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Carpenter Ants


In Western Washington we have the good fortune of living with very few detrimental insect pests.

No recluse spiders or black widows, no highly destructive termites (yet), no scorpions or killer bees.  This dearth of pests gives many Washington homeowners  the impression that there is no need to regularly maintain against insect pests.

While it may be true that termites afflict very few homes here, virtually every home will be exposed to carpenter ants.

Carpenter ants occupy every continent and most islands on the planet with the exception of Antarctica.

We actually have at least four different species here, the most common of which is camponotus modoc.  Carpenter ants are the most common wood damaging insect pest of structures in Washington.

This ant is responsible for the swarms of large, winged, black ants seen every year around mother’s day.  With an overall size of almost an inch and a half these winged, would be queens can be unnerving and intimidating.  Unless they are emerging from your home, the winged reproductive form of the carpenter ant is generally incapable of infesting your home.

The smaller male carpenter ants all have wings and are the first to swarm in the spring.  If they survive they begin releasing pheromones, volatile chemicals that they use to signal their presence to females. 

Females are more hesitant to swarm and will wait for higher temperatures and the presence of sufficient levels of pheromones before making their departure.  As a result, the female swarms tend to be somewhat synchronized with separate colonies releasing hundreds of them simultaneously.

Fortunately for us, most of these ants end up being fish food or bird food and only a tiny percentage survive to establish viable colonies.
After the nuptial flight from her mother’s colony the female must mate and find a suitable place to establish a nest. This usually occurs in a rotting tree, stump, or log where moisture is present  and she can more easily avoid predators.  Her need for specific conditions limits her ability to start a successful colony in a home and it is generally believed homes are not suitable for starting a colony.

When a colony matures, at about ten years of age, the workers will begin establishing brood nests or satellite nests where conditions are drier.  These are the infestations typically found in homes. 

Carpenter ants do not consume wood but they excavate extensive nesting galleries that weaken and damage it.  The ant actually feeds on nectar from aphids and scale bugs and is incapable of consuming solids.

With a size closer to a quarter of an inch,  workers are often overlooked.  Homeowners often claim that they only see a few each spring but then, they “go away”. Even a few workers found inside a home can signal the presence of an infestation and should not be ignored.

What is actually happening is related to the availability of food.  Carpenter ants sleep through the winter when aphids and scale bugs are unavailable.  When they wake in the spring they occasionally wander indoors until they reestablish feeding trails outside.  Then you stop seeing them inside but they are not gone, they’ve just gone outside.  Any nest building activity continues unabated.

Brood nests are typically established in the Spring and Fall and can invade a home in just a few hours. They may consist of several hundred or several thousand insects depending on the size and maturity of the parent colony.

Workers will utilize joints between boards as ready-made nest sites or may simply move into insulation until a nest can be excavated.  They are evolved to nest in wood but will readily nest in polystyrene, cardboard, and compacted beauty bark.

Because brood nests have no queen of their own the workers must maintain contact with their parent colony for a supply of larvae and replacement workers.  This need to maintain contact is both a blessing and a curse.  Treatment can sever the contact with the parent colony driving the brood nest into decline for want of replacement workers.  However, even when treatment is successful, the parent colony remains to re-infest and the conditions that attracted the ants in the first place (dry sound wood) still remain.

This constant pressure from the ants and the short lifespans of today’s pesticides is why there is no effective “one time” treatment to permanently eliminate carpenter ants.

Our general pest maintenance program is designed around preventing carpenter ant infestations and to our credit, we have not had a home become infested while under maintenance in over 25 years of operation.

May 2006


For the past two weeks I've been inundated with inquires about the giant winged ants seen all over town and unless you are a long time resident of Washington you are probably wondering, What’s going on here?

What you are seeing is the reproductive form of the carpenter ant.  Every year, usually in early May around here, carpenter ant colonies release thousands of winged males that make there way into the woods.  If there is a freeze or foul weather many of them die but as temperatures rise and conditions improve they release pheromones that signal the females that it’s safe to swarm. At which point the winged females depart the colony en mass.

