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 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.

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.

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)