Life History and Habits
Mating flights of Texas leaf cutting ant reproductives take place on clear, moonless nights during April, May and June. In areas of higher rainfall, swarms can occur at any time during the spring; however, to more arid areas swarms invariably occur after a heavy rainfall. Prior to her nuptial flight the virgin queen stores a small portion of the fungus garden in a small cavity inside her mouth. After mating the winged males die, while mated queens drop to the ground, lose their wings and attempt to establish small nests beneath the soil.
After digging a small gallery in the soil, the queen takes the fungus wad from her mouth and begins to culture it as food for her first eggs. Initially the fungus is nourished by fecal material. Approximately 90 percent of this first brood will be eaten by the queen. The first worker ants will be quite small because of their limited food intake; however these first workers bring back leaf fragments to enlarge the fungus garden, thus providing more food for later broods. As the colony grows, worker ant size increases and becomes more variable. In mature colonies worker ants vary in size from 1/16 to 1/2 inch-long, with the larger ants serving as soldiers for nest defense.
Individual colonies can exist for years. Where adequate food is available, colonies may expand to contain over 2 million ants. Leaf cutting ant colonies are frequently seen along roadsides, in open fields, in brush land or forestland where soils are deep, well drained sand or loam. They can be quite large, 50 to 80 feet across. Colony size depends on its age and the availability of food. In heavily-infested areas it is difficult to distinguish where one colony ends and another begins.
Above ground, the colony is marked by numerous crater-shaped mounds, 5 to 14 inches-high and 1 to 1 1/2-feet in diameter. Each mound has a central entrance hole. Above the underground central nest cavity, several entrance holes will be marked by typical crater shaped mounds and a buildup of soil. On flat land, this buildup of soil is very apparent. With older colonies, this central area is as much as two to three feet higher than surrounding land. Below ground, the nest consists of several chambers that may reach 15 to 20 feet deep. All chambers are interconnected by narrow tunnels. Vertical tunnels extend to mound openings, and lateral foraging tunnels may lead outward 500 feet away. These lateral exits are commonly referred to as “feeder holes”. The complex structure of the cavities and tunnels allow the ants to escape predators underground, and provide an efficient air circulation system. Coincidentally, the large complex nest structure makes control with insecticides difficult.
During the summer, leaf cutting ants forage almost exclusively at night. The rest of the year, foraging takes place during the day, when air temperatures range between 45 to 80 degrees F. Most mound building activities occur during the cool hours of the day. Leaf cutting ants are usually inactive on cold, wet or cloudy days.
On the soil surface leaf cutting ants have clearly defined foraging trails. Ants commonly travel 600 feet or more to reach a suitable plant. Once located, the plants are attacked in large numbers, with worker ants cutting leaves and carrying the fragments in their mouths (mandibles). Leaf fragments are carried umbrella-like, over the head–hence the common name, “parasol ant”. Hundreds of ants can be seen picking up and carrying off the piles of leaf fragments that accumulate under the trees or bushes “under attack.” At the nest entrance, ants chew the fragments into small pieces that are better suited for their underground fungus gardens.