The sting is among the most painful of any North American ant, and considerably worse than a fire ant's. It is also delivered by one ant rather than fifty, and they are far less inclined to use it.
We identify, we don't diagnose. If you've been bitten or stung and symptoms develop, or you're worried, seek medical attention.
Size5–10 mm
MarkingsLarge for an ant, 5–10 mm, red to reddish-brown · A cleared circle of bare ground around the nest, often a metre or more across
WhereOpen dry ground — desert, grassland, pasture and unwatered lawn edges in the west and southwest.
SeasonActive in warm months, foraging in the cooler parts of hot days
How to tell it apart
Large for an ant, 5–10 mm, red to reddish-brown
A cleared circle of bare ground around the nest, often a metre or more across
A beard of long hairs under the head, used to carry soil
Single obvious entrance hole, frequently surrounded by discarded seed husks
Slow, deliberate movement compared with a fire ant
Where you’ll find it
The southwestern and central United States, with related Pogonomyrmex species through the west.
Open dry ground — desert, grassland, pasture and unwatered lawn edges in the west and southwest.
Active in warm months, foraging in the cooler parts of hot days.
How it behaves
They collect seeds, which is where the name comes from, and store them in granary chambers underground. The cleared ring around the nest is deliberate — vegetation is stripped away — and it makes a colony very easy to spot and avoid. They are not aggressive foragers and will not swarm out of the nest the way a fire ant does; stings almost always follow somebody standing on the nest or picking an ant up. Harvester ants are also the main food of horned lizards, whose decline tracks theirs closely.
What a bite looks like
A red weal with swelling that can spread along the limb, and can persist for several hours. No pustule, which distinguishes it from a fire ant.
Intense, deep, radiating pain that builds and can last several hours — long out of proportion to the size of the animal.
We identify, we don't diagnose. Seek medical attention for difficulty breathing, swelling away from the sting, faintness, or multiple stings, and for any sting to a small child.
A skin mark cannot confirm which animal caused it. Read the bug bite and sting guide for the limits and the symptoms that should end an online search.
You’ve found one indoors
Give the cleared circle a wide berth — it is an obvious warning and the easiest avoidance measure available. They are ecologically valuable and there is rarely a good reason to control them; keeping play areas and paths away from an established nest achieves more than treating it.
Common questions
Is a harvester ant sting worse than a fire ant's?
Individually, yes — considerably. The difference is quantity: fire ants sting in numbers, harvester ants sting singly and reluctantly.
What is the bare circle around the nest?
The ants clear it themselves. It keeps the nest sunlit and free of cover, and