1984] 
Sorensen, Busch, & Vinson — Solenopsis invicta 
327 
Discussion 
Colony fitness in S. invicta is maintained by an efficient system of 
resource provisioning which is responsive both to the nutritional 
requirements and degree of hunger of its members and to how much 
food is available (Howard and Tschinkel 1981; Sorensen and 
Vinson 1981; Sorensen et al. 1983). In the present study, we utilized 
this system of resource provisioning to examine whether or not 
temporal subcaste members could change their roles of either 
feeding larvae (nurses), relaying food (reserves), or foraging 
(foragers) when other subcastes were removed. 
We found that queens were fed protein preferentially regardless of 
amount available, presumably assuring their current and future 
reproductive output. Larvae were also fed protein preferentially as it 
entered the colony. The same partitioning of protein in response to 
supply was seen even after the experimental elimination of two of 
the three worker subcastes. This indicated that the behavior of 
workers was flexible enough to allow the colony to maintain 
priorities of resource provisioning even during severe disruption. 
Foraging activity was greater in groups of foragers than in 
reserves or nurses and when they were present, significantly more 
food entered the colony than when they were absent. Similarly, 
nurses were slightly more active than reserves at feeding larvae and 
significantly more active than foragers. Reserves were intermediate 
between foragers and nurses in their ability to forage and feed 
larvae, performing the latter task more actively. Differences among 
colonies in feeding activity on egg yolk were reflected in similar 
differences among the subcastes isolated from those colonies. 
Differences in feeding preferences of fire ant colonies have been 
documented by Glunn et al. (1981) for both laboratory and field 
colonies. 
Assessing the degree to which workers could switch to a different 
behavior, we found that reserves and nurses were considerably less 
active than foragers at food gathering. When nurses were grouped 
by themselves, they did not leave the brood chamber for 3 days and 
then only a few nurses ventured into the foraging chamber. The few 
foraging workers which appeared were probably mature nurses 
making the transition to reserve since marked nurse-foragers did not 
return to brood tending once colonies were reconstituted. However, 
