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Understanding a Fire Ant Colony

By Mark Justin Wolfe
Red imported fire ants are miserable landscape nuisances.

Red imported fire ants are miserable landscape nuisances. Their repeated bites cause nasty welts, and their mounds can wreck a beautiful lawn in no time. Keeping these pests under control is a matter of safety, comfort and household aesthetics.

In order to meet this challenge effectively, it is important to understand the lifestyle habits of fire ant colonies:

  1. Habitat
  2. Mounds
  3. Lifecycle
  4. Feeding
  5. Colonies
  6. Control

Fire Ant Habitat

Imported fire ants were accidentally introduced into the United States in the 1930s. Because they require moisture, as well as a food source to survive, these opportunistic insects are typically found in the humid Southeastern United States. However, they've spread north and west, stopping where there is severe cold or lack of water. Native fire ants prefer the arid southwestern United States and northern Mexico, where imported fire ants are rare.

Fire Ant Mounds

Fire ants are social insects that build nests, called mounds, by pushing up soil as they tunnel in the earth. They nest in almost any type of soil, but prefer open, sunny areas, such as meadows, pastures, parks, playgrounds, lawns and golf courses, as well as agricultural land and wilderness areas.1

Unlike other kinds of ants, fire ants have no nest entry on the mound itself. They enter the nest via tunnels that may reach several feet or more beyond the mound itself. Though it is the most recognizable sign of the presence of fire ants, a mound is not necessary for the survival of a fire ant colony. During especially hot or dry weather, colonies tend to move deeper into the ground, foregoing the palatial mounds that are so obvious in moderate weather. New colonies may not build a visible mound for months or longer, depending on soil and weather conditions.

Imported fire ant mounds may be as large as 18 inches high and 30 inches wide, and feature no entry hole.
Imported fire ant mounds may be as large as 18 inches high and 30 inches wide, and feature no entry hole.

Fire Ant Lifecycle

Queen fire ants lay eggs, which hatch into grub-like larvae. After undergoing four developmental stages, larvae then molt into pupae, which although whitish in color and not fully mobile, resemble adult fire ants. The pupae darken in color as they develop, and then molt a final time into adults.

Most larvae develop into small, wingless female workers. Those workers rear the young and scavenge for food for the queen. Some larvae develop into larger winged males or female reproductive adults. Female reproductives are future queens for new colonies.

Spring through fall, when conditions are favorable, reproductives break through the mound to mate in mid-air. They spend a few minutes drying their wings as they sit atop the broken mound, then take flight to copulate fifteen feet or more above ground. Afterward, the males die and the new queens lose their wings before digging into the ground to begin building nests and laying eggs. New workers emerge within a month.

Fire Ant Feeding

In morning and evening, workers scavenge for food. Fire ant food preferences include plants, microscopic organisms, invertebrates and vertebrates such as reptiles, birds and mammals.2 Scavenging workers carry the bounty back to the nest for distribution among the entire colony: queen, larvae, developing reproductives and other workers.

Fire Ant Colonies

Imported fire ant colonies can have a single queen or multiple queens. Single-queen colonies are territorial in nature, limiting populations to approximately 150 mounds containing 7 million ants per acre. Multiple-queen colonies tend to share resources and are tolerant of other colonies in close proximity. These characteristics may allow for up to 300 mounds and 40 million ants per acre.

Colonies frequently migrate from one site to another. The queen needs only half a dozen workers to start a new colony. Workers can develop a new mound several hundred feet away from their previous location almost overnight.3

Fire Ant Control

The use of bait, such as AMDRO Fire Ant Bait or AMDRO Kills Fire Ant Yard Treatment Bait, is the most effective method of fire ant control. Unlike contact insecticides, which are not selective and do not penetrate mounds easily, bait uses the biology and structure of the colony as the means of dispersal. Scavenging workers carry bait to the larvae, and the larvae quickly disperse the active ingredient to the queen(s) and the other workers. To destroy the mound, the queen(s) must be killed.

Fire ants are an irritating part of life for many homeowners. Although these insects are stubborn, opportunistic and abundant, following a consistent schedule of bait applications will minimize their threat.

AMDRO is a registered trademark of Central Garden & Pet Company.

Sources:

  1.  "Fire Ant Habitat and Food Sources," Extension.org, May 2014
  2.  "What do Fire Ants Eat?" Extension.org, March 2015
  3.  Texas Imported Fire Ant Research and Management Project, Texas A&M Extension

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