The females will seek out a mate and will promptly try to locate a suitable site to start a nest.  This is usually a damaged tree or stump or other wood that is in a state of decay.  She needs a moist area to start because once she sets up camp she will not leave the nest for food or water.  The good news about this need for moisture is that it is extremely unlikely she can survive in a structure unless it is in an advanced state of disrepair. 

In a typical year the swarm occurs around Mothers Day and extends over a period of about two  weeks.  In the normally mild temperatures a few females can be seen occasionally taking flight for short distances about three feet off the ground and many can be found walking around  looking for mates and nest sites.

This year several things coincided to cause a truly spectacular event.  In the days immediately following Mothers Day we were deluged with rain, inches of it, that soaked any exposed wood thoroughly making lots of potential areas for nesting.  Then, when it stopped raining, the winds tapered off and the temperature shot up to 80 degrees and more.  This appears to have had two effects.  One, the pheromones released by the males were able to accumulate in the warm air in fairly large amounts.  And two, the females got a significant energy boost from the heat and humidity.  The combination caused the females to make their nuptial flights almost simultaneously and allowed them to fly higher, farther and faster than usual.

With tens of thousands of these ants running around, virtually every home on the north beach will have a few find their way inside.  As previously noted, a home in good repair is not vulnerable to this ant starting her colony in it.  However, the presence of them is a clear sign of just how many homes are at risk to infestation.  While they may not infest buildings directly the colonies that produced them can. 


May 2005

Things I never thought I'd need to know.

In the 25 years that I have been in the pest control industry I've picked up some pretty strange information.

Fact is, if someone had told me in high school that I'd need to know any of this stuff I'd have thought they were crazy.

With spring fast upon us I thought I'd share some of the highlights about carpenter ants.  Maybe next time you're entertaining friends you can wow them with some of these.

Did you know that even though carpenter ants live in solid wood they can't eat it?  Sure enough!  Despite their size they can't swallow solids.  They are so highly specialized that they have to rely on aphids and other sap feeding insects for most of their food.  Most of their foraging time is spent stroking aphids and scale bugs for honeydew.

A carpenter ant queen can live in excess of 40 years.  After mating males die. (makes me glad I'm not an ant!)  A carpenter ant colony is considered mature when it can produce new queens and males called “reproductives”.  This takes from 6 to 10 years.  When a colony reaches maturity the workers will start setting up additional nest sites called satellite or brood nests.  Well established colonies can have 10 to 12 brood nests.

A carpenter ants life starts as an egg which quickly hatches into a larva.  From egg to adult takes about 60 days.  Larva have Velcro like fuzz on the outside of their bodies and workers literally hang them on the walls of the nest. (Time was I could have wished to do that with my own kids to keep them out of stuff.)  Larva are completely helpless.  They have no legs.  Workers feed them by depositing nectar in a depression in front of their mouths.  Larva weave cocoons just like caterpillars.  The mature ant can not open its own cocoon and must be delivered by the workers.

Like most ants the workers are all sterile females.  Carpenter ant workers come in different sizes ranging from just under 1/4 inch to almost 1/2 inch.  Unlike termites, there are no soldier ants in the colony.  The largest ants act as tank cars to transport nectar.

Carpenter ants have been found nesting in some really strange materials.  They have a strong preference for soft wood and seem especially fond of cedar.  I personally have found these ants nesting in cardboard boxes, fiberglass and  foam insulation, compressed beauty bark, and creosote treated railroad ties.

A mature colony can have in excess of  20,000 workers but only about 10% of the colony forages.  The rest tend the nest.  They do most of their foraging between 10 pm and 4 am.  They may travel over 100 yards to food or satellite nests and will mow grass and move pebbles to keep frequently used trails clear.

So there you have it.  Enough carpenter ant trivia to fascinate your friends for about 10 minutes.  Hard to believe it took me 25 years to be able to remember all this.  Now if I could just remember where I put my keys.


April 2004

It's spring again and after a winter of fasting and napping carpenter ants are waking up to go find some groceries. 

For the most part carpenter ants are beneficial insects.  Their nesting activities help to return damaged trees to the soil.  Through their feeding they help control insect populations in the forest and their foraging and excavation helps aerate the soil.  A mature colony can consist of over 70,000 insects divided between a parent nest and 6 to 12 satellite nests, and be spread over several acres.  Carpenter ants have been known to forage for distances up to 100 yards from their nest sites.

