Southern fire ant: Solenopsis xyloni


July 21, 2023

Photo: Eli Sarnat, Antkey, USDA APHIS PPQ S&T, via ITP Node

A frontal view of the head of a Solenopsis xyloni adult. Photo: Eli Sarnat, Antkey, USDA APHIS PPQ S&T, via ITP Node

The red imported fire ant (S. invicta, or RIFA) might grab all the “fire ant” headlines, but it’s not the only Solenopsis species in the U.S. Many of the ants in this genus are called fire ants because their venom — injected by the ovipositor, or stinger — causes intense irritation. It may cause severe reactions and even death in sensitive people. Fire ants in general are active and aggressive, and may kill young wildlife or produce sores and nausea in humans.

The southern fire ant is a native species; several sources report its colonies are increasingly becoming displaced by the even-more-aggressive RIFA species. It is found, not surprisingly, in mostly southern states from the Atlantic Coast to California. The abdomen is brown to black, and usually the head and part of the thorax are yellow or reddish. Workers are polymorphic, or of various sizes according to tasks, and range from 0.07 to 0.25 inch long.

Southern fire ant nests usually occur in loose soil, although they may also occur in the woodwork or masonry of structures. Nest entrances may be craters in the ground scattered over an area of about 3 square feet. They may also reside under boards and stones; near a tuft of grass; in cracks in concrete; or underneath structures. Foragers collect a variety of foods, including meat, grease, butter, nuts, seeds and vegetables.

Per the University of Florida’s Institute of Food and Agricultural Sciences (UF/IFAS) office, the queen(s) must be killed to control any fire ant colony. Even afterward, “surviving ants may inhabit the mound or make a new mound until they die off.” With that in mind, the extension office offers a variety of control methods on its web page devoted to fire ants. Top methods include baits, which can be used as a broadcast or individual mound treatment; traditional, appropriately labeled pesticides with such active ingredients as hydramethylnon, sulfluramid, avermectin and various insect growth regulators (IGRs); and organic pesticides such as rotenone, nicotine sulfate, d-limonene, spinosad and various pyrethrins.


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