Spring is Coming: What Ant Is Invading My Kitchen?

By Ann M Mason, Fairfax Master Gardener Intern
Spring is a welcome visitor; but to me the Spring ants are not. Especially when I see them in the kitchen walking single file as if they are following a ‘trail.’ So, what are these ants? And importantly, are they evidence that the structure of my home is slowly being eaten and destroyed?

First, we need to confirm that these crawly creatures are ants, not termites. Ants have elbowed antennae, a thin waist constricted at the thorax and hind wings smaller than the front wings. In contrast, termites have straight antennae, a broad abdomen with no apparent waist and wings that are about the same size.

Ok, so now we know that our unwelcome visitor is an ant. What’s next?

To identify the ant, university experts suggest observing the ant’s physical characteristics starting by determining whether there are one or two nodes on the petiole, the first portion of the abdomen. In some ant species, the node may be hidden beneath the abdomen.

While there are about 1,000 ant species in the United States, our focus narrows to those most commonly mentioned by Virginia pest control companies. Each is grouped by the number of nodes.

Common One-Node Ants in Virginia
Black Carpenter Ant (Camponotus pennsylvanicus) is distinguished by its evenly rounded thorax and a circle of hairs at the tip of the abdomen (Place Figure 2). These black ants are the largest in size seen in homes. Worker ants vary from about 3/4 inch (19.1 mm) to about ¼ inch (6.4 mm). If carpenter ants are first seen in the home during February and March, they are associated with nests in the home. If they are first seen in May and June, they are likely nesting outdoors and entering the home to forage for water and food scraps. These ants start nests in deteriorating wood exposed to water. They do not eat wood but can cause significant structural damage to wood and to foam insulation. The long-lived colonies can reach 2,000 or more workers, in five or more years, and expand their nests into intact, sound wood.

Odorous House Ant (Tapinoma sessile) conceals its node by the abdomen, has an unevenly shaped thorax and no circle of hairs at the tip of the abdomen (Place Figure 3). The odorous house ant is small (about 1/8 inch or 3.2 mm), dark brown to shiny black and emits a strong odor like rotten coconut when its body is crushed. This ant feeds on dead and living insects but also seeks out the honeydew of aphids and scale. The odorous house ant lives in large colonies outside in shallow nests in soil and under stones, wood and debris, and inside in wall voids, around water pipes and heaters. If one sees a few wingless workers in the home, it is likely that they live outdoors and enter homes to seek out sweet-tasting foods. If one sees large numbers consistently, they might be nesting in the home. This ant can appear to wander, but it often sets pheromone trails along baseboards, edges of carpets, on tree branches and beside foundations. When disturbed, these ants become erratic and walk with their abdomens raised in the air.

Common Two-Node Ants in Virginia
Pavement Ant (Tetramorium caespitum) is a small (1/8 inch or 3.2 mm), dark brown to black ant with one pair of spines on the thorax and 12-segmented antennae ending with three enlarged segments called a club and ridges parallel up the front and sides of the head. It also has seven teeth in the mandible and a modified triangular-shaped stinger at the end of its abdomen for the application of pheromone (Place Figure 4). With large colonies containing over 10,000 workers, they build nests in a variety of soil types (sand to loam) with minimal vegetation. The nests usually have multiple crater-shaped mound entrances, which might slowly collapse after rain. Using pheromones, the pavement ants create tracks for workers to bring back foods including arthropods, honeydew, seeds and pollen to the nest. While pavement ants prefer to inhabit areas like sidewalks, patios and open soil close to buildings, they are known to forage for sweet and greasy foods in homes. Outside, pavement ants defend their colonies from other ant species. Scientists have observed them battling with invading red imported fire ants, which help to limit the introduction of these more damaging ant invaders.

Acrobat Ant (Cremastogaster lineolata) is a small 1/8 inch (3.2 mm) ant with a pair of spines on the thorax, 12-segmented antennae ending with a three-segmented club and a heart-shaped abdomen (when viewed from above). These ants hold their abdomen above their thorax when disturbed, which is the source of their name. The acrobat ant prefers to nest in decaying wood and even old termite galleries and are known to nest in house voids around doors and windows, in walls and in insulation.

Two additional two-node ants in the Monomorium species might visit VA homes — the Little Black Ant (Monomorium minimum) and the Pharaoh Ant (Monomorium pharaonic). Both are small (1/16 inch or 1.6 mm), with 12-segmented antennae ending in a three segmented club. They do not have spines on the thorax. These ants differ in color; the little black ant is black, and the pharaoh is light brown to red with a dark abdomen. Both ants can establish nests in homes, especially in voids around doors, cracks in foundations and occasionally in cabinets close to food sources. They are known to forage indoors looking for both sugars, proteins and fatty foods. Pharaoh ants are particularly difficult to eradicate from homes and deserve their infamous reputation for “getting into things.”

Armed with a magnifying glass, I am ready to identify my unwelcome Spring ant visitors. Sanitation is key to preventing foraging ants looking for sweets, proteins and grease. Plugging possible entrances and putting foods into air-tight containers might discourage ants. If or when they come, physical removal by a vacuum and continual cleaning, along with ant deterrents (boric acid and diatomaceous earth) and chemical baits can control them. If their invasion is more extensive, consulting a certified professional pest company might be needed.

Resources
• Key to Identifying Common Household Ants, Ant Key, University of California Integrated Pest
   Management
• Ant Identification Key: 1-Node Ants, University of Nebraska – Lincoln
• Ant Identification Key: 2-Node Ants, University of Nebraska – Lincoln
• Household Insect Pest Identification, Identification of Ants, Virginia Tech
• Ants, University of Maryland Extension
• Identification of Ants, Virginia Tech
• Quick Tips to Identifying Ants — Ant Anatomy, University of California Integrated Pest
   Management
• Key to Identifying Common Household Ants, University of California Integrated Pest Management
• Distinguishing Ants from Termites, University of California Integrated Pest Management

Ant Species
• Acrobat Ants, North Carolina State University Extension
• Carpenter Ant, Eric Day, Virginia Tech, Publication 3104-1573 (2011)
• Little Black Ant, Ant Pests, eXtension
• Carpenter Ant, Steve Jacobs, Sr, Pennsylvania State University Extension (2014)
• Odorous House Ant, Iowa State University Extension
• Odorous House Ant, University of California IPM
• Pavement Ant, Iowa State University Extension
• Pavement Ant, University of Florida
• Pharaoh Ant, University of Florida
• School Integrated Pest Management (IPM) for Ants, Marc L. Fisher and Dini Miller, Virginia Tech