Ants

Ant Identification

Image of ants tending aphids.

Order: Hymenoptera Family: Formicidae

  • Ants are social insects that form colonies and forage for food.
  • There are many different species of ants that may be found in and around homes.
  • Ant identification is an important first step in management.
  • Traditional management of ant includes the use of toxic baits or directly treating nests.
  • Some ants, like carpenter and acrobat ants, nest in wood and may cause structural damage.

Identification

Ants are usually identified by their distinctive segmented body and elbowed antennae. Ant species can differ widely in their food requirements, behavior and nesting preferences. While many ants are simply nuisances that invade human dwellings in search of food, water or shelter, some ants, such as carpenter or acrobat ants, nest inside of wood and may cause structural damage. Because there are so many different species of ants, proper identification is an important first step in management before choosing a treatment:

To help identify ants, they are grouped into "one-node" and "two-node" ants. The "nodes" are an important identification characteristic located in the constriction between their thorax and abdomen. In order to see key features of ants, you'll likely need a hand lens or microscope.

For questions regarding ant identification and management, contact your state Extension office.

Acrobat Ants

  • Identification: Two-node petiole, one pair of spines on the thorax, abdomen is heart-shaped when view from above, 1/8 inch long.
  • Importance: Nest in dead or rotting wood but not cause structural damage like carpenter ants.
  • Feeding preference: Aphid honeydew, dead insects.
  • Nests: Under bark, rotting wood, logs, forest floor, sometimes forage near homes and structures if moisture damage.
  • Management: Remove infested wood and fix moisture issues.
Image of an acrobat ant.

Black Carpenter Ants

  • Identification: One-node petiole, evenly rounded thorax, hairs on abdomen, black in color.
  • Importance: Wood destroying insects that excavate galleries in wood but do not consume the wood. Often a household nuisance when found foraging indoors.
  • Feeding preference: Do NOT consume wood. They instead chew into wood to create tunnels and galleries for their nests. Prefer to eat both sugary and proteinaceous foods, including other insects.
  • Nests: In live and standing trees, in firewood and logs, in lumber in human structures, or in hollow voids. Commonly nest in wood with moisture issues.
  • Management: Contact a pest management specialist. Must locate and treat the nest to eliminate the entire colony. In situations where the nest cannot be located, toxic baits labeled for carpenter ants may be effective.
Image of black carpenter ants.

Red and Black Carpenter Ant

  • Identification: One-node petiole, evenly rounded thorax, black abdomen, red head and thorax, smaller than black carpenter ant.
  • Importance: Wood destroying insects that excavate galleries in wood but do not consume the wood. Often a household nuisance when found foraging indoors.
  • Feeding preference: Do NOT consume wood. They instead chew into wood to create tunnels and galleries for their nests. Prefer to eat both sugary and proteinaceous foods, including other insects.
  • Nests: In live and standing trees, in firewood and logs, in lumber in human structures, or in hollow voids. Commonly nest in wood with moisture issues.
  • Management: Contact a pest management specialist. Must locate and treat the nest to eliminate the entire colony. In situations where the nest cannot be located, toxic baits labeled for carpenter ants may be effective.
Image of red and black carpenter ants.

Citronella/Yellow Ants

  • Identification: One-node petiole, thorax is uneven in shape, hairs on abdomen, small eyes, yellow in color, smells like citronella when threatened or crushed.
  • Importance: Often swarm in or around homes any time of the year. Primarily a nuisance.
  • Feeding preference: Aphid honeydew (sweet).
  • Nests: Outdoors in the soil, under vegetation, rocks logs and under slab. Rarely seen unless swarming.
  • Management: Vacuum to remove swarming ants.

Image above - citronella ants farming root aphids. 

Image of citronella ants farming root aphids.

Field Ants

  • Identification: One-node petiole, unevenly rounded thorax, workers are 3/8 inch long, variable in color and have 3 ocelli or simple eyes.
  • Importance: Considered outdoor ants. Unlikely to forage indoors.
  • Feeding preference: Sugary foods, aphid honeydew, other insects like caterpillars, seeds.
  • Nests: arge mounds built in the open away from trees, disturbed areas, like prescribed burn prairies, but also in yards.
  • Management: Indoor invasions are not usually an issue. Management in turf is more common since their mounds may ruin equipment. Then outdoor bait stations or granular ant bait would be recommended.
Image of field ants.

Odorous House Ants

  • Identification: One-node petiole hidden by the abdomen, thorax is uneven in shape, workers are 1/8 inch long, black in color, emits a rotten smell when crushed.
  • Importance: Common ant that nests indoors close to people, especially in the spring.
  • Feeding preference: Sugary foods.
  • Nests: Can be found indoors under sinks and appliances or outdoors along the foundation under rocks and items in the garden.
  • Management: Search the perimeter of the home for outdoor nests and treat the nest directly. If unable to find and/or treat the nest directly, provide a steady supply of liquid sugar bait.
Image of odorous house ants.

Pavement Ants

  • Identification: Two-node petiole, one pair of spines on the thorax, workers are 1/8 inch long, reddish-brown-black in color.
  • Importance: Ants are often found in large numbers on the sidewalk and driveway. Can be found indoors foraging for food, especially in the spring and summer.
  • Feeding preference: A variety of food including sugar- and grease-based foods.
  • Nests: Excavate soil from underground and form mounds in the cracks. Commonly found under slabs, bricks or pavement as well as grassy areas near sidewalks.
  • Management: Search for nests outdoors and treat directly.
Image of pavement ants.

