Argentine Ants

Although ants seem little and insignificant to us, once we look into their world, they become important. The way Argentine ants build their homes and the way they communicate are unique.

In addition, the social structure of the Argentine ant is different from other ants. To get into their world, it’s necessary to learn more about them. Are you ready? Let’s march into the underground world of the Argentine ant. Left . . . left . . . left, right, left . . .

Argentine ants can usually be found in the top six feet of soil. They can live in moist soil underneath buildings and by sidewalks. Boards can also be used as shelter. Sometimes colonies develop in potted plant soil. Nests can be made of rocks, twigs, dirt, and so forth. Argentine ants relocate their nests often. Food sources and temperature affect where nests are built. Other types of ants live in anthills that look simple on the outside but contain a labyrinth of specialized chambers.

Argentine ants are in the order Hymenoptera and the family Formicidae. This amazing ant is only about 1/16 of an inch long! It is also light to dark brown in color, and it has six legs, like all other insects. The Argentine ants’ antennae have twelve segments. The thorax joins the abdomen by a thin pedicel, a thin stalk. There is no smell if one ant is squashed alone, but if many are, there is a musty, greasy smell. Workers forage for food and chew it. The food substance is given to the larvae. They digest and regurgitate it for the adults. This must happen because the adults have a very thin esophagus and cannot swallow large particles of food.

The Argentine ant is one species among more than 175 known species of ants in California. Although it seems no different from other ants, it is. Argentine ants are social insects. Edward Ruppert and Robert Barnes, in Invertebrate Zoology (Sixth Edition), describe a social organization as having “individuals functionally interdependent yet morphologically separate.” They stated that no “individual can exist outside of the colony, nor can it be a member of any colony, but the one in which it developed.”

Argentine ants were accidentally imported by coffee shipments to New Orleans circa 1891. They have since spread eastward into the Carolinas, as far south as Southern Florida, and westward into Texas and California. These ants are also located in Argentina, Brazil, Australia, and Africa.

Usually ants of the same species, in different colonies, will fight each other. However, Argentine ants cooperate with each other, They can be aggressive to other insects, exterminating termite colonies and killing or driving off paper wasps and carpenter bees.

An Argentine ant has more than one stomach. One stomach is for itself, while the other is the public crop that is used to feed others. Ants pass messages while they pass food. They turn their food into liquid, which goes into their crops. To feed and be fed, two ants stand up with their mouths pressed together, and the liquid comes out of one ant’s crop and into the other ant’s mouth.

Secretions called pheromones come with the food in a form that can be smelled. Because each nest has its own distinct smell, ants can use pheromones to recognize each other. They communicate excitement, danger, and what jobs need to be done. Pheromones also act to attract mates, sound alarms, and provide food trails from the nest among other purposes. Secretions can create a bond or friendship between colony members, helping them to work together.

Argentine ants have a special social structure. While most ant colonies have only one queen, Argentine ants can have as many as eight queens for every 1,000 workers. All male ants hatch from unfertilized eggs. Their life span is only about a year, and their only role is to mate with the queen (or queens). Fertilized eggs hatch into females, which are usually sterile workers. The workers are around 1/12 to 1/8 inches long, or two to three millimeters.

Polymorphism comes into play with workers. Physical and behavioral variety determine labor division. The soldiers of the colony are usually the largest ants with big, muscular heads and swordlike jaws. Most ants are medium-sized and forage for food.

Deborah Gordon of Stanford University conducted an experiment to see how ants find food. She put a layer of dried sugar water in an arena. Different Argentine ant colonies searched for the food, then came back empty-handed. She traced the trails the ants made, and found that few ants in a big space moved in somewhat straight lines; when the ants became crowded, the ants made more curved paths. “The overall patrolling pattern resembles an elastic net whose lines stretch and straighten when ants are few, but contract into convoluted curls when they are plentiful, (“Networking Ants”).

William Creighton conducted an experiment to see how ants forage for food. He found they do it in files. “Although the ants in the file are close together they evidently follow a scent path . . . I repeatedly observed that in the case of Iridomyrmex humilis, the file can be thrown into great confusion by simply drawing a finger across the path. A ‘traffic jam’ immediately develops at either side of the patch of foreign scent, and this persists until a few bold spirits have ventured across the finger mark and reestablished the proper scent trail,” (The Ants of North America).

A traffic jam example could be seen in the movie A Bug’s Life. In the beginning of the movie, a trail of ants is interrupted when a leaf falls in front of one of the insects. The ant complains of losing the path. This is an accurate depiction of observed ant behavior.

The smallest Argentine ant workers become nurses. They care for the eggs, larvae, pupae, and young ants. Other workers have jobs such as slave-making, where the ants sneak into other ant colonies and steal eggs. Workers also herd and milk aphids. All workers generally live about four years. Colonies may consist of hundreds to thousands of members. If one ant does not do its job, the other ants will suffer from that ant’s lack of responsibility. New colonies form from older ones. This is called budding.

Some roles of the Argentine ant colony are unique. Part of the queen ant’s role is to mate with the male ants of the colony. Argentine ants rarely swarm, and they mate in the nest. Queens will leave the nest with a band of workers to start a new colony elsewhere. In most ant species, the queens and the males (also called drones) fly away and leave the nest in a big cloud. On a few occasions, people have called a fire department, seeing the cloud and thinking it was smoke (Valerie Pitt and David Cook, A Closer Look at Ants).

Some of the ants mate in shrubs and trees, while others hold onto each other and mate in the air. After an hour or so, the flight ends and the ants fly down to the ground. Since the males’ purpose in life is over, they die. Some are eaten by birds or other insects, while others simply decay on the ground.

After mating, the queen gets rid of her wings because she doesn’t need them anymore. She then makes a tunnel with her front legs and jaws, seals herself in, and begins to lay her eggs. While she waits for the eggs to hatch, she feeds herself by absorbing some from her wings and sometimes cannibalizing some of the smallest eggs. When the larvae come, she feeds them with her own saliva and, sometimes, other eggs. After workers are born, she stays in the nest, and the workers treat her well.

Argentine ants have made quite an impact on California today. They have monopolies over other ants because of their social rules and drive out or kill the native ants of a newly invaded territory. They also steal seeds from their beds and gnaw ripening fruit. These ants can drive poultry from their nests, kill newly hatched chicks, and even disrupt beehives. While Argentine ants have taken a foot hold in California and Hawaii, other widespread infestations can be found in Arizona, Missouri, Oregon, Illinois, Indiana, Washington, and Maryland.

Horned lizards were once abundant in southern California. The Argentine ant moved in and conquered native ant nests. Since they will only eat ants native to California, the horned lizards are dying out due to starvation. This single event reminds us of the delicate balance of our environment and cautions us to be mindful of introducing new species to our environment.

“Man tends to look up and tries to figure out what is happening up above, and at the same time, he cannot even figure out the ants . . If we get the chance to understand them, this world would run on a different basis. Without understanding ants, I don’t think we can understand other things.” (Lech Walesa)