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Q: carpenter ants (insect) ( Answered 4 out of 5 stars,   0 Comments )
Subject: carpenter ants (insect)
Category: Miscellaneous
Asked by: howard1234-ga
List Price: $10.00
Posted: 22 Jul 2003 19:36 PDT
Expires: 21 Aug 2003 19:36 PDT
Question ID: 234033
identifying carpenter ants vs other ants  type of damage to home
(stick constructon)  effective treatment  and is this treatment fairly
Subject: Re: carpenter ants (insect)
Answered By: tehuti-ga on 23 Jul 2003 04:32 PDT
Rated:4 out of 5 stars
Hello howard1234,


The University of California Statewise Integrated Pest Management
Program has produced  a very useful key, which you can use to identify
common ant species, including carpenter ants.

To access the key from the start, go to:
and select “Begin Key”

The site gives some quick tips on identification as well, which can be
accessed from the same page.  One of the most important identifiers is
whether the ant has 1 or 2 petiole nodes.  Petiole nodes are the
segments on the first part of the abdomen (the narrowest part).  There
is a detailed picture at:
You can also see a close up picture of a carpenter ant at:
The comment is made: “When identifying carpenter ants, be sure to look
for the smooth, evenly rounded thorax and the 1 petiole node.”

The key should help you to identify whether carpenter ants are indeed
your problem.  However, here is a general description as well:
Carpenter ants are usually black, but the color can vary and can
include some red or brown.  However, the main feature is that they are
unusually large for ants, being between  and  inch long.  The winged
forms are sometimes mistaken for termites, but can be distinguished
from them because of their smaller waist, elbowed rather than straight
antennae, and by the fact that their second pair of wings is smaller,
while the termite has two pairs of the same size,
There is a drawing of these differences at the University of Kentucky
Entomology Department web site: 

Some more helpful drawings to help you distinguish between carpenter
ants and other species are presented on the University of Minnesota
web site:

Carpenter ants make their nests in galleries they bore out of wood. 
The nest can be inside or outside the house.  The University of
Virginia web site says:
“Carpenter ants are active indoors during many months of the year,
usually during the spring and summer. When ants are active in the
house during late winter/early spring (February/March), the
infestation (nest) is probably within the household. When carpenter
ants are first seen in the spring and summer (May/June), then the nest
is likely outdoors and the ants are simply coming in for food. The
natural food of the ants consists of honeydew from aphids, other
insects, and plant juices, but they will readily forage for water and
food scraps within the house.”

The University of California web site lists some of the most obvious
“ Main colony often outside on tree stumps, dead tree, firewood pile,
or fence post.  Consist of extensive networks of galleries usually
begun in areas of wood, soft from decay.  May contain several thousand
individuals; indoor nests may be satellite colonies of a larger nest
outdoors.  Up to 20 satellite colonies can be associated with main
colony that contains the queen(s).  Indoor colonies always associated
with moisture and may occur in hollow doors, window or door frames, or
the subfloor.” 

And the University of Kentucky web site adds:
“Wood which has been damaged by carpenter ants contains no mud-like
material, as is the case with termites. Shredded fragments of wood,
similar in appearance to coarse sawdust, are ejected from the
galleries through preexisting cracks or slits made by the ants. When
such accumulations are found (typically containing dead ants and bits
of insects which the carpenter ants have eaten), it's a good
indication that a carpenter ant nest is nearby.”
“Wood which has been damaged by carpenter ants contains no mud-like
material, as is the case with termites. Shredded fragments of wood,
similar in appearance to coarse sawdust, are ejected from the
galleries through preexisting cracks or slits made by the ants. When
such accumulations are found (typically containing dead ants and bits
of insects which the carpenter ants have eaten), it's a good
indication that a carpenter ant nest is nearby.”


It is the fact that the ants bore holes into wood to make their nests
that accounts for the damage they cause.  The three university web
sites cited above agree that the damage can sometimes be serious, but
often is not.  Obviously, it will depend on what wooden structures
have been colonized by the ants in the house and how important these
structures are.  Carpenter ants cause less damage than termites,
because unlike termites they do not actually use wood as a source of
food.  Also, the damage they cause will take a number of years to
build up to being a problem.  Another factor that determines the
amount of damage is the number of nests that are present, because it
is only the construction of the nest galleries that causes the damage.
 The ants first establish a parent nest, but can go on to establish
satellite nests in the vicinity once their numbers have increased.

