Tapinoma sessileodorous house ant

Geographic Range

Odorous house ants (Tapinoma sessile) are one of the most widespread ant species in North America. Native to the Nearctic region, they are found in all 48 contiguous American states. Recently, they have also been found in Hawaii. Their range also extends into southern Canada and northern Mexico. (Buczkowski, 2010; Buczkowski, 2012)


Odorous house ants are said to have the greatest ecological tolerance of any North American ant species, and will build their nests in a large variety of temperate habitats and locations. They can be found in urban and natural areas, and nest in altitudes from sea level to over 4,000 meters in elevation. In natural areas, they live in forests, meadows, grasslands, riparian areas, bogs, pastures, and sandy areas along coasts. They also nest in areas that have experienced natural disturbances, such as areas that have recently flooded. Their shallow nests are typically under leaf litter, matted grass, in dried cow dung in pastures, in above-ground cavities in trees, beneath stones, in rotten logs and stumps, or in discarded galls. In urban areas, they nest in city parks, backyards, and essentially any disturbed area, such as in and around buildings, and in mulch and debris piles. Nests are rarely out in the open in urban areas, and are usually close to man-made structures. (Buczkowski and Bennett, 2008a; Buczkowski, 2010; Buczkowski, 2012; Menke, et al., 2010; Milford, 1999; Smith, 1928)

  • Range elevation
    0 to 4000+ m
    0.00 to ft

Physical Description

Ants of genus Tapinoma are distinguished by a flattened petiole slightly covered by the base of the abdomen. Among odorous house ants, workers are monomorphic; they are about 2.4 to 3.2 mm in length and weigh 0.35 to 0.87 mg. Workers have an oval-shaped head, a short, robust thorax, and a slightly arched body. They have few light yellowish hairs on parts of their body including their mandibles, clypeus, and coxae. Their body is deep brown or black, with lighter mandibles and appendages. Queens are larger, at 3.75 to 4.3 mm in length; they have a square head, large eyes, and stout antennae when compared to the workers. Queens also have a brown to black color on their body, with a lighter thorax and abdomen. When wings are present, they are gray with yellow-brown veins. After mating, queens lose their wings. Males are 3.60 to 4.44 mm in length and have a similar body shape as queens. They also have large, noticeable genitalia. Their body is deep brown to almost black, their mandibles and appendages are sometimes lighter in color. (Botz, et al., 2003; Smith, 1928)

Eggs are subelliptical in form and pearly white in color, measuring 0.24 by 0.39 mm. They become more opaque as they get closer to hatching. Larvae are the size of the egg when they first emerge, and grow to about 0.72 by 1.74 mm. As they grow, their head starts to curve. Their body is segmented and yellowish in color, and becomes very plump and thick when full grown. They have a distinct protuberance on the caudal end of their body. Prepupae look like full grown larvae, measuring about 1.8 mm in length. As they approach the pupal stage, the integument starts to dry and wrinkle. Pupae lack cocoons, and are naked and white, with no markings. They are typically 1.82 to 2.29 mm in length. After a couple days, their eyes begin to turn brown, then black, as their mandibles also turn brown and their body begins to turn shades of yellow. After emerging from pupation, in the callow stage, it takes a few days for adult ants to attain full color. (Botz, et al., 2003; Smith, 1928)

  • Range mass
    0.00035 to 0.00087 g
    0.00 to 0.00 oz
  • Range length
    2.4 to 4.4 mm
    0.09 to 0.17 in


Odorous house ants are holometabolous. Eggs are laid throughout much of the season, from late April until cold weather begins, usually in November. Eggs hatch after 11 to 26 days. The larval stage takes 13 to 29 days, the prepupal stage takes 2 to 3 days, and the pupal stage lasts anywhere from 8 to 28 days, averaging about 14 days in the summer. Following the molt from pupae to adult, there is a callow stage that lasts anywhere from 2 days days to several weeks before the ant becomes a fully-functioning adult. Total developmental time depends on the time of year that the eggs are laid. For eggs laid in April to June, total development from egg to adult takes 5 to 9 weeks. For eggs laid from June to September, development takes 6 to 7 weeks. Eggs that are laid later in the season overwinter as larvae, which can take 6 to 7 months to complete development to adulthood. Alate females are present in the nest in the middle of June or July, while males appear a little earlier, suggesting that the eggs that develop into reproductives are typically laid early in the season. In indoor nests, when temperatures remain warm year-round, egg laying likely also occurs year-round. (Smith, 1928)


