16 
Psyche 
[March 
ground as demonstrated by Geiger (1965) influences communal 
tangle formation. Spiderlings emerging high in the vegetation ex- 
perience greater exposure to wind which might stimulate ballooning 
(discussed below). Argiope aurantia locate egg sacs higher in the 
vegetation than A. trifasciata. In 1974-1975 and 1975-1976 the 
means and standard errors of A. aurantia egg sac heights were 
0.91 ±0.11 and 1.10 ±0.13 m, respectively (Tolbert, 1976). Argiope 
trifasciata egg sacs by comparison, were 0.30 ± 0.04 m in 1975-1976 
(Tolbert, 1976). 
Spiderlings on a communal tangle were tolerant of one another 
at all times and readily accepted conspecifics from different egg 
sacs. Several such “transplants” were made during the spring of 
1975 with spiderlings from one egg sac transferred to the communal 
tangle of spiderlings from a different egg sac. After a brief flurry 
of activity produced by the arrival of the transplants, activity de- 
creased to levels noted before the introductions. 
At night, early in the morning, and on overcast days Argiope 
trifasciata spiderlings maintained individual spacing of several times 
their own body length while on the communal tangle (Figure 2). 
If disturbed by predators, wind gusts, or rain, spiderlings became 
agitated but quickly resumed a quiescent attitude if their body 
temperatures were less than 26° C. On the other hand, if exposed 
to full sunlight individuals clustered closely together on the com- 
munal tangle (Figure 3). If cues were not present for dispersal, the 
spiderlings remained clustered until after nightfall before spacing 
out. Though not timed, clustering appeared to take less than a 
minute. A longer period was required for clustering if the group was 
partially shaded. The exact cue or clues producing clustering are not 
known, but clustering occurred only after full exposure to bright 
sunlight. Air temperatures, spiderling body temperatures, light 
levels, and perhaps other factors which might provide the required 
stimuli for clustering all change at this time. More experimenta- 
tion is needed for elucidation of this problem. 
When Argiope trifasciata spiderlings are clustered and their body 
temperatures equalled or exceeded 26° C they were susceptible to 
dispersal. As indicated in Figure 4, dispersal ceased below 26° C 
and the preferred temperature range for dispersal was between 33° 
and 38° C. Ninety-two percent of all A. trifasciata spiderlings be- 
came airborne or “ballooned” when their estimated body tempera- 
tures were between 33° and 38° C. Argiope aurantia also dispersed 
