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Carpenter Ants

(© Copyright 2011 Shawn Cole. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)

Common Name            Scientific Name
Carpenter Ants             Camponotus supp.

Carpenter ants DO NOT create mounds in the soil and your lawn.  Those ant  mounds are created by the species of Formica, which also contain a species of large black ants.  This article will focus on the species called Camponotus spp. commonly known as carpenter ants.

While most people have heard of termites, these insects are not common in northern Illinois, since they prefer the southern part of the U.S., where it is warm and moist and without the cold winters in the North.  Both termites and carpenter ants destroy wood in your homes.  Carpenter ants are easily distinguished from termites by the following characteristics:

Carpenter Ants
Workers usually black but can have red or yellow on a black body
Light brown

Size 1/4 " to 1/2" inch for workers - 3/4" inch for queens

Commonly seen in sunlight
Avoid light and rarely seen

Different size wings
Wings of equal length

Narrow waits
Thick waists

Elbowed antenna
Straight antenna

DO NOT eat wood
Eat wood

Honeydew, syrup, honey, sugar, jelly, grease and fat

May eat foam insulation

Excavate wood creating galleries and tunnels

Damaged wood is clean without sawdust or frass

Damaged wood has sandpaper appearance

Structural damage can occur in months

Nest indoors and outdoors

Behind bathroom tiles

Around tubs, sinks, showers and dishwashers

Under roofing, in attic beams, under floors

Hollow doors and wall voids

Stored clothing, sleeping bags, outdoor mulch, tree bark

Landscape timbers

Outdoor trees and logs

Wood posts and porch steps that touch the ground

Nest Building

Carpenter ants live in decayed, damp wood with a moisture content greater than 15% but they do not eat the wood.  Instead they carve out living spaces  called "galleries".  These ants receive their name "carpenter" ants because of their skill at constructing their homes inside the wood in your home and in outdoor wood.

Carpenter ants live in damp climates where the wood is damp and in any dark voids.  Homes built in wooden areas or having trees that contain carpenter ant infestations are especially vulnerable to having the ants invade the building structure.  The carpenter ants do not eat wood as do termites but will carve out nests inside the wood beams, doors, and building structure studs and beams to form nests.  These ants tunnel into the wood against the grain and then remove the sawdust to another location away from the wood tunnels.  This habit of removing the wood chips makes it more difficult to find their nests because all that is visible is a small 1/8 inch oval hole in the wood.  When there is a large  enough colony of ants tunneling, the sound can be heard when the house is quiet and you put a stethoscope (listening device) against the wood.  You will hear the chewing or a  rustling sound like crinkling cellophane inside the wood.

Since carpenter ants do not eat wood but only hollow out cavities for a nest, they can be located in tree stumps and the foam insulation on the outside of your rigid foam on the outside of your foundation.  If they can enter your home and build a nest, they can live in the walls, subfloors, or roofs of your buildings where they can cause extensive damage if not discovered.

Carpenter Ants Do Not Sting

Carpenter ants can't sting but they can inflict a painful bite with their powerful jaws.  They also spray formic acid into the wound that causes a burning sensation.

Foraging for Food

Carpenter ants that are living in a tree or under damp, decayed wood will travel up to 100 yards (300 feet) when foraging for food.  Carpenter ants will seek out sugary materials, and proteins (insects).  The source of the "sugar" for ants is often the sticky dripping that come from aphids and other insects that feed off your plants called "honeydew". 

Honeydew is a sugar-rich goo that is the main source of nutrition for carpenter ants.  Carpenter ants  will come into your home to seek out proteins that can be found near your stove, grease dripped on the counter and food dropped on the floor and blown under your refrigerator and appliances.  You may also see a lot of white pieces of their old silk cocoons from the pupa stage of ants that are no longer needed.    This substance may be mixed with pieces of insects that the ants did not eat and has discarded.

There is a common myth that carpenter ants "herd" aphids and keep them for food like people have herds of cattle.  This is not true.  The ants will find the aphids and collect the secreted honeydew and bring that food back to the nest or eat it there and regurgitate it in the nest to feed other ants and  pupae.  Carpenter ants eat other insects but generally do not harm the aphids.

Carpenter ants forage for food most often at night between the hours of 8:00 p.m. and 5:00 a.m., though they are also seen during the day in bright sunlight. 

Finding the Outdoor Nest

Finding the source of the outdoor nest is not complicated -- only time-consuming.  Ants travel along well defined "trails" that will allow the ants to find their way back to the main nest and allow ants to journey to find a source of previously discovered food location.  Carpenter ants also prefer to establish trails along liens that we provide for them such as garden hoses, edges of walls or boards laying on the ground  Carpenter ants do not lay down a "scent" trail as do other ants so it is quite common to see them walking around in a haphazard pattern when foraging for food.

How to Prevent Ants From Entering Buildings

Inside the building, ants travel along electric wires and pipes that run through the walls of the building.  The ants will enter your home through cracks and crevices in  the outside of the building and also climb along tree branches that hang over your building.  Homeowners can help prevent carpenter ants from invading their home:

Life Cycle of Carpenter Ants

In the early spring a solitary female flies and mates with the male.  The male's life ends shortly after mating.  The female searches out a location to form a new colony, where she is the queen.  She spends her life laying eggs to create worker ants.  Once the female finds a new location for a nest, she sheds her wings by chewing them off and burrows into the soil or some soft wood to create a small chamber for herself and the brood that will hatch from her eggs.

