Ants In and Around the Home

HYG-2064
Date: 
02/06/2013
David Shetlar, Barbara Bloetscher, and Jennifer Andon, Department of Entomology

Ants can be one of the most annoying pests encountered in homes and buildings. Fortunately, most of Ohio ant species are not known for their bites or stings like the fire ants that inhabit southern states. However, their constant searching for food and water around areas occupied by humans is not well tolerated.

Common Name Scientific Name
Carpenter Ant
Cornfield Ant
Larger Yellow Ant
Pharaoh Ant
Thief Ant
Pavement Ant
Little Black Ant
False Honey Ant
Allegheny Mound Ant
Lawn Ant
Acrobat Ant
Odorous House Ant
Crazy Ant
Camponotus spp.
Lasius alienus (Foerster)
Acanthomyops interjectus (Mayr.)
Monomorium pharaonis (Linn.)
Solenopsis molesta (Say)
Tetramorium caepitum (Linn.)
Monomorium minimum (Buckley)
Prenolepis imparis (Say)
Formica exsectoides Forel
Lasius neoniger
Cremastogaster lineolata (Say)
Tapinoma sessile (Say)
Paratrechina longicornis (Latrielle)

Ant control is not as easy as spraying a residual insecticide around baseboards! Ants are usually able to quickly detect treated surfaces and simply avoid them until the pesticide residues have dissipated. Currently, professionals try to treat ant nests or colonies or use baits that are especially liked by particular ants.

To effectively manage ant problems, one of the first things to do is to get a correct identification of the ant species being encountered. Some ants feed on proteins (meats), fats and oils, or sugary foods, and some ants change their food preferences during the season! Some species nest only in soils while others can occupy small cavities, including wall voids of buildings. If you cannot identify the ant you are dealing with, collect several specimens in a watertight vial, add isopropyl or 70 percent alcohol (not water), and enclose in a crush-proof box. Take these specimens to your county office of Ohio State University Extension or mail to the C. Wayne Ellett Plant and Pest Diagnostic Clinic (a nominal fee is charged by the clinic). The clinic and specimen submission instructions are located at ppdc.osu.edu

Identification

There are several kinds of ants that may occur in and around the home ranging in size from about 1/32 to 3/4 inch long and colored yellowish, light brown, reddish-brown, brownish-black, or jet black. Ants, as all insects, have three body regions—head, thorax, and abdomen. Most are wingless, but the homeowner sometimes may confuse swarming, winged ants with swarming, winged termites, causing alarm. Ants can be easily distinguished from termites by several characteristics:

  • Ant bodies appear constricted or pinched in at the waist (shaped like a figure 8), while termites do not have the waist constriction.
  • Ants have elbowed antennae, while termites have straight, bead-like antennae.
  • The forewings of ants are much larger than the hindwings. Termites' wings are equal in size and shape.
  • Ant wings are transparent or brownish, while termite wings are milky-white or grayish and longer than the body.
  • Ant wings are firmly attached, while termite wings are easily removed or shed (fall off).

Life Cycle and Habits

Ants are social insects that live in colonies or nests usually located in the soil near the house foundation, under concrete slabs, in crawlspaces, in structural wood, in the yard or garden, in trees, and in other protected places. Ants have three castes, namely queens, males, and workers. Queens and males are the reproductives. Workers are sterile wingless females. New ant colonies are started by a single fertilized queen that lays eggs and tends her brood (larvae and pupae) that develop into worker ants. Tending of the brood is then taken over by the worker, which may shift the brood from place to place as moisture and temperature fluctuate in the nest. When workers forage for food for the queen and her young, they often may enter houses and become a nuisance by their presence and contaminate food.


Carpenter Ant

 
These ants are the largest found in Ohio and rank number one in inquiries over all other ants. They are a nuisance when found in parts of the home such as the kitchen, bathroom, living room, and other quarters. They do not eat wood, but chew out areas to expand their nest size, sometimes causing structural damage. They prefer areas where there has been water damage. Winged males are smaller than winged queens. Wingless queens measure 5/8 inch, winged queens 3/4 inch, large major workers 1/2 inch, and small minor workers 1/4 inch. Workers have some brown on them, while queens are black. Workers have large heads and a small thorax while adult swarmers have a smaller head and large thorax. The petiole has one node and the profile of the thorax has an evenly rounded upper surface (workers only). See OSU Extension fact sheet HYG-2063 at ohioline.osu.edu.

Cornfield Ant

 
Nests are very commonly found in fields, lawns, between bricks in the walk, beneath rocks, in pavement cracks, etc. Numerous mounds of its nests are commonly seen in the lawn. They invade the home for sweets. They live on nectar of flowers, live and dead insects, and are very fond of honeydew. They collect the eggs of corn root aphids, storing them in burrows during the winter, then in the spring, carry young to the roots of corn. Yellowish, retarded corn and the presence of anthills around the injured corn plants are evidence of this dependent relation between the ant and aphids. They also transport strawberry root aphids to the crowns and roots of strawberries. Workers are about 1/10 to 1/4 inch long, light to dark brown, soft-bodied, robust, one node petiole (long pointed segment), 12-segmented antennae, without an antennal club, with the anal opening at the end of the abdomen, circular, and surrounded by a fringe of hairs. They have large eyes on the head and, when crushed, emit a strong odor of "formic acid."

