1979] Christenson, Wenzl & Legum — Nephila clavipes 143 
Starks (1972) and Jackson (1978) found that eggs of the second 
clutch of Metaphidippus and Phidippus, respectively, hatch with a 
lower frequency than those from the first clutch. Gametic inviabil¬ 
ity, infertility due to sperm depletion, and the production of “tro¬ 
phic” eggs as food for the first few instars could, in part, explain the 
lower frequency of late season hatching (Jackson, 1978). The timing 
of maturation may also relate to inviability. From their study of 
temperate N. maculata, Thakur and Tembe (1956) suggest that 
some females may mature late in the season after the disappearance 
of males. Eggs laid by these females, therefore, could be infertile and 
inviable. This assumes that parthenogenesis does not occur in N. 
clavipes ; an assumption that has yet to be evaluated. The timing of 
male maturation may also be significant; males maturing on their 
own orbs toward the end of the season may be less healthy and 
vigorous due to reduced prey availability. Some males who mate at 
the end of the season may be older and incapable of normal sperma¬ 
togenesis. We are presently assessing the relationship of egg inviabil¬ 
ity to sperm depletion, seasonal variation in male vigor, and the 
extent to which females mature after the males have disappeared. 
We are also attempting to determine if parthenogenesis occurs in 
our population. 
Wise (1976) has noted that Linyphia egg weight may be adapted 
to the temperate ecology of his population. He suggested that eggs 
laid later in the season were heavier as an adaptation to the reduced 
amount of prey available to spiderlings who mature- late in the 
summer. Similarly, the seasonal variability of N. clavipes egg 
weights may be an adaptation to the length of the overwintering 
period. Since eggs laid early in the season must overwinter one to 
two months longer than those laid afterwards, spiderlings from 
early clutches may require additional yolk to maintain themselves 
during this period. If we assume a relationship between egg weight 
and spidering weight at emergence, then large early season egg size 
may minimize the chances that early spiderlings would be at a com¬ 
petitive disadvantage upon emergence in the spring (Kessler, 1971). 
To understand the role of egg weight as an adaptation to a temper¬ 
ate ecology, we must examine its relationship not only to egg 
number, discussed below, but also to the possibility that siblings 
may prey and/or feed upon one another during the overwintering 
period. We are currently examining the relationships between these 
variables and spiderling survival. 
