Two Very Different Threats
Not all ants are created equal. The common black ant found in most Sydney homes is a nuisance pest with minimal health risk. The red imported fire ant, by contrast, is one of the most dangerous invasive species in Australia — and its range is expanding. Here’s what you need to know about both.
Black House Ant (Ochetellus glaber)
The small black ant most commonly found in Sydney kitchens and gardens is typically the black house ant. It is native to Australia and found across the continent.
Identification:
- Uniformly shiny black
- Small — 2–3mm
- Trails in large numbers to food sources
Behaviour and risk:
- Primarily a nuisance pest — they contaminate food and are difficult to eliminate without treating the colony
- Do not sting. Can bite if threatened but bite is very mild
- Nest in soil, under paving, inside wall cavities and in subfloor spaces
- Attracted strongly to sweet and greasy food residues
Risk level: Low
Red Imported Fire Ant (Solenopsis invicta)
Fire ants are an invasive species that was first detected in Queensland in 2001. As of 2026, they have been found in south-east Queensland and are under active eradication management by biosecurity authorities. Their range is expanding southward, and they pose a credible threat to NSW — including Sydney.
Identification:
- Reddish-brown head and thorax, darker abdomen
- Variable size within the same colony — 2–6mm
- Build distinctive dome-shaped mounds of loose soil, typically in open sunny areas (lawns, gardens, roadsides)
- Extremely aggressive when the nest is disturbed — swarm rapidly and sting repeatedly
Behaviour and risk:
- Deliver a painful sting that causes an intense burning sensation — hence the name “fire ant”
- Sting sites develop into fluid-filled pustules within 24 hours
- Can cause anaphylaxis — allergic reactions to fire ant stings are potentially fatal
- Omnivorous — attack ground-nesting wildlife, livestock, and have caused significant agricultural damage
Risk level: Extreme — a notifiable biosecurity threat
What to Do If You Find Fire Ants
If you find what you believe are fire ants — particularly dome-shaped mounds in grassy areas — do not disturb the nest. Report the sighting immediately to the NSW Department of Primary Industries biosecurity hotline (1800 680 244) or via the Fire Ant Portal. Fire ants are a notifiable pest and must be reported by law in NSW.
Do not attempt to treat fire ants yourself — this can spread the colony. Authorised biosecurity officers will conduct treatment.
Dealing With Common Black Ants
While far less dangerous, black house ants still need to be controlled when they infest your home. Professional bait treatment is the most effective method for long-term control.
Pestyologist provides ant control across Sydney for all common species. Book a treatment today.