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Carpenter ant infestation photo guide:
This article describes carpenter ants and how to inspect a building for carpenter ant damage. We explain and illustrate how to identify carpenter ants - what carpenter ants look like, why and where they attack buildings, and how to cure a carpenter ant infestation using pesticides or other methods.
We describe and include photographs of building details that increase the risk of carpenter ant attack - which tells you where to look for ant damage as well as how to prevent carpenter ant infestations in buildings without reliance on pesticides.
We also describe how to distinguish carpenter ants from termites and how to tell a carpenter ant from other ants. We include many photo-examples of building damage caused by carpenter ants. And we provide citations to authoritative sources for more carpenter ant identification & control information.
Our photo at page top illustrates a closer to actual size view of carpenter ants found during demolition in an area where the evidence of carpenter ant activity and damage justified tearing some building surfaces apart. .
Carpenter Ants Guide: what they look like, how to find carpenter ant damage, how to get rid of carpenter ants, how to prevent carpenter ant infestations
Where to Look for Carpenter Ant Activity on buildings
Carpenter ants (Camponotus pennsylvanicus) attacking a wood structure, if not discovered and evicted (or treated), can cause substantial structural damage to the building.
The black carpenter ant (Camponotus pennsylvanicus) is the most common carpenter ant member of the species found in wood structures in North America, though there are about 1000 members of the group.
[Click to enlarge any image]
Both black and red carpenter ants are found further north including some areas of Quebec.
Carpenter ants may be winged (shown enlarged to about 5 x life size in our photo at left) if the colony is swarming, but more often you'll find them wingless (see our next carpenter ant picture just below).
Here are the principal approaches to inspecting a building for carpenter ant activity & damage:
Look for frequent appearance of carpenter ants themselves on the building exterior or interior; in spring in some climates it's common to find one or two ants exploring indoors; but if you keep seeing ants in a particular building or location it's time to watch them more closely for frequency, population level, and directions of travel.
Look for past or current building leaks. Because carpenter ants prefer to tunnel (for carpenter ant nest building purposes) in damp rather than dry wood, building leaks are a common trigger for ant infestation.
Look for wood close to or in contact with the ground. Wood less than 8-inches from soil is an invitation to carpenter ant (or termite) infestation.
Look for a combination of wood close to ground combined with water (from roof spillage, surface runoff, plumbing leaks, or any other source. The combination of wood close to ground and wet conditions is a red letter invitation to carpenter ants.
Look for a combination of wood close to ground, water or wet conditions, and a difficult-to-access or inaccessible area (such as a very tight crawl space) - these conditions are a platinum invitation to carpenter ants to attack the building.
Look for carpenter ant frass or sawdust in areas of recent or current ant activity, typically below and/or around exit holes.
Our photo at below left provides an example of discovering carpenter ant frass right in the living area - in this case our client points out this "sawdust" on a window sill. At below right our second photo shows a significant amount of carpenter ant frass at a wood framing juncture. You might find carpenter ant frass on the floor below an area of damage like this before you look "up" to see the actual area of activity.
Look for signs of structural damage such as sagging, bending, bowing of wood framed floors, walls, ceilings, roofs. Our carpenter ant damage photo shown at below left illustrates mature but still active carpenter ant nesting. This structural member is practically hollow - the carpenter ants like to leave the more dense latewood or winter wood when cutting their galleys.
The extensive structural damage to the wood floor in the building shown at below-right occurred in a wood framed structure over an inaccessible crawl space. Wood framing was at ground level, in ground contact, and wet from roof leaks as well as surface runoff. We demolished the original structure, rebuilt the floor and sills using pressure-treated wood, we raised the foundation height to above ground level, and we corrected the water and leak problems.
Don't restrict your carpenter ant inspection to ground level. Overhanging tree branches provide an easy path onto a building roof.
Leaks into a wood framed roof structure (often around a chimney) are an inviting condition for carpenter ants - they don't have to go downstairs to get a drink.
Our photo at left illustrates just how subtle a leak can be in a flat or low slope roofed structure.
That small area of ponding combined with improper type of drip edge (Gravel stop on an EPDM roof) directed water into the roof structure. That was enough invitation to start a carpenter ant colony. Details of what we found are below at Exploring Building Framing for Carpenter Ant Damage
Common roof leak areas such as around chimney flashing and at leaky eaves (or at areas of ice damming) are common sites for carpenter ant infestation.
