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How to identify it
- Workers are very small, about 1/16 inch, light yellow to reddish brown with a somewhat darker abdomen. Texas A&M gives a range of about 1/16 to 1/12 inch, and all workers in a colony are about the same size.[1][2][4][5]
- Two nodes at the waist and no spines on the thorax. Sources differ on the stinger: Ohio State says there is none, while Texas A&M says a stinger is present but not always visible, and that they do not sting people.[1][4]
- The antennae end in a three-segmented club (the similar thief ant has a two-segmented club).[1][4][5]
- Because they are so small, Minnesota says Pharaoh ants are easily confused with thief ants and a microscope is often needed to tell the two apart.[5]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Thief ant | Even smaller (about 1/32 inch), yellow to light brown, with a two-segmented antennal club. Minnesota instead puts thief ant workers at about 1/20 inch, calls them the smallest household ants in the north central states, and says they often nest outdoors in soil and rotting wood and steal larvae from other ants.[1][2][5] |
Where it lives
Nests in warm, dark places in buildings, such as wall voids, under floors, behind baseboards, near hot water pipes and heating systems, and in light fixtures and linens; it also nests outdoors in warmer climates, such as parts of California.[1][2]
Biology and life cycle
Colonies breed all year in heated buildings, and mating happens inside the nest. Ohio State says mature colonies hold several queens and can reach 300,000 or more members. Texas A&M describes colonies made of many nests whose members move freely between them, ranging from a single queen with a few hundred workers to hundreds of queens with several thousand workers.[1][4]
Ohio State says the whole life cycle takes about 38 to 45 days, depending on temperature and humidity. Texas A&M says workers develop from egg to adult in 36 days and winged males and females in about 44 days, and a 2024 developmental study put egg-to-adult development at 45 days in total.[1][4][8]
Ohio State says a female can lay 400 or more eggs in her lifetime. Texas A&M says queens may live for a year and lay up to 35 eggs a day, and workers live about 70 days.[1][4]
New colonies form by budding: a queen and some workers carrying brood move to a new site. Budding can be triggered by crowding, heating and cooling changes or a repellent pesticide. Minnesota notes that Pharaoh ants have no mating swarm: when a colony gets too big or is stressed, workers carry brood to a new site and one or more queens often go with them.[1][5][4]
Nests are tiny and very hard to find. Ohio State says one can fit in a thimble and may be in wall voids, under floors, behind baseboards, in light fixtures or between sheets of paper, usually in dark, warm spots near hot water pipes. Minnesota lists spaces behind countertops and baseboards and in wall voids, near warmth and moisture.[1][5]
They prefer fats and proteins as well as sweets. Minnesota says they especially like grease and fats, also take sweets, dead insects, toothpaste and soap, and often look for water in kitchens and bathrooms.[2][5][4]
Damage and signs
- Workers forage through drains and trash as well as food and, in hospitals, have been found in wound dressings and IV solutions. Ohio State adds that they gnaw holes in silk, rayon and rubber goods.[1]
Health risk
Pharaoh ants can carry bacteria on their bodies, which is why they matter in hospitals. In a 2020 study in a hospital in Brazil, Pharaoh ants were both the most common ant collected (39.2% of 9,687 ants) and the most often contaminated with bacteria (38.3%); Pseudomonas aeruginosa was the disease-causing bacterium found most often. The authors say bacteria on ants may be linked to the spread of hospital infections.[6]
Control
Traps and physical control
Find feeding sites and trails first; small cards with dilute honey or peanut butter help locate hot spots.[1]
Where insecticides can't be used, such as around medical equipment, Ohio State suggests barriers: sticky or double-sided tape, masking tape wrapped glue side out, a ring of petroleum jelly, or glue boards under equipment legs.[1]
