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Odorous House Ant

Odorous house ants are small ants about 1/8th inch long and dark brown in color. They are found throughout the U.S. and in spite of their name, are only an occasional pest in the house. Their name comes from the disagreeable odor similar to the smell of rotten coconuts, that is given off when the worker ants are crushed.

Odorous house ants commonly nest outdoors in the soil under stones, logs, mulch, debris and other items. They will also nest indoors in wall and floor voids, particularly in moist or warm areas. If only a few workers (wingless ants) are observed in the house it is an indication that they are nesting outdoors and entering the house in search of food. If winged swarmers are found indoors, or if workers are consistently seen in great abundance, it likely indicates they are nesting within the house.

Odorous house ants regularly forage for food along well-traveled trails. They feed on dead insects, sweets and meats. One of their favorite foods is the sweet honeydew produced by plant sap feeding insects such as aphids and mealybugs.

Control of odorous house ants should begin with an attempt to locate the origin of the ants. Careful and frequent observation may be necessary to develop an opinion about the source. Ants entering from outdoors can be discouraged by sealing as many cracks and gaps in exterior walls as possible. A insecticide labeled for use outdoors in ant control can be used to control individual ant hills near the house or to create a protective barrier to stop foragers from wandering into the house.

Pavement Ant

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.

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.

Pharoah Ant

The ant, Monomorium pharaonis (Linnaeus), is commonly known as the Pharoah ant. The name possibly arises from the mistaken tradition that it was one of the plagues of ancient Egypt (Peacock et al. 1950). This ant is distributed worldwide, is one of the more common household ants, and carries the dubious distinction of being the most difficult household ant to control.

The Pharaoh ant colony consists of queens, males, workers, and immature stages (eggs, larvae, pre- pupae, and pupae). Nesting occurs in inaccessible warm (80 to 86°F), humid (80%) areas near sources of food and/or water, such as in wall voids. The size of the colony tends to be large but can vary from a few dozen to several thousand or even several hundred thousand individuals. Approximately 38 days are required for development of workers from egg to adult.
Mating takes place in the nest, and no swarms are known to occur. Males and queens usually take 42 days to develop from egg to adult. The males are the same size as the workers (2 mm), are black in color and have straight, not elbowed, antennae. Males are not often found in the colony. The queens are about 4 mm long and are slightly darker than the workers (Smith and Whitman 1992). Queens can produce 400 or more eggs in batches of 10 to 12 (Peacock et al. 1950). Queens can live four to 12 months, while males die within three to five weeks after mating (Smith and Whitman 1992).

Part of the success and persistence of this ant undoubtably relates to the budding or splitting habits of the colonies. Numerous daughter colonies are produced from the mother colony when a queen and a few workers break off and establish a new colony. Even in the absence of a queen, workers can develop a queen from the brood which is transported from the mother country. In large colonies there may be as many as several hundred reproductive females (Smith and Whitman 1992).

Red Imported Fire Ant

Although the red imported fire ant (Solenopsis invicta) is common in 12 southern states, it is new to California and has recently been found infesting numerous residential and commercial areas in Orange, Los Angeles, Riverside, San Bernardino, and to a lesser extent, San Diego counties. The spread of these ants has largely been a result of the movement of infested soil to uninfested areas.

IDENTIFICATION Key to identifying common household ants
Red imported fire ant workers are variable in size (1/16 to 1/5 inch long) and dark reddish brown. Unlike our native southern fire ant (Solenopsis xyloni) and harvester ant (Pogonomyrmex californicus), the red imported fire ant can quickly produce many nests and colonize a yard. Harvester ant workers are all the same size (1/5 inch long) and are red in color. Many people refer to these as “red ants.” The most common ant around homes in California is the Argentine ant, Linepithema humile, a small grayish black ant that is uniform in size (1/10 inch long) and is seen moving along in long trails. While there are several physical characteristics that distinguish red imported fire ants from other common ant species found in California, one way to recognize this pest is to observe its aggressive behavior when its nest or food source is disturbed or to experience its painful bite and sting.

