144 
Psyche 
[June-September 
The decreased weight of individual eggs laid near the end of the 
season may be due to reduced female prey intake as a function of 
prey availability at this time. Turnbull (1962) and Kesler (1971) have 
noted that prey intake can, in part, determine egg weight in Liny- 
phia and Pardosa, respectively. This could explain why the egg sacs 
we collected in 1978 appeared to contain heavier eggs than those 
collected in 1977. In 1978 eggs came from an area of the forest 
bordering a cleared drainage ditch near which many adult females 
maintained orbs. During the mating season the biomass of flower¬ 
ing plants and prey seemed much greater and the females relatively 
larger in this area. In contrast, 1977 clutches were collected from 
within the forest, where the biomass of prey and female size seemed 
restricted. We obviously need to do more sampling. Habitat can, 
however, influence egg productivity. Kessler (1973) noted that the 
variance in the number of eggs produced by Pardosa in different 
localities was greater than that noted in the same locality from year 
to year. 
Reduced prey intake by the female near the end of the season may 
also reduce the number of eggs in later clutches. Kessler (1971) 
noted that in some species of Pardosa decreased food intake 
resulted in fewer eggs per clutch. This decrease in egg number could 
also be explained, in part, by the observation that successive 
clutches contain fewer eggs in N. maculata (Bonnet, 1930) and in a 
variety of other genera ( Phidippus —Jackson, 1978, and Gardner, 
1965; Tegenaria —Mikulska and Jacunsksi, 1968; Achaearanea — 
Valerio, 1976; Enoplognatha —Seligy, 1971; and Chiracanthium — 
Peck and Whitcomb, 1970). In Linyphia female size is related to egg 
number in that clutches of the larger early maturing females con¬ 
tained more eggs than those of smaller later maturing females (Wise, 
1976). 
In an interesting discussion Jackson (1978) suggested that female 
Phidippus may invest more of their energy in the first clutch as an 
adaptation to the increased risk of desiccation and reduced prey 
availability experienced by spiderlings from later clutches. Early 
season N. clavipes might invest more of their reproductive energy, in 
terms of egg number, in the first clutch as an adaptation to the 
possible detrimental effects of cooler late season temperatures. We 
suspect that the number of spiderlings in a clutch determines, in 
large part, how successful the siblings are at constructing a succes- 