Larger Yellow Ant

 
These ants are often mistaken for winged termites since the winged adults swarm through cracks in basement walls or floors, crawl around, and are attracted to lights. They live in the soil next to the building foundation, under basement floors, in concrete voids or in rotting wood, and feed on honeydew of subterranean aphids and mealybugs, which live on the roots of shrubs planted near residences. Winged forms are dark brown or blackish-brown with brownish, somewhat clouded wings and bodies measuring 3/8 to 1/4 inch long to the wing tips. Workers are pale yellowish-brown, about 5/32 to 3/16 inch long. They cluster around cracks and crevices and, when crushed, give off a strong odor, smelling like "citronella" or a certain kind of toilet soap. They are smooth, shiny, quite hairy, have 12-segmented antennae, one node petiole (long, pointed segment), small eyes on the head, uneven thorax profile, and the anal opening at the end of the abdomen is circular surrounded by a fringe of hairs. Workers stay underground during the day and forage at night.
David Cappaert, Michigan State University, Bugwood.org

Pharaoh Ant

This ant is a serious nuisance in hospitals, rest homes, apartment dwellings, hotels, grocery stores, food establishments, etc. They feed on jellies, honey, shortening, peanut butter, corn syrup, fruit juices, soft drinks, greases, dead insects, and even shoe polish. They have been found in surgical wounds, I.V. glucose solutions, and sealed packs of sterile dressing in hospitals. These ants are capable of mechanically transmitting diseases, Staphylecoccus and Psuedomonas infections in hospitals. Workers are very small about 1/16 inch long, light yellow to reddish-brown colored with the hind portion of the abdomen somewhat darker. The petiole has two nodes and the thorax is spineless. The antennae have 12 segments with the antennal club composed of three segments.


Thief Ant or Grease Ant

These ants are prevalent around kitchen sinks and in the cupboards, feeding on grease, oils, cheese, meat, dead insects, etc. They don't seem to feed on sweets. Workers are very small ants, about 1/32 to 1/20 inch long, smooth, shiny, yellowish to bronze colored with two nodes in the petiole, a 10-segmented antennae with a two-segmented club, thorax without spines, and small eyes on the head. It nests in the soil or wood, robs the food and brood of other ants, hollows out seeds for the oil content, and may feed on dead rodents.

Pavement Ant

 
This is one of the most common tiny house-invading ants in Ohio with nests usually found outdoors under stones, in pavement cracks, along the curb edges and in crevices of masonry and woodwork. Pavement ants may forage in the home throughout the year, feeding on grease, meat, live and dead insects, honeydew, roots of plants, and planted seeds. Workers are sluggish, between 1/12 to 1/4 inch long, light to dark brown or blackish, hairy, 12-segmented antennae with a three segmented club, a pair of short spines at the rear of the thorax, two nodes in the petiole, pale legs and antennae, and the head and thorax furrowed with parallel lines or grooves running top to bottom. In winter, nests may be found in the home near a heat source.


Little Black Ant

 
These are the common house ants which nest in woodwork, masonry, soil, and rotted wood. They feed on sweets, meats, vegetables, honeydew, and other insects. Workers are about 1/8 inch long, slender, shiny black, sometimes dark brown with two nodes in the petiole and a 12-segmented antennae with a three-segmented club. Nests in the ground are detected by very small craters of fine soil.
© Alex Wild, myrmecos.net, 2004

False Honey Ant or Small Honey Ant

 
These ants, sometimes called "cold weather ants," normally nest outdoors in the soil, but occasionally can be found in kitchens feeding on food and beverages. They forage along scent (pheromone) trails on counter tops with 12 or more ants in a line. Workers vary from light to dark brown (almost black) in color, are very shiny, have a triangular abdomen, and are about 1/8 inch long. The petiole has one node, the profile of the thorax is uneven, and the first antennal segment (scape) is longer than the head.
Jim Occi, BugPics, Bugwood.org

Allegheny Mound Ant

This ant normally lives outdoors with nests consisting of huge conical mounds, sometimes measuring nearly three feet high by six feet in diameter. Undoubtedly, some enter homes occasionally since they are fond of sweets, but normally attend honeydew-secreting insects on plants and are predaceous on other insects. Workers are about 1/4 inch long with a blackish-brown abdomen and legs, while the head and thorax are rust red. New colonies are founded by extension of or breaking off from existing colonies when workers migrate away with one or more queens. Related field ants may be brown, black, red, or various combinations of these colors.

Turfgrass (Lawn) Ant

 
This ant nests in well-drained, clay or gravelly soil and makes the well-known small anthills with a central entrance. Workers are about 1/4 inch long, yellowish in color occurring in lawns, golf courses, pastures, under walks or stones, and on trees. The abdomen is light tan with a darker brown band on each segment on the under and hind region. The head, thorax, and legs are slightly darker orange-brown than the abdomen.

