Sunday, March 20, 2011

Black Carpenter Ant

This very large ant is a queen carpenter ant (Camponotus pennsylvanicus) in the family formicidae. They are one of the most commonly seen ants in my area and possibly easiest to identify. They are listed as a pest species because of their habit of turning up where they are not wanted, such as our homes. Moisture is a huge attractant, they tunnel into moisture damaged wood and can cause structural damage to homes, and other buildings. To keep them away from these structures, make sure water drains  away from your home and buildings. Do not leave boards lying on the ground, as this draws moisture and may attract the ants. In the wild they are beneficial in breaking down rotting wood into organic matter that adds nutrients back into the soil. You will find them in decaying logs, and trees (where this queen was photographed). The workers come in many sizes, some can be quite large. While they do not sting, they can give a pretty good bite, then to make matters worse they may spray formic acid in the wound for good measure. These ants are fiercely territorial  and will defend their colony from other ants or other invaders. 

While they live in wood, they cannot digest the cellulose that is in wood. They chew into wood only to make their tunnels and excavate their home. These ants are omnivores and will eat most anything including animal matter, fruit and plant juices, dead insects, syrup, honey, sugar, fruit, grease, meat, and a wide variety of other substances. A favorite is the honeydew secreted by aphids and other tiny insects. They will forage up to 100 yards away from the colony.

In late spring winged individuals may make an appearance. These are young males and females called alates. They are leaving the colony to seek mates and to start a colony of their own. As soon as the females are mated the males all die and the females will chose a nesting site to begin her colony then her wings will drop off. She has been mated for life and her sole purpose is to lay eggs for the rest of her life. She will begin by laying 15 or so eggs, they will hatch in about 24 days, she will feed them a liquid diet that consists of  her own stored fat reserves and wing muscles. 

Once these larvae have matured they will take over the care of future offspring of the queen, as well as cleaning the nesting site and searching for food. They will also guard the colony, queen and their siblings. Later in the season "major" and "minor" workers are created, these will be highly variable in size and have different responsibilities in regard to the colony. Some are the foragers that gather food, and others remain in the colony to expand it and care for the offspring. If the colony is disturbed the ants will carry the larvae and pupae to safety. They must be tended to or they will perish. In about 5 years the colony may contain up to 3,000 individuals. In the fall alates will be created, but they will not swarm until the following spring, then the cycle will start all over again. In some cases workers may leave the colony taking larvae and pupae with them and create a "satellite" colony away from the original colony. This is one other way they divide and expand besides swarming. 

With the return of spring upon us it is very common to find these ants in our homes, especially in bathrooms and kitchens where they are looking for water as well as food. Typically they will be found at night as they are nocturnal by nature. How do we control them? Prevention goes a long way, as mentioned above, remove lumber, firewood or anything else that is stacked near your home to discourage them from showing up to begin with. Make sure you repair any damaged wood on your home, do not let wood window frames, siding, railings, porches and other features of your house decay to the point that it will attract these ants. Repair cracks in foundations to keep them from entering your house that way. Make sure you do not have leaky outdoor faucets or any other outdoor water source. If you already have an infestation, you can try bait traps. Insecticide sprays rarely work well anyway, as the ants may just move elsewhere inside your home, until the residue is gone from the spray then they return. Additionally sprays can be harmful to us to inhale as well as to pets, especially pet birds. Baits on the other hand seem to be more effective and much safer to use. Regardless of the method you may decide to use to control them, please read all labels and follow the directions carefully.


  1. We get lots of these here in SC. We also get a lot of Camponotus Americanus (which is even bigger then the black carpenter ant usually). Thanks for the interesting post.

    Hey and would you mind checking out my new insect blog? Also... my latest post on SC beetles.

  2. Hello Ryan, happy to have you visit and hope to see you around here again. I checked out your blog and you are off to a great start, I really like it. If there is ever anything I can do to help you with your blog please feel free to ask. I will add your blog to my blog list and hopefully this will encourage people to come visit.