Citronella Ants

What Are Citronella Ants?

Citronella ants are a group of ants belonging to the genus Lasius, commonly referred to as Lasius interjectus in North America. These ants are most notable for the distinctive lemon or citronella-like odor they emit when crushed, which is how they got their common name. Though they may cause alarm when seen indoors, citronella ants are generally not harmful and do not pose a structural threat like carpenter ants or termites.

Are Citronella Ants Harmful?

Citronella ants are not harmful in the traditional sense—they do not bite, sting, transmit disease, or damage structures like carpenter ants or termites. Their presence can be alarming, especially during swarming events, but they are best categorized as a nuisance pest rather than a threat:

• No Structural Damage: Citronella ants do not chew through wood, insulation, or building materials. While they may nest under foundations or slabs, they aren’t capable of causing the type of structural destruction associated with termites or carpenter ants.
• No Biting or Stinging: These ants are non-aggressive and lack a functional stinger for defense. They do not pose a risk to people or pets through physical harm.
• No Disease Transmission: Unlike some pests (e.g., cockroaches or rodents), citronella ants are not known to spread pathogens or contaminate food. In fact, they rarely enter living spaces in search of food and are not attracted to kitchens or pantries.
• Indoor Presence is Temporary: When citronella ants are seen inside, it’s usually due to a seasonal swarming event by reproductive ants (alates), particularly in late winter to early spring. While swarms may appear dramatic, they are short-lived, and the ants typically die off or leave within a day or two.

Citronella Ant Appearance

Citronella ants, scientifically known as Lasius spp., are small insects with distinct physical characteristics. They measure approximately 3 to 4 millimeters in length, which is roughly the size of a typical household ant. Their appearance is notable for the following features:

• Coloration: Citronella ants are typically yellow to light brown in color, and their bodies often exhibit a shiny or glossy appearance. This coloration is a key identifying characteristic, and it contributes to their common name, as they resemble the hue of citronella oil.
• Body Segmentation: Like all ants, citronella ants have a distinct body segmentation consisting of three main parts: the head, thorax, and abdomen. Their bodies are divided into these segments, with a clear separation between each.
• Antennae: They possess elbowed or bent antennae, which are a notable feature of ant anatomy. These antennae are used for sensing their environment, detecting pheromones, and communicating with other ants.
• Wings: During certain stages of their life cycle, citronella ants, particularly the reproductive individuals known as alates, have wings. These wings are clear and transparent and are more prominent in the winged males and females. They use these wings for mating flights before shedding them.
• Mandibles: Citronella ants have small, noticeable mandibles near their mouthparts. These mandibles are used for various tasks, including cutting food and manipulating objects.
• Size: Their small size distinguishes them from larger ant species. While workers are around 3 to 4 millimeters long, the winged reproductive ants may be slightly larger.

Citronella ants are small insects with a yellow to light brown coloration, segmented bodies, elbowed antennae, and, in some stages of their life cycle, clear wings. These physical characteristics help differentiate them from other ant species and contribute to their unique appearance.

Citronella Ant Habitat

Citronella ants (Lasius interjectus and related species) are widely distributed throughout the United States, but they are most commonly found in eastern and central regions, particularly in areas with moist soil and decaying organic matter. Their range includes states from the Northeast through the Midwest and down into the Southeast, although some species are also found in the West, especially in cooler, forested, or mountainous areas.

Typical Habitats

Citronella ants thrive in moist, protected environments, both outdoors and occasionally indoors. Here are the environments where you're most likely to encounter them:

Outdoors

• Beneath rocks, logs, and mulch
• Under landscaping timbers or railroad ties
• In rotting stumps or old tree roots
• In the soil near foundations, porches, and patios
• Under concrete slabs and walkways
• At the base of shrubs or in mulched beds where honeydew-producing insects (like aphids and mealybugs) are present

They often form large, underground colonies, which can go unnoticed for years due to their non-aggressive nature and lack of visible foraging trails.

Indoors

Citronella ants do not typically nest indoors, but they may appear in structures due to:

• Seasonal swarming: Especially in late winter or early spring, winged reproductives (alates) may emerge inside homes or commercial buildings, especially in basements or utility rooms.
• Nests adjacent to or beneath foundations: Colonies located under slabs or near foundation walls may release swarmers indoors through cracks, expansion joints, or utility penetrations.
• High-moisture areas: If conditions inside a structure mimic the moist environments they prefer (e.g., leaky pipes, damp basements, crawlspaces), citronella ants may be drawn inside or temporarily set up satellite colonies.

Geographic Distribution in the U.S.

