Males: These exist solely to mate with virgin queens. After mating, they die. Their lifespan is measured in weeks, while workers can live for months and queens for years.

Colony Recognition Pheromones: Each colony has a unique chemical signature. Ants can instantly identify whether another ant is a nestmate or an intruder. This is why most ant species are fiercely territorial and will attack ants from other colonies.

Odorous House Ants (Tapinoma sessile)

Threat Level: 4/10*

These are the ants I encounter most frequently in Colorado homes.

Identification: Dark brown to black, very small (1/10 inch or 2.5-3mm), with an irregularly shaped thorax when viewed from the side. The telltale identifier is the smell—crush one and you’ll immediately smell rotten coconut or blue cheese.

Where They’re Found: Native to North America, odorous house ants nest in wall voids, under floors, behind baseboards, in attics, and outdoors under rocks and mulch. They love moisture and are often found near bathroom and kitchen plumbing.

Diet & Behavior: They prefer sweet foods—spilled soda, honey, fruit—but they’ll also feed on protein. They’re attracted to the honeydew produced by aphids, which can bring them into homes as they follow aphid infestations on houseplants. When their outdoor nests are disturbed by rain or temperature changes, entire colonies will relocate indoors.

Colonies: Colonies contain multiple queens and can number in the thousands. When threatened, they practice “budding”—splitting into satellite colonies. This is why spraying them with repellent often makes the problem worse.

Why They’re a Problem: While not dangerous, they contaminate food and are incredibly persistent. Small ant infestations can become major problems quickly because of their rapid reproduction and tendency to establish multiple nesting sites.

Pro Tip: The rotten coconut smell is actually their alarm pheromone. When you crush one, you’re alerting every ant nearby to danger—which is why you see them scattering when you try to kill them.

Pavement Ants (Tetramorium caespitum)

Threat Level: 3/10*

If you’ve noticed tiny brown ants emerging from cracks in your driveway or sidewalk, you’re dealing with pavement ants.

Identification: Dark brown to black, very small (1/16 to 1/10 inch or 2.5-3mm), with parallel lines (striations) on their head and thorax. They have a pair of tiny spines on their back.

Where They’re Found: True to their name, pavement ants nest primarily under pavement—driveways, sidewalks, patios, and building foundations. They create vast underground tunnel networks, and you’ll see small dirt mounds at the entrance holes between pavement cracks.

Diet & Behavior: Pavement ants are omnivores but show a particular fondness for greasy foods. I’ve seen them swarm dropped French fries, bacon grease, and cooking oil spills. They also eat sweets, bread, nuts, and cheese. They’re not picky eaters.

Colonies: A single colony can contain thousands of workers and multiple queens. In spring, you might witness pavement ant “wars”—rival colonies battling for territory on sidewalks. It looks like writhing masses of ants locked in combat, and it can last for days.

Why They’re a Problem: While not dangerous, they contaminate food and can damage buildings by excavating soil from beneath concrete slabs, causing settling and cracks. They’re particularly problematic for businesses with outdoor patios or walkways.

Pro Tip: Pavement ants are often found in older neighborhoods where decades of pavement cracks have created ideal nesting habitat. If you see consistent trails leading from pavement cracks to your home, you’ve identified their highway.

Carpenter Ants (Camponotus spp.)

Threat Level: 8/10*

These are the ants that keep me up at night—not because they’re dangerous to humans, but because of the structural damage they cause.

Identification: Large—the biggest ants in Colorado at ¼ to ⅜ inch (6-13mm) long. Black or reddish-black with a well-defined waist. Workers come in different sizes (polymorphic), with larger “major” workers serving as soldiers.

Where They’re Found: Carpenter ants prefer moist or rotting wood but will excavate sound wood once established. I find them in:

• Dead trees and stumps
• Firewood piles
• Wooden deck posts
• Window and door frames with water damage
• Roof eaves and fascia
• Wall voids near leaky plumbing
• Foam insulation

Diet & Behavior: Carpenter ants don’t eat wood—they excavate it to create nesting galleries. They feed on insects (they’re predators), honeydew from aphids, and household sweets and proteins. They’re nocturnal, most active from dusk through early morning.

Colonies: A mature colony contains 2,000-10,000+ workers and one queen. It can take 3-6 years for a colony to become large enough to produce winged reproductives—so if you see carpenter ant swarmers, you’ve had an established colony for years.

