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Published on 14th June 2022 by staff

Odorous House Ant

Tapinoma sessile

Odorous house ants are small ants that are often considered pests as they set up colonies inside homes and contaminate foods. Also known as stink ants and coconut ants, they leave a foul smell, like rotten coconut, if crushed – earning them their name. Though not poisonous or dangerous, they are a nuisance as they quickly establish colonies in your house and wouldn’t go away anytime soon.

Odorous House Ants

Scientific Classification

Family: Formicidae
Subfamily: Dolichoderinae
Tribe: Tapinomini
Genus: Tapinoma
Species: T. sessile

Odorous House Ant Image

Description

These ants have a shiny black or dark brown body, no larger than 1⁄16 to ⅛ inch (1.5-3.2 mm). The gaster portion or stomach (the largest segment of an ant’s body) lies on top of the petiole (the small narrow ‘waist’ part), hiding one of its nodes. It makes the petiole appear tiny.

The gaster points downward, which is another characteristic feature that helps distinguish the odorous house ants from other similar ants. The abdominal end of the gaster has a slit-like opening instead of a sting.

The thorax (the section right behind the head) looks uneven from the side.

Their antenna has 12 segments, but no club. Like any other ant, the queens and reproducing males have two pairs of wings.

Odorous House Ant

Distribution: All over the US, as well as southern Canada and Northern Mexico

Habitat: Indoors, near heaters, under sinks, beneath the floor; Outdoors, beneath logs, debris

Diet: Anything they can find; Prefer high-sugar foods, nectar, honeydew

Do They Bite: No

Lifespan: Queen and workers – up to a year; Males – up to 10 days after mating

Predators: Birds, toads, and larger ants

Behavior and Characteristics

Foraging

Like most other ants, they target sugary foods and proteins over lipids (nuts and oils) and are particularly fond of honeydew. They prefer to live near food sources instead of carrying the food too far, so they change nests every 3-4 weeks and set up new nests near their current food source. During winter, they stick together in a single nest. Then in spring and summer, they build multiple nests near different food sources (seasonal polydomy).

Known for being hardy — worker ants with severe injuries can live and work for days. Queens can survive for months without food and lay eggs even when their abdomen is crushed. They are also extremely tolerant to both heat and cold.

Their habitat often overlaps with others like the Argentine ant and cornfield ant. But being a peaceful species, the odorous house ants avoid confrontation with other insects.

Nest and Colony

Their colonies can contain thousands of ants and have multiple colonies at a time, having more than one queen. The queen ants lay eggs that hatch after 2-3 weeks, with the larval stage lasting another 2-4 weeks. The larva then enters the pre-pupal and pupal stages, taking approximately 2-3 weeks to become adults.

Adult winged ants ready to reproduce are called swarmers, which appear between May and July. Seeing them in or near your home usually indicates they already have a well-established colony.

Some studies suggest that these ants can co-exist with other species in compound nests.

Odorous House Ants Nest

Comparison With Similar Species

 Odorous House AntCarpenter AntPavement Ant
SmellRotten smellNoneNone
SizeAround ⅛ inchAround ½ inchAround ⅛ inch
AppearanceTiny, black-brown, with a small petioleBlack or reddish-brown, much largerTiny, black-brown; petiole is more defined
Common Infestation SiteInside houses, under sinks, floorIn and around wooden furnitureOutdoors, in driveways and sidewalks
Damage CausedContaminate foodsDamage wooden objectsContaminate foods
Odorous House Ants Picture

Getting Rid of Odorous House Ants

As already mentioned, they are challenging to eliminate, especially if it’s a well-established infestation. Though it is not impossible to kill them using insecticides and traps, eliminating one colony is never enough. When using lures or baits, keep them out for about 2-3 weeks, replacing them when necessary.

Tapinoma sessile

FAQs

Why do odorous house ants smell?

Ans. When you kill or step on these ants, they emit a chemical similar to a penicillin mold – the same one that causes foods to rot. This is what causes them to leave the rotten smell, often described as that of rotting coconut, overripe fruits, stale butter, or blue cheese. Entomologists Clint Penick and Adrian Smith were the first ones to research and discover the reason for the smell.

Image Source: objects.liquidweb.services, extension.umd.edu, inaturalist-open-data.s3.amazonaws.com, hort.extension.wisc.edu, callnorthwest.com, calphotos.berkeley.edu

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