Skip to main content

Argentine Ant – Linepithema humile

Written by Peter Horn on .

Argentine Ant – Linepithema humile Description of Insect: Argentine ants (Linepithema humile) are small, social insects native to South America. These ants are light to dark brown in color and measure approximately 2.2 to 2.6 mm in length. Unlike some other ant species, Argentine ants lack stingers, but they emit a musty odor when crushed. They have a single-node petiole connecting the thorax to the abdomen. The worker ants exhibit a uniform body size, distinguishing them from other species. Argentine ants are highly adaptable and form large colonies, often containing millions of workers and hundreds of queens. The queen is larger than the workers and exhibits a pair of wings when unmated. After mating, the queen sheds off her wings, leaving behind wing scars. Compared to other Linepithema species, Argentine ants have a hairless thorax. This helps differentiate them from other species in the genus. They are notorious for their cooperative behavior, with different colonies merging to form expansive supercolonies. This social structure allows them to dominate environments and outcompete native ant species. Life cycle of Argentine Ant: Their life cycle consists of 4 stages- egg, larva, pupa, and adult. Queens lay approximately 60 eggs per day in late winter, which develop into larvae by May. The larval stage is followed by pupation, lasting approximately two weeks. Once pupae emerge as adults, they take on roles as workers, queens, or males within the colony. Their high reproductive capacity and overlapping generations contribute significantly to their ability to form massive colonies and rapidly invade new areas. Damage they cause: Argentine ants are ranked among the 100 worst invasive animal species in the world, and for good reason. They are invasive pests that cause significant ecological, agricultural, and economic problems.
  1. Ecological Impact: These ants disrupt local ecosystems by outcompeting native ant species for food and nesting sites. Their aggressive behavior also affects other plants and animals by impeding their source of pollination and food, in turn reducing biodiversity in the invaded regions.
 
  1. Agricultural Damage: Argentine ants are known to protect and farm sap-feeding insects such as aphids, scale insects, and mealybugs. By defending these pests from natural predators, they indirectly contribute to crop damage caused by the pests’ feeding and excretion of honeydew, which promotes mold growth in plants.
 
  1. Economic Impact: In homes, Argentine ants forage for food and water, invading kitchens, pantries, and bathrooms. They are a persistent nuisance in residential and commercial spaces, especially in the rainy season.
How Argentine Ant got into USA: Argentine ants were introduced to the United States in the late 19th century through trade and shipping activities. Native to regions of South America, including Argentina, Paraguay, Bolivia, and southern Brazil, these ants hitchhiked in soil, plants, and cargo transported via ships to North America. The earliest recorded specimen in the US was noted in New Orleans. Aided by their highly adaptable nature and ability to thrive in urban and riparian environments, the ants spread rapidly to subtropical sites across the Southeast US and California.   Today, they are established across many Mediterranean climate areas, such as South Africa, Australia, Easter Island, and the contiguous United States. Their spread is further facilitated by human activities such as landscaping and transportation of infested materials.