There is little information available about the mating habits of odorous house ants. Mating likely takes place both within and outside the nest. Alate females appear in the middle of June or July, males appear shortly before. Mating takes place during this time and males die shortly afterward. (Smith, 1928)

Colonies might not produce sexual forms until they are well-established. Queens can lay up to 20 or 30 eggs in a day, but average around 1 to 2 eggs per day. In the course of a season, one queen averages about 350 eggs. This data is based on ants from large polygynous colonies in urban areas, so oviposition rates could vary depending on the number of queens present in the nest. While urban nests have many queens, nests in natural habitats typically only have one queen. In outdoor nests, oviposition occurs through most of the season, from April until October or November. In indoor nests, where temperatures remain warm throughout the winter, egg laying takes place year-round. Workers tend to the queens, providing general care and food via trophallaxis. Workers may lay eggs without mating. In one study, eggs that hatched were killed by workers upon reaching pupation. In other studies, researchers have reared workers from worker-laid eggs, which is interesting as unfertilized eggs normally develop into males. These eggs take longer to reach maturity, at about 11 to 12 weeks. (Smith, 1928)

  • Breeding interval
    Odorous house ants only breed once.
  • Breeding season
    Mating occurs in the middle of summer, while egg-laying occurs from early spring to fall.
  • Average eggs per season

Among odorous house ants, workers exhibit significant brood care, as do many ant species. When relocating, or when their nest is disturbed, workers carry the broods from nest to nest. Workers feed the brood via trophallaxis, which is regurgitating liquid food from mouth to mouth. They also lick and clean the brood, and help larvae when molting into prepupae. Males die shortly after mating and therefore do not provide any parental care. Likewise, queens do not provide any care either. Once the offspring develop into adults, brood care stops and they join the colony. (Buczkowski and Bennett, 2008a; Smith, 1928)

  • Parental Investment
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female


In natural conditions, queens likely live a year or longer, while workers likely live several months to a year or more. Males die about 1 week to 10 days after mating. (Smith, 1928)

  • Typical lifespan
    Status: wild
    3 to 12+ months


Odorous house ants nest in both natural and urban areas. Colonies of odorous house ants are only active from April to October in natural habitats, but year round in heated buildings and homes. These ants are active during the day and night, and will forage at any hour. They forage on well-established trails. Unlike many ant species, odorous house ants have no division of labor or any worker castes. All workers perform all tasks, including brood care, foraging, and constantly moving the contents of the nest from one location to another. In natural areas, odorous house ants are a subordinate species, living peacefully with many other ant species. However, in urban areas, colonies typically dominate resources and tend to exclude other species. Workers aggressively defend their territory from other ant species in urban areas. Individuals usually fight alone, and do not attack cooperatively with nest mates. This is likely because defensive chemicals function as alarm pheromones, so nest mates tend to flee when encountering a nest mate fighting, rather than joining in. Likewise, when a nest is disturbed, chaos ensues and ants run in a rapid jerky motion and may also elevate their abdomens. (Buczkowski and Bennett, 2008a; Buczkowski, 2010; Fellers, 1987; Klotz and Reid, 1992; Smith, 1928)

Odorous house ants have an unusual flexible colony structure that changes between urban and natural habitats. In natural habitats, colonies are typically small and monogynous (only 1 queen). These colonies live peacefully in the same area as other ant species. In urban areas, these ants form supercolonies, with many nests per colony (polydomous) and many queens per nest (polygynous). Nests are typically close together, and no aggression is exhibited between ants from different nests. This structure allows odorous house ants to become a dominant species, and also function as a pest species to human structures. Nests are moved frequently, changing locations as quickly as 21 days. Colonies reproduce by budding. The number of nests tends to change throughout the year; most of the colony overwinters in a central location, in one or a few nests. As soon as the temperatures begin to increase, the number of nests rapidly grows, peaking during the summer and remaining steady until late fall, when the number drops. While nests may move frequently, colonies can use the same overwintering and nesting sites for years. (Buczkowski and Bennett, 2008b; Buczkowski, 2010)

