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Pest of the Month - Carpenter Ants

Pest of the Month - Carpenter Ants, Nebraska Extension Acreage Insights for June 2018,
A typical carpenter ant is black and large but for definitive ID, look for the characteristics described in this diagram.

Getting acquainted with carpenter ants

We have had a rash of carpenter ants being brought in to the office by our clients. When people think of carpenter ants they typically think of a large, black ant. While it is true that major workers are around ½ inch long there are minor workers that are only ¼ inch long. We can also find carpenter ants in Nebraska that are not just black, one particular species is a mixture of both red and black. Just like those alternative uniforms the Cornhuskers wear every year!

If you have an ant that you want to definitively ID as a carpenter ant, use a microscope to see if the thorax is evenly rounded (like the top of a football helmet) and there is only one node between the thorax and abdomen. In the diagram above you can see the node, which looks like a thorn between the two body sections.  

But, there is much more to learn about these large and impressive ants!

1. Carpenter ants do not eat wood

While carpenter ants are considered wood destroying organisms, they do not actually ingest wood as food. This separates them from the termites, which do actually consume and digest wood, carpenter ants merely live in wood (sort of like us!). When a colony begins they hollow out portions of dead wood in trees or lumber in structures in order to have a home for their colony. Typically these ants need some assistance from water so they utilize wood that is damp from decay or a leak, making it easier to carve out. But, they can move into drier wood around them as the colony expands. As for their diet, carpenter ants actually eat sugary items like insect honeydew, syrup, and honey as well as protein based foods like live and dead insects.

Ant tunnels in wood

Figure 2: A log cut to show the tunnels the ants construct for their nest

2. Some carpenter ants have wings

Carpenter ant colonies produce new males and queens in order to have a mating flight to send out new colonies. These queens and males have wings so they can fly around and mate with one another. After mating the female queen will fly away and search for a new nesting site. When she lands and begins searching, her wings will fall off. When people see winged ants they often mistake them for swarming termites. You can look at the insect’s wings to determine if you are looking at an ant or a termite. Ants have four wings, two large top ones and two noticeably smaller ones on the bottom. Termites also have four wings but they are all of equal size.

Carpenter Ant Vs Termite

3. Carpenter ants have other symptoms of their presence

Aside from adult ants foraging or winged ants, there are other signs that indicate an active nest is nearby. This may include small piles of coarse sawdust or wood shavings (figure 4). Sound detection may be helpful in locating a nest. Active colonies make a dry, rustling sound that becomes louder if the colony is disturbed. This sound, thought to be a form of communication, is made with the mandibles (jaws) and is not related to wood chewing. When trying to detect carpenter ants, tap the suspected area and then press an ear to the surface in order to hear any sound. Pest management professionals may use a stethoscope to locate a nest. They may also use a moisture meter to find areas prone to carpenter ants. Once the nest is located, management of the ants can begin.

Wood Shavings from Carpenter Ants

Figure 4: Wood shavings mixed with ant colony debris like dead ants and discarded food.

4. What should you do if you find carpenter ants?

Due to their nests being in hard to reach spots in attics, ceilings, and wall voids and their general disinterest in ant baits, it is usually best to hire a pest control professional to deal with carpenter ants. They will typically sound for the nest and then drill small (about 1/8 inch) holes and apply an insecticidal dust into the nest area. If a cline would prefer to attempt control on their own, let them know traditional ant baits may not work against carpenter ants. There are specific “carpenter ant baits” that can be purchased for use against these ants though. Control with baits can take between 7-10 days and they must not kill workers that are foraging near the baits. They need to take the bait back to the nest and feed it to one another for success to happen. If the damage from the ants is severe enough, it is advisable to remove and replace damaged wood.

Image of Jonathan Larson
Jonathan Larson
Extension Educator - Entomology

Jonathan Larson is the Nebraska Extension entomologist for Douglas and Sarpy counties. His main focus is lawn and landscape pests but he also helps with bed bugs, roaches, and any other home invader that has six or more legs. Jonathan has his Bachelor of Science in Entomology from Purdue University, and his Ph.D. in Entomology from the University of Kentucky.

Contact Jonathan at:
Douglas/Sarpy County Extension
8015 W Center Rd.
Omaha, NE 68124-3175
(402) 444-7804