Thief/Grease Ants

  • Identification: Two-node petiole, no spines on the thorax, workers are 1/20 inch long, orange-brown in color, often confused with the pharaoh ant.
  • Importance: Often found foraging on kitchen counters.
  • Feeding preference: Prefer greasy and proteinaceous foods. Will steal and eat larvae from nearby ant nests.
  • Nests: Nest around other ants in human structures, forests and grassy areas. Can live in microhabitats indoors without being detected.
  • Management: Use protein-based baits.
Image of thief ants.

Ant Lifecycle

Image of yellow ant queen (top) and worker ant (bottom).
Yellow ant queen and worker. Image from UNL Entomology. 

All ants are social, which means they live in colonies in a caste system, where they function as a superorganism working for the good of the colony. All ants undergo complete metamorphosis and go through four stages of development: egg, larva, pupa and adult. Rarely are the eggs, larvae and pupae seen unless the nest is revealed and many adult/workers (all female) ants will quickly pick them up and move them to safety because they have no means of locomotion on their own. Queen ants lay eggs for the entire colony. Seasonally/annually, winged forms of male and female ants will emerge from the nest, find a mate and disperse as a way to increase genetic diversity and begin new nests. This emergence behavior is called swarming.

 

Management

The majority of ant species, regardless of whether you find them inside the home or not, will actually be nesting outdoors. Signs of frass, soil particles, insulation, wood shavings or sawdust indicate ants nesting inside the home and is an indication that there is a more significant structural or moisture problem and should be investigated more thoroughly. Treatment of the nest to eliminate ants and repair of the structure to prevent reinfestation is recommended.

Because ants are social insects that live in large colonies, the most effective way to manage them is to treat the nest either directly (sprays, dusts, granules) or indirectly (baits), and killing the queen. Stepping on or spraying foraging ants that enter the home will have no effect on the overall health of the colony. Additionally, proper sanitation and are important in preventing ants from entering structures to forage. Ants foraging from outside, come indoors through cracks and crevices and other small entry points and are masters when it comes to finding crumbs, drips and drops of sugar. Seal gaps to the outside with caulking or sealants, quickly clean up spills off of floors, desks and countertops, and keep all food items in sealable containers.

 

Baits

Insecticidal baits are a convenient solution when nests cannot be found or easily treated directly. Baits must be placed in areas where ants frequent so they can be found and taken back to the nest to be shared with the colony. They are also slow-acting so they allow transfer of the toxicant to colony members. Once a baiting program is started, that ants are allowed to forage freely so they can use their social behavior to eliminate the colony. It can take 24 hours up to several weeks for a bait to be successful, consider a variety of formulations and locations, and be patient. Different species of ants may prefer different types of baits.

Liquid Bait (usually sugar-based) can be used indoors or outdoors according to the label where ants can come and feed, and then take toxic bait back to the colony.

  • Amdro Kills Ants Ant Killer Liquid Bait Stations (A.I. Hydramethylnon 1%)
  • Hot Shot Ultra Liquid Ant Bait / Hot Shot Ultra Clear Roach & Ant Gel Bait (A.I. Dinotefuran 0.05%)
  • Spectracide Ant Shield Outdoor Killing Stakes (A.I. Indoxacarb 0.05%)
  • Terro Liquid Ant Bait/ Terro Outdoor Ant Bait Stakes (A.I. Boric Acid 5.40%)

Bait Stations are ready-to-use, pre-packaged plastic stations where ants can come feed and then take toxic bait back to the colony.

  • Amdro Ant Killing Bait (A.I. Propoxur 0.25%)
  • Raid Ant Bait III (A.I. Avermectin 0.01%)
  • Raid Double Control Ant Bait II (A.I. Avermectin 0.05% Protein, Sugar)*
  • Raid Ant Gel (A.I. Thiamethoxam 0.003%)*
  • Raid Max Double Control Ant Bait (A.I. Avermectin 0.05%)*

Granule Bait can be applied outdoors so that foraging ants can pick them up and take them back to the colony.

  • Terro Perimeter Ant Bait Plus/ Terro Multi-Purpose Insect Bait (A.I. Boric Acid 5%)
  • Amdro Ant Block Home Perimeter Ant Bait Granules (Granule A.I. Hydramethylnon 0.88%)

 

Insecticidal Sprays & Dusts

If nests are easily accessible, they can be treated directly with an insecticidal spray or dust. Liquid sprays and dusts can be applied according to the label as residual, contact insecticides.

Sprays

  • BioAdvanced Carpenter Ant & Termite Killer Plus (A.I. Beta-Cyfluthrin 2.5%)
  • Ortho Home Defense Insect Killer (A.I. Bifenthrin 0.05%, Zeta-Cypermethrin 0.0125%)
  • Spectracide Ant Shield Home Insect Killer Ready-to-Use (A.I. Lambda-Cyhalothrin 0.03%)
  • Spectracide Bug Stop Home Barrier (A.I. Gamma-Cyhalothrin 0.025%)
  • Spectracide Termite & Carpenter Ant Killer Concentrate (A.I. Lambda-Cyhalothrin 0.5%)

Dusts

  • Terro Ant Dust (A.I. Deltamethrin 0.05%)

Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the University of Nebraska–Lincoln is implied. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area.

Authors:
Kait Chapman, M.S., Urban Entomology Extension Educator, Nebraska Extension in Lancaster County
Jody Green, Ph.D., Urban Entomology Extension Educator, Nebraska Extension in Douglas-Sarpy Counties