

Carpenter ants are social insects that live in colonies made up of

several different forms called castes. Each caste has its own

specific function necessary for the success of the colony. They

develop through several stages: egg, larva, pupa and adult. Pupae

are legless, white and grub-like. The pupal stage follows larval

development and is completed inside cream-colored cocoons, often

mistakenly referred to as "ant eggs." The adult is the familiar

ant-like insect with 6 legs, 3 distinct body regions and prominent

elbowed antennae.



Carpenter ant adults



The carpenter ant is one of the largest ants common to the United

States. Adults vary in length from about 1/4 inch (6 mm) for a

minor worker, 1/2 inch (12 mm) for a major worker, and up to 3/4

inch (18 mm) for a queen. All have constricted waists, unlike

termites. Workers are not winged, but reproductives are. Carpenter

ant adults are predominantly black; however, some species show

brown, red or yellow on parts of the body and legs.



Carpenter ant development



Under optimum conditions, egg to adult development takes about two

months--three weeks each for egg, larval, and pupal stages.

However, colder weather may lengthen this period to as long as 10

months.



Development of a mature colony--The few workers to emerge from the

first brood pupae are small, but they energetically assume the

duties of the colony. They open the chamber to the outside, collect

food, excavate galleries to enlarge the nest and tend the eggs,

larvae and pupae of the second generation. Workers regurgitate food

to nourish the developing larvae. Fed in the same manner, the queen

has few, if any, duties except to lay eggs.



During the first year the colony contains the queen, 10 to 20 small

workers and various immature forms. If conditions are favorable,

the size of the colony increases rapidly in the next few years.



The colony is considered mature when winged reproductives are

formed. This occurs in three to six years when the colony contains

CARPENTER ANTS
2,000 to 3,000 individuals or more. It is unlikely that numbers
will increase thereafter, due to the constant drain of the many
swarmers produced each year.

Winged males and females may be produced any time, but usually
develop in late summer. After wintering in the nest, they swarm in
the spring or early summer. From 200 to 400 winged individuals are
produced each year in a mature colony.

Usually there is only one queen per nest, but colonies with two
queens have been reported.

Carpenter ant nests

From spring through early summer, large numbers of winged males and
females emerge from established colonies. Emergence is triggered by
environmental conditions and may occur over several days or weeks,
which allows for interbreeding of individuals from different
colonies. Mating occurs in flight, after which the males die and
the females begin searching for a nest site. The new queen breaks
off her wings just before or after selecting a nesting site.

Nest establishment--Carpenter ants burrow into wood, not to feed
but to make nests. Outdoors, the site selected for a new colony may
be a stump, log, fence post, telephone pole, or similar large piece
of wood. Wood that is moist or partially decayed is preferred,
although cracks and crevices are frequently used as are cavities
under the bark of stumps and logs. The dead, often hollow,
heartwood portion of living trees is sometimes used. Access is
gained through a knothole, axe scar, decayed spots, insect tunnel,
or similar defect.

Building timbers that are soft, moist (not wet), and decayed are
frequently selected as nesting sites. Occasionally, however, a new
queen establishes herself in existing cavities or void areas in
wood that is perfectly dry.

Characteristics of a nest--As a colony grows, so does its nest.
Workers are constantly cutting galleries in the wood to accommodate
the enlarging colony. These galleries are irregular but, in
general, are excavated with the grain and follow the softer
portions of the wood. Harder layers often remain as walls
separating the many tunnels. Openings are cut into these walls at
frequent intervals allowing movement from section to section.

Access to the outside may be through natural cracks in the wood.
Sometimes, however, the ants cut special openings, or "windows."

Occupied galleries are kept immaculate. Shredded wood fragments
from the excavations are carried from the nest and deposited
outside. Conical piles of these fragments sometimes build up
beneath the "windows" or other openings to the nest. The piles may
also contain Inedible portions of insects, bits of soil and sand,
empty coats and general debris. This "sawdust" is not always
evident, because ants may dispose of it in hollow portions of
trees, void areas in structures, or unused galleries in the nest.

Unlike termite tunnels, the walls of a carpenter ant nest are
smooth and clean, having a sandpapered appearance. Nests usually
begin in soft, decaying wood while subsequent excavations are
frequently made into sound, dry lumber.

What do carpenter ants eat?

Carpenter ants are omnivorous; their diets include a great variety
of both animal and plant foods. They don't eat and digest wood as
termites do. Honeydew from aphids, scale insects and other plant-
sucking insects provides much of their sweet food. The ants
congregate around groups of these insects and collect secreted
honeydew. Carpenter ants feed on other types of insects, but the
aphids usually are not harmed. Indeed, they are even protected in
some cases. This phenomenon has led to the popular conception that
ants collect and herd aphids much as humans herd cows.

Plant juices, fresh fruits and other sweets are also readily eaten
by carpenter ants. Most carpenter ants' animal food consists of
living or dead insects and other small invertebrates. Common sweets
and meats are attractive to carpenter ants. They readily eat syrup,
honey, jelly, sugar, fruit, and most kinds of meat, grease and fat.

Foraging workers collect all the food for the colony. Sometimes
this is carried back to the nest, but more often it is ingested
where it is found. Later it is regurgitated in the nest for use by
the queen, developing larvae and non-foraging workers.

Carpenter ant control

When carpenter ants are found in a structure, it means the colony
is either nesting within the building proper, or somewhere outside
and merely entering to forage for food.