Our sketches show the difference in appearance between a winged termite (swarming) and a winged carpenter ant. [Click to enlarge any image]
Look for dead carpenter ant bodies in an area where you have applied an ant spray or pesticide. The carpenter ant colony will toss out their dead members.
Look for live carpenter ants in number and carpenter ants that are swarming (and winged) carpenter ants in the spring. When an ant colony has grown large enough it may send out a new branch - you may see hundreds of carpenter ants milling about, including winged ants.
Pest control experts sometimes use a chemical spray that when injected into a building cavity will cause the ants to come streaming out - as a means of finding the carpenter ant nest. It's very exciting.
Look for live carpenter ants at nearby sources of food and water. Carpenter ants don't eat the wood they are tearing into, so you can count on local food and water to attract carpenter ants out of their wooden galleys.
Our photo illustrates how easy it is to entice carpenter ants into the open if they are already nearby.
We left these apple cores on a kitchen cutting board in early spring - a time of peak carpenter ant exploring activity.
In less than an hour our local carpenter ants had found and were enjoying fresh apple juice.
Signs of Carpenter Ant Activity: Exploring Building Framing for Carpenter Ant Damage
Here is a photo of carpenter ant frass or "sawdust" beneath an area of carpenter ant infestation in a building.
Unlike wood destroying termites, carpenter ants aren't "eating" the wood but rather tunneling through wood members to make space for their colony. As a result, where there is fresh, current carpenter ant activity you will often find fresh, light colored sawdust (carpenter ant frass) below or at the area of entry or exit of the ant infestation.
Notice a second relevant clue to carpenter ant attack: the water stain on the plywood wall sheathing at the upper right corner of the photo. This stain and carpenter ant frass were found beneath a flat roof over a garage.
Without opening this wall and removing the insulation one would not be likely to see this carpenter ant colony nor any damage the ants are making to the structure until conditions were much more severe.
Below we illustrate further investigation of the carpenter ant attack whose clues were just above. At below left you can see much more compelling evidence of carpenter ant activity on the sill plate atop the same wall - a place no one might have looked without the first clue.
At below right you can see our disclosure of active carpenter ant activity and a sawdust trail (carpenter ant frass trail) that was located between the plywood roof deck and the wall top framing.
Signs of Carpenter Ant Activity: Exploring for Carpenter Ants at an Interior Wall at Floor Baseboard Trim
Our carpenter ant activity photos below illustrate the results of deciding to investigate further for ant activity and damage at the ground floor of a slab-on grade structure. After observing frequent carpenter ant traffic on the floor in this area we watched the ants to see where they seemed to be most busy (coming and going) at the wall bottom.
That led to a spot between two sliding exterior doors and an area where there had been some leakage into the wall cavity. Pulling off a small section of floor baseboard trim (below left) we found the main entry/exit point for our carpenter ants (below right).
Probing into the wood post bottom in this location did not discover significant damage. We decided to address this carpenter ant problem by two simple DIY steps:
We used a simple carpenter ant killing spray on the exposed surfaces inside and outside this immediate area combined with
We repaired the exterior leak that was sending water into the wall at this post bottom.
Examples of Ants that are Not Carpenter Ants & that do not attack wood structures
Here we illustrate ant activity that is not carpenter ants.
These little ants appeared within a few hours of our leaving a dead insect on a brick walkway. These ants are not carpenter ants and are of no risk to the structure itself.
In addition to noticing where we found them (not attacking wood) one can observe that they are about 1/3 the size of a carpenter ant (shown at page top).
Below our photo at left illustrates a large area free of grass and other plant growth - a large red ant colony typical of what one might find in the Southwestern U.S. or in Mexico. These ants do not attack wood structures. At below right is a closeup of these ants.
Watch out: these biting red ants are capable of a painful bite injecting a good dose of formic acid. If you are hiking in an are where these ant colonies are found, don't stand idly around atop the ant colony or you'll find yourself invaded and attacked.
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 Jeffrey Hahn, Colleen Cannon, and Mark Ascerno, "Carpenter Ants", University of Minnesota Extension, retrieved 9/19/2012, original source: http://www.extension.umn.edu/distribution/housingandclothing/dk1015.html, copy on file as [Carpenter_Ants_UMinn.pdf]
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Carpenter ants, retrieved 9/21/12, original source http://en.wikipedia.org/wiki/Carpenter_ant
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