Home Range

While nests move often, colonies of odorous house ants tend to nest in the same places from year to year, and nest locations are usually nearby. Foraging trails between nests range from 10 to 50 feet long, ants rarely stray from these trails. (Buczkowski and Bennett, 2008a; Smith, 1928)

Communication and Perception

Odorous house ants forage on well established trails. They primarily use odor trails, but visual cues, such as light sources, and tactile cues are also important. These ants are thigmotactic, responding to physical touch, and tend to follow structural guidelines, such as grooves in the pavement and ridges in surfaces, particularly when foraging in the dark. Having trails that can be followed using different senses is useful for an ant species that forages both during the day and at night. Trails are rarely in open areas; in urban habitats, trails often follow structural guidelines, which are often man-made. Hydrocarbons on their cuticles are used to identify nest mates. Their antennae are used to detect these hydrocarbons, as well as other odors and chemicals in the environment. Their ability to identify nest mates is important because they form large colonies with many nests in urban areas. They can identify colony members from distant nests, and do not display aggression. Their lack of inter-nest aggression is key for their success. Defensive chemicals produced by odorous house ants serve as the colony alarm pheromone. These ants become highly agitated and erratic when they come upon a fighting nest mate; they deploy defensive chemicals and run away, rather than joining the fighting. (Buczkowski and Bennett, 2008a; Buczkowski and Bennett, 2008b; Klotz and Reid, 1992)

Food Habits

Odorous house ants are omnivorous. Honeydew secreted by aphids, scale insects, and membracids makes up a significant portion of their diet. These ants also feed from extra-floral nectaries, as well as eat tree sap. Odorous house ants prey on small insects and spiders, generally individuals less than 4.0 mm in length. They have also been observed feeding on vertebrate carrion. In urban areas, odorous house ants are "opportunistic", and will eat nearly any available human food. They have a preference for sweets, and will eat sugar, honey, butter, and ice cream, as well as non-sweet foods, such as beef, fish, potatoes, cheese, and milk. Odorous house ants bring prey back to the nest or store foods such as honeydew in their crop. Upon their return, they use trophallaxis to regurgitate the liquid food mouth to mouth to colony members that do not forage. (Buczkowski and VanWeelden, 2010; Buczkowski, 2012; Clark and Blom, 1991; Fellers, 1987; Klotz and Reid, 1992; Smith, 1928)

  • Animal Foods
  • carrion
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • nectar
  • sap or other plant fluids


Birds are significant predators of odorous house ants. They are preyed upon by northern flickers (Colaptes auratus), black-billed magpies (Pica hudsonia), chimney swifts (Chaetura pelagica), American crows (Corvus brachyrhynchos), red shafted flickers (Colaptes cafer collaris), and house sparrows (Passus domesticus). Toads of genus Bufo also prey on these ants. Larval antlions also consume odorous house ants that fall into their pits. To defend themselves, odorous house ants secrete defensive chemicals and display physical aggression towards predators and other ant species. (Botz, et al., 2003; Buczkowski and Bennett, 2008b; Gow, et al., 2013; Smith, 1928)

Ecosystem Roles

In natural areas, odorous house ants form small colonies and co-exist near the nests of other ant species, although they are never a dominant species. However, in urban areas, odorous house ants become dominant, and are found in close proximity with few, if any, other ant species. They form large polydomous colonies with huge numbers that out-compete other ant species for resources. Even though they are a native species, they can function as an invasive species in urban areas. Recently, they have been found in Hawaii, where they have the potential to become an invasive species. Since their nests can be found at elevations as high as 4,000 meters, odorous house ants have an advantage over many other invasive ant species that cannot live in altitudes as high. Odorous house ants are often found in the same areas as Argentine ants, a significant invasive species. They are often studied together, although one is native and one is invasive, they have similar biology, morphology, behavior, and colony makeup. Both species also colonize areas disturbed by human activity, and are household pests. They also tend many of the same aphid species. Argentine ants tend to out-compete odorous house ants for most resources, especially food sources. These species are very aggressive towards each other, and although odorous house ants can win one-on-one fights, large groups of Argentine ants can easily dominate groups of odorous house ants. (Buczkowski and Bennett, 2008a; Buczkowski, 2010; Buczkowski, 2012; Powell, et al., 2009)

