92 
Psyche 
[March 
There were five of these nest assemblies per species (except only 
one for M. mimicus ), with 30 ants in each. The 26 arenas were lined 
up side by side, the first replicate of each species, then the second of 
each, etc. Heating tape was stretched alongside the whole row of 
arenas so that it was about 1 cm from one side of each arena, it 
provided constant heat throughout the experiment. 
The ants were kept in a constant temperature room. The nest 
dishes averaged 24.3° C±0.5°. The hot side of the arenas was kept at 
least 10° (±1°) hotter than this. Twelve hours of fluorescent light 
(2000 lux) was alternated with 12 hours of darkness (the last 2 nights 
there was dim incandescent light [15 lux] to permit observations). 
The ants were installed May 25 and observations began May 27. 
Each hour during the light periods of May 27-31, and also during 
the 2 nights beginning May 30 and 31, the number in the hot half of 
the arena, in the warm half of the arena, and in the tube were 
counted visually. In addition, the total number active (moving) in 
tube and arena were counted. 
Except where noted, an arc sine transformation was used, treating 
the count as a proportion of the 30 ants available (Dixon and Mas¬ 
sey 1969). Then the transformed counts for the 3 days May 27-29, 
when the ants were in the best condition, were averaged for each 
replicate. Finally the hourly observations were fitted to a 24-hour 
cosine-curve for determination of the best-fit peak (acrophase) and 
other rhythm parameters. 
Variables evaluated 
The fitting method used (Halberg et al. 1972) provides the acro¬ 
phase, the level (average), the amplitude, and the sinusoidality 
(probability of sine shape) of the fitted rhythm. Each of these four 
parameters (dependent variables) could serve as a potential charac¬ 
ter, and each was applied to every one of the following four types of 
assay (Table 1). 
Listed first are the variables related to the total number of ants 
out (i.e., in tube and arena) at each hour (TOTAL. OUT). This would 
represent choice of an area exposed to alternating light and dark, as 
well as drier and warmer than the dark humid next dish. 
The second type of assay was the number of ants in the hot half of 
the arena (TEMPERATURE). This represents the extreme distance out 
from the nest dish, and/or the preference or tolerance of high 
temperature. 
