Leafcutter ants are also known as town ants, cut ants, parasol ants, fungus ants or night ants. Sterile female worker ants are rust brown, 1/16 to 1/2 inch long and have three prominent pairs of spines on the thorax. The queen is much larger with the body being about 3/4 inch long. Damage to plants produced by Texas leaf cutting ants can resemble damage produced by some other chewing insects such as leaf cutting bees; however, ants and characteristic ant mounds around damaged plants should help determine the cause. Several other Texas ants produce mounds, including the red imported fire ant. The only other large ant that produces colony entrances with a central opening surrounded by course soil is the red harvester ant, Pogonomyrmex barbatus Smith. However, the red harvester ants do not have spines on the thorax and usually only gather seeds.
Life Cycle: Leaf cutting ants are social insects. Queen ants deposit eggs that hatch into cream colored larvae. Fully developed 1/4 to ½ inch long larvae form pupae. In the spring, some larvae develop into larger (3/4 inch long) winged male and female ants, called reproductives. Males have much smaller heads than do females and both have long smoky black wings. Sometime between April and June, on clear moonless nights, and usually after heavy rains, these winged ants leave the colony on mating flights. These ants are attracted to porch lights and are some of the largest ants encountered in Texas. Virgin queens carry a small piece of the fungus from their parent colony in a small cavity inside their mouths. After mating, the males die. The queen loses her wings and digs a small tunnel or gallery in which they begin laying eggs and culturing her fungus garden on her feces. The queen feeds largely on her own eggs until small worker ants develop from the surviving eggs and begin to collect foliage on which to culture the fungus. Colonies can survive for many years and colonies may contain over 2 million ants. The nest interior may be 15 to 20 ft. deep and contain numerous chambers interconnected by tunnels.
Habitat, Food Source(s), Damage: Mouthparts are for chewing. Worker ants remove leaves and buds from weeds, small grains, forage and turf grasses, fruit and nut trees including plum and peach trees, blackberry bushes, and many ornamental plants. Pine trees and pine seedlings may also be damaged when other plant material is scarce. Defoliation is particularly noticeable during winter months. Worker ants forage when temperatures range from 45 to 80 degrees F during the year, but mainly at night during the summer. Worker ants travel up to 600 ft. or more along foraging trails and dismantle foliage into leaf pieces that they carry back to the colony over their bodies. In the colony, the pieces of leaves are used to raise a fungus. All members of the colony feed exclusively on the fungus.
Pest Status: Worker ants bite and are primarily a pest of plants because they remove leaves for growing fungi. Large underground colonies are marked on the surface by the presence of many 5 to 14 inch tall, 1 to 1-1/2 ft. diameter mounds made of course particles of sandy soils and with single central openings. Around colonies, foliage can be stripped from plants in an area over an acre. They are more commonly encountered in deep, well drained sandy or loamy soils. Large colonies can excavate soil from underneath roadways, causing a structural threat.
References and Resources: For additional information, contact your local Texas Cooperative Extension agent or search for other state Extension offices. Stewart 1982. http://insects.tamu.edu.