Yellow ants, also called citronella ants, are mostly harmless insects that live underground and rarely cause structural damage. Getting rid of them comes down to eliminating moisture around your home, sealing entry points, and treating nests directly when you can find them. Most infestations only become visible during swarming season, which means the colony has likely been there for a while before you noticed it.
Identifying Yellow Ants
Yellow ants (Acanthomyops interjectus) are small, about 4 to 4.5 mm long, with yellow to brownish-yellow bodies. The easiest way to confirm you’re dealing with them is the smell: crush one and it releases a strong lemon or citronella scent. That’s unique to this species and is why they’re commonly called citronella ants.
Workers are the small yellow ones you’ll see crawling around. Swarmers, the winged reproductive ants, are roughly twice the size of workers and appear darker, sometimes reddish-brown with smoky wings. These swarmers emerge in large numbers during early spring (March and April) or fall (September and October), which is usually when people first realize they have an infestation. Swarms often appear near sidewalks, patios, concrete slabs, foundation walls, or in basements.
Yellow Ant Swarmers vs. Termites
When winged yellow ants swarm indoors, many people worry they’re seeing termites. The differences are straightforward. Ants have elbowed antennae, a thin pinched waist, and two pairs of wings where the front pair is noticeably longer than the back pair. Termites have straight antennae, a thick waist with no pinch, and two pairs of wings that are all the same length. If you see that thin waist and those bent antennae, you’re dealing with ants, not termites.
Where Yellow Ants Nest
Yellow ants are largely subterranean. They build colonies in moist soil, under rocks, in decaying wood, and along or under foundations. You can go years without knowing a colony is there because the workers forage underground, feeding on honeydew from root-feeding insects rather than your food. The colony only announces itself when swarmers emerge and push through cracks in your foundation, basement floor, or slab.
Common nest locations include soil beneath concrete slabs, crawlspaces with poor drainage, areas near leaking pipes, and rotting wood in contact with the ground. If you’re seeing ants inside, they’re almost certainly nesting in or near the foundation rather than deeper inside the home’s structure.
Reducing Moisture to Eliminate Nesting Conditions
Because yellow ants depend on damp environments, moisture control is the most effective long-term strategy. Without it, any chemical treatment is a temporary fix, and colonies will rebuild.
- Fix plumbing leaks. Even a slow drip from a pipe or faucet provides enough moisture for a colony. Check under sinks, around toilets, and behind appliances regularly.
- Improve ventilation in damp areas. Use exhaust fans in bathrooms and kitchens, and run a dehumidifier in basements and crawlspaces where humidity stays high.
- Clear gutters and redirect downspouts. Clogged gutters pool water around your foundation, which is exactly where yellow ants want to nest. Make sure downspouts direct water well away from the house.
- Move firewood and debris. Woodpiles, leaf piles, and other organic material absorb moisture and create ideal nesting sites. Keep them at least 20 feet from your home’s foundation.
- Grade soil away from the foundation. If soil slopes toward your house, water collects against the foundation walls. Re-grading so water flows away makes the area less hospitable to colonies.
Sealing Entry Points
Yellow ants get inside through remarkably small gaps. Inspect the perimeter of your foundation for cracks, and check around windows, doors, and where utility lines enter the house. Seal gaps with caulk or weather stripping. Pay special attention to basement-level openings, since that’s where swarmers most commonly emerge indoors. This won’t kill an existing colony, but it stops the ants from entering your living space.
Using Diatomaceous Earth
Diatomaceous earth (DE) is a non-chemical option that works through physical action rather than poison. The powder is made of microscopic fossilized particles with sharp edges that cut through an ant’s exoskeleton, causing it to lose moisture and die from dehydration. Some ants die within hours of contact, while others take a few days.
To use it, sprinkle a thin, even layer of food-grade diatomaceous earth along ant trails, around entry points like baseboards and windowsills, and near any visible nest openings outdoors. Use a duster for even distribution. Ants don’t carry DE back to the nest intentionally, but they do transfer it to other ants through contact, which helps spread its effect beyond the individuals that walk through it directly.
The main limitation is moisture. DE stops working when wet and needs to be reapplied after rain or watering. Indoors, vacuum up the old layer and reapply every few days until ant activity stops. Always use food-grade DE for indoor applications to keep it safe around children and pets.
Chemical Treatments and Their Limits
Perimeter sprays using pyrethroids are commonly sold for ant control. These products can knock down visible ant numbers, but according to the University of California’s Integrated Pest Management program, ants quickly rebuild and reinvade after perimeter treatments. These sprays also pose environmental risks, particularly when applied to hard surfaces like driveways, sidewalks, or foundations, where they can wash into waterways.
A bait-based approach is generally more effective than perimeter sprays because bait gets carried back to the colony. The challenge with yellow ants specifically is that they feed primarily on underground honeydew from root aphids, not on the sugars and proteins in most commercial ant baits. This makes baiting less reliable for citronella ants than for species like pavement ants or odorous house ants that actively forage for food.
If you can locate the nest, a direct treatment into the nest opening is the most targeted chemical approach. Insecticidal dust applied into cracks along the foundation or into soil where ants are emerging reaches deeper into the colony than surface sprays. For colonies nesting under concrete slabs or deep within foundation walls, professional pest control may be necessary because the nest simply isn’t accessible with consumer products.
When Yellow Ants Don’t Need Treatment
Yellow ants are nuisance pests, not destructive ones. They don’t eat wood, don’t contaminate food, and don’t bite in any meaningful way. If you’re only seeing swarmers once or twice a year and they’re coming from outside the home, the infestation may not require treatment at all. Swarms typically last only a day or two, and vacuuming up the winged ants is often enough to deal with the immediate problem.
The situation changes if swarmers are emerging inside your home repeatedly, if you’re finding workers in living spaces, or if there are signs of excessive moisture damage near the nest. In those cases, the ants are a signal that you have a moisture problem worth addressing regardless of the ants themselves. Fixing the moisture issue solves both problems at once.