(Linepithema humile, formerly Iridomyrmex humilis)
Physical Characteristics: Argentine worker ants are 1/16 inch long; queens are two to four times larger than workers (1/8 to 1/4 inches in length). They are light to dark brown in color. Their antennae each have 12 segments, and there’s no “club” at the end. Viewed from the side, their thorax isn’t rounded but humped; their pedicel, or waist, has one segment. There’s no stinger at the end of the abdomen, but the Argentine ant can bite.
Behavior: The Argentine ant prefers sweets like fruit juices, candy and plant secretions. They will tend aphids and scale insects for their “honeydew” – a sweet, sugary secretion that aphids and scale insects produce – much like the way farmers tend cows for milking; it’s estimated that 70 percent of the Argentine ant’s diet comes from these farming activities. The Argentine ant will nest near a source of moisture – household plumbing, sinks or potted plants. Workers follow routine trails while seeking food, and may be accompanied by winged queens. These ground-nesting ants may nest as deep as 24 feet, and will forage for food up to 200 feet from their nests. These ants will make use of tree branches and even utility lines to travel. One difference between Argentine ants and other ant species is that Argentine ants will combine into massive supercolonies, sometimes hundreds of miles long (one Argentine supercolony stretches from San Francisco to San Diego), rather than launch into wars between different ant colonies, making these six-legged pests the urbanized ant of the future. Wherever Argentine ants are introduced, they quickly become the dominant ant species, not because they’re stronger warriors – although they do a pretty good job taking out fire ant and carpenter ant colonies – but because they’re better organized and can get along with each other.
Treatment: The Argentine ant will try to enter your house during hot, dry weather, looking for the cooler temperatures and moisture it prefers. Any potential points of entry need to be blocked, and bridges to your house, such as branches that touch the structure, need to be trimmed back. And because of this ant’s fondness for sweets, keeping surfaces and floors clean in your kitchen helps to keep the Argentine ant away. If you should experience a heavy, difficult infestation of Argentine ants, your friendly local Clark Pest Control branch is a phone call away.