1988] 
Cornell, Stamp, & Bowers — Hemileuca lucina 
55 
Table 5. Patterns of larval variability in total distance traveled over 5 trials by 
larvae in groups. Gini coefficients (unbiased estimator, G') are shown, with 0 repre- 
senting complete equality and 1 indicating total inequality among larvae. First instar 
larvae of group D were tested but remained aggregated. 
Group 
Instar 
1 
2 
3 
4 
5 
A 
0.569 
0.612 
0.380 
0.365 
0.282 
B 
0.640 
0.543 
0.486 
0.401 
0.418 
C 
0.532 
0.583 
0.310 
0.450 
0.342 
D 
- 
0.405 
0.279 
0.272 
0.212 
The changes in larval activity of H. lucina revealed by the Lorenz 
curves and Gini coefficients parallel other developmental changes 
we have observed in H. lucina. These larvae exhibit distinct changes 
in behaviors between the early and late instars. While they have 
strong aggregation tendencies through the third instar and remain in 
groups in the fourth and fifth instars unless disturbed, the tendency 
to aggregate declines steadily and sixth (last) instar larvae are soli- 
tary (Cornell, et al., 1987). H. lucina larvae also have a repertoire of 
defensive and escape behaviors that changes from one instar to the 
next. The most dramatic changes occurs between the third and 
fourth instars, from primarily defensive behaviors to largely escape 
behaviors (Cornell, et al., 1987). The marked inequalities in distance 
traveled among early instar larvae compared to the more normal 
distribution of distances traveled of later instars may reflect those 
changes in behavior, in particular the declining tendency to aggre- 
gate. Thus, a pattern of a few leaders and many slower individuals is 
less likely when larvae are older and less compelled to stay with the 
group. 
Another factor contributing to the pattern of some larvae travel- 
ing long distances with others hardly moving may be digestive peri- 
ods. H. lucina larvae alternate feeding with periods of inactivity, as 
is true for many caterpillars (Edwards, 1964; Ma, 1972; Fitzgerald, 
1980; Capinera, 1980; Fitzgerald and Costa, 1986; Reynolds, et al., 
1986). Hungry and, therefore, temporarily active larvae tend to stir 
up the group, by tactile stimulation of group members. As a result, 
quiescent individuals eventually follow the other, more active group 
members, as long as the tendency to aggregate is strong (which it is 
through the third molt, Cornell, et al., 1987). That tendency to 
aggregate, which could induce less hungry larvae to follow hungrier 
