cocoon. 
Life history 
The breeding season of P. coccineus appears to be a very early one. 
In 1964, six adult males, nine adult females, and about 90 immature 
spiders of this species were collected near Reno, Nevada. The males 
were found first, even before the final snowstorms of early June; adult 
males were found from early April to early July, adult females, 
from early May to mid-July. All but one of the females collected 
in May were already gravid and laid eggs within the following 
fortnight; all females obtained later in the summer (mainly, in July), 
were found in a nest with an egg cocoon. Two spiders in the penulti- 
mate instar were found in late May, and these became mature in the 
laboratory toward the end of June. But from mid-July on, only 
immature spiders could be found and none of these attained maturity 
during the summer or fall of 1964, though they have molted as many 
as four times since coming to the laboratory. It is of some interest 
to note that the females survived the males by almost two months 
when kept under identical conditions in the laboratory, and that, 
for each sex, all the adults died within a short span of time (e.g., all 
the females between 18 Sept. 1964 and 6 Oct. 1964). 
The early breeding season of P. coccineus contrasts with that of 
P. opifex and P. apache anus found in the same habitat. Adult males, 
adult unmated females, and females in the penultimate instar of 
P. opifex were collected in the first half of July; the nests containing 
the egg cocoons of this species were abundant in the sagebrush late 
in August. Phidippus apacheanus had the latest breeding season 
among the three species: while immature spiders of this species were 
abundant throughout the spring and summer, adults were only found 
after the third week of September. Six immature P. apacheanus kept 
in the laboratory since early July molted three times and became 
mature around the end of October (see Table I). 
The seven P. coccineus females kept in the laboratory during the 
summer of 1964 laid either two or three successive batches of eggs, 
each batch containing fewer eggs. A median of 44 spiderlings hatched 
from the first batch of eggs, 30 from the second, and three from the 
single third batch that did hatch. By contrast with females that 