Acrobat Ant

 
These ants may invade the home for food (sweets and meat). They feed on sweet juices such as honeydew of aphids, nectar, plant sap, etc. They build "cowsheds or tents" of plant or earthen material over aphids, which they tend. Workers are about 1/8 to 1/4 inch long, light brownish-yellow, and are recognized by a heart-shaped abdomen, flattened on the upper surface and curved below. They have a two-node petiole attached to the upper part of the abdomen and a pair of spines on the thorax. When disturbed, they elevate their abdomens, directing them forward in an acrobatic manner, and bite fiercely. They nest under wood, such as stumps, under boards, in hollow trees, under trash, rocks, in windows, and in door frames. They have an objectionable odor.

Odorous House Ant

 
These ants occasionally forage indoors for sweets and other foods. They give off an unpleasant odor when crushed, smelling like "rotten coconuts." Workers are brown to dark-brown in color, about 1/10 inch long. The petiole has one node (hidden by the abdomen) and the profile of the thorax is uneven.
Susan Ellis, Bugwood.org

 


Crazy Ant

 
These ants will feed on sweets and kitchen scraps, but prefer to feed on animal matter and insects such as fly larvae and adults. Ants present the appearance of running aimlessly about a room and, thus, named "crazy." Workers are about 1/10 inch long, with slender long legs, dark brown to black in color, one node petiole, the profile of the thorax not evenly rounded, and the abdomen tip has a circular fringe of hairs.

Control Measures

The most important step in ant control is to locate the nest and destroy the colony. Sometimes a drop of jelly, spoonful of honey, pile of sugar, or piece of bacon, placed near the site where ants are found, will attract them and help in locating their nest. Once an ant trail is established and followed, treatment can be made in the crack or crevice from which the ants are emerging, or an appropriate bait can be placed for easy access by the ants. An integrated pest management (IPM) approach is recommended. Try to eliminate food and water sources (sanitation), seal cracks and crevices where ants are entering (exclusion), and treat (chemical controls).

In the Home (Indoors)

Never treat entire walls, floors, countertops, cupboards, etc. Not only are these applications likely to contaminate foods, but the residues are often detected by the ants and they will simply avoid these areas until the residues have evaporated or have been removed by cleaning! Apply all ant insecticides only as crack, crevice, or hole treatments, or apply baits in appropriate tamper-proof containers, thereby avoiding food, children, and pet contamination. Dusts are often puffed into holes where they can provide good coverage of voids where ants are active. Hopefully, the worker ants will carry some of the chemical back into the nest, killing others. Aerosol sprays can be applied, but dispersal or area coverage may not be quite as good. So-called "bug bombs" (i.e. total release aerosols) are ineffective for ant controls as the fumes do not reach the ant nesting sites.

Depending on the kinds of ants, certain commercial baits can be ingested by workers, taken back to the nest for consumption, or regurgitated to feed and kill others in the colony. Toxic fast-acting baits kill foraging workers quickly, but are less effective than those that are slow-acting, which are taken back to the nest for consumption. Place bait stations directly on the ant trails away from children and pets. Over-the-counter "ant hotels" and similar small ant bait containers may contain small amounts of bait and these may have to be frequently replaced until the ant colony is eliminated.

House Foundation Spray (Outdoors)

To prevent ants from entering the house, use a perimeter treatment of the foundation. Sprays can be applied as high as two feet and out three feet into the soil, especially around windows, doors, etc., with the insecticide mixed in water. Only use pesticides that have this method on the labels in order to avoid plant injury. Over-the-counter granules for perimeter treatments are placed as a band around the base of the foundation. Be sure that all trees, shrubs, and flowers that are touching the foundation or walls of the house are pruned back or removed. These can provide access to the structure without crossing the insecticide barrier. Periodic treatments are often needed as this strategy does not normally eliminate colonies living outside.

In the Yard and Garden (Outdoors)

Many of the house-invading ant species live in the flower beds and turf surrounding houses. When these colonies are visible, sprays or dusts, applied directly in the ant mounds and around the area a few feet, can eliminate the problem. There are granular baits that are more effective for elimination of these colonies. Do not completely cover the nesting site with the bait! Sprinkle the amount recommended on the label on and around the nesting site so that the worker ants will pick up the bait and take it into the nest. Too much disturbance of the nesting site may cause the ants to move the nest to a nearby area!

On Trees and Shrubs (Outdoors)

Insects such as aphids, mealybugs, and soft scales excrete honeydew (a sugary waste product) that is highly attractive to ants, bees, and wasps! Insecticides that are used to control these plant pests can also help reduce ant populations. Be sure to select specific tree and shrub insecticides that list these insects on their labels.

Labeled insecticides

There are literally hundreds of insecticide formulations labeled for ant control. Some are labeled for general use (homeowners) while others are restricted use (licensed pesticide applicators only). In many cases, once an ant infestation has been found, control measures are best accomplished by a licensed, professional pest control firm. Homeowners often do not have the experience, availability of certain insecticides, and equipment needed to perform the job effectively on certain ant species.

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