Why They’re a Problem:THIS IS SERIOUS. Carpenter ants cause structural damage. Their galleries weaken wood framing, floor joists, wall studs, and roof trusses. I’ve inspected homes where carpenter ant damage required $10,000+ in structural repairs.

Warning Signs:

• Large black ants, especially with wings
• Piles of sawdust-like material (frass) near baseboards or outside
• Hollow-sounding wood when tapped
• Rustling or crunching sounds in walls at night
• Small holes in wood with smooth, clean edges

Pro Tip: If you see carpenter ants indoors during the day, you likely have a satellite colony nearby. The main colony (parent nest) is usually outdoors, but mature colonies establish satellite nests indoors near food sources. Learn more about strategies for removing carpenter ants.

Argentine Ants (Linepithema humile)

Threat Level: 7/10*

These invasive ants are relatively new to Colorado but are becoming more common—and they’re a nightmare to control.

Identification: Light to medium brown, small (2-3mm or about 1/10 inch), with a single node on their petiole. They move quickly in erratic patterns.

Where They’re Found: Originally from South America, Argentine ants were first recorded in the U.S. in the late 1800s. They nest in a huge variety of locations: in soil, under concrete slabs, inside wall voids, in mulch beds, under potted plants, basically anywhere that provides moisture.

Diet & Behavior: They’re attracted to sweet and greasy foods but will also feed on insects. What makes them especially problematic is their lack of aggression toward other Argentine ant colonies. Most ant species are territorial and fight other colonies. Argentine ants from different nests recognize each other as allies and form massive “supercolonies” that can span entire neighborhoods.

Colonies: Argentine ant supercolonies can contain millions of ants and hundreds of queens. In California, researchers documented a supercolony that stretched 600 miles. When you have that many queens, eliminating the colony becomes incredibly difficult.

Why They’re a Problem: Argentine ants dominate and displace native ant species. They form persistent foraging trails and will invade homes in massive numbers. They’re particularly attracted to moisture, so bathrooms and kitchens are prime targets. Because of their supercolony structure and multiple queens, traditional control methods often fail.

Pro Tip: If you spray Argentine ants with repellent, they’ll bud—the colony fragments into multiple satellite colonies, making your problem worse. Baiting is essential, but it requires patience because you need to eliminate hundreds of queens.

Pharaoh Ants (Monomorium pharaonis)

Threat Level: 6/10*

These tiny ants are particularly problematic in hospitals, nursing homes, and multi-unit buildings.

Identification: Pale yellow to reddish-brown, extremely small (1.5-2mm), with a darkened abdomen and two-node petiole. They’re one of the smallest ant species you’ll encounter.

Where They’re Found: Originally from tropical Africa, Pharaoh ants have spread worldwide. They nest in warm, humid locations: inside wall voids, behind baseboards, under floors, inside electrical outlets, in folded linens, even inside food packages.

Diet & Behavior: Pharaoh ants eat almost anything—sweets, grease, proteins, even shoe polish and toothpaste. They’re particularly attracted to moisture and warmth, which is why they thrive in hospitals and commercial kitchens.

Colonies: Colonies contain multiple queens and can grow to hundreds of thousands of workers. They establish satellite nests throughout a building, creating a distributed colony network that’s extremely difficult to eliminate.

Why They’re a Problem: Pharaoh ants carry and spread disease-causing bacteria including Salmonella, Staphylococcus, and Streptococcus. In hospitals, they’ve been found in sterile surgical equipment, IV bags, and wound dressings. They can also damage electrical equipment by nesting in outlets and switches, creating fire hazards. Like Argentine ants, they bud when threatened with repellents, making them one of the most difficult pests to eliminate.

Pro Tip: NEVER use spray pesticides on Pharaoh ants. Spraying triggers budding, and suddenly your one colony becomes five colonies. Professional bait-only treatments are the only effective control method.

Field Ants (Formica spp.)

Threat Level: 2/10*

Also called wood ants or thatching ants, these are primarily outdoor pests.

Identification: Medium to large (4-8mm), typically black or red, with a segmented body, narrow waist, and elbowed antennae. They have a distinctive “bearded” appearance around their mandibles.

Where They’re Found: Field ants build large mounds in open areas—lawns, meadows, fields, and gardens. These mounds can reach impressive heights (up to 2 feet in diameter) and are constructed from soil particles, pine needles, and twigs. The genus name Formica actually means “ant” in Latin.

