Comparison of Diets of Two Fire Ant Species (Hymenoptera: Formicidae): Solid and Liquid Components

Diets of the red imported fire ant, Solenopsis invicta Buren, and the native fire ant, Solenopsis geminata [F.], were studied in adjacent field colonies in south central Texas. A comparison of solid food diets of the two species revealed a 59% overlap of identifiable arthropods and other solid food matter. The major difference was that S. geminata collected eight times more seeds than did S. invicta. Both species collected liquid food much more frequently than solid food; in fact, an average of 70–80% of successful foragers returned with liquid. Rates of liquid collection were approximately 40% higher for S. invicta than for S. geminata. Foraging rates fluctuated with season but the percent of successful foragers returning with liquid remained relatively constant. Plants and honeydew producing homopterans are the most probable sources of this liquid based on sugar and amino acid analyses of S. invicta foragers. Use of liquid carbohydrate energy sources helps explain how fire ant colonies can collect sufficient food to sustain extremely dense field populations.