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.
Habitat
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.
- Habitat Regions
- temperate
- terrestrial
- Terrestrial Biomes
- savanna or grassland
- forest
- Wetlands
- bog
- Other Habitat Features
- urban
- suburban
- agricultural
- riparian
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.
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.
- Other Physical Features
- ectothermic
- heterothermic
- bilateral symmetry
Development
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.
- Development - Life Cycle
- metamorphosis
Reproduction
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.
- Mating System
- eusocial
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.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- asexual
- fertilization
- oviparous
- sperm-storing
- delayed fertilization
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.
- Parental Investment
- female parental care
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-independence
-
provisioning
- female
-
protecting
- female
-
provisioning
Lifespan/Longevity
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.
Behavior
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.
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.
- Key Behaviors
- diurnal
- nocturnal
- motile
- sedentary
- hibernation
- territorial
- colonial
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.
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.
- Other Communication Modes
- pheromones
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.
- Primary Diet
- omnivore
- Animal Foods
- carrion
- insects
- terrestrial non-insect arthropods
- Plant Foods
- nectar
- sap or other plant fluids
Predation
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.
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.
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
,
Aphis viburnicola
,
Anuraphis cardui
,
Myzus cerasi
,
Macrosiphum solanifollia
,
Aphis 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 (
Myrmecophila oregonensis
,
Myrmecophila manni
and
Myrmecophila 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
).
- membracids ( Vanduzeea segmentata )
- membracids ( Entylia sinuata )
- aphids ( Aphididae )
- melon aphids ( Aphis gossypii )
- black citrus aphids ( Toxoptera aurantii )
- box elder aphids ( Periphyllus negundinis )
- American snowball lice ( Aphis viburnicola )
- aphids ( Aphis )
- scale insects ( Coccoidea )
- scale insects ( Kermes )
- Harris' bark lice ( Chionaspis furfura )
- coccids ( Coccus hesperidum )
- citrus mealybugs ( Planococcus citri )
- American grape mealybugs ( Pseudococcus maritimus )
- frosted elfin larvae ( Callophrys irus )
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.
- 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.
Additional Links
Contributors
Angela Miner (author), Animal Diversity Web Staff, Leila Siciliano Martina (editor), Texas State University.
- Nearctic
-
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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- temperate
-
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).
- terrestrial
-
Living on the ground.
- 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.
- savanna
-
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.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- bog
-
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.
- urban
-
living in cities and large towns, landscapes dominated by human structures and activity.
- suburban
-
living in residential areas on the outskirts of large cities or towns.
- agricultural
-
living in landscapes dominated by human agriculture.
- riparian
-
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- heterothermic
-
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.
- 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.
- metamorphosis
-
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.
- eusocial
-
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
- iteroparous
-
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).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- asexual
-
reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents
- fertilization
-
union of egg and spermatozoan
- internal fertilization
-
fertilization takes place within the female's body
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- sperm-storing
-
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.
- 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.
- female parental care
-
parental care is carried out by females
- diurnal
-
- active during the day, 2. lasting for one day.
- nocturnal
-
active during the night
- motile
-
having the capacity to move from one place to another.
- sedentary
-
remains in the same area
- hibernation
-
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.
- territorial
-
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
- colonial
-
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.
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- chemical
-
uses smells or other chemicals to communicate
- pheromones
-
chemicals released into air or water that are detected by and responded to by other animals of the same species
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- chemical
-
uses smells or other chemicals to communicate
- carrion
-
flesh of dead animals.
- omnivore
-
an animal that mainly eats all kinds of things, including plants and animals
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