Facts, Identification & Control
Latin Name: Linepithema humile
Argentine ants range from light to dark brown and measure about 2.2 to 2.8 mm long. Their antennae have 12 segments.
Behavior, Diet & Habitat
Argentine ants are readily adaptable and can nest in a great variety of places. Colonies are massive and may contain hundreds of queens. Nests are usually located in moist soil, next to or under buildings, along sidewalks or beneath wood and boards. These ants travel in trails.
Argentine ants can eat almost anything, but they prefer sweet foods.
Like other ant species, Argentine ants pass through the development process called complete metamorphosis. Eggs are white, and larvae emerge from them after about 28 days. They reach adult stage in about 74 days.
Argentine ants may live in soil, under wood, logs, debris or mulch. They may also nest in cavities at the base of shrubs and trees. Their nests are often shallow, measuring up to 20 cm (~8 in) in depth in open habitats.
Signs of an Argentine Ant Infestation
The foraging trails of Argentine ants are their most visible sign. The trails can be observed traveling up buildings, trees and into homes
All Argentine ants are the same size. They travel with well-defined trails between their web of nests and their food sources. Argentine ants feed on sweets, honeydew and oily household foods.
Nests & Colonies
While other ant species have seasonal nuptial swarming flights, Argentine ants do not establish new nests through swarming. They produce reproductives that do not swarm from the nest but instead mate inside the nest. At times, due to temperature or colony pressures, a queen Argentine ant will leave her nest on foot to establish new colonies. New nests are constructed around the original, and remain connected to the queen’s old colony, so workers are sometimes shared between colonies.
Queens are different when comparing with other ant species:
Argentine ant queens are small, about 1/6 – 1/4 inches in length, much smaller than most other species of ant queens
- Argentine ant queens are mobile and may be seen outside the nest along with workers, unlike other ant queens who reside inside the nest for life. Queen mobility enables the rapid movement and establishment of nests to other areas if conditions become inhospitable.
- Winged Argentine ant queens mate once with a winged male, after which they can continuously produce fertile eggs for as long as they live. While other ant species have seasonal swarming flights, these ants do not form new nests through mating swarms. Instead, they mate inside the nest.
- A single Argentine ant colony will have several queens, each of them capable of laying as many as 60 eggs per day.
- Argentine ant queens help workers by feeding their young. Most other ant queens primarily lay eggs and depend on the ant workers to feed and care for the young.
- At times, due to temperature or colony pressures, an Argentine ant queen will leave her nest without taking flight and establish a new nest.
Male Argentine ants hatch from the queen’s unfertilized eggs and are fairly short lived. The single function of a male Argentine ant is to mate with a queen to preserve and proliferate the colony. The males usually die soon after mating.
Argentine ants kill other insects and invade human dwellings. Over time, the network of interconnecting colonies could become a massive infestation. Each colony of Argentine ants can contain millions of insects and multiple queens. These colonies can populate entire city blocks. Argentine ant infestations are best left to a professional pest control operator to identify and treat.
Argentine Ant Colony
Argentine ants were introduced into the United States from South America during the late 1800’s, and they have become an agricultural and urban pest problem. The Argentine ant can be found in the southern United States from North Carolina to Florida and west through the gulf states and throughout much of coastal California. They thrive in moist warm climates.
While Argentine ants, who will eat almost anything of plant or animal origin, prefer sweets, and will feed on honeydew and plant nectar. They will also scavenge on dead insects. Inside homes, they will eat sweet and greasy substances and may infest food products.
Argentine ants nest in many different habitats. Outdoors, nests are usually associated with moist, protected locations such as in the soil under rocks, refuse piles, mulch, concrete slabs, wood debris and fallen or dead logs. Inside a home, Argentine ants may make nests in the walls of bathrooms and kitchens, in crawl spaces beneath the floor and around places where moisture from water leaks. Due to their rapid proliferation, it is important to control Argentine ants before their nests infest a very large area.
Reproduction and mating within Argentine ant colonies is quite different than other ant species. Winged queens mate once with a winged male, after which the queen can continuously produce fertile eggs for as long as 10 years or until her death. Unlike most other ants, several productive queens can share the same colony. When colonies become too crowded, one or more queens will leave with some workers to form a new colony in another location. (Usually in the spring and summer).
For ant colonies with only one queen, when that queen dies the entire colony dies because no more ants are being produced. However, for multi-queen colonies such as the Argentine ants, another queen simply moves into the nest and takes over the role of laying eggs formerly carried out by the deceased queen. In addition, Argentine ant reproductive winged males and females do not leave the nest in a swarm, unlike other ant species. Instead, they mate within the nest, a behavior that is important since it reduces exposure of the reproductive to predators such as birds and other small animals.