After a few years, this queen carpenter ant can produce a colony of up to 10,000 worker ants.  This colony can then split into other colonies called "satellite colonies" that are nearby.  All these ants work all summer long during the warm weather to bring in food to the colonies.  All these worker ants are females.  The queen stays in the original nest location producing more eggs.

These first workers hatch and start building the nest for the colony.  They open the chamber to the outside, collect food and tend the eggs, larvae and pupae.  They feed the queen who continues to lay more eggs.  The workers eat the food when they find the food and then the workers regurgitate the food to nourish the developing larvae and the queen back at the colony.

During the first year after the queen forms a new colony, there are about 10 to 20 small workers (called minors or minor workers) and some immature forms.  These ants are small because they are fed only from the food produced by the queen.  These workers take over the function for foraging for food and feeding the larvae and pupae and defending the nest.

After the colony starts to grow rapidly.   After about three (3) to six (6) years a colony is well established and contains 2,000 to 3,000 ants.  At this point there is usually a strain on the original colony for food and the queen produces some winged males and female reproductives in the late summer which spend the winter in the nest.  In spring or early summer, about 200 to 400 winged reproductives will warm, mate and find a new location for a new colony.

>From spring through early summer, large numbers of winged reproductives (male and female) emerge from these established colonies which breed with the winged reproductives from other colonies.  Mating occurs at night.  The males die after mating and the new queen breaks off her wings after selecting a new site for a colony and a new nest forms.

The Cast System of Carpenter Ants

Carpenter ants are social insects.  There are several "castes" or adult forms that perform different jobs in the colony.  The adult ants are females that are in two different sizes.  The larger ants forage for food and defend the nest.  The smaller adults are the workers which feed the immature ants (larvae).  Larvae are white, legless and maggot-looking.  They remain in the nest and develop into pupae which are tan and capsule-shaped.  Eventually these pupae hatch and emerge as adults.  Workers are produced at a slow rate and a colony of 200 to 300 workers is at least 3 to 4 years old.

Under optimum conditions, the eggs to adult development takes about two months -- three weeks for each egg, larval and pupal stages.  Cold weather may lengthen this period to as long as 10 months.  During the first year, the colony contains the queen and about 10 to 20 workers.  Then form a new colony as described above.  The original colony will continue to grow.  Mature black carpenter ant colonies contain 15,000 to 50,000 individuals, with large colonies having 100,000 ants. 

The original colony communicates with the satellite colonies throughout the life of the colonies.  It is possible to see carpenter ants from the satellite colony located inside a building moving back to the original colony and those ants in the original outdoor colony moving across the lawn into the satellite colony in a nearby building.    This is one way to find the outdoor colonies.  Trailing the ants back to the outdoor colony will help in the eradication of the outside colony.  Without removal of that outside colony, any indoor building will be re-infested.

Ants will generally be seen traveling between:
Life Cycle

Carpenter ant workers are polymorphic -- which means workers are different sizes.  The larger ants are called "major" workers and the smaller workers are referred to as "minor" workers.  The minor workers are not "baby" ants -- they just have different tasks in the colony and are each adults.   The complete metamorphosis (change) from egg to adult workers takes about 60 days.


The colony also has the queen

Satellite Colonies

After a while, during the drier periods of weather, these female workers will move the larvae and pupae out of the primary colony in the soil  or wood logs or trees and find their way into your building through cracks and crevices in the outer frame of the building.  They will crawl under your garage door, find cracks in hollow doors and wall voids spaces between the insulation and flooring in the crawl spaces.  These carpenter ants can  even bite their way through solid wood to enter the building and form nests. 

If they are tunneling their way through the 2x4 studs in your building, they may go undetected for years inside your building walls.  The sawdust from the tunnels simply  piles up inside the wall voids where you cannot see the sawdust until you do some sort of construction and remove the wall.  This damage can go on for years undetected and cause major damage to the structure of the building.

The female ants carry the older larvae, pupae into the new location in the satellite colonies where these ants hatch and grow.  After a period  of time, some of the eggs will form new winged reproductive males and  females    that are capable of mating and laying eggs themselves.  Once one satellite colony establishes itself, there s a huge probability that there are many satellite colonies inside the same building.

Satellite nests are composted of workers, pupae, and mature larvae.  The satellite nest  does not require moisture.  In many ways the satellite nests are far more destructive because it has most likely the one that has moved into a building and will carve out tunnels for nests in the building studs and beams.

How to Know if You Have a Carpenter Ant Problem Inside a Building
Carpenter Ants During the Different Seasons

Carpenter Ants During the Spring

Seeing carpenter ants in the home during the spring does not automatically mean the nest is in the house.  If you see carpenter ants within a week of the first warm days of spring, the ants could be coming from the outside nest and simply foraging for food or the next may be located inside the building as a satellite nest trying to get outside the building

Carpenter Ants During the Summer

When you first see carpenter ants during the summer in your building, these ants are probably simply foraging for food and their nest is on the outside of the building

Carpenter Ants During the Winter

When you see carpenter ants inside your building during the winter, it means that you have the nest within your building.  The only exception is if you have recently brought in firewood from outside and they were simply carried in with the firewood.