1972] 
Fergusson — Hypochilus thorelli 
197 
27 October. This sac, like all others observed (including those left 
over from previous years) , had been opened at the top. 
The spiderlings probably disperse from the sac simply by scattering 
out over the substrate. The small first web is similar to that built 
by adult spiders, though the tangle appears to be relatively less ex- 
tensive than in the adult webs, and resembles a flat sheet more than 
a three-dimensional tangle. The lampshade portion of the web ap- 
pears to be shallower than in adult webs. The spiderlings assume 
the same resting position as adult spiders. 
Life cycle. After constructing webs, the spiderlings begin feed- 
ing, and grow until fall. I did not determine the number of molts 
involved. They do not attain sexual maturity during the August 
following eclosion. They apparently spend the winter in crevices in 
the rock substrate. (I found one at Mull Creek in March by pull- 
ing large loose rock flakes off an overhang.) These spiders appear 
again in the spring. The first ones were found 14 March at White- 
water Falls and 15 March at Wolf Creek. By early May all the 
overwintering spiders are again active. They then grow and reach 
sexual maturity in August (see Reproductive Biology). All males 
die during the fall; a few females survive until the following spring. 
(I found thre active adult females during April and May.) 
Data for the length of the life cycle were obtained by measuring 
the sizes of webs and by measuring the sizes of the spiders. On the 
assumption that the size of the web base is proportional to the size 
of the spider ( which sits with its legs radiating out to touch the sides 
of the web base), and that the size of the spider is proportional to 
its age, I measured web base diameter of 134 webs (Figure 9) of 
H. thorelli during August and September, 1970. (The length of 
time involved may have introduced some bias into the results.) Fig- 
ure 9 shows that there are two classes of web size, with a break be- 
tween 3.2 and 3.8 cm. This suggests that there are two age classes 
of spiders during late summer: those that had hatched the previous 
spring, and those that are of reproductive age. 
For another sample of spiders, I measured the length of the tibia 
of the first leg to determine size classes. Carapace width or length 
were not discrete enough to measure reliably. Collections of spiders 
for measurement were made from 23 October until 1 November. 
Because two broad groups were in evidence at the time — large, ac- 
tively reproducing spiders and smaller, non-reproducing ones — an 
attempt was made to collect only a large number of smaller ones 
to determine the number of years required to reach sexual maturity. 
However, five adults were collected during that time period. Fig- 