Normally, carpenter ants nest outside in standing and hollow trees, stumps, logs, landscape ties, even railroad ties treated with creosote.  However, they have been found nesting in such diverse materials as foam and Fiberglas insulation, and between layers of tar paper and shingles.

Most species of ant are smaller than 1/4 inch but, carpenter ant workers average between 1/4 inch to 3/8 inch in length.  With some members reaching 1/2 inch in length and reproductives up to 2 inches including their wings.  Their color is black or black with some brown in the middle segment.  Their most distinguishing characteristic is their size.

These ants are adapted to nesting in solid wood.  Unfortunately, they can not tell the difference between a fallen log and your home.  Their individual nest sites can often contain over 20,000 insects and their combined activities can greatly weaken the structure of a home in a relatively short period of time.

Carpenter ants will nest in virtually any home.  Some homes have built in conditions that are more favorable to infestation than others.  Improperly installed insulation, missing vapor barriers, inadequate ventilation and other conditions which other wise raise the humidity within the structure.

Some of the more common signs of infestation are often over looked.  Frequently only a handful of the insects will ever be found foraging inside the house.  In the spring scouts emerge from the colony to establish feeding sites.  Once these sites are established you will seldom see the insects indoors.  Because carpenter ants feed on insects most of their foraging activities go on outside of your home.  Wood does not provide a source of food for them.

They sometimes make a scratching sound in the nest site similar to a bowl of Rice Crispies.  Piles of excavated sawdust are sometimes found close to nest sites.  However, this sawdust is not always evident as the ants will often deposit it in adjacent wall voids or other areas not readily visible to inspection.

Foraging trails along decks or along the exterior of your home are also signs that nesting activities are likely within the structure.

During the months of May and June, reproductive males and females will swarm from nest sites to establish new colonies.  Finding these large winged ants coming from any part of your home is a sign of well established nest site and professional assistance should be sought.

Because most over the counter materials make surfaces repellent and have extremely short life spans, ants tend to avoid them until they break down.  Effective treatment requires specialized materials, application tools, and treatment techniques not available to then average home owner.

In order to reduce our dependence on chemical control, a thorough inspection should accompany any treatment to help identify what favorable conditions should be eliminated to make the structure less vulnerable to re-infestation.


Feb 2003

Carpenter ants are an annual right of spring.  After a long winters nap they are starting to move around and many homeowners are already discovering these invaders.

Carpenter ants only damage wood in the process of building a nest.  They feed mostly on aphids and scale bugs (milking them for honeydew) and those insects play a large role in explaining carpenter ant behavior.    Because insects like aphids feed on sap they are slaves to what plants do and plants are slaves to the seasons.  So, it goes something like this,  Plants move their sap into their roots for the winter, aphids cant get the sap so they lay eggs or go dormant, aphids aren't producing honeydew so the ants go dormant. 

That brings us around to spring.  The sap returns, the aphids start producing honeydew and the carpenter ants wake up.

Now in nature many insects have built in alarm clocks but when carpenter ants nest in a heated structure this can get thrown off kilter.  If you see carpenter ants in your home before May it is usually because there is a nest in the building.  These ants are often still half asleep wandering around looking for water and sweets.  If you do nothing at all you will stop seeing the ants indoors as they find sap feeding insects and establish feeding trails outdoors.  This doesn't mean they are gone, just foraging outside.  The colony will continue expanding in the building and if left untreated can do significant damage.
This time of year, aside from ants inside, you should be on the lookout for ants standing around on the foundation or decks.  They can often be detected at corners of the foundation.  Carpenter ants will avoid hiking over rough terrain and will trail along sidewalks, decks, landscape edging and garden hoses.  Utility lines coming to your home can also provide a pathway for them especially if they pass through tree branches.

If you find these ants this time of year (Jan thru April) it is too late for prevention.  Steps should be taken promptly to avoid damage.  Even though there are many products available over the counter for carpenter ant control, treatment for active infestations should be performed by trained, experienced people.  The most effective materials are not available to the general public and no one has figured out how to put experience in a can.