Pavement Ants

Scientific Name:Tetramorium caespitum (Linnaeus)
CLASS/ORDER/FAMILY: Insecta/Hymenoptera/Formicidae
METAMORPHOSIS: Complete

Introduction:

The pavement ant is an introduced species and is one of the most commonly encountered house-infesting ants in Pennsylvania. The ants were likely carried to the United States in the holds of merchant vessels during the 1700s to 1800s. These ships were filled with soil from Europe to provide ballast on the trip to the States. Once in port, the soil was removed, and goods were loaded on the ships to carry back across the Atlantic.The pavement ant is a soil-nesting species that currently has a distribution from New England to the Midwest, and south through the Mid-Atlantic States to Tennessee. It is also found in parts of California and Washington.

This ant gets its name from commonly locating its nest in or under cracks in pavement. Pavement ants were introduced from Europe by the early colonists. They are found in most of the eastern half of the United States and in California and Washington.Swarmers can be distinguished from other ant swarmers by the presence of fine furrows/grooves on their head and thorax, similar to those of the workers.

Similar Groups

(1) Harvester ants (Pogonomyrmex spp.) have underside of head with a brush of long bristles (coarse hairs/setae).

(2) Acrobat ants (Crematogaster spp.) with pedicel attached to upper surface of abdomen (gaster).

(3) Other small dark ants with only 1 node/segment in pedicel or if with 2 nodes,then thorax lacks spines on upper surface.

Biology

The pavement ant workers are about 2.5–4 mm long and vary in color from dark brown to black, with parallel furrows or lines on the head and thorax. The pedicel, which connects the thorax and abdomen, has two segments. The posterior/dorsal thorax has two spines that project upward to the rear, and they carry a stinger in the last abdominal segment.The swarmers or reproductive ants are winged, about twice the size of the workers, and also have a furrowed head and thorax. The spines are evident on the females but absent on the males.

Habits

Inside, pavement ants will occasionally nest in walls, in insulation, and under floors. The most likely place is in ground-level masonry walls of the foundation and especially near some heat source in the winter. They often follow pipes which come through slabs for access to upper floors of buildings.Outside, these ants typically nest under stones, in cracks in pavement, and next to buildings. They enter buildings through cracks in the slab and walls, slab expansion joints, and the natural openings of buildings. Although not aggressive, workers can bite and sting.

Pavement ants also dwell in the undersides of logs, bricks, stones, patio blocks and boards. Pavement ants may also nest under mulching or open soil close to building foundations. They also can nest indoors, such as under floors, inside insulation and within walls.

Pavement ants undergo complete metamorphosis, passing through the egg, larval and pupal stages before becoming mature adults.A typical colony of pavement ants includes multiple queens and numerous workers. A queen establishes a new colony of pavement ants by laying eggs. Pavement worker ants then tend the queen’s brood until they develop into adults. During their development, broods are transferred from location to location to protect them from fluctuations in moisture and temperature.

These ants feed on almost anything including insects, honeydew, seeds, plant sap, and household foods such as meats, nuts, cheese, honey, and bread, but show a preference for meats and grease. They forage in trails, and for distances of up to 30 feet (9 m).

Why do some of them have wings?

The winged ants or "swarmers" are the kings and queens. Researchers are not certain of the exact cause for the pavement ants to swarm out but it appears to be related to the size of the nest, the age of the nest, and perhaps the weather conditions. Most swarming occurs between May and July. Once they emerge and complete their mating, the newly fertilized queens look for a suitable spot to start a new colony. Fortunately, most of them are unsuccessful and die off.

Control

The use of baits and/or liquid sprays are currently the most effective methods of control.

BAITING: Baits are very effective and efficient in eliminating a pavement ant infestation provided the ants will accept the bait. Ant baits contain a slow acting poison and are formulated as gels, solids, and liquids. The worker ants are unable to eat solid food so they gather the bait and carry it back to the nest where they feed the immature stage (larva). The larvae process the bait and then through a process known as trophalaxis they regurgitate a liquid to feed the queen and the other workers. The workers get their "reward" so they will continue to go out and bring back more food and do the other work required by the colony. This process spreads the slow acting poison throughout the nest and causes the entire colony to die off. This is a very successful method provided the ants take the bait. Sometimes, and for reasons that are still unknown, pavement ants will not accept certain baits. When this occurs, the choice is to try a different bait material or to use a liquid insecticide.

When using baits, always read and follow the directions on the label of the product you are using. Baits need to be placed in areas inaccessible to young children and pets or in tamper resistant containers such as the Ant Caf. Look for pavement ants moving about, especially the trailing activity. Place small amounts of bait directly in the path the ants are traveling, but do not cover or block their entrance to the colony with the material. They are likely to gather around the bait or immediately pick it up and transport it back to the colony. It is not unusual for many pavement ants to suddenly appear after the bait is placed. This is normal foraging activity so please do not disturb the ants or apply any insecticides to kill them. Let them feed on the bait. Over the next three days inspect the feeding sites and replenish the baits that are consumed. Within a week the pavement ants should be gone. If the foraging activity continues longer than a week you may need to place more baits or consider the use of liquid sprays.