Carpenter ants are not considered to cause damage to trees.  The nests
they make in trees take advantage of damage from other causes which
has made the wood soften.


The key to management of a carpenter ant problem is to find and
destroy the nest(s).  This can involve some detective work and patient

The University of Kentucky makes  the following suggestions, based on
the fact that the ants follow scent trails between satellite colonies
and the parent nest, and also make scent trails to lead their
colleagues to sources of food:
“When carpenter ants are observed, don't spray them; instead, feed the
ants small dabs of diluted honey placed onto the back (nonsticky side)
of pieces of masking tape. The best time to do this is late at night
since this is when carpenter ants are most active. After the ants have
fed on the honey, follow them on their journey back to their nest. Be
patient-- eventually the ants will disappear behind a baseboard,
cabinet, or into some other concealed location such as the hollow
space (void) within a wall, door casing, or porch column.”
The University of California suggests enticing the ants out with some
milk and sugar or chopped up crickets (!!!) and then following them
back to their nests.
And the University of Minnesota adds: “During spring, carpenter ants
are particularly attracted to protein sources, such as tuna packed in
water. (Carpenter ants are not attracted to tuna packed in oil.) Set
out small pieces of tuna for the ants to take back to their nest. It
is easier to follow the ants when they are carrying food.”

Once you have found the nest(s), there are a number of things that can
be done.

The University of Minnesota takes the view that much of the work
should be left to professionals, especially when the nests are
“It is usually necessary for a professional pest control applicator to
drill small (about 1/8 inch) holes and apply an insecticidal dust into
the nest area. It is best to determine the nest’s location as
specifically as possible. Control should not be applied randomly
through the home. There are no insecticides available to the public
that are labeled for this type of application.”

Kentucky provides some points  to consider if you do call in
“Pest control companies approach carpenter ant problems differently.
Some attempt to locate the nest and selectively treat only in specific
areas. Other companies take more of a "shot-gun" approach, drilling
and dusting as many potential wall voids and nesting sites as
possible. Most companies also apply a perimeter spray treatment around
the outside foundation of the home in an effort to temporarily prevent
reinvasion. The approach which should not be used is simply to spray
each month where carpenter ants are seen. If no effort is made to
locate the nest(s) or probable nest areas, the problem will most
likely continue.  Typically, there will be wide differences in price
depending on the company and amount of effort expended. Since
carpenter ant problems are not always solved on the first attempt, the
type of guarantee and reputation of the company should be factored
into the purchasing decision.”

If the nest cannot be traced, then an alternative strategy suggested
at Minnesota, which is effective but takes longer, is to apply an
insecticidal dust into wall voids through electrical outlets, taking
the appropriate precautions to avoid electric shock.  This takes
advantage of the fact that the ants like to use electric wiring as a
pathway, and so will come across the dust.  Boric acid powder, which
is readily available, can be used for this purpose.

Kentucky suggests that boric acid powder can also be used to treat
concealed nests:
“Treat wall voids and other hidden spaces where ants are entering by
carefully drilling a series of small (1/8 inch) holes and puffing
boric acid (available at most hardware stores) into the suspected nest
areas. The boric acid powder will disperse in the hidden void and
contact and kill the ants. If you suspect the nest is in a wall, drill
and treat at least 3-6 feet on either side of where ants are entering
so as to maximize the chances of contacting the nest. Carpenter ants
prefer to travel along wires, pipes and edges. If you suspect the nest
location is in a wall, also treat behind pipe collars and behind --not
in-- the junction box for electrical switch plates/receptacles. NEVER

California says that dessicant dusts can also be useful:
“Desiccant dusts are inert dusts combined with absorptive powders
(diatomaceous earth or silica gel) that destroy insects by absorbing
their protective outer body cover, causing them to dry out, or
desiccate. Of the desiccant dusts, diatomaceous earth is readily
available in retail stores, but silica gel may only be applied by a
licensed pesticide applicator. Desiccant dusts are low in toxicity to
people and do not lose their effectiveness over time, as long as they
do not get wet. Avoid inhaling these materials, however, because they
can cause serious lung irritation.”