Odorous house ants are ardent farmers of honeydew-producing insects, as honeydew is a significant portion of their diet. In exchange for the honeydew, the ants protect the aphids and other insects from predators and parasitoids. They form mutualisms with a large variety of insects, including membracids (Vanduzeea segmentata and Entylia sinuata), aphids (Aphis gossypii, Toxoptera aurantii, Periphyllus negundinis, Ceruraphis viburnicola, Anuraphis cardui, Myzus cerasi, Macrosiphum solanifollia, Lipaphis pseudobrassicae, and other members of genus Aphis), scale insects (members of genus Kermes, Chionaspis furfura, Coccus hesperidum, Planococcus citri, and Pseudococcus maritimus), and have been seen taking honeydew from butterfly larvae (Callophrys irus). Many insect species also live in their nests, since these species do not benefit odorous house ants, these relationships are not mutualistic. These species include crickets (Myrmecophilus oregonensis, Myrmecophilus manni and Myrmecophilus nebrascensis), wingless wasps (Isobrachium myrmecophilum), rove beetles (Staphylinidae, Zyras tapinomatis, Mymoecia lugubris, and Nototaphra lauta), as well as springtails (Collembola), termites (Isoptera), and pill bugs (Armadillidium). (Albanese, et al., 2007; Buczkowski, 2012; Powell and Silverman, 2010; Powell, et al., 2009; Smith, 1928)

Mutualist Species

Economic Importance for Humans: Positive

There are no known positive effects of odorous house ants on humans.

Economic Importance for Humans: Negative

Odorous house ants are significant pests in homes and buildings throughout much of North America. They often nest in mulch and debris piles, and will also nest inside buildings. Usual methods of eradicating pest species are not entirely effective on odorous house ants due to their polygynous, supercolony structure in urban areas. Pesticides and baits may kill a few nests, but other nearby nests can easily re-colonize the area. The widespread use of pesticides may also contribute to infestations of odorous house ants by removing other competing ant species. With the competition removed, colonies of odorous house ants are free to move into the area. The landscaping trend of placing mulch outside of buildings has also facilitated their status as a household pest. Their population can be controlled by removing the mulch or by replacing it with other substrates, such as aromatic cedar mulch. Additionally, odorous house ants tend many aphid species that could be crop pests. By maintaining and protecting these aphid populations from predators and parasites, odorous house ants indirectly cause crop and other plant damage. (Buczkowski, 2012; Meissner and Silverman, 2001; Powell and Silverman, 2010; Powell, et al., 2009; Scharf, et al., 2004; Smith, 1928)

  • Negative Impacts
  • household pest

Conservation Status

Odorous house ants have no special conservation status.

Other Comments

Odorous house ants get their common name from the distinct odor produced by their anal gland when they are killed or crushed. Reportedly this odor smells like coconuts. (Smith, 1928)


Angela Miner (author), Animal Diversity Web Staff, Leila Siciliano Martina (editor), Animal Diversity Web Staff.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in landscapes dominated by human agriculture.


reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.


flesh of dead animals.


uses smells or other chemicals to communicate


used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.

  1. active during the day, 2. lasting for one day.

