48 
Psyche 
[Vol. 95 
the course of a trial?); 2) variation from one trial to another within 
an instar (i.e. were larval ranks consistent from one trial to 
another?); and 3) variation from one instar to the next. 
One-tailed Spearman rank correlation was used to assess the 
degree of changing ranks within trials by larvae (i.e. due to turning 
around or possibly passing one another) with 1 indicating perfect 
agreement between ranks (i.e. no change) and 0 indicating no 
agreement. 
To examine whether individual larvae were consistently ranked 
the same with regard to distance traveled, over the five trials within 
an instar, we used Kendall’s coefficient of concordance (W) (Con- 
over, 1080; Edgerly and Fitzgerald, 1982). If individuals were con- 
sistently ranked the same among trials, W = 1.0, whereas if rank 
varied randomly from trial to trial, W = 0. 
To determine whether distance traveled by individual larvae was 
consistent from one instar to the next, larvae were ranked on the 
basis of total distance traveled in 5 trials per instar and Spearman’s 
rank correlation (r s ) was used. 
Frequency distributions of distances traveled by individuals 
within an aggregation tend to exhibit a graded series (or hierarchy), 
in which relatively few individuals travel far and many individuals 
travel relatively short distances over a short test period (e.g. Fitzger- 
ald, 1980; Edgerly and Fitzgerald, 1982). Following the terminol- 
ogy and definitions of Weiner and Solbrig (1984), we believe that 
the analytical methods used by plant ecologists to evaluate a graded 
series of sizes of individuals within a population are particularly 
appropriate for behavioral data such as distance traveled when: 1) 
the aggregation yields large variation in individual distances, 2) 
there are relatively few large distances and many small ones, and 3) 
the few large distances contribute greatly to the observed pattern. 
Weiner and Solbrig (1984) indicate that standard measurements of 
skewness are inappropriate because they are designed to be insensi- 
tive to the degree of variability and only reflect the second aspect of 
the three listed above. Specifically in our study, it is inequality 
among larvae in distance traveled, not asymmetry in the distribution 
of distances ((2) above), that is of biological interest here. 
Therefore, the variation in distance traveled was represented 
graphically using Lorenz curves and evaluated using the Gini 
statistic (Weiner and Solbrig, 1984). Gini coefficients take into 
