1985] 
Cokendolpher & Francke — Fire ants 
95 
Four species of fire ants ( Solenopsis spp.) from Texas were used: 
S. invicta Buren from Bandera, Kerr, and Harris Counties; S. gemi- 
nata (Fabricius) from Kimble and Val Verde Counties; S. xvloni 
McCook from Bandera, Garza, Kerr, Kimble and Nolan Counties; 
S. aurea Wheeler from Garza, Lubbock, and Reeves Counties. All 
ants were collected during the summer months except for some S. 
invicta : those from Kerr County (1 April) and Harris County (1 1 
January). The colonies were maintained in the dark at three differ- 
ent temperatures (12 ± 2°, 22 ± 2°, 32 ± 2°C) for a minimum of 14 
days prior to experiments. Colonies of ants were collected, sepa- 
rated from the soil, and housed following the methods of Banks et al. 
(1981). All colonies were maintained similarly, being fed cock- 
roaches [Nauphoeta cinerea (Saussure)], and mealworms [Tenebrio 
sp.], and supplied free water and a 50% aqueous honey solution 
daily. 
Worker ants without brood failed to make “scorable” choices in 
the linear temperature gradient. Therefore, workers with brood 
(larvae and pupae) were utilized. For both experimental and control 
studies, approximately 25-50 individuals of all worker castes and 
some brood were introduced to the test chamber via entrance ports 
located in the lid approximately 35 cm from each end (Fig. 1 A-9). 
Preliminary studies indicated that ants given less than two hours 
would not settle into a clump; therefore, the ants were allowed at 
least two hours to move the brood and settle. The temperature 
where the ants settled was recorded at the termination of each exper- 
iment. Like Brian (1973), we found that pheromones left by the ants 
attracted conspecifics during the following trials. This interference 
was eliminated by exposing the substrate to light (lid of chamber 
removed) from a Sylvania Black Light Blue Fluorescent Lamp, 
F15T8/BLB, at a distance of 30 cm for at least one hour after each 
trial. After exposure to U.V. light, the chamber was resealed and 
allowed to equilibrate (humidity and temperature) for at least one 
hour. 
Control trials differed only by having a constant temperature 
throughout the test chamber (22 ± 1°C). The number of replica- 
tions and the number of colonies used per species varied, depending 
on the number of brood tending ants which could be obtained 
(Table 1). 
To determine if the ants showed any preferences during control 
trials, the Kolmogorov-Smirnov test was used (Siegel, 1956). Differ- 
