Arizona homeowners often use the phrase large red ants to describe several very different insects. Getting the identification right matters enormously — because the treatment that works for one species is completely ineffective for another. The three most common large red ants in Arizona are: red harvester ants (Pogonomyrmex barbatus and related species), which build large, bare-soil mounds in yards and deliver extremely painful stings; imported red fire ants (Solenopsis invicta), which are an invasive species spreading through southern Arizona and build dome-shaped mounds; and native southern fire ants (Solenopsis xyloni), which are smaller and less aggressive than imported fire ants but still sting.

Red harvester ants are the large (3/8 inch), reddish-brown ants most commonly seen in Arizona yards. They are seed-eaters that create large, cleared areas around their mound entrances and forage in long trails. Their sting is one of the most painful of any insect in North America — rated 3 out of 4 on the Schmidt Pain Index — and the venom can cause severe allergic reactions in sensitive individuals. Imported red fire ants are smaller (1/8 to 1/4 inch), more aggressive, and sting repeatedly. They are a serious agricultural and public health threat and are subject to state and federal eradication programs in Arizona. If you find a dome-shaped mound with no cleared area and the ants swarm aggressively when disturbed, contact your county extension office.

Treatment for harvester ants typically involves applying granular bait around the mound perimeter, combined with a liquid drench for active mounds. Fire ant treatment uses similar bait products but may require multiple applications and follow-up monitoring. Never pour gasoline or boiling water on ant mounds — these methods are ineffective, dangerous, and can damage your yard. For persistent or large infestations, professional treatment is the most reliable option. Pest Control Bros provides ant control across Maricopa, Chandler, Casa Grande, Tempe, Gilbert, and Mesa — free inspections, no contracts.