Citronella ants are not harmful. They don’t bite, don’t sting, and don’t damage your home’s structure. Named for the lemon-like scent they release when crushed, these ants are almost entirely a nuisance pest, and usually a temporary one at that.
Why They Show Up Inside
Citronella ants (primarily the species Lasius claviger and Lasius interjectus) live underground, where they tend root-feeding aphids and mealybugs and collect the sugary honeydew those insects produce. They don’t forage for human food, raid pantries, or search your kitchen for crumbs. Their diet is entirely based on that underground honeydew farming operation.
The reason they end up inside your house is swarming. Winged reproductive ants emerge in large numbers, typically in early spring (March and April) or in fall (late September to October), looking for mates. If their colony is nesting beneath or near your foundation, those swarmers can push up through cracks in basement floors, gaps around pipes, or expansion joints in concrete slabs. Seeing dozens or hundreds of winged, yellowish-brown ants suddenly appear in your basement is startling, but it’s not a sign of an infestation that will take hold indoors. The ants will not reproduce inside your home and will not attack stored goods or structures.
No Risk to People or Pets
Citronella ants pose zero direct health risk. They have no functional sting, they don’t bite defensively, and they don’t carry or transmit diseases. If your dog or cat encounters them, there’s nothing to worry about. The worst they’ll do is release that citrus smell if you step on them, which is actually formic acid, the same compound most ants produce.
Their presence can, however, signal moisture conditions worth paying attention to. Citronella ants prefer damp soil, so colonies thriving right next to your foundation may indicate poor drainage, leaky pipes, or excessive moisture around the base of your home. Those conditions can eventually attract other pests or contribute to mold growth, so it’s worth investigating even though the ants themselves aren’t the problem.
They’re Not Termites
The most common concern when winged citronella ants swarm indoors is that they might be termites. The two look similar at a glance, especially to someone who hasn’t seen either up close. But there are three reliable differences you can check:
- Antennae: Citronella ants have elbowed (bent) antennae. Termite antennae are straight, like a string of tiny beads.
- Wings: Ant swarmers have two pairs of wings that are clearly different sizes, with the front pair noticeably longer. Termite swarmers have two pairs of roughly equal length.
- Waist: Ants have a pinched, narrow waist between the middle and rear body sections. Termites have a thick, straight-sided waist with no visible pinch.
Unlike termites, citronella ants do not eat wood or cause structural damage of any kind. Carpenter ants are another common lookalike, but citronella ants are typically lighter in color (yellow to yellowish-brown) and produce that distinctive lemon scent when crushed. If you’re unsure what you’re looking at, capturing a few in a sealed bag and comparing them to reference images can save you an unnecessary call to a pest control company.
How to Handle a Swarm
Because swarming typically lasts only three to four days, the simplest approach is to vacuum up the winged ants as they appear. Once the brief mating flight is over, you won’t see them again until the next swarming season. No chemical treatment is needed in most cases.
If swarmers are entering through visible cracks in your foundation or gaps around utility pipes, sealing those entry points with caulk will prevent future intrusions. Reducing moisture around your foundation also helps. Make sure gutters direct water away from the house, fix any leaking outdoor faucets, and ensure the soil near your foundation slopes away rather than pooling against it.
For the rare situation where ants keep appearing in large numbers over multiple seasons and the entry points aren’t obvious, a pest control professional can locate the colony outside and treat it directly. But for most homeowners, a vacuum and a few days of patience is all it takes. The ants aren’t eating your food, damaging your walls, or putting anyone at risk. They just picked an inconvenient exit route.