Identifying all types of carpenter ants can be difficult. Most people have a good understanding of what they think a carpenter ant looks like. Home owners can usually identify a major worker carpenter ant but miss all the others. Unnfortunately, most people cannot identify the various forms carpenter ants come in.
Let’s start with color. Here in Ohio, the most common type of carpenter ant is camponotus pennsylvanicus which is the big black ant we typically think of as a carpenter ant. While many carpenter ants are black, they can also be brown, tan, reddish, yellowish, or a mixture of the colors. So color is not definite, but black will help clue you in to find the most common type of carpenter ant in Ohio. Below are two different colored carpenter ants I found.
The other way people identify carpenter ants is through size. Carpenter ants are big, right? Many times yes, but not necessarily. There are four different types of carpenter ants, each with a different size and shape. The big black ant is a major worker. Major workers are responsible for protecting the nest and foraging for food. These ants can measure around ½ inch which is quite larger than other ants.
The minor workers are responsible for tending to the nest and the young. These ants can be as small as ¼ inch. Here is where many people go wrong. Minor carpenter ant workers at ¼ inch long are the same size as other species of ants. A field ant can look almost identical to a carpenter ant if not for one major identifying feature which I will get to in a minute. But first, let’s finish the two other types of carpenter ants.
Carpenter ants also produce winged male and female ants (they lose their wings after finding a place to start a colony). When the colony matures it sends out winged male and female ants to start a new colony. The winged males are about the same size as the major workers but with wings. The females, on the other hand, get quit big at around ¾ of an inch. The females also have a slightly larger and different shaped mesosoma (think thorax).
Male winged ant.
So how do can you be sure an ant is a carpenter ant just by looking at the? Here in northern Ohio a major worker is the biggest ant your likely to come across. To identify the minors you need to use two, or possibly three, identifying features.
First, all carpenter ants have a round thorax as can be seen below on the left. The field ant, which can be mistaken for a carpenter ant, has an indented thorax as can be seen below on the right. (photo courtesy of April Nobile available at www.antweb.org)
The next major identifying mark is a single petiole with a few hairs on top. The petiole is a node between the thorax and abdomen. Other ants can have none, one, or two. Carpenter ants always only have one petiole node. Below on the left is the location of the single petiole. The photo on the right is a microscopic view of a carpenter ant petiole I took from a specimen I found.
The third identifying feature is actually quite hard to see without magnification. At the end of the abdomen is the acidopore surrounded by a ring of small hairs. Below on the left is the location of the acidopore and on the right is a magnified view.
These physical characteristics are enough to identify carpenter ants from other species of ants. But, if you find the physical characteristics a little difficult where you find the ants is equally important. Carpenter ants do not build nests in the ground or under pavement. Field ants build mounds in the dirt while pavement ants locate their nests under sidewalks, stones, and ‘pavement.’ Carpenter ants live in wood usually. Wood framing in houses is just as good as a log in the woods for carpenter ants. It should be noted that carpenter ant colonies you find in houses are usually satellite nests.
Carpenter ants prefer to build their main nest (where the queen lives and eggs are laid) outside homes in big old trees. The nests you find in homes or garages are usually satellite nests where the pupa and larvae are sent to be raised.
It is quite common to find non-carpenter ants in or on your house. During winter small ants like to roam houses for food and warmth. It's also common to find small ants around trash cans. However, they do not infest and damage houses. They are typically just visiting.
Carpenter ants can be a real problem for your home. They chew tunnels, called 'galleries', in wood to nest in. The galleries they excavate cause damage your house. Once established, carpenter ants in your house can live for years if all of their requirements are met.
So, the next time you see an ant don't judge it by size alone. At a glance, the minor carpenter worker ant looks just like some non-carpenter ants. Follow the ant or catch it for a better identification. Knowing what to look for is the first, and most important step, for keeping your house free of carpenter ants.