1984] 
Wise — Phenology of filmy dome spider 
281 
Table 4. Estimated stages, when collected from natural populations on 21 July 
1982, of spiders that were alive as immatures in mid-September or that had matured 
by then. Stages were estimated by comparing tibia lengths to a distribution derived 
from a previous laboratory rearing study (unpubl). A. Numbers in each stage on 21 
July that had matured. B. Numbers in each stage on 21 July that were immature 
and alive in September. All spiders that matured before winter had done so by 
mid-September. 
1 
2 
Stage in July 
3 
4 
5 
A. Matured 
Patuxent 
2 
1 
19 
9 
Liberty 
6 
25 
3 
Total 
8 
26 
22 
9 
B. Immature 
Patuxent 
3 
5 
1 
1 
Liberty 
9 
19 
2 
1 
Total 
12 
24 
2 
2 
1 
ditions (Browning 1941, Jones 1941, Deevey 1949, Turnbull 1962, 
1965). Rearing studies with hatchlings of Patuxent females show 
that food supply can affect rates of growth and development of the 
filmy dome spider (Wise, submitted). Martyniuk has also demon- 
strated the plastic response of developmental rate in N. radiata to 
variations in prey abundance in a laboratory study, and in a field 
experiment has established that local differences in prey abundance 
influence web-site selection and tenacity in this species (Martyniuk 
1983). Although the 1981 field experiment at Patuxent provided no 
evidence of food limitation, other research has demonstrated that 
natural prey levels can limit the fecundity and growth rate of filmy 
dome spiders in nature (Wise 1975). Differences in temperature 
between web sites also possibly contribute to intra-populational 
variation in developmental rate. Comparison of the phenologies at 
Patuxent and Liberty provides indirect evidence of the effect of 
temperature on developmental rate, since the stage of development 
was accelerated at the warmer location. 
Environmentally induced variation in growth and development of 
filmy dome spiders partially explains their maturing at different 
times during the spring. In addition, seasonal selective constraints 
associated with the timing of reproduction by summer-maturing 
adults (to be discussed later) have apparently interacted with this 
variation to expand the spring reproductive period even further. 
