In late September and early October, on warm days, you may notice a buzz in the air. This is the time of year when citronella ants swarm, and they can overwhelm a backyard with winged queens and kings looking for a mate and a new home. Citronella ants are a bit larger than pavement ants and are yellow to amber in color. Winged swarmers are larger and darker in color with smoky tinted wings. When crushed, they smell just like a citronella candle.
Citronella ants care for, or tend, root aphids.
The life and habits of citronella ants aren’t well-studied, but they do have one fascinating trait. They tend herds of underground aphids, known as root aphids as if they were cattle, and harvesting sweet honeydew excreted by the sap-loving aphids. Root aphids feed on the roots of shrubs and plants, in my case flowering dogwoods. Root aphids may contribute to poor health of some plants, but they are extremely common and remain mostly undetectable beneath the soil.
Citronella ants are not a home-invading species of ant, although they may accidentally fly indoors during a mating flight. Swarmers may also end up indoors if the roots of shrubs have reached a structure foundation that, due to gaps or cracks, provides an exit into the building. Either way, these ants are not household pests, preferring to remain in their own habitat, tending their herds and minding their own business.