Effects of nutrition on worker body size variation in the red imported fire ant

Body size is an important life history trait that figures directly into the ecology, physiology, behavior and survival of an organism. For social insects, body size can vary at the individual level (worker size) and the colony level (distributions of workers body sizes). Variation in body size is potentially optimized in response to environment fluctuations and colony needs. In ants, body size is determined by both the quality and quantity of food resources acquired during larval development. Thus changes in food resource availability likely influences worker body size. We examined the role of food supplementation on worker body size distributions within colonies of the red imported fire ant (Solenopsis invicta). We examined the effect of amino acid, sugar, and amino acid and sugar diet supplementation on worker number, body size, and biomass. Overall, diet supplementation did not effect mean size of workers between colonies. However, colonies supplemented both amino acid displayed greater biomass than those not supplemented with amino acids. In addition, colonies supplemented both amino acid and sugar tended to have a greater numbers of workers than other treatments. By comparing the effect of diet on colony investment into worker body size, we gain a better understanding of how social insects invest food resources into worker size versus number and deal with important tradeoffs that can limit colony growth and survival.