96 
Psyche 
[March 
Several miscellaneous variables are also shown in Table 1, such as 
“shift of acrophase.” They and the fitted variables will be referred to 
as “processed” variables to distinguish them from the “hourly” ones. 
Multivariate analysis of variance (MANOVA) and multidiscnmi- 
nant analysis were used for comparison of species by groups of 
variables. These methods apply even where variables are highly 
correlated, which many of those here certainly are. On the basis of 
known group membership, discriminant analysis emphasizes varia¬ 
bles that have a high ratio of among-group to within-group varia¬ 
tion. Thus the variables are weighted so as to discriminate optimally 
between the groups (here species). An introduction to these methods 
is given by Cooley and Lohnes (1971), and application to behavioral 
research, by Pimentel and Frey (1978). 
RESULTS 
Daytime observations 
For both species of Pogonomyrmex the total number out rose in 
early midday and remained high through the afternoon (Figure 1). 
For the other species the number rose in the afternoon and con¬ 
tinued rising through the end of the light period. 
In V. pergandei and F. pilicornis few ants ever came out as far as 
the arena; the rhythmic count was made up largely of those in the 
tube leading to the arena (Figure 1). In V. andrei the proportion in 
the tube was relatively high at the first and last of the light period. 
The proportion reaching the hot side of the arena was the greatest in 
P. californicus. 
For most of the analyses, only these daytime observations were 
used. 
24-hour observations 
After 3 days very dim lights were left on at night, permitting 
counts then. It was now 6 days after collection from the field, and 
some of the ants were dead or else came out into the tubes or arenas 
less frequently. Nevertheless the patterns for the “day” part of the 
cycle were similar to before. And now it could be seen that all six 
species were prominently out in the arenas during the night. 
That this nocturnal behavior might be explained by the constant 
high temperature is suggested by field observations, Tevis (1958) 
found that nocturnal foraging of V. pergandei is rare, but could 
occur if temperatures are higher than normal; Wheeler and Rissing 
