Carpenter ants are large (0.25 to 1 in (0.635 to 2.5 cm)) ant

Ant

Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...

s indigenous

Indigenous (ecology)

In biogeography, a species is defined as native to a given region or ecosystem if its presence in that region is the result of only natural processes, with no human intervention. Every natural organism has its own natural range of distribution in which it is regarded as native...

 to many parts of the world. They prefer dead, damp wood

Wood

Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

 in which to build nests. They do not eat it, however, unlike termite

Termite

Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...

s. Sometimes carpenter ants will hollow out sections of trees. The most likely species to be infesting a house in the United States is the black carpenter ant

Black carpenter ant

The black carpenter ant is a species of carpenter ant. It is the most common carpenter ant pest in the United States.-Appearance:...

 (Camponotus pennsylvanicus). However, there are over a thousand other species in the genus Camponotus.
All ants in this genus, and also some related genera, possess an obligate

Obligate

Obligate means "by necessity" and is used mainly in biology in phrases such as:* Obligate aerobe, an organism that cannot survive without oxygen* Obligate anaerobe, an organism that cannot survive in the presence of oxygen...

 bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

l endosymbiont called Blochmannia.