INTRODUCTION
The black carpenter ant, Camponotus pennsylvanicus (DeGreer), is a native species
and the common species in the east. Camponotus modoc Wheeler is the common western
species. These ants get their common name from their habit of hollowing out galleries in
pieces of wood for nesting purposes. This nesting habit can result in structural damage.
Carpenter ants are found throughout the United States.
RECOGNITION
Workers polymorphic, large (1/8-1/2" or 3.5-13 mm) but vary greatly in size;
queens about 1/2-5/8" (13-17 mm) long. Color black, combinations of red and black, or
completely red or brown. Antenna 12-segmented, without a club. Thorax lacks spines,
profile evenly rounded on upper side. Pedicel 1-segmented. Gaster with anal opening round,
surrounded by circlet of hairs. Stinger absent. Workers capable of emitting a strong
formic acid odor.
Camponotus pannsylvanicus with workers about
1/4-1/2" (6-13 mm) long and completely black except top of gaster with long, pale
yellowish hairs pressed against its surface. Camponotus modoc with workers about
1/4-1/2" (5-11 mm) long, dull black with reddish logs and with golden hairs covering
abdomen. Queens up to 518+" (17+ mm) long. Other species black, various combinations
of red and black, or completely red or brown. Although carpenter ants do not sting, their
bites can be quite painful, especially when they inject formic acid into the wound.
SIMILAR GROUPS
- Dark field (Formica spp.), larger yellow (Acanthomyops interjectus),
and Allegheny mound (F. exsectoides) ants have profile of thorax not evenly rounded, with
distinct impressions); in addition dark field ants with front and hind margins of node
steeply or equally sloped.
- Velvety tree ants (Liometopum spp.) lack circular anal opening
surrounded by circlet of hairs.
- Other medium to large dark ants with 2-segmented pedicel.
DAMAGE
The only external indication of infestation other than the presence of workers
and/or swarmers is the appearance of small openings or windows on the surface of the wood.
Through these, the workers expel debris which consists of sawdust-like shavings and/or
fragments of insulation and insect body parts. The accumulation of such debris below such
holes is a good indication of an infestation. Inside, the galleries follow the softer
spring wood with numerous connections through the harder/dark summer wood. The gallery
walls are smooth, with a sand-papered appearance. The active galleries are kept clean of
debris. They prefer to attack wood softened by fungus and are often associated with
moisture problems.
BIOLOGY
Black carpenter ant colonies are of moderate size, usually containing over 3,000
workers (up to 10-15,000 including satellite nests) when maturity is reached in about 3 to
6 years. The typical western carpenter ant (C. modoc) mature colony contains about
10-20,000 workers, with large colonies having up to 100,000 workers. Developmental time
(egg to adult) for workers takes at least 60 days. Workers are polymorphic, with majors,
minors and intermediates present. There is usually only one functional, wingless queen per
colony. Swarmers are not produced until the colony is more than 2 years old, usually 3.5-4
years old for C. pennsylvanicus and often 6-10 years old for 0. modoc. Swarmers appear
from May until August in the east and from February through June in the west.
HABITS
Most carpenter ant species establish their first nest in decayed wood and later
expand or enlarge this into sound wood. Inside, nests are located in wood (preferably
softened by fungus rot), in insulation, and/or in wall voids. Workers are a nuisance when
out searching for food but are destructive to timbers utilized for nesting activities.
Outside, nests are typically located in rotting fence posts, stumps, old firewood, dead
portions of standing trees, and under stones or fallen logs. The presence of a carpenter
ant nest is sometimes indicated by a rustling sound coming from wall voids or from wood
where the colony is located. Otherwise, the emergence of swarmers indoors may be the first
indication of an indoor colony. Carpenter ants feed primarily on insect honeydew, plant
and fruit juices, insects, and other arthropods. Inside, they will also feed on sweets,
eggs, meats, cakes, and grease.
The workers forage for distances of up to 300 feet
(91.4m) from the nest. They typically enter buildings around door and window frames,
eaves, plumbing and utility lines, and shrub and tree branches in contact with the
building. Although some workers are active during the day, most activity is from dusk till
dawn, with peak activity between 10 pm and 2 am. The trail between the parent and
satellite nest is usually about 1/4- 13/16" (6-20 mm) wide and is kept clear of
vegetation and debris. It usually follows contours but typically will cut across lawns.
