92 
Psyche 
[Vol. 92 
1984) examined their responses to humidity gradients in the absence 
of superimposed thermal gradients, and here we examine their re- 
sponses to temperature gradients in the absence of superimposed 
humidity gradients. 
Numerous variables have been reported to alter temperature pref- 
erences in insects: age, sex, desiccation, hunger, rearing and mainte- 
nance temperatures prior to experiments (Deal, 1941; Madge, 1965), 
relative humidity (Gunn and Cosway, 1938; Deal, 1941), aggrega- 
tion (Henson, 1960), and experiment duration (Deal, 1941; Fergu- 
son and Land, 1961). In this study treatments consisted of three 
acclimation temperatures and two experimental relative humidities. 
Temperature preferences have been previously investigated in 
only a few species of ants. Furthermore, the results obtained from 
most of those studies (Herter, 1923-1925; Hertzer, 1930; Bodenheim- 
er and Klein, 1930: all cited in Deal, 1941) are either inconclusive 
or the reliability of the measurements are suspect. Although Deal’s 
(1941) study of preference in Aeanthomyops sp. is not very precise, 
it demonstrates that the preferred temperature in that species 
increases with an increase in relative humidity. The temperature 
preferences of the ant Formica polyctena Foerst were reported by 
Ceusters (1977). In that study a temperature gradient ranging from 
about 10 to 30° C was established in a battery of 14 consecutive nest 
cells and numbers of individuals (of workers, queens, eggs, each 
larval stage, and pupae) were recorded through 12 brood rearing 
periods (four years). Ceusters (1977) found that each development 
stage had a different “preferred” temperature, except the differences 
between eggs/ hatchling larvae and small larvae were not statistically 
significant. Brian (1973), working with the ant Myrmica rubra L., 
determined temperature preferences with both an alternate tempera- 
ture chamber and a linear gradient chamber. The preferences of the 
ant Camponotus mus Roger, have been investigated by Protomas- 
tro (1973). The optimal rearing temperature and thermal preference 
were considered to be the same by Protomastro (1973). 
Few studies have compared temperature preferences among more 
than two congeneric insect species. The primary objective of this 
study was to compare the temperature preferences of four fire ant 
species of the genus So/enopsis Westwood. These four species differ 
in their ecogeographical distributions: one is xerophilous, two are 
mesophilous, and one is widespread. The northern limits of distribu- 