Diet & Behavior: Field ants are omnivores, feeding on plant material, honeydew from aphids, and other insects. They’re quite aggressive and will bite defensively if their nest is disturbed. They’re most active during the day and can be seen foraging on plants and trees.

Colonies: Large colonies with a single queen can contain thousands of workers. They’re very territorial and will defend their mound aggressively against intruders.

Why They’re a Problem: Field ants rarely invade homes, but their large mounds can damage lawns, undermine pavement, and damage plant roots. Their aggressive biting behavior can be a problem for homeowners with children or pets who might accidentally step on a mound.

Pro Tip: Field ants are actually beneficial in many ways—they aerate soil, control other pest insects, and serve as food for birds and other wildlife. If their mounds aren’t causing problems, consider leaving them alone. Learn more about what animals eat ants.

Cornfield Ants (Lasius alienus)

Threat Level: 4/10*

Despite the name, you’ll find these ants in yards and gardens, not just cornfields.

Identification: Small (2.5-4mm), brown to black, with a smooth, shiny appearance. They’re often confused with pavement ants but lack the striations on the head and thorax.

Where They’re Found: Cornfield ants nest in soil, creating small mounds in lawns, gardens, flower beds, and yes, agricultural fields. They’re common throughout Colorado in both urban and rural areas.

Diet & Behavior: These ants feed heavily on honeydew produced by aphids, which they actually “farm” by protecting aphids from predators and moving them to fresh plants. They also feed on seeds, nectar, and sugary substances. With their strong mandibles, they can cut through plant roots and damage crops.

Colonies: Colonies are moderately sized with a single queen. They’re not as aggressive as field ants but will defend their nest when threatened.

Why They’re a Problem: Cornfield ants can damage crops (especially corn, hence the name) by feeding on seeds and creating root damage. They also attract other pests by farming aphids. In homes, they contaminate food and can cause structural damage by nesting in walls and insulation.

Pro Tip: If you see a lot of aphids on your garden plants accompanied by ants, you’re likely seeing the ant-aphid farming relationship in action. The ants are actually protecting the aphids so they can harvest the honeydew they produce.

Fire Ants (Solenopsis invicta)

Threat Level: 7/10*

Fire ants are becoming more common in Colorado as they adapt to colder climates—and they’re as dangerous as their reputation suggests.

Identification: Reddish-brown, medium-sized (1/8 to 1/4 inch or 3-6mm), with a distinctive two-node petiole. Workers come in multiple sizes within the same colony (polymorphic).

Where They’re Found: Originally from South America, fire ants build distinctive dome-shaped mounds (up to 18 inches tall) made of soil particles and small pebbles. They prefer sunny areas—lawns, pastures, fields, and along roadsides. Unlike other ant mounds which have a central entrance hole, fire ant mounds have no visible entrance.

Diet & Behavior: Fire ants are predators and scavengers, feeding on plants, seeds, and other insects. They’re extremely aggressive and will attack in large numbers if their mound is disturbed. Their sting is what earns them their name—they bite to anchor themselves, then sting repeatedly while pivoting in a circle, creating a ring of painful welts.

Colonies: A single colony can contain 100,000-500,000 workers and multiple queens. Mature colonies produce winged reproductives in spring and early summer.

Why They’re a Problem: FIRE ANTS ARE DANGEROUS. Their venom contains alkaloids and proteins that cause intense burning pain, swelling, and pustules. Multiple stings can cause severe allergic reactions requiring medical attention. They pose serious risks to children, pets, and livestock. They also damage crops, electrical equipment, and can create soil erosion problems. A single fire ant colony can devastate local ecosystems by displacing native species.

Warning Signs:

• Dome-shaped mounds with no visible entrance
• Ants that boil out of the ground when the mound is disturbed
• Painful, burning stings that develop into pustules
• Presence of dead insects and small animals near mounds

Pro Tip: Fire ants are resilient and require ongoing control efforts. They can rebuild mounds within days of treatment. If you see fire ant activity, don’t attempt DIY control—their aggressive behavior makes them dangerous to approach without proper protective equipment.

Don’t let ants take over your home. Call OMNIS Pest Control at 720-583-4126 for a free inspection and let us put our expertise to work for you.

OMNIS Pest Control provides professional ant identification and elimination services throughout Castle Rock, Highlands Ranch, Parker, Castle Pines, and the greater Denver metro area. We use integrated pest management techniques and species-specific treatments to solve ant problems permanently.