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


the condition in which individuals in a group display each of the following three traits: cooperative care of young; some individuals in the group give up reproduction and specialize in care of young; overlap of at least two generations of life stages capable of contributing to colony labor

female parental care

parental care is carried out by females


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

internal fertilization

fertilization takes place within the female's body


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


an animal that mainly eats all kinds of things, including plants and animals


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


chemicals released into air or water that are detected by and responded to by other animals of the same species


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.


living in residential areas on the outskirts of large cities or towns.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


living in cities and large towns, landscapes dominated by human structures and activity.


uses sight to communicate


Albanese, G., M. Nelson, P. Vickery, P. Sievert. 2007. Larval feeding behavior and ant association in frosted elfin, Callophrys irus (Lycaenidae). Journal of the Lepidopterists' Society, 61/2: 61-66.

Botz, J., C. Loudon, J. Barger, J. Olafsen, D. Steeples. 2003. Effects of Slope and Particle Size on Ant Locomotion: Implications for Choice of Substrate by Antlions. Journal of the Kansas Entomological Society, 76/3: 426-435.

Buczkowski, G. 2010. Extreme life history plasticity and the evolution of invasive characteristics in a native ant. Biological Invasions, 12/9: 3343-3349.

Buczkowski, G. 2012. The odorous house ant, Tapinoma sessile (Hymenoptera: Formicidae), as a new temperate-origin invader. Myrmecological news, 16: 61-66.

Buczkowski, G., G. Bennett. 2008. Aggressive interactions between the introduced Argentine ant, Linepithema humile and the native odorous house ant, Tapinoma sessile. Biological Invasions, 10/7: 1001-1011.

Buczkowski, G., G. Bennett. 2008. Seasonal polydomy in a polygynous supercolony of the odorous house ant, Tapinoma sessile. Ecological Entomology, 33/6: 780-788.

Buczkowski, G., M. VanWeelden. 2010. Foraging Arena Size and Structural Complexity Affect the Dynamics of Food Distribution in Ant Colonies. Environmental Entomology, 39/6: 1936-1942.

Clark, W., P. Blom. 1991. Observations of Ants (Hymenoptera: Formicidae: Myrmicinae, Formicinae, Dolichoderinae) Utilizing Carrion. Southwestern Naturalist, 36/1: 140-142.

Fellers, J. 1987. Interference and Exploitation in a Guild of Woodland Ants. Ecology, 68/5: 1466-1478.

Gow, E., K. Wiebe, R. Higgins. 2013. Lack of diet segregation during breeding by male and female Northern Flickers foraging on ants. Journal of Field Ornithology, 84/3: 262-269.

Klotz, J., B. Reid. 1992. The use of spatial cues for structural guideline orientation in Tapinoma sessile and Camponotus pennsylvanicus (Hymenoptera, Formicidae). Journal of Insect Behaviour, 5/1: 71-82.

Meissner, H., J. Silverman. 2001. Effects of aromatic cedar mulch on the Argentine ant and the odorous house ant (Hymenoptera : Formicidae). Journal of Economic Entomology, 94/6: 1526-1531.

Menke, S., W. Booth, R. Dunn, C. Schal, E. Vargo, J. Silverman. 2010. Is It Easy to Be Urban? Convergent Success in Urban Habitats among Lineages of a Widespread Native Ant. PLOS ONE, 5/2: e9194. Accessed October 15, 2013 at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0009194.

Milford, E. 1999. Ant Communities in Flooded and Unflooded Riparian Forest of the Middle Rio Grande. Southwestern Naturalist, 44/3: 278-286.

Powell, B., R. Brightwell, J. Silverman. 2009. Effect of an Invasive and Native Ant on a Field Population of the Black Citrus Aphid (Hemiptera: Aphididae). Environmental Entomology, 38/6: 1618-1625.

Powell, B., J. Silverman. 2010. Impact of Linepithema humile and Tapinoma sessile (Hymenoptera: Formicidae) on three natural enemies of Aphis gossypii (Hemiptera: Aphididae). Biological Control, 54/3: 285-291.

Scharf, M., C. Ratliff, G. Bennett. 2004. Impacts of residual insecticide barriers on perimeter-invading ants, with particular reference to the odorous house ant, Tapinoma sessile. Journal of Economic Entomology, 97/2: 601-605.

Smith, M. 1928. The biology of Tapinoma sessile Say, an important house-infesting ant. Annals of the Entomological Society of America, 21: 307-330.