Ant Control

The control of ant infestations in and around structures can often be difficult. This process can be made even more difficult if control attempts are made without taking the time to make proper identification of the ant involved. A service technician working in midwestern or northeastern states only needs to learn to identify three or four different ant species. A technician in Florida or southeast Texas, however, may need to learn how to identify 10 or 12 different ants, because he or she could encounter any of these at any time.

Identification of ants need not be a daunting task. Experience is the best teacher; the more often a particular ant is seen, the easier it will be to remember its identifying characteristics.

BASICS OF ANT ANATOMY. A basic knowledge of ant anatomy is necessary in order to know where to look for critical identifying characters. All ants have certain basic characters that distinguish them from other insects. Ants most closely resemble wasps because both are found in the order of insects known as Hymenoptera. Although there are many different families of wasps, ants belong to one family called Formicidae.

Ants have the three body regions shared by all insects. A unique character of ants is the presence of a thin segment called a pedicel, which separates the thorax from the abdomen. The pedicel is actually the first one or two segments of the abdomen, and the thin shape gives ants the appearance of a pinched "waist." The remaining portion of the abdomen is called the gaster. The fact that the pedicel has either one or two segments is a key character for identifying ants. These one or two segments are commonly called "nodes," and are the first thing one looks at when attempting to identify an ant.

Ants fall into two basic groups one-node ants or two-node ants. The shape of the nodes can sometimes play a role in ant identification. For example, the single node of the odorous house ant is flat and is hidden from view by the abdomen. In the acrobat ant, the two nodes of the pedicel are attached at the top of the gaster, while in most ants, the pedicel attaches at the middle of the gaster.

Once the number of nodes has been determined, the second area to examine on an ant is the thorax. The shape of the thorax is an important character for identifying carpenter ants and velvety tree ants. In these two ants, the thorax is evenly rounded, while in all other structure-infesting species, the thorax has an uneven shape. Some ants have one or more pairs of spines on the thorax. The pyramid ant does not have thoracic spines, but it does have a single pyramid-like bump on the top rear of its thorax. In other species, a key identifying character might be the presence of grooves on the thorax, such as those found on the pavement ant.

Ants have elbowed antennae, with the first segment, called the scape, being extremely long. The other antennal segments branch off of the scape at a sharp angle, giving the antenna its "elbow" shape. When counting the number of segments of the antennae this is an important identifying characteristic for some species the scape is counted as the first segment. Most structure-infesting ants have 12-segmented antennae, but the fire ant and the thief ant have only 10 segments in their antennae.

Another important identifying clue for some ants is the presence of an antennal club. A club is formed when the last two or three antennal segments are greatly enlarged. The number of enlarged segments in this club can be a key identifying character. For example, thief ants are quickly distinguished from pharaoh ants because thief ants have a two-segmented club, while the club of the pharaoh ant has three segments.

The gaster itself generally plays little role in the identification of most ants. Certain characters, however, can be helpful in confirming the identity of an ant when combined with the other identify ing characters. Carpenter ants, for example, have a circle of tiny hairs around the anus. The shape of the gaster is a key character for acrobat ants. When viewed from above, the acrobat ant's gaster is heart-shaped.

Some ants have a stinger present at the tip of the abdomen, although in several structure-infesting ants, the ant may be incapable of stinging a person. Pavement ants and thief ants are two ants that possess stingers but do not sting. Fire ants, little fire ants, and harvester ants, however, put their stingers to good use in defending their colonies.

A common mistake made in trying to identify ants is to rely too much on color and size. Polymorphic ants such as carpenter ants and fire ants have many different sizes of workers. For example, a mature carpenter ant colony may have workers ranging in size from ¹/₈ inch up to ⁵/₈ inch. Carpenter ant species also range in color. The primary structure-infesting species along the east and west coasts are black; the Florida carpenter ant and a couple of other carpenter ant species are red and black. Other carpenter ants can be brown in color. Always rely on the anatomical characters for a definitive identification of an ant specimen.

IDENTIFYING ANTS. The most difficult thing about identifying ants is remembering the identifying characters of each ant and keeping the characters of one ant from becoming confused with the characters of another. For this reason, keeping a good reference material handy is important. The PCT Field Guide for the Manage ment of Structure-Infesting Ants was designed to be carried in the field to help make ant identification easier.

Ants are small creatures, so a good magnifying device is important. Service technicians in the field should be equipped with at least a 30× hand lens. Radio Shack and other outlets sell a nice 30× lighted magnifier that costs about $10 to $15. It is also a good idea to carry vials of rubbing alcohol to collect ants that cannot be identified in the field. These specimens can be brought back to the office for more careful observation. The office should have a more powerful microscope available to aid identification efforts. If identification is still not possible, the specimens can be mailed to an entomologist at a state university for identification. The latter should only rarely be necessary, but if it is, it is important to have more than one or two specimens. Make it a routine to collect as many as 15 to 20 worker ants if possible.

• Step #1. When an ant specimen is collected for identification, the first step is to look at the pedicel to see if the ant is a one-node ant or a two-node ant. The number of different ants you have to choose from is then cut basically in half.

One-node ants include carpenter ants, field ants, crazy ants, Argentine ants, odorous house ants, ghost ants, velvety tree ants, pyramid ants, small honey ants, and large yellow (or citronella) ants.

Two-node ants include acrobat ants, fire ants, thief ants, little fire ants, pavement ants, pharaoh ants, little black ants, big headed ants, harvester ants, and leaf cutter ants.

• Step #2. The next step is to look at the thorax. Is it evenly rounded (carpenter and velvety tree ants), or is it uneven in shape (all other ants)? Is a pair of spines present (big headed, acrobat, or pavement ants), or is there more than one pair present (leaf cutter ants)? Are there grooves present on the thorax (pavement ants)?

• Step #3. The antennae are the next character to examine. How many segments does the antenna have? Does the antenna have a club? If so, how many segments are in it?

• Step #4. Look at other characters to confirm or deny an identification. For example, is the pedicel attached to the top of the gaster (acrobat ants) or is it hidden (odorous house and ghost ants)? Is the gaster heart-shaped from above (acrobat ants), or is a circle of hairs present around the anus (carpenter ants)? Does the head have grooves or sculpturing (pavement and little fire ants), or does the head have pairs of spines (leaf cutter ants)? Is the head of the major worker huge in comparison to its body (big headed ants)?

• Step #5. Compare any of these identifying characters with the ants described in a reference book. Don't rely on one or two characters. Make sure all of the characters for the type or species of ant you believe your specimen to be actually do match your specimen. If one or more characters do not match up, the ant is likely some other type or species of ant. After seeing a particular ant several times and comparing it to the reference guide, it will become easy to identify that ant in the future. Much of the skill in identifying insects comes with the experience of seeing specimens time after time.

Stoy Hedges is manager of technical services for Terminix International, Memphis, Tenn. He authored the PCT Field Guide For The Management Of Structure-Infesting Ants.