If an outdoor nest has been found, Kentucky suggests:
“spraying or drenching the nest with an insecticide such as carbaryl
(Sevin), diazinon, or chlorpyrifos (Dursban). If outdoor nests are
suspected, the homeowner should also inspect around the foundation of
the building at night with a flashlight, especially around doors, weep
holes and openings such as where utility pipes and wires enter the
and Minnesota adds:
“If the nest is exposed (e.g. due to remodeling or reroofing) you can
use a liquid or aerosol ready-to-use insecticide, such as bifenthrin,
cyfluthrin, deltamethrin, or permethrin. Spray the insecticide
directly into as much of the nest as possible. The more of the colony
that is exposed, the better your chance of destroying it. It is
necessary to anticipate a carpenter ant colony and have a product
ready at the start of construction. Once the nest is exposed, that
portion of the colony will try to relocate to protect themselves.
Sprays on surfaces where ants travel or congregate, such as along
baseboards or in holes or cracks in the walls and floors, may reduce
the frequency and number of ants you see. However, they are not
effective in eliminating a nest because 1) the ants carry very little
insecticide back to their nests and 2) most ants forage outside and do
not come in contact with the insecticides.”

A further strategy, especially when the nest(s) cannot be found is to
use toxic bait.  According to the California site, at any time, not
more than 10% of the colony is out foraging.  Therefore, it is
important to use slow-acting formulations which can be taken back to
the nest to act on the ants and larvae there.  Boric acid baits
containing less than 1% boric acid and produced as a sweet liquid fit
this purpose. However, California suggests trying a number of
different baits that are listed as acting against ants and letting the
ants choose which one they prefer, because they are apparently fussy
Minnesota once again gives preference to calling in a professional
company to put down baits: “There are a few baits available to
nonprofessionals for carpenter ant control. Most retail products are
liquid or granular formulations containing hydramethylnon,
sulfluramid, abamectin, or boric acid. An inexpensive liquid bait of
1% boric acid in a 10% sugar water solution can be mixed at home, but
it is very slow acting and must be constantly replenished. Baits vary
a great deal in their effectiveness. Carpenter ants have complex food
preferences, and some of the sugar-based baits will not be attractive
to the ants long enough to be successful.”
and adds “Never apply insecticides on or around baits because this
will prevent feeding and render baits useless. Do not spray or dust
other areas of the home, especially where carpenter ants are seen, as
this can reduce the effectiveness of the bait. Be patient—baits can
take weeks or months to achieve control.”


The measures described above should eliminate carpenter ant colonies,
however, it is also important to try and prevent any recurrence of the
problem and achieve a permanent solution.  Here is a combined list of
suggestions from the 3 cited web sites:

The most important thing that can be done is to eliminate the damp
conditions that the ants prefer, especially dampness in wood.
Check for any leaks, or any other causes of damp and repair them. 
Keeping the house well-ventilated will also help to prevent damp.  If
you store any wood in a garage or near the house, keep it dry and
raised off the ground if possible to stop it becoming damp.  Firewood
is one of the main nesting areas for carpenter ants, so try to store
it as far away from the house as possible.
Replace any decayed or damaged wood, since this is what the ants like
to colonize,  and deal with any obvious causes of the damage, such as
clogged up gutters.

Remove other potential nesting areas around the house, by removing
tree and shrub stumps and roots.  Trim away any branches that overhang
the house.  If any tree branches touch any wires connected to the
house, make sure these are cut away as well, so that the ants can no
longer get from the branches to the wire and then travel along the
wire into the house.

Make sure that there is no mulch or soil piled up against exterior
wood structures of the house. Instead, place gravel around the house
to discourage the ants from approaching.

Make it as difficult as possible for the ants to enter the house by
sealing up any cracks, for example, where pipes come in through the
wall.  If any do get in, make the interior uninteresting for them, by
keeping all food shut away in ant-proof containers.

I hope that this information will help you in your ant problem. 
However, please do request further clarification if needed.

University of Minnesota
University of Kentucky 
University of California

Search strategy on Google: “carpenter ants”
howard1234-ga rated this answer:4 out of 5 stars
answer appears very thorough  hope treatment is effective  if we can locate nests

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