The most common newbie mistake I’ve seen in identifying North American ants is to confuse Formica (field ants) and Camponotus (carpenter ants).

Both are common, medium-large in size, with a single waist segment. As they are in the same subfamily, Formica and Camponotus have a similar appearance and are easily confused. If you keep your eyes open you’ll find both nearly everywhere you go.

Here’s an identification trick that will work 95% of the time in temperate regions of North America to separate the two genera.

Look at the worker thorax in side view. If the back forms a single, even curve, you’ve got Camponotus:

A continuous profile indicates Camponotus. (Image by

If the silhouette is broken into two distinct curves, you’ve got Formica:

A profile with two distinct convexities indicates Formica. (Image by

Wasn’t that easy?

Caveats apply, of course:

1. This trick works to separate only Formica from Camponotus. Many similar formicine genera occur in our area: Lasius, Prenolepis, Nylanderia, and several others. These are usually smaller than Formica & Camponotus, but be aware they exist.

2. In the tropics, some Camponotus species start appearing with a Formica-like profile. Thus, this trick is only effective regionally.

3. To properly confirm an identification, you’ll want to check your ant against the appropriate taxonomic literature using the full suite of diagnostic characters.

To test your new identification skills, have a go at the following ants.

Formica or Camponotus?