Carpenter ants get their name because they excavate wood in order to build their nests. Their excavation results in smooth tunnels inside the wood. Carpenter ants range in size from one-quarter inch for a worker ant to up to three-quarters inch for a queen.

Habits

Carpenter ants eat insects and they drink fluid given off by aphids (honey dew).  They are important for healthy forests because they help to recycle dead trees.  They cause problems for people because they damage our homes and other structures made of wood. 

They are not active in the winter.  At certain times of the year, the nests produce thousands of winged ants in a sudden swarm.  They are most active at night and don't seem to make thick "ant trails" like other ants. 

Biology

Carpenter ants are social insects, like honey bees.  They live together in a nest called a colony. 

They have different casts (or biological rolls they play).  Most of the ants in a colony are called workers.  Some of the big workers are specialized to defend the nest and they are sometimes called soldiers.  Smaller worker ants are often called minor workers. The Queen ant(s) are normally the largest ant in the nest.  This ant lays eggs that hatch. The ants with wings are called the reproductives.  The reproductives are virgin male and female ants that will try to form new colonies.

The most common carpenter ants in the Portland metro area build a main nest (called a parent colony) and satellite colonies.  The parent colony is usually located in a rotting stump, a stack of wood on the ground or some other place where wood is moist.  The queen (the ant that lays eggs) lives here because the newly laid eggs require a lot of moisture. 

After the eggs hatch and grow, the workers take the developing young into satellite colonies.  In nature, this would include a dead or living tree exposed to sunlight.  Sometimes, the ants will place the satellite colony in homes or other structures.  They seem to prefer the southern exposure of most buildings. 

Carpenter ants damage wood through their nest building. If they gain entry to a structure, they pose a property threat.