1980] 
Eberhard — Bolas Spider 
161 
Individual females produced up to eleven sacs. The average time 
between sacs was 9.5 days (23 sacs; range 5-13 days). One representa¬ 
tive sac weighed 331 mg and had 826 eggs (.40 mg/egg). 
Newly emerged spiderlings 
In some Mastophora species males emerge from the egg sac already 
mature (Gertsch 1947, 1955), but this was not the case in M. 
dizzydeani. Males of this species emerged an estimated one to two 
moults from maturity. On several occasions I found spiderlings 
which had especially swollen abdomens apparently feeding on 
shrivelled unhatched eggs when I opened a sac. Some shrivelled 
spiderlings were also seen, and when masses of spiderlings were 
observed under the microscope I saw that a typical behavior that was 
associated with the periodic waves of activity that swept through the 
mass was to “lunge” ventrally one or more times with the chelicerae 
open and snap them shut. Cannibalistic feeding could result in the 
growth of spiderlings within the sac, and should be looked for in 
species like M. cornigera in which males normally emerge mature. A 
suggestion that such cannibalism occurs comes from Gertsch’s report 
(1947) that only about 150 spiderlings emerged from each sac of M. 
cornigera. Since this species is slightly larger than M. dizzydeani and 
thus almost certainly lays more rather than fewer eggs per sac (clutch 
size is strongly correlated with spider size in Araneidae Eberhard 
unpub.), and since M. dizzydeani lays on the order of 800 eggs per 
sac, it is likely that the 150 M. cornigera spiderlings resulted from a 
much larger number of eggs. 
The sexes of newly emerged spiderlings could be distinguished by 
the slightly swollen pedipalps of the males. The sex ratios of samples 
of spiderlings from three egg sacs were T.787, 1:1.09, and 1:1.49 
male-female (373 spiderlings, total ratio 1:1.01). This approximation 
to 1:1 is similar to those found by Gertsch (1947) for M. cornigera and 
Lowry (in McKeown 1952) for D. magnificus. 
Spiderlings of both sexes had a row of strong bristles on the 
prolateral surfaces of the tibiae and metatarsi of legs I and II (Fig. 17) 
which seemed to be essentially identical to the spines on the same legs 
of mature males. The spines are apparently soon lost, however, since 
a third or fourth instar female lacked them. 