• Northeast (e.g., New York, Pennsylvania, Massachusetts) – Common in wooded areas and around older homes with stone foundations or moist basements.
• Midwest (e.g., Ohio, Illinois, Michigan) – Frequently found in lawns and gardens, particularly near shaded, damp foundations.
• Southeast (e.g., Georgia, North Carolina, Tennessee) – Thrive in the warm, humid climate and are often found in landscaping and under exterior slabs.
• West (e.g., Colorado, parts of the Pacific Northwest) – Less common but present in forested or mountainous terrain with cool, moist conditions.

If you're encountering citronella ants regularly or inside a structure, it’s worth conducting a foundation inspection and moisture assessment, particularly in basements, crawlspaces, and perimeter landscaping.

Citronella Ant Diet

Citronella ants have a distinctive diet primarily centered around sugary substances. They are considered omnivores, but their food preferences are skewed toward carbohydrates and sugars. Here's what citronella ants eat:

• Honeydew: The primary food source for citronella ants is honeydew, a sweet, sugary liquid excreted by aphids, mealybugs, and other sap-feeding insects. Citronella ants have a fascinating relationship with these insects, often referred to as "farming." They protect aphids from predators and collect honeydew droplets that aphids release when they feed on plant sap.
• Nectar: In addition to honeydew, citronella ants also feed on flower nectar. They are attracted to the sweet nectar produced by various plant species. Nectar serves as an additional source of carbohydrates and energy for the ants.
• Insects: While carbohydrates make up the majority of their diet, citronella ants do consume small insects and other protein-rich food sources occasionally. They may capture and carry small insects or arthropods back to their nests to feed the colony, especially when they require protein for raising their brood.
• Fungi: Citronella ants exhibit a unique behavior known as "fungus farming." They cultivate a specialized fungus within their underground nests, and this fungus serves as a supplementary food source. The ants consume the fungus, which in turn feeds on organic matter within the nest.

Citronella ants are not scavengers like some other ant species, and they do not typically forage for solid foods or crumbs in human dwellings. Instead, they primarily rely on their mutualistic relationship with aphids for honeydew and seek nectar from plants in outdoor environments. This specialization in sugar-rich foods and their interaction with aphids are key aspects of their dietary habits.

Citronella Ant Life Cycle

The life cycle of citronella ants (Lasius interjectus and related species) follows a complete metamorphosis, consisting of four distinct stages: egg, larva, pupa, and adult:

Egg Stage

The life cycle begins when the queen lays tiny, oval, white eggs. These are fertilized from stored sperm and develop into either worker ants (females) or new reproductives (males and queens), depending on the colony’s needs and seasonal cues.

• Time in stage: A few days to a week, depending on temperature and humidity.
• Egg viability is strongly influenced by environmental conditions—moisture and warmth are critical for successful development.

Larval Stage

The eggs hatch into grub-like, legless larvae that are completely dependent on worker ants for food and care. Larvae are fed a protein-rich diet, often derived from trophallaxis (regurgitated food), or in some cases, fluids harvested from underground root-feeding insects like aphids or mealybugs.

• Function: Growth; the larvae molt several times before pupating.
• Duration: Several days to a couple of weeks, depending on environmental conditions.

Pupal Stage

After reaching a sufficient size, the larvae spin a cocoon-like structure (in some species) or remain exposed in the pupal form. This is the transformational stage, where the insect develops its adult features—legs, antennae, eyes, and mandibles.

• Duration: One to three weeks in ideal conditions.
• The ant emerges as either a worker, queen, or male, depending on its genetic and developmental path.

Adult Stage

The final form is the adult ant, which takes on one of three roles:

• Worker ants (sterile females): Perform all tasks for the colony, including foraging, brood care, nest maintenance, and defense.
• Males: Sole purpose is to mate during the nuptial flight; they die shortly afterward.
• Queens: Fertilized females who establish new colonies or continue laying eggs in established ones.

Nuptial Flights and Reproduction

One of the most distinctive features of the citronella ant life cycle is the seasonal swarming of reproductive adults, often occurring in late winter or early spring (unlike most ants, which swarm in warmer months). During this period, winged males and females (alates) leave the nest in a swarm. After mating, males die, and fertilized queens shed their wings and attempt to establish new colonies in suitable soil conditions. A newly founded colony may take several years to mature, as initial growth is slow and dependent on a single queen and a small number of workers.

Colony Longevity and Growth

• Colonies can persist for many years, gradually growing in size as environmental conditions permit.
• Colonies are typically large and subterranean, and may have multiple queens in some cases, although Lasius interjectus is usually monogynous (single queen).
• The colony’s life cycle is seasonally driven, with growth and activity peaking in warmer months and slowing during the winter.

The citronella ant life cycle is typical of ants but is strongly influenced by moisture, soil temperature, and underground ecology, particularly their symbiotic relationships with root-feeding insects. Their swarming behavior in cooler months is unusual and can lead to misidentification as termites, especially when they emerge inside buildings.

If you're encountering citronella ants regularly, especially swarmers, it likely indicates a mature colony nearby or beneath a structure.