The most important, sometimes the most difficult, part of carpenter
ant control is locating the nest or nests. When this can be done,
elimination is relatively easy. Sometimes more than one colony is
present in a structure, so a thorough inspection is important. The
inspection should not stop when one probable source is located, but
should include the total structure and grounds.

Inspection indoors--Carpenter ants are usually associated with a
high moisture condition. The optimum development of a colony occurs
in wood with a moisture content above the normal 12 to 15 percent.
This requires the wood to be wet by rain, leaks, condensation, or
high continuous relative humidity.

Typical locations include:

1. Wood affected by water seepage from plugged drain gutters,
poorly fitted or damaged siding, improper pitch of porch floors,
damaged flashing, wood shingle roofs (especially if asphalt roofing
has been applied over the shingles), between the roof and ceiling
of flat deck porches, hollow porch posts and columns or leaking
door and window frames.

2 . Wood in contact with soil, such as porch supports, siding and
stair risers.

3 . Wood in areas of poor ventilation or condensation such as
cellars, crawl spaces, attics or under porches.

4. Wood scraps in dirt-filled slab porches.

What to look for indoors:

1. Piles of wood debris ejected from the colony. Do not confuse
ordinary sawdust with carpenter ant debris. The latter has a
shredded quality, resembling the shavings found in pencil
sharpeners. Close examination of the debris reveals many parts of
dead insects.

2. "Windows" or small openings to the nest. These are not always
present, since the ants may use an existing crack.

3. Ant activity. Ants frequently forage in kitchens, pantries, and
other food storage areas. They may also be found in bathrooms
around sinks and tubs. Keep in mind, however, that even when a nest
is established in the structural timbers, very few ants are seen
inside the building. They are more active at night than during the
day, and workers usually forage for food outdoors.

4. Swarmers (sometimes found ensnared in spider webs in
out-of-the-way places).

5. Damaged timbers. The wood surfaces probably will not be
paper-thin, as is frequently the case with termite damage, so
detection is more difficult.

Inspection outdoors--Inspect the grounds. Carpenter ants may travel
as far as 100 yards from nest to food source. Workers do not lay
down scent trails, used by some other ants, so workers are found
scattered about. Look for:

1. Ants traveling between a nest and food sources. This could be
from a tree or stump to a structure, or from one tree to another.
Many times vines on buildings are used to gain access.

2. Tree with overhanging branches or vines in contact with roof or
other parts of a structure. Ants frequently travel over branches
into a building.

3. "Windows" or other openings to the nest. In living trees these
are usually in knotholes, scars, dead areas, crotch angles, or the
like.

4. Piles of shredded wood debris near posts, firewood, stumps,
logs, and trees. Check interiors of hollow trees if possible.

Control methods

Protecting structures from carpenter ants requires ensuring that
the desired nesting conditions are avoided and destruction of ants
in all colonies in and near the structure.

Prevention

Eliminate high moisture conditions to prevent future attacks and
also to prevent fungus infections. Ensure proper clearance between
structural wood and soil. Provide good ventilation under the house
and in the attic as well as drainage away from the house. Repair or
replace roof flashing and roof eaves, porch supports, and other
places that are exposed to moisture. Use pressure treated wood or
wood pretreated with pentachlorophenol. Remove stumps, logs and
wood debris near the house. Store firewood away from the house.
Keep exposed exterior wood in good condition with paint, caulking
and sealer as appropriate.

Chemical control

Remove or treat with insecticides any carpenter ant colonies found
within 100 feet of the house. Apply insecticides to the nest and
nest areas. Dusts are particularly effective for treating nest
galleries. They may be used in infested areas instead of, or in
conjunction with, sprays. Spraying or dusting an infested area with
residual insecticides, without locating and treating the nest,
usually does not give complete control. Many foraging workers will
contact the insecticide and die; however, some ants are active only
inside the galleries, and will survive this type of treatment.
Also, the queen and developing larvae would not be affected. The
fact that individual carpenter ants can live for well over six
months without feeding requires that the galleries of the nest be
treated.

Residual insecticides usually are preferred, but sometimes volatile
or contact insecticides may also be useful to flush out and kill
carpenter ants. Under favorable conditions, vapors can penetrate
inaccessible areas of the nest that cannot be treated directly,
thereby aiding in eradication of the colony. Such insecticides
should be injected or flushed directly into the galleries.

Many products are available under many trade names. The better ones
contain one or more of the following active ingredients, which are
listed on the label. Consult the label for specific directions and
rates for the following insecticides:

Bendiocarb, boric acid, carbaryl (Sevin), chlorpyrifos (Dursban),
diazinon, dichlorvos (DDVP)*, malathion, propoxor (Baygon),
pyrethrins**, resmethrin**. The come in several formulations,
including dusts, baits, and aerosols, for both indoor and outdoor
use.

*Ready-To-Use.

**Generally considered effective in flushing out as well as killing
carpenter ants. There are a few labels that have directions for
tank-mixing these materials with residual insecticides.

Dewey M. Caron
University of Delaware 
Cooperative Extension Entomologist
11/90

To the best of our knowledge, all recommendations in this are in
accordance with those on product labels. However, if there is
disagreement between recommendations in this bulletin and what is
stated on the label, always follow the label directions.

Commercial companies or products are mentioned in this publication
solely for the purpose of providing specific information. Mention
of a company or product does not constitute a guarantee or warranty
of products by the Agricultural Experiment Station or Delaware
Cooperative Extension or an endorsement over products of other
companies not mentioned.
.
