ANTS: Argentine (Iridomyrmex humilis)

Description: The most common structure-infesting ant in Southern California is the Argentine ant. They are small, a little more than an eighth of an inch long; they are light brown to shiny black and are often seen actively traveling in trails in large numbers.

Eddie’s Joke: How do we identify Argentine ants? By their accent, lol…

Background: The Argentine Ant is, as its name suggests, native to South America (Argentina and Brazil), and is not native to southern California but is an undesirable alien. (Please let Trump know.) The Argentine Ant was apparently introduced into this country at New Orleans before 1891 in coffee shipments from Brazil.

The ants invade our homes and offices through minute crevices and cracks—filing along baseboards, across sinks, and over walls and tables in endless trails. Single colonies may harbor many thousands of workers.

What we have learned: It is a serious mistake to think that these colonies can be eliminated with pest sprays. Pest sprays like those you find in the grocery store will kill the foraging worker ants. You might think the foragers would be the young, strong warriors in the colony but, no, that is not the case. This toxic spray makes things worse. Why? Ant colonies are well-organized societies with the ability to communicate with others of their kind. They are capable of simple types of learning and carry on their activities according to inherited instinctive patterns. Communication is achieved by means of touch (antennae tapping), or by the passing of odors of glandular secretions from one ant to another. They don’t have language as such but they do have a form of chemical communication, what is termed an “odor trail.” Once an individual has located a food source it will mark the path between this food and the nest with a chemical substances it secretes from its abdomen. Other members of the colony then follow the path back to the food, aided by sensitive smelling orbans located on the antennae and mouth.

Why don’t the grocery sprays work? We can’t really say that they don’t work because they do kill on contact. That is, they kill the ants they contact. So the typical housewife sprays her kitchen counters down with a harsh smelling chemical that will cause most people to get a flash headache, since the chemicals are absorbed by the mucous membranes in our heads. But the ants that are killed are the foragers. Who are the foragers? They are the aging worker ants. They are expendable. Remember, the colony has communication abilities and instinctive wisdom. When the aging workers do not return, the multiple queens in the colony become aware that the colony is diminished. As a result they will step up their reproductive activities.

So what happens? A week later the ants are back with a vengeance. The colony is now younger and stronger and the housewife is about to pull her hair out.

This is why professional pest control is needed. More is not better in this instance. What is needed is something so weak that it will not kill on contact but rather be carried back to the nest and the queens with lethal effect. The bottom line: you do not have to learn to live with ants. With modern treatment methods they can be effectively eliminated from your home and your office environment.

Biology:  The Argentine ant is the most persistent and troublesome ant in our environment. We have noted that most other ants are only an occasional nuisance. Argentine ants are very aggressive and will drive out other ant species from their territory. They nest and proliferate in the damp soil of landscapes, under rocks, ground covers, walks and even in a crack of a concrete slab. They also commonly nest in the sheaths of palm trees and under plastic sheeting covered with decorative landscape bark. When aphids are present on the landscape plants, the Argentine ants will harvest the honeydew secretions and tend the aphids as caretakers and protectors. Argentine ants develop huge colonies with endless trails going to and fro in and around structures, invading everything in an occupied building in search of food. Entomologists at the University of California at Riverside have determined that the huge colonies are actually just one monstrous, super colony covering all of Southern California. That is because, unlike other ants, Argentine ants readily accept each other, from colony to colony. They are particularly fond of sweets and thus prodigious numbers of them can be in a lunchroom, kitchen or food area. They can readily locate food in an office environment. When they do, they bring an army of scavengers. These ants gain access through the most minute cracks and openings and will travel up trees and shrubbery, even telephone wires, to enter a building.

Economic Impact: The fear of having thousands of ants show up in a lunchroom, kitchen or workspace is intolerable and can cause an immediate response if even one ant is seen. The presence of an ant in our home, office or work environment seems to trigger an emergency alarm in most people! We have found that Argentine ants are at times attracted to electrical switching equipment, computers, and control devices and can die in large numbers, causing a shut down of sensitive communication equipment. We have seen them coming and going from the outside of a refrigerator to the inside, freezing to death when they reach the freezer.

Contributed by Ed Pritts, Sales Manager, Pestgon, Inc., a Gold Friend of IREM (760) 801.7572.

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