Length: Workers are 6-13 mm. Queen is 25 mm or more
Colour: Reddish brown or black.
Other Features: Large mandibles, rounded thorax, single node, cone hairs on tip of abdomen. In their natural surroundings, Carpenter ants, the largest of our common ants, are beneficial insects. Their excavation of galleries in wood, together with meticulous finishing and cleaning of surfaces within wood, has earned them their name. Carpenter ants primarily take advantage of moist conditions in structural wood, wall voids, insulation, and hollows of doors etc., to construct their colonies. A colony will consist of different castes (i.e., larvae, pupa, minor and major workers, reproductives and a founding queen). A nest located in a structure can usually be found to be a satellite colony of a nearby colony located in an outdoor location. In buildings, they make their nests in moist area or slightly humid places for example, between panelled doors, in wood cabinets near dishwashers, in damp locations behind baseboards, fireplaces, window frames, and may also nest in polystyrene insulation, fibreglass and other insulating materials which have not been treated to withstand attack. Carpenter ants will rarely do extensive damage to wood. They usually limit the size of the colony to the area of the damp wood but can do extensive structural damage. Both minor and major workers will travel 100 metres or more to forage for food. Only 10 per cent of the workers forage at one time. Most foraging occurs during the night. The life cycle will take approximately 66 days. Carpenter ants may be seen in infested buildings at any time of the year, searching for food at considerable distances from their nest. In some colonies, especially those located against an outside wall or other cool location, dormancy or a diapause period occurs for several weeks during the winter months. Activity of Carpenter ants in a structure in the middle of winter indicates a nest location near an interior wall or other location. Although they chew their way through wood, leaving frass particles resembling sawdust, they do not eat wood. Instead, they feed on a wide range of insects, plant materials and, occasionally, on household foodstuffs. All insect and material waste are ejected through the nest opening, so the nest itself is kept clean. This behaviour often reveals the nest site. Other ant species, such as the Acrobat ant, Thief ant and Little black ant, will also nest in decaying wood and produce frass.