ID Please

In ant management, the most fundamental tip is to identify the ant in question. Not all ants were created equal. Just as there are many types of flies or many kinds of beetles, there are also many species of ants. To successfully control an issue with flies or to manage a beetle infestation, you would begin your attack with the proper identification of the flies or the beetles involved. Ant management follows the same protocol. Even though many people think there are only large ants, tiny ants and regular ants, as a professional, the precise identification is critical for success.

Checking the index in Stoy Hedges’ “Field Guide for the Management of Structure-Infesting Ants,” there are 35 ants listed, and many of the individual listings include a number of species. For example, carpenter ants include 24 pest species. Some common features among all ants include the life cycle with development from the egg to larva to pupa, and finally the adult. But even flies and beetles have these features. Ants, like honey bees and some wasps, have a history of social behavior where a division of labor occurs with a queen or queens reproducing individuals for the colony and workers performing all other activities. Species of ants differ from one another in color, structure, biology, behavior and habitat, plus differences in food and foraging trails.

THE BIG THREE. In surveys of pest management companies, the three most common ants found in and around structures are carpenter ants (Camponotus spp.), odorous house ants (Tapinoma sessile) and pavement ants (Tetramorium immigrans). Comparison of the differences and similarities of these three will demonstrate the importance of correctly identifying the specific ants in an infestation. Keep in mind that each of the more than 50 pest ants occurring in North America also have these differences and similarities. By correctly identifying the species of ant involved in an infestation, knowledge of the features of biology and behavior can be used to successfully manage and eliminate an ant problem.

Carpenter ants, odorous house ants and pavement ants, like all ants, have three major body parts with a thin pedicel (waist) and a node (projection from the waist). This distinguishes ants, even winged reproductives, from bees and wasps. Carpenter ants have a prominent single node, pavement ants have a two-segmented node and odorous house ants have a small flat node. Other ants will be identified by other features: number of antennal segments, presence of an acidopore (circular opening at end of abdomen), presence of spines and hairs, etc.

Odorous house ants and pavement ants are similar in size, whereas carpenter ants are much larger. A common way to distinguish these three groups is by odor. Odorous house ants have a distinctive odor for which they are named. Some describe it as sweet or like blue cheese.

It is definitely not the acidic smell produced by carpenter ants. Pavement ants produce no odor but do possess a stinger. This ant has difficulty inserting a stinger through human skin unless it can brace against a substrate. Because a sting gland is involved, these stings may produce an allergic reaction.

Description of workers varies according to size and morphology. In carpenter ants, some workers have proportionately larger heads (soldiers or majors) than other workers (medias and minors). This produces changes in morphology of the head. In odorous house ants and pavement ants, there are minor differences in sizes, but the morphology remains the same; therefore, there are no soldiers. Size of individual workers is determined by the amount of food available in the larval stage, as adult ants cannot grow.

BIOLOGY & BEHAVIOR. Correct identification will lead to information on differences in biology and behavior. In social order, carpenter ants have a single queen; both odorous house ants and pavement ants have many queens. This should be a clue about the importance of finding the nest(s). Carpenter ants have a permanent or main nest and possibly many satellite nests. Carpenter ants are associated with wood. In nature, nest sites occur in dead timber or in living trees where there is access to the heartwood through injury to the tree. Nests selected by various species of carpenter ants vary from softwoods to hardwoods and wood in various stages of decomposition. Main nests containing the queen and brood are most often located outside structures, whereas satellite nests may be located within structures in wall voids or attics or under insulation. Infestation in structures makes these ants particularly troublesome.

Odorous house ants have temporary nest sites and many subnests. These nests are not found in wood and are found in very loosely maintained sites such as under a piece of wood, stack of vegetation, base of a plant, etc. Nests for these ants also may occur within structures, particularly in wall voids in kitchens and bathrooms. Satellite nests are an extension of the parent nest and will not possess a reproductive queen; subnests represent a group of ants established away from a main nest and contain queen(s). Subnests with queen(s), if not eliminated, can reestablish a colony. Satellite nests without a queen cannot. Nests of pavement ants may have either a single queen in small nests or many queens in a large nest. Pavement ant nests are found in the soil, often under rocks or pavement, and can divide to establish other nests in a process called budding. These ants also may nest under pavement in basement floors and foundations, and their nests are characterized by excavated mounds of sand or soil at entrances.

Reproduction in ants occurs by one of two methods: (1) releasing winged males and females that mate followed by the mated queen starting a new colony or (2) budding, where a portion of the original colony will leave a parent colony to establish a new colony at a different location. Some species reproduce by both strategies. Carpenter ants reproduce only by releasing winged forms. This occurs in late spring from April to June, depending on the climatic conditions. Odorous house ants and pavement ants reproduce by budding or by releasing winged reproductives. Odorous house ants reproduce chiefly by budding, but some winged forms are reproduced in late spring. Pavement ants also reproduce by both strategies, with winged forms released from April through August and release most common in midsummer.

Climatic features such as temperature and humidity will influence nesting sites. The main nest of all three groups is dependent on high humidity. Pavement ants nest in moist soil and in arid areas where depth of the nests will facilitate the required humidity. Odorous house ants with their temporary nesting sites and subnests will move to areas that have the required humidity. Main nests of carpenter ants will have a constant high humidity to provide conditions for rearing brood. Satellite nests may be in extremely dry areas such as attic spaces and wall voids, and water is carried to these sites by workers.

Food for all three groups of ants is similar: carbohydrates are required for energy. The term “sugar” ant could be applied to all three groups. These ants will feed on honeydew and secretions from aphids and scales, sweets, fruit and nectar from flowers. Each of the three species also will require some protein that is available from other food sources such as pet food, other insects or meats. Pavement ants also will forage on seeds. All are attracted to a variety of food sources and should be considered scavengers.

These three groups of ants will forage to food sources along trails that they will build or follow along a structural guideline. Guidelines may be the edge of a lawn, pavement or vegetation. Carpenter trails produce a pheromone trail from the hindgut and workers may follow one another at a distance of a few inches to a few feet. Their trails are more active after sunset and before sunrise, with the number of ants declining to only a few during the day.

Odorous house ants trail during the day and may trail in areas protected from direct sunlight. Ants on these trails can be very numerous, with ants often two to three abreast and running in tandem (in contact with one another).

Pavement ants are not as aggressive in trailing as odorous house ants and usually are only formed when a food source is nearby. With the more permanent nesting sites of pavement ants, food is taken into the nest and not as many foraging ants are present.

CONCLUSION. Only three groups of ants are compared here. More than 50 species of ants are involved in ant infestations in or near structures. Similarities and differences occur. The correct identification will lead to understanding the differences, and management strategies can be developed to control the troublesome species. Some strategies include baits: either gel on trails or granulars around a perimeter where ants are foraging. Sprays can be applied to interior or exterior trails; dusts and sprays can be applied to nesting sites depending on location. Time to locate nests and trails during inspections will be shortened if the biology and behavior of the specific ant is known.

Success in ant management is dependent on the identification of the ants involved, which leads to knowledge of biology and behavior. This facilitates the inspection and leads to an integrated approach including application of materials.

The author is an instructor in the biology department at Spokane Falls Community College, Spokane, Wash.