In areas that are not disturbed, red imported fire ants typically make dome-shaped mounds that are about 18 inches across and about 8 to 12 inches tall. They resemble large gopher mounds or look like crumbly earth with small holes; these mounds readily distinguish red imported fire ant colonies from other California ant colonies. Nests of the native southern fire ant, for instance, are usually irregular and consist of scattered soil with multiple obscure entrances. Unlike the other ant species mentioned, red imported fire ants tend to build nests in open, sunlit, grassy areas that are typically irrigated. They will readily run up any object that touches their mound, whereas the other species are much less aggressive. Because red imported fire ants often build their nests in turfgrass areas in California, frequently the mounds have been mowed and are nearly flat, appearing as soft, loose dirt that obscures the grass and looks like a bald spot in the turf.

In some instances red imported fire ants do not build mounds but nest in places such as rotten logs, walls of buildings, or under sidewalks.

Little Black Ant

The Little Black Ant is common throughout the world. It gets its name from its jet-black color and its small size. Worker ants are tiny, only about 1/16th of an inch long! Queen ants are bigger at about 1/8th of an inch. Like all insects, ants have 6 strong legs and antenae that they use not only to touch but also to smell. Adult ants also have strong jaws, but they cannot chew food! Instead they suck the liquid out of their food and leave behind the dry solid parts.

Black ants are active both during the day and at night, often carrying food back to its nest. Did you know that ants can carry 20 times their body weight? They live at the edges of forests and near human homes. Black ant nests are usually built underground, but we can see the small domes that are the tops of their homes in the dirt aboveground. Sometimes these ants will also build nests in rotting wood or trees. Black ants often eat whatever ‘human food’ they can find: sweet fruit cores, bits of meat, cooked vegetables, or even crumbs of bread. They will also eat other insects that they find dead.

Ants live together in colonies. Each colony has at least 1 queen ant. The queen lays eggs that the worker ants will guard and care for. Like honeybees, worker ants look for food, feed the young, and defent the colony against enemies. At night workers will move the eggs and the young larvae deeper underground to protect them from the cold. Most of these eggs will hatch into grubs that become worker adults. It usually takes about 10 days for the eggs to hatch. Some ants have wings; when the colony gets too big, these ants will fly away, mate, and start a new colony.

Harvester Ant

The common species of harvester ants – the Red, Western, and California harvester ants each have unique behaviors, castes and tasks, feeding, nesting patterns and defense mechanisms. The harvester ant behavior differs between each species, seen through their feeding and nesting habits. In addition, unlike other ants that infest indoor structures, all species of harvest ants prefer not to invade houses and buildings, but will establish their nests around gardens or yards, often destroying vegetation.

The red harvester ants can be aggressive. They give out a painful sting. Sometimes, the stings of red harvest ants can cause allergic reactions, especially to those sensitive to their venom. Aside from their powerful stings, the red harvester ant also bites viciously. However, due to the competition for food with the ferocious red fire ants, the population of red harvester ants appears to be declining.This is an important agricultural pest in many areas.

The feeding habits of red harvester ants can be seen as they leave their nests and crawl to their food sources, leaving a distinct scent throughout their paths. Once the scent paths stop, the red harvester ants go their own ways and forage for food.The Western harvester ant is found in the west at high elevations.

This is a red colored ant that can be almost one half an inch long. This ant can cause damage to highways by encouraging erosion under roads. Galleries have been found to go over 9 feet deep.Leafcutter ants also have been considered harvester ants. They exhibit high degrees of polymorphism with castes including the minims, mediae, minors and majors.

They are divided based on their size to perform different tasks. For instance, the majors are considered the leafcutter ant soldiers, while the mediae are known as the foragers of food. The minims tend their fungus gardens, while the minors guard the nest from predators. Leafcutter ants, particularly the majors, are strong enough to cut through leather.

Carpenter Ant

Carpenter ants are among the largest ants in North America with workers of C. modoc and C. vicinus ranging from 1/4 to 1/2 inch long. They have only one bulge at their narrow “waist” (the single node on their petiole) and an evenly rounded back, when viewed from the side (known as a smooth dorsal thoracic profile).

