Some of us might be relieved to find dead ants in our home -- it seems much better than live ants, right? Sorry to disappoint, but the presence of dead ants means there is indeed a problem with live ants. Worse, these live ants have built a nest inside the home. Many ants are nocturnal, so they could be prowling around your home without your knowledge.
Ants have a strong sense of smell that they use to find food, alert each other to dangers and identify members of their colony. When an ant dies, it releases an odour that signals the other colony members to remove it. Removing the body keeps the nest clean and free of disease. The dead ants are usually very close to the nest, which means it's likely somewhere inside your home. Ants nesting outside won't carry the dead inside to get rid of them.
Identifying which ants have invaded your home can help you locate the nest and decide on an extermination method. Piles of dead ants are usually associated with carpenter ants. Carpenter ants are about 1/2 to 3/4 inch long and are either black, yellowish red, or black and red. If you notice sawdust -- known as frass -- near the dead ants, then the invaders are definitely carpenter ants. Since other ant species can also leave piles of their dead, you should take a few of the dead bodies to your local county extension office for identification.
Locating the Nest
Finding ant nests can be nearly impossible; luckily, you already have a clue. The nest should be near where you found the dead ants. Carpenter ants burrow in rotted wood and can usually be found in areas where water may have been a problem, like around doors and windows or in bathrooms. Once you find the nest, you should treat it with insecticidal dust. Look for dust that uses pyrethrins, cyfluthrin or deltamethrin. These are not always available commercially. A carbaryl dust called Apicide, made to control bees and wasps, will also work against ants, according to Barb Ogg, an extension educator with the University of Nebraska.
If you can't locate the nest, consider calling in a pest control expert. The technicians have access to insecticidal dusts that are effective against ants. Find one that will attempt to locate the colony, rather than using those that suggest monthly sprays or simply inject chemicals into the soil. Using ant bait is another option that works well on most ants, but it is rarely successful with carpenter ants. Spraying over-the-counter pesticides is largely a waste of time, no matter what type of ants you have. Spraying won't affect the colony, which is the only way to eliminate the problem.
If you can't locate the nest, your other option is to use ant baits. Baiting is not the most effective treatment for carpenter ants, because they have a varied diet and usually don't feed on the bait long enough to kill the colony. According to John Hopkins and Kelly Loftin, extension entomologists with the University of Arkansas, use bait that contains abamectin B1, fipronil, hydramethylnon or sodium tetraborate decahydrate and is labelled for indoor use against carpenter ants. Baits should be applied for at least three to four weeks to be effective. Switch baits if the ants seem uninterested in it or stop eating it.