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Psyche 
[Vol. 91 
continued for 17 days after supplemental feeding had ceased, and on 
14 September the experiment was terminated by removing and 
measuring all remaining spiders. 
Rearing Field-Collected Juveniles 
A major advantage of the field experiment was that biotic and 
physical factors that limit growth and development were at natural 
levels. However, because the populations were open the develop- 
mental fates of individual spiders could not be monitored without 
error. More direct evidence of the variable developmental fates of 
the progeny of spring adults was obtained by collecting spiders from 
natural populations and rearing them individually to the end of the 
season or until they had matured. 
On 1 July 1980, 47 of the largest juveniles in the population were 
collected from Liberty. This collection included those offspring of 
spring adults most likely to complete development and reproduce 
that summer. In the following year a different sampling strategy was 
employed. In 1981, 89 of the smallest spiders (stages 1-3) in the 
Liberty population were collected on 6 July. These were the progeny 
of spring adults least likely to complete development within the 
season. I sampled the extemes of the size distribution in order to 
uncover the limits to the developmental potential of the population 
at a particular time. Logistical constraints prevented sampling of the 
entire range of size classes in a single season. 
In 1982 juvenile spiders were collected from Liberty and Patux- 
ent. As in 1981, the smallest spiders that could be found were 
removed, but they were collected two weeks later in the season. On 
21 July I collected 41 immature spiders from Patuxent and 80 from 
Liberty. As in the previous two years, these spiders were also the 
progeny of spring adults, judging from the minimum time elapsing 
from maturity to hatching of progeny from the first egg sac (19-21 
days; unpubl. data). 
In all three years the collected spiders were reared in individual 
containers with a super-abundance of fruit flies. Although in nature 
the developmental rate of some juveniles might be limited by a 
shortage of prey, I provided a surplus of food in order to uncover 
the developmental potential of each individual. In 1980-81 rearings 
were done in the laboratory under natural photoperiod. In 1982 the 
juveniles were reared on the porch at Patuxent. 