The western black carpenter ant, C. modoc, is uniformly black with dark red legs, while C. vicinus varies in color but usually is red and black. A smaller, yellow and black species, C. clarithorax, which also is common in California, ranges from a little longer than 1/8 of an inch to not quite 5/16 of an inch long.

Carpenter ants can’t sting but can inflict painful bites with their powerful jaws and spray formic acid into the wound, causing a burning sensation.

Homeowners might confuse the winged males and females that leave the nest on mating flights with termites. However, you can distinguish between ants and termites by the differences in their antennae, waist, and wings. Also, carpenter ant sawdust is fibrous versus the 6-sided shaped pellets of drywood termites.

Carpenter ants feed on dead and living insects, nectar, fruit juices, and sugary honeydew excreted by plant-sucking insects.

They will enter buildings in search of nesting sites or moisture and can build nests containing several thousand ants. Typically, the nests they construct indoors are satellites of a larger, parent nest located outside in a live or dead tree, a woodpile, or landscaping materials. Several satellite nests can be associated with a single parent nest, where the queen or queens reside, as in the case of C. vicinus, which can have as many as 40 queens in a single nest.

New reproductives have wings and leave the nest on mating flights in the spring. The timing of these flights varies for each species. For example, C. modoc swarms in the late afternoon, often after a heavy rainfall. After the mating flight, males die, and inseminated queens disperse in search of potential nest sites such as a dead tree or stump. Here, the newly mated queen excavates a chamber, seals herself in, and begins laying eggs. Colony growth is slow at first and only after several years does the colony reach maturity and begin producing a new generation of winged ants to begin the cycle again.

Argentine Ant

Since its introduction to the United States from South America in the late nineteenth century, the Argentine ant, Linepithema humile, has become a serious agricultural and urban pest throughout much of California and in numerous urban developments in the southeastern U.S. This invasive ant has disrupted ecosystems worldwide by directly displacing other ants (including fire ants) and other insects. Honeydew produced by aphids, scale and whiteflies is an important food source for the Argentine ant. Consequently, Argentine ants can be a serious problem when they tend these insect pests and protect them from natural enemy predation creating a problem in the ornamental landscape.

In the urban environment, Argentine ant colonies can reach high population levels around homes, schools, hospitals, etc. It is the dominant urban ant pest in California and Georgia and a significant localized pest in the other southeastern states such as South Carolina, Alabama, Mississippi, Louisiana, Florida, Tennessee and North Carolina. An urban ant distribution survey in North Carolina in 2000 determined that Argentine ants were present in over 20% of the samples submitted by professional pest control operators (PCOs). Either ants were misidentified earlier or have more recently become a problem in North Carolina as natural and agricultural habitats have been cleared for urban development.

Argentine ants do not bite or sting, but heavy ant activity in the urban landscape creates a nuisance for individuals seeking to spend time out-of-doors. Additionally, foraging workers will frequently migrate indoors in search of food and/or in response to outdoor extremes of drought or flooding. Activity of these ants indoors and outdoors provokes homeowners and businesses to apply remedial pest control themselves or have commercial pest control companies perform the work. Chemical insecticides, alone, without an overal management strategy are often inadequate for the long term.


Workers are about 1/8 inch (2.2 to 2.6 mm) in length. Argentine ants have a constricted petiole with one node and the12-segmented antenna has no club. Workers are usually a uniform light brown to brown in color, are slender-bodied with an oval to somewhat triangular shaped head. Mandibles (jaws) have two large teeth neat the tip followed by a series of small teeth.


The Argentine ant nests in diverse habitats and may support multiple reproductive queens in a colony. Related colonies may also be interconnected creating a web-like super population. They nest in soil exposed or protected under mulch, rotten wood, standing dead trees, debris, bird nests, bee hives, and many other places. Indoor nests are often found in walls of bathrooms and kitchens and in crawl spaces beneath the floor. They have a general diet and feed on sweets or fruit and will readily utilize honeydew from certain insects. Indoors they may also feed on grease-containing foods. They can exist in harmony with other related Argentine ant colonies but eliminate competing species within their range. The number of ants in large colonies is almost inestimable.