Texas Leafcutter Ant

Atta texana — the Texas leafcutter ant — is one of about 15 species in genus Atta and one of only two leafcutter ant species established in the United States (the other is the smaller Acromyrmex versicolor of the desert Southwest). The species is widespread across eastern Texas and Louisiana and into adjacent areas of Oklahoma, Arkansas, and northeastern Mexico. Like all Atta leafcutters, the species is a cooperative LEAF-CUTTING fungus farmer — workers cut leaf fragments from trees and shrubs, carry them back to the nest in long visible trails, and feed them to a symbiotic Lepiotaceae fungus garden inside the nest. The fungus garden is the colony's sole food source — workers, larvae, and queens all eat only the fungus, not the leaves themselves. The fungus produces specialized hyphal swellings (gongylidia) that the ants harvest and consume. The mutualism between Atta and the Lepiotaceae fungus has co-evolved over approximately 50 million years and is one of the most ancient documented agricultural systems in any animal lineage. Atta texana colonies are among the largest leafcutter colonies in temperate North America: mature colonies contain 1-2 million workers across multiple worker castes (small minor workers tend the fungus garden, larger media workers cut and transport leaves, large major worker 'soldiers' defend the colony), excavated in underground chambers that may reach 8 m deep and span 60+ m across. Single colonies can contain 1,000+ chambers. The species causes substantial agricultural damage in Texas and Louisiana — primarily to commercial pine plantations (the species defoliates young pines, slowing growth), pecan and peach orchards, and citrus production. Annual control costs across the species' range are estimated in the millions of dollars. The species is the dominant Atta in temperate North America and a flagship example of fungus-farming social insect biology in the country.