Since the Argentine ant colonies are so large and their habitat so diverse, well established nests and colonies are not likely to be totally eliminated from either outside or inside the home. If Argentine ants are a problem, contact your pest management professional who will use his expertise and knowledge to plan and execute an integrated pest management program. The key components of an Argentine ant control program are habitat removal, moisture removal, food source removal, sanitation and treating both inside and outside with insecticide baits.
Argentine ants are a nuisance in orchards, households and the other areas they infest. Unlike other ant species, Argentine ant queens develop their colonies a short distance away from their original nest. As a result, the web of interconnected nests could infest and damage a startling 200 meters of land each year. Measuring slightly less than 3 mm long, these small ants can have multiple queens that rapidly establish new colonies. Argentine ant workers feed on honeydew from aphids and other sap-sucking insects. They protect aphids from predators and, in turn, the aphids damage plants, vegetation and other agricultural products. In addition, Argentine ants can be a danger to the ecosystem because they prey on bees, snakes, lizards and other beneficial animals.
There are many treatments for Argentine ants. One treatment that is sometimes used is a liquid boric acid bait solution. When Argentine ant workers ingest boric acid solution, they bring it back to their colonies. The workers then feed larvae, workers and queens with the boric acid solution.
Each Argentine ant queen can establish new nests and produce thousands of workers within close range to the original nest, producing a wide network of nests. An Argentine ant colony can be destroyed only by killing all of its queens. The severity of an infestation of Argentine ants depends upon the length of time they are allowed to proliferate. For this reason, be sure to thoroughly examine the area near any nest you find.
Challenges of Control
A boric acid mixture can become effective in killing Argentine ants only when the correct concentration of the bait has been formulated: too weak a concentration may have no effect, while too high a concentration may kill the foraging Argentine workers before they have a chance to bring the poison back to the colony. Killing individual Argentine ants is impractical because queens so easily produce new workers. Pesticides also must mixed and applied according to the label. In order to ensure the elimination of all established nests, a pest control professional should be contacted.
ARGENTINE ANT INFESTATION
Argentine ant (Linepithema humile)
This ant’s infestations are associated with populations that inhabit both the outside and inside of a building or home. Outdoors, nests are in moist areas typically under mulch piles, wood debris or in trees, stumps or fallen logs, under rocks and concrete slabs. Indoors, nests are found around moisture and damaged wood and in wall voids. Argentine ants will move inside a building if they find a good food source inside or if their outside habitat is disrupted. Foraging ants will gain access to the inside via, power, plumbing and communication lines or tree branches. Argentine ants have a variety of foods they love to feed on, but tend to prefer sweets. Colonies have a large number of workers with multiple queens. The size of a colony may number as many as several hundred thousand workers. Workers generally live about one or more months, but queens can live up to 10 years or more.
Prevention & Control
- The first step to setting up an ant control program is to identify the ant species that you want to control. More often than not, professional help is needed to obtain a correct identification.
- Argentine ants are very persistent and one of the most troublesome species that challenge the homeowner. Sometimes, a property owner might experience comeback infestations year after year, unless control is complete and all nests are eliminated. Using insecticides as you only defense usually will be unsuccessful for long-term control, so preventive measures also are needed. Incomplete control is often followed by a “bounce-back” of the ant population because of this ant’s ability to reproduce. So, when you need to control Argentine ants, contact your pest management professional who can provide recommendations and control measures that work.
- Eliminate or reduce the ant habitat. Remove anything that attracts the ant such as ground clutter. For example, boards and other wood piles, decaying plant material, rocks and other places that hold ground moisture. Repair water leaks. Ensure that water from the roof is directed away from the foundation and do not over water areas that could attract the Argentine ant.
- Inspect landscape plants for aphids and other honeydew-producing insects. Reducing this food source is important. Argentine ants eat the sweet honeydew produced by such insects. If needed, treat plants.
- Inspect for ants by locating and following trails leading either to or from the ant’s nest.
- Seal cracks and other openings or spaces on the outside of the structure to help stop forager ants from entering your home’s interior.
- Trim shrubs, bushes and other vegetation around your home. Trim tree limbs that touch your house because they provide an easy path inside.
- Remove food sources, and keep food crumbs and other wastes to a minimum. Regularly clean counter tops, pantry shelves, floors and garbage containers. Don’t leave bits of food or dirty dishes in the sink, and keep the dishwasher clean. Store human and pet foods in sealed containers with snap-on lids or glass jars with sealing gaskets.