This is a native species in western North America. While there are many other species of carpenter ants in North America this species is one of the most common in the West. Images for another common western species are also shown.
The usual habitat of a colony of carpenter ants is within wood, often wood buried or partially buried in the soil. They also commonly establish “satellite” colonies that may be in a structure, maintaining contact between the two colonies with the workers who travel to and from over well-defined trails. They are normally nocturnal. Generally there is a single queen in the colony but often supplementary queens as well. Colonies typically are around 15,000 workers when mature, but potentially could be over 100,000 workers. Foods are both carbohydrates and protein, with insects a major part of the diet. As they expand their colony they eject “frass”, which is wood chips and other debris such as leftover insect parts. This frass is often seen in structures before the ants are, as they are primarily nocturnal in habit. Carpenter ants are also typically polymorphic, with various sizes of workers in the colony.
Adults of C. modoc are large and black in color, but with reddish legs and sometimes with a reddish caste to the thorax. Two characteristics that distinguish carpenter ants are the "ring" of short hairs around the anal opening and the evenly rounded profile to the top of the thorax, which then tends to drop off vertically down to the thin waist area. There also is only a single node and no stinger is present. Workers vary from 5.5 to 11 mm long and winged females may be much larger at 20 mm long.
Characteristicts Important to Control:
Finding and treating directly into the nest with a residual insecticide will result in effective kill of the ants there, and a dust insecticide may be most effective. Satellite colonies in structures may be treated directly, or with applications into voids the ants travel through. Bait products seem to be accepted readily as well. Reduction of excessive moisture in the structure and removal of unnecessary wood materials outdoors will reduce the attraction of an area.