Regulation of diet in the fire ant, Solenopsis invicta

In social insects, colony nutrition depends upon the volume and quality of food distributed, ingested and assimilated by its members. The ability of S olenopsis invicta workers and Inn,ae to regulate the volume of food ingeste d individually has been well documented in this paper the ability of fire a nt workers and larvae to regulate the quality and type of food ingested is demonstrated. Larvae displayed independent appetites for solid protein, ami no acid solution, and sucrose solution. When larvae that had fed on one foo d type were switched to another they fed on the second food type at rates c haracteristic of that food type, not of the volume of food previously inges ted. Larvae preferred concentrated sucrose and amino acids solutions over d ilute solutions. Larval "fullness" was thus a relative property, depending upon the nature of food as well as the volume ingested The number of worker s recruiting to food sites also depended upon food concentration and food t ype. Workers preferred sucrose to amino acids, concentrated to dilute solut ions, and novel to accustomed food, The absence of protein in the worker di et rather than the presence of larvae caused workers to switch their prefer ence from sugar to amino acids solutions. When the colony was offered sucro se and amino acids solutions simultaneously: individual workers ingested fr om one or the other sire, but not both. Little mixing of crop contents occu rred when workers solicited from one another inside the nest. Workers tende d to regurgitate to larvae after ingesting amino acids and to other workers after ingesting sucrose. The mechanism regulating the distribution of prot ein pellets, which workers do nor ingest, among larvae is unknown. In summa ry, colony nutrition was regulated by a chain of demand Forager hunger dete rmined the rate at which food flowed from the environment into the nest. La rval hunger and nest-worker hunger determined the rate and direction in whi ch food moved within the nest.