Ant Identification

Classifying ants into one of three artificial groups makes their identification a little easier. Group one is composed of ants with one node (the node is the projection on the pedicel separating the thorax from the “gaster,” or abdomen) and a tuft of hair at the tip of the gaster. Group two is composed of ants with one node and without a tuft of hairs at the tip of the gaster. Group three is composed of ants with two nodes (called the petiole and postpetiole).

One-node varieties
If your ants belong to group one, first check the shape of the thorax when viewed from the side. If it is evenly convex and the ants are generally large (there are small species), then you probably have carpenter ants. Very small eyes and a yellow body indicate that you have yellow ants. If the posterior portion of the thorax is almost vertical (parallel with the node), you have cornfield ants. When the thorax is heavily constricted in the middle, you have small honey ants.

For ants that fit into group two, check the node and the shape of the thorax and the pilosity (hairs). An ant with a pyramid-shaped projection on the thorax is, surprisingly enough, a pyramid ant. If the node and thorax are different sizes (polymorphic) and hairy, it is a velvety tree ant. Ants with very small, difficult-to-see nodes that have dark brown or black bodies are odorous house ants. If the ant has a small node with a white gaster and legs, it is a ghost ant.

If the ant in question doesn’t have any projections on the thorax, is almost hairless and the node is not very small, check the thorax for hairs. It is a Forelius ant if there are two or four hairs on the thorax, but it is an Argentine ant if it is completely hairless.

Double-node characteristics
For ants that fit into group three, check the thorax for spines. Look at the tip of the antennae and check whether there’s a stinger. Ants with distinct spines on the thorax and a gaster that is flat when viewed from the side and heart-shaped when viewed from the top are acrobat ants. Thief ants are extremely small, and have a two-segmented antennal club and a visible stinger. An ant with the same characteristics as the thief ant but is larger is a fire ant. If the ant is dark brown or black and has distinct ridges on its face, no antennal club and a pair of small spines on the thorax, it is a pavement ant. Very small, black ants with a three-segmented club are (here we go with the creative common names again!) little black ants.

Pharaoh ants have a three-segmented club and are yellowish or light brown. If the ant has very small, hard-to-see eyes, it is a legionary ant (also called the army ant). Ants in a series with unusually large heads are bigheaded ants. Minor workers of bigheaded ants have normal-size heads, long antennae with a gradual club, a pair of spines on the thorax and no stinger.

Keep in mind that many other species of ants can occasionally turn up in a structure. If your ants do not fit into the descriptions above, you need to get them identified by an entomologist.