NC State Extension Publications

Introduction

Formica (FORM' ic a) ants produce a loose mound that might slightly resemble that of a fire ant mound, but these ants are quite large in comparison to small fire ants. These three species tend to build in the forest edge or at the interface between wooded and open areas which gives them a lot of interaction in the sprawling suburbs. Mounds and colonies can become huge over many years, if undisturbed.

Formica integra is sometimes loosely referred to as one of the "red wood ants." Unfortunately, there is no common name for this ant. Formica integra is a little smaller than a carpenter ant. It is a red two-tone color with the abdomenal area often much darker. Eyes are hairless. It feeds heavily on arthropods and might be considered beneficial within the forest when it suppresses other tree pests. It is known to feed on sawfly larvae, Ips bark beetles, termites, honey bees, and other arthropods. It also tends aphids, psyllids and scale insects for carbohydrates in honeydew. It occurs across most of the eastern United States. Nests may have multiple queens and can produce extremely large populations. Mounds are often reported against the base of a tree or stump with leaf litter and debris incorporated. The nest system can also branch out and cover an acre or more. On occasion, it can become quite dominant in the landscape and be considered a nuisance. It has been observed moving in troops from one nest location, 30 yards away to a new location.

Formica subsericea is a second common Formica species. This ant is all black and has also been observed feeding on other insects. It likes the same open wooded areas and has loose mounds. It is primarily active during the day and will forage far from its nest. Winged alates are produced in the spring. These ants are also somewhat nomadic. They may also tend honeydew producing insects, even including treehoppers.

Formica exectoides, a third species, and commonly known as the Allegheny mound ant, occupies most of the country east of the Mississipppi River valley. If undisturbed, this ant may contruct large mounds and will kill any vegetation near the mound by attacking the roots and using its formic acid. This ant will also tend aphids and scale insects in nearby trees and shrubs for their sugary honeydew. Color is variable between reddish to black, or both. The head and thorax tend to be reddish, while the legs and abdomen tend to be more black.

Formica integra worker

Figure 1A. Formica integra worker.

Logy Bay, Newfoundland/Labrador, Canada

Figure 1B. Formica integra mound.

Figure 1B. Formica integra mound.

Stephen Bambara

Formica ant nest against a log

Figure 2. Formica integra nest built against a fallen log.

Michael Waldvogel

Figure 3. Formica integra ants at the base of a tree.

Figure 3. Formica integra ants at the base of a tree.

Stephen Bambara

Figure 4. Formica subsericea.

Figure 4. Formica subsericea attacking a white grub.

Figure 5. Formica subsericea mounds.

Figure 5. Formica subsericea mounds.

Stephen Bambara

ants tending aphids

Figure 6. Ants tending aphids.

Michael Waldvogel

Management

Just because there are ants in the yard, does not mean they need to be eliminated. Ants serve a useful role in the ecosystem. Frequent disruption of a mound by digging or flooding with a garden hose may not kill the colony, but could cause the mound to relocate to a less objectionable location. If you decide that you need to control any of these ants, Sevin or Orthene are two possible choices that may be used for control directly on the mound. For Formica integra located next to a structure, a gel bait containing fipronil may be used. Bait stations should be used in places where pets may have access. If you wish to use a bait, choose one listed for sweet-loving ants and tested for attractiveness. Fire ant baits are not attractive to these ants. Aloft™ is a good general nuisance ant product for professionals. For additional chemical choices, see the North Carolina Agricultural Chemicals Manual.

Authors

Specialist (Ret.)
Entomology
Extension Specialist (Household & Structural Entomology)
Entomology and Plant Pathology

Publication date: June 1, 2007

Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by NC State University or N.C. A&T State University nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your local N.C. Cooperative Extension county center.

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