Grease ants and sugar ants are named for the foods they prefer, and that single difference changes everything about how you identify and control them. “Grease ant” typically refers to the thief ant (Solenopsis molesta), a tiny species drawn to fats and proteins. “Sugar ant” is a catch-all term most often describing the odorous house ant (Tapinoma sessile), which targets sweets. Using the wrong bait on the wrong ant is the most common reason DIY ant control fails.
How to Tell Them Apart
Size is the fastest clue. Grease ants (thief ants) are the smallest household ants in the northern United States, with workers measuring roughly 1/20 of an inch, barely visible without close inspection. They’re yellow to light brown, with disproportionately small eyes relative to their heads and a distinctive habit of curling up when dead. Their antennae have 10 segments ending in a two-segment club, which helps distinguish them from pharaoh ants, a common lookalike.
Odorous house ants are noticeably larger, around 1/8 of an inch, and dark brown to black. The classic identification test: crush one and smell it. Odorous house ants release a rotten-coconut smell. Grease ants produce no notable odor. If you’re squinting to see the ant at all, it’s more likely a grease ant. If you can see it clearly and it’s dark-colored, you’re probably dealing with sugar ants.
What Each Species Eats
Grease ants gravitate toward oils, proteins, meats, and pet food. They get their nickname honestly: a greasy stovetop or an unwashed pan with cooking oil is a magnet. They also raid the nests of other ant species to steal larvae and pupae, which is where the formal name “thief ant” comes from. This protein preference holds year-round without significant seasonal shifts.
Sugar ants target sweets, syrup, honey, jelly, and anything with simple carbohydrates. They forage day and night along well-established trails, typically following structural edges like siding, deck boards, and door frames. You’ll often see them in long, visible lines heading toward a food source, while grease ants tend to appear in smaller, less organized clusters near greasy residues.
Where They Nest
Grease ants form relatively small colonies of a few hundred to several thousand workers, but they compensate with multiple queens per colony. They’re highly adaptive nesters. Outdoors, they settle under rocks, along walkways and foundations, in rotting wood, and in exposed soil. Their signature move is building tiny tunnels that connect to the nests of larger ant species, giving them easy access to steal food and brood. Indoors, they squeeze into any small crevice: woodwork, masonry, wall voids, under floors, and behind baseboards. They invade homes most aggressively during hot weather.
Odorous house ants prefer moist areas and build networks of interconnected nests that can house thousands of workers and many queens. Outside, they nest in mulch beds, beneath stones or wood, and under loose tree bark. Inside, they favor wall voids, attics, areas with damp wood or insulation, and spots near plumbing fixtures. When disturbed, they relocate fast. Colonies also expand through “budding,” where a queen leaves with a group of workers to establish a new nest elsewhere, which is why a single colony can seem to pop up in multiple locations around your home simultaneously.
Why Bait Type Matters
This is where the grease-versus-sugar distinction has real consequences. A liquid sweet bait placed near grease ants will go completely untouched. They simply aren’t interested. Likewise, a protein or oil-based bait won’t attract odorous house ants that are foraging for carbohydrates. Matching bait to the species is the single most important step in ant control.
For sugar ants, liquid borate baits in a sugar-water solution work well. Lower concentrations (0.5 to 1% active ingredient) are actually more effective than stronger formulations because foraging ants survive long enough to carry the bait back to the colony and share it. For grease ants, you need protein or oil-based bait products. Look for active ingredients like fipronil, hydramethylnon, boric acid, or avermectin on the label. These come as gels, solid bait stations, or tubes designed for cracks and crevices.
A few rules apply to both species. Place bait stations along trails and near entry points, spaced every 10 to 20 feet around your home’s foundation. Never spray insecticides while baiting, because sprays kill foragers before they can carry poison back to the nest. Avoid granular products containing cyfluthrin or permethrin, which look like baits but are actually fast-acting contact killers that eliminate individual ants without touching the colony. Similarly, baits with propoxur or indoxacarb kill too quickly to be carried back to the queen.
Keeping Both Species Out
Sanitation targets differ depending on which ant you’re dealing with. For grease ants, the priority is cleaning cooking oils and grease splatters. Wipe down stovetops after every meal, clean behind and under appliances weekly, and pick up pet food bowls between feedings. For sugar ants, focus on sticky residues, crumbs, and open sweeteners. Store dry goods in airtight containers and rinse dishes immediately rather than stacking them in the sink. For either species, keep trash cans sealed with tight-fitting lids and rinse recycling before binning it.
Physical exclusion is especially important for grease ants because of their minuscule size. They can slip through gaps that would stop larger species. Use silicone caulk to seal around pipes, baseboards, and window frames, starting at ground level. Install door sweeps on any exterior door where daylight is visible at the bottom, replace torn window screens, and confirm that weather stripping sits flush with no gaps.
Moisture control helps with both species but particularly discourages odorous house ants, which actively seek damp nesting sites. Check under sinks, around toilets, and near water heaters for slow drips or condensation. Run a dehumidifier in crawl spaces and basements. Move sprinkler heads away from your foundation so water doesn’t pool against the slab, and trim back plants and mulch that trap moisture against exterior walls.
To disrupt existing trails, mix equal parts white vinegar and water, spray along baseboards, countertops, and windowsills, then wipe toward the entry point. This breaks the chemical scent markers both species use to guide other foragers. Repeat daily until activity stops. A thin line of food-grade diatomaceous earth along baseboards, around pipe entry points, and under appliances acts as a physical barrier by damaging the ants’ exoskeletons on contact.