Feeding Preferences for Sugars and Amino Acids in the Red Imported Fire Ant, Solenopsis invicta Buren

TL;DR

This study explores what sugars and amino acids red imported fire ants prefer to eat, which could help in creating better baits to control them.

Contribution

A new feeding preference assay system was developed to study ant foraging behavior under near-natural conditions.

Findings

S. invicta workers prefer sucrose and leucine over other tested compounds.

Feeding preferences for sucrose and leucine increase with concentration.

A mixture of sucrose and leucine significantly enhances field attraction compared to single solutions.

Abstract

Associations between ants (Hymenoptera: Formicidae) and honeydew-producing hemipterans are canonical examples of mutualism in ecosystems. Honeydew, rich in sugars and amino acids, serves as a key factor regulating ant foraging behavior. This study focused on the globally invasive pest, the red imported fire ant, Solenopsis invicta Buren. Employing a newly developed feeding preference assay system, laboratory and field experiments were conducted to systematically evaluate the feeding preferences and attraction preference of worker ants for sugars and amino acids, respectively. The results demonstrated that S. invicta workers exhibited significantly stronger feeding preferences for sucrose and leucine over other tested compounds. Furthermore, these preferences for both sucrose and leucine intensified with increasing concentration of each compound. Notably, ants preferred single-component sucrose or leucine solutions over multi-component sugar or amino acid mixtures. However, a mixture of sucrose and leucine solutions significantly enhanced the field attraction of S. invicta workers. This study clarifies the foraging strategy of S. invicta toward key honeydew nutrients and provides a scientific basis for developing efficient and target-specific liquid baits to control fire ants.

Ant–hemipteran mutualism is mediated by honeydew through long-term coevolution. To clarify the feeding preferences for the main honeydew components (sugars and amino acids) in the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), this study employed a self-developed feeding preference assay system to systematically determine the feeding and attraction preferences of workers for ten sugars, eleven amino acids, and their different concentrations and combinations in both laboratory and field experiments. Results showed that: (1) S. invicta workers exhibited a significant feeding preference for sucrose and leucine among all tested sugar and amino acid solutions; (2) Feeding preferences for both sucrose and leucine were concentration-dependent. Specifically, preferences for 20% sucrose and 0.5% leucine were significantly higher than for lower concentrations, while not significantly different from higher concentrations; (3) The feeding preference for 10% sucrose or 0.5% leucine alone was higher than that for multi-sugar mixtures or a mixture of all eleven amino acids. However, a mixture of sucrose and leucine solutions significantly enhanced field attraction compared to single solutions of sucrose or leucine. The self-developed feeding preference assay system provides a new tool for measuring feeding preferences in ant colonies under near-natural conditions. Overall, this study systematically clarifies the feeding preference for key nutrients in S. invicta workers and establishes a critical theoretical basis for understanding its foraging ecology and developing highly effective liquid baits.

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