Pesticides
Avoid repellent sprays such as pyrethrins: they can trigger budding and spread colonies throughout a building. About 90% of the colony stays hidden in the nest, out of reach of sprays.[1][4][5]
Use baits made to attract Pharaoh ants (they favor fats and proteins as well as sweets) along trails so workers carry the toxicant back to the queens; non-repellent boric acid dust can be used in wall voids near active colonies. Texas A&M says the most successful approach is to place bait stations widely through the building along active trails, make sure workers from every colony feed on them, and check and replace them regularly.[1][2][4]
Bait speed matters. In a lab study of four linked colonies, a fast-acting hydramethylnon bait cut worker, brood and queen numbers near the bait within 3 weeks, but ants from colonies farther away moved back into those nests. A slow-acting insect growth regulator bait (pyriproxyfen) spread to all the nests and gave gradual, longer-lasting control.[7]
Total-release foggers (bug bombs) don't reach the colonies, and Ohio State says that if the fumes do reach a nest, the ants may quickly move it somewhere else.[1]
When to call a professional
Control is difficult and slow. Ohio State says it often takes months to years and a single hospital can hold dozens or hundreds of colonies; Texas A&M says a baiting program may take several months to a year. Cooperation from the property manager and every resident is essential.[1][4]
Minnesota highly recommends an experienced pest management service and says the baits available to residents are generally not effective against Pharaoh ants. Ohio State likewise says these treatments are best left to commercial applicators.[5][1]
Common questions
- Why did spraying make my ant problem worse?
- Repellent sprays can cause Pharaoh ant colonies to bud into new colonies elsewhere in the building. Texas A&M and Minnesota also warn that repellent insecticides cause budding.[1][4][5]
- How do I know if they're Pharaoh ants?
- Look for tiny (about 1/16 inch) yellowish ants with a darker abdomen trailing indoors year-round, often near warmth and water. A microscope is often needed to rule out the thief ant.[1][2][5]
- Can I get rid of Pharaoh ants myself?
- It is hard. Minnesota says store-bought baits are generally not effective against Pharaoh ants and recommends an experienced professional, and Ohio State says baiting is best left to commercial applicators who understand it. Whatever you do, avoid repellent sprays and foggers, which spread the colonies.[5][1]
Sources
- Ohio State University Extension, “Pharaoh Ant, HYG-2136 (2011).” ohioline.osu.edu/factsheet/HYG-2136-10 (accessed 2026-11-11)
- University of California Statewide IPM Program, “Pest Notes: Ants, Publication 7411 (October 2012).” ipm.ucanr.edu/legacy_assets/PDF/PESTNOTES/pnants.pdf (accessed 2026-11-11)
- iNaturalist, “Monomorium pharaonis taxon page (order and family).” www.inaturalist.org/taxa/69320 (accessed 2026-11-11)
- Texas A&M AgriLife Urban and Structural Entomology Program, “Pharaoh Ant, Monomorium pharaonis.” urbanentomology.tamu.edu/urban-pests/ants/pharoah/ (accessed 2026-11-11)
- University of Minnesota Extension, “Ants.” extension.umn.edu/insects-infest-homes/ants (accessed 2026-11-11)
- Journal of Medical Entomology, via PubMed, “do Nascimento et al. (2020), Ants (Hymenoptera: Formicidae) as potential mechanical vectors of pathogenic bacteria in a public hospital in the Eastern Amazon, Brazil, J Med Entomol 57(5):1619-1626.” pubmed.ncbi.nlm.nih.gov/32368780/ (accessed 2026-11-11)
- Journal of Economic Entomology, via PubMed, “Oi, Vail and Williams (2000), Bait distribution among multiple colonies of Pharaoh ants (Hymenoptera: Formicidae), J Econ Entomol 93(4):1247-1255.” pubmed.ncbi.nlm.nih.gov/10985038/ (accessed 2026-11-11)
- Journal of Experimental Zoology Part B, via PubMed, “Rajakumar et al. (2024), From egg to adult: a developmental table of the ant Monomorium pharaonis, J Exp Zool B Mol Dev Evol 342(8):557-585.” pubmed.ncbi.nlm.nih.gov/39584621/ (accessed 2026-11-11)