The pavement ant, Tetramorium caespitum (L.), is a ground-nesting ant. The workers make nests under rocks and logs. In urban areas, they make nests under sidewalks, driveways, and slabs of homes.
The workers are about 1/8″ long. Their bodies are brown. The legs and antennae are lighter than the body. Colonies of pavement ants can have 4,000 workers and multiple queens. The queens are slightly larger than the workers, but they look similar.
In large fire ant colonies, queens can produce as many as 1,500 eggs per day. The queens of pavement ant colonies produce many fewer eggs per day. Scientists suspect that one reason pavement ant queens produce a small number of eggs may be because pavement ant colonies have fewer workers to feed and care for the immature ants as they develop. Another reason might be that since there are fewer workers in the colony, the colony needs fewer replacements for the workers that die.
Researchers have found that the number of eggs that the queen produces is related to the number of larvae that are about to change into adult ants. They have also found that there is a relation between the amount of food the queen is given and the number of eggs she produces.
During the summer, winged ants appear in the pavement ant colonies. Scientists call them alates. These are male and female ants. Their job is to fly out of their nest and mate with alates from other colonies. Because they often fly out in a sudden rush, many people call the winged ants swarmers.
After the female alates have been inseminated, they burrow into the soil to start new colonies. Scientists have found that if several inseminated females nest in the same burrow, they can start a new colony together. Research shows that their new colony has a better chance of surviving than a colony that was started by a single inseminated female alone.
As the colonies grow, they compete with neighboring pavement colonies. There are bitter struggles. Many times, the smaller colony is completely eliminated.
Pharaoh ants can be frustrating. They live in very large colonies – often hundreds of thousands of workers. There can be hundreds of queens in the colony. The colony is often spread out in several nest sites and the workers move between nests.
In warm weather, pharaoh ants can live outside of a home and forage indoors for food or water. When the weather changes or when the ants find a food supply that they like, they make a nest indoors.
Pharaoh ants have a nasty habit that many other ants do not. When the pharaoh ants sense danger, the queens scatter. A group of workers go with each queen. They carry eggs and immature ants with them as they go. Scientists call this behavior budding. When the pharaoh ants do this, they create many colonies. This multiplies the original problem.
Many people use repellants for ants and other insects. There are a number of things that people have used. Some people recommend things like powdered red chili, vinegar and water (apple cider vinegar 0.5 and 0.5 with water), cinnamon, and peppermint.
For pharaoh ants, repellants can work best if the whole colony is outdoors. The repellant can keep the ants outdoors and prevent them from coming inside. If the pharaoh ants are already inside, repellants might help keep them confined to one part of the building. Since they are so tiny, pharaoh ants can travel inside of walls along electric wires and pipes. They can often get around the repellant to get the food or water that they need.
If pharaoh ants encounter a strong substance, insecticide, cleaning product, or a natural repellant in the area where they have been active, they react by budding. Using a repellant where you have seen the ants can make them scatter and cause a worse problem.
Experts recommend combining techniques. Outside, eliminate their harborages. Rake mulch and dead leaves away from the foundation and make a 12″ bare zone. They will avoid nesting in this area.
Make sure exterior doors close tightly and replace missing weather-stripping. If the home has a brick exterior, try inserting small pieces of plastic screen into the weep holes. This will help keep the ants out but it will allow air to circulate.
If the pharaoh ants are inside, ant bait may be the best solution. Put it where the ants have been spotted. Make sure there is no strong scent on your hands when you handle the bait. If pharaoh ants have been active in several areas, it may be helpful to put bait in each area.
If the pharaoh ants accept the bait, they will swarm over it in great numbers. For a day or two, the ant problem may even appear to be getting worse! The workers will take the bait back to the nest and share it with the other ants. It is important that all of the ants get some of the bait.
The bait treatment can take several days to eliminate the whole colony. Do not disturb the bait while the ants are feeding, but make sure to keep the bait stations filled with fresh bait.
Controlling pharaoh ants requires some detective work and a lot of patience. For that reason, many people prefer to let a pest control professional deal with these pests.