Pest Library
Argentine Ant
The Argentine ant is a light brown trailing ant that forms enormous, interconnected colonies with many queens, so an infestation is usually a landscape-wide problem rather than a single nest. Trails run along foundations, irrigation lines and tree limbs, and indoor activity follows moisture and sweets.
Profile
- Scientific name
- Linepithema humile
- Identification
- Uniform light to medium brown, single node, no sting, and no strong odor when crushed. Trails are unusually wide and persistent.
- Typical size
- About 1/8 inch (2.2-2.8 mm).
- Behavior
- Supercolonies with many queens cooperate instead of fighting, which lets numbers build very high. Nests shift with moisture.
- Habitat
- Soil under mulch, irrigation boxes, landscape timbers, planters and wall voids.
- Diet
- Honeydew from aphids and scale insects, sugars, and protein when brood is developing.
- Lifecycle
- Perennial colonies that bud rather than swarm; populations peak in warm months.
- Why it matters
- Nuisance and contamination; no sting and no structural damage.
- DIY considerations
- Spot spraying trails only redirects them. Because the colony is large and multi-queened, control depends on sustained exterior work.
- Professional considerations
- Programs target the exterior colony structure and food sources, with recurring service typically needed to hold numbers down.
Signs of activity
- Wide, heavily used trails along walkways and foundations
- Ants tending aphids or scale on ornamental plants
- Indoor foraging in kitchens and bathrooms during dry or wet extremes
- Nests appearing under anything left on the ground
Prevention
- Manage aphid and scale insects on landscape plants
- Keep mulch thin and pulled back from the foundation
- Repair irrigation leaks and adjust watering schedules
- Seal exterior gaps and keep tree limbs off the roof
Sources
Related information
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