Task selection by workers of the fire ant Solenopsis invicta

The effects of worker size, age, and crop fullness on the flow of food into the colony were assessed using video recording and playback. Regardless of the level of colony satiation, small workers seldom had full crops and wer e more involved in larval grooming than in food traffic. Large workers play ed little role in larval care, but tended to be recruited easily to a food source and to store food in their crops. Medium workers had crops ranging f rom empty to full because they alternated between ingesting from and donati ng food to other colony members. Medium workers were the most versatile, en gaging competently in food recruitment, larval grooming, and larval feeding . They displayed considerable variation in the frequency at which they fed larvae: some fed a few larvae before switching to other tasks, others fed o ver a hundred larvae before switching. The persistence, or lack thereof, of a worker's feeding response suggests a flexibility unaccounted for by the fixed-threshold-response hypothesis. Worker coverage of the brood pile was a dynamic equilibrium process unaffected by worker size, age, or crop fulln ess, or by differences in the nutritional or hygienic states of larvae. In summary, it appeared that worker size and age offered coarse regulation of task selection by workers, whereas crop fullness, flexible response, and ta sk switching fine-tuned task selection.