Terro liquid ant bait uses borax (sodium tetraborate) mixed into a sweet, syrupy liquid that attracts foraging ants. The ants carry the poisoned food back to their nest and share it with the queen, other workers, and larvae, gradually killing the entire colony rather than just the ants you can see. Individual ants die within 24 to 48 hours of consuming the bait, but full colony elimination can take anywhere from a few days to several weeks depending on colony size.
The Active Ingredient: Borax
The active ingredient in Terro is borax at a concentration of about 5.4%. That’s a deliberately low dose. Borax disrupts an ant’s stomach and can damage its nervous system, but at this concentration it works slowly enough that the ant doesn’t die on the spot. Instead, the ant survives long enough to make it back to the colony and pass the bait along. A faster-acting poison would kill foragers before they ever returned to the nest, which would only thin the visible trail without touching the colony.
The sugary liquid surrounding the borax is what draws ants in. Terro is formulated specifically for sweet-feeding species: odorous house ants, pavement ants, ghost ants, little black ants, and Argentine ants, among others. It’s not effective against fire ants, carpenter ants, pharaoh ants, or harvester ants, which have different dietary preferences.
How the Bait Spreads Through the Colony
Ants are social feeders. A foraging worker’s job isn’t to eat for itself; it’s to collect food and bring it back to the nest. Once there, the forager shares the liquid with nestmates through a process called trophallaxis, which is essentially mouth-to-mouth regurgitation. Workers feed other workers, the queen, and the larvae this way. It’s the primary method of food distribution in nearly all major ant families.
This sharing behavior is what makes liquid bait so effective. The borax doesn’t just reach the ants walking across your kitchen counter. It moves through the colony’s own food supply chain. Research on ant baiting has shown that toxicants stored in an ant’s infrabuccal pocket (a small pouch near the mouth) come into contact with glandular secretions, which release the active ingredient during trophallaxis. The poison then spreads rapidly among workers without even needing to be digested by larvae first. In practical terms, a single forager can set off a chain reaction that delivers borax deep into the nest.
Why You’ll See More Ants at First
One of the most common surprises with Terro is that ant activity gets worse before it gets better. When a forager finds the bait station, it lays down a chemical trail back to the nest, recruiting dozens or even hundreds of additional workers to come collect the food. Your kitchen counter may suddenly look like it’s hosting an ant highway.
This is actually the product working as intended. Every ant feeding at the station is one more carrier bringing borax back to the colony. Resist the urge to spray the trail or move the bait. You may continue to see heavy ant traffic for a week or more after placing the stations. The visible surge means the colony is actively consuming the poison.
Timeline for Colony Elimination
Each ant that feeds on the bait dies within 24 to 48 hours. But killing the colony is a different timeline. Small colonies with a few hundred workers might collapse in a matter of days. Larger colonies, or those with multiple queens, can take several weeks to fully eliminate. The queen is the key target. She never leaves the nest, so she relies entirely on workers to feed her. Once enough borax reaches her through trophallaxis and she dies, the colony can no longer produce new workers and collapses.
If you’re still seeing significant ant activity after two to three weeks, the colony may be larger than expected, or there may be multiple colonies foraging in the same area. Replacing dried-out bait stations with fresh ones keeps the supply consistent. The liquid tends to dry out or get consumed within a few days, especially in warm weather.
Which Ants It Works On
Terro targets ants that prefer sugary food sources. The most common species it handles effectively include:
- Odorous house ants, the small dark ants that smell like rotten coconut when crushed
- Argentine ants, which form massive supercolonies and long foraging trails
- Pavement ants, typically found nesting in cracks in driveways and sidewalks
- Little black ants and ghost ants, both common indoor invaders
Species that prefer protein or grease-based diets won’t be attracted to the sweet bait. Carpenter ants, which nest inside wood and cause structural damage, generally require different treatment approaches. If you’re unsure what species you’re dealing with, the size, color, and trail behavior of the ants can help narrow it down.
Safety Around Pets and Children
Borax is a naturally occurring mineral, but “natural” doesn’t mean harmless in large amounts. The concentration in Terro bait stations is low (5.4%), and the total volume of liquid per station is small. A child or pet licking a single bait station is unlikely to consume a dangerous dose. For context, the minimum lethal dose of boric acid in humans is estimated at 3 to 6 grams for children and under 5 grams for infants, far more than what’s in one station.
That said, ingestion of larger amounts can cause nausea, vomiting, and abdominal pain, sometimes with a distinctive blue-green coloration. In animals, significant ingestion can lead to tremors, coordination problems, and more serious symptoms. The enclosed bait stations are designed to limit access compared to the open liquid drops, so if you have curious toddlers or pets, the station format offers a practical layer of protection. Placing stations behind appliances or inside cabinets where ants travel but children and pets don’t reach is the simplest precaution.
Getting the Most Out of Bait Stations
Place stations directly on or near active ant trails rather than in random spots around the house. Ants follow pheromone paths, and putting bait in their existing route means faster discovery. Avoid using sprays or cleaning products near the bait, since these disrupt the scent trails ants rely on to find and recruit others to the station.
Multiple stations work better than one, especially if ants are entering from several points. Keep the bait fresh. Once the liquid dries out or is fully consumed, replace it. Consistency matters because a large colony needs sustained exposure to borax over days or weeks before enough of the population, including the queen, has been dosed. Removing competing food sources (crumbs, pet food, sticky residue on counters) also pushes ants toward the bait as their primary food supply.