222 
Psyche 
[Vol. 88 
listed. The fourth element, female positioned at the entrance axil 
(Figure 2), was repeated most frequently, although the element was 
not itself significant. There was more variation in the female’s posi- 
tion on the stem at the beginning of the alarm response than at the 
end. 
DIRECTION OF MOVEMENT 
Aggregations with and without the female present were studied in 
order to determine the significance of the female’s role in feeding 
movements or alarm responses. It was hypothesized that the 
female’s presence would keep the aggregation together and inhibit 
random movements on the plant. The relocation of the group was 
studied in terms of the direction of movement on the plant (up, 
down, or in both directions) and the choice of a new leaf on which to 
feed. Movement was considered directed if a group moved in one 
direction or the other, but not in both. A table for a binomial 
distribution was used to evaluate significance at the 95% confidence 
level (Table 2, partial sums, Eisenhart 1952; Table A-22, confidence 
intervals, Natrella 1963). The results for upward and directed 
movements of aggregations, with and without the female present, 
are recorded in Table 2 as percentages of groups observed. Those 
results significant at the 95% confidence level are marked with an 
asterisk. 
Feeding Movements 
In light or in darkness, feeding movements with or without the 
female present were directed rather than random, and the group 
usually moved upward. When the source of light was 180° away 
from the usual direction, neither moving upward nor directed 
movement was significant; but the aggregations did not reverse their 
direction of movement and move toward the light. It is possible that 
the abnormal position of the light source acted as a conflicting 
stimulus which confused some of the aggregations. 
A small field sample of horse nettle plants (13) showing damage 
from G. solani was examined for evidence of group movements. 
Eighty-five percent of the groups had moved upward on the plants 
from leaves containing the remains of egg masses. Moving up was 
significant at the 95% confidence level and closely matched the 
results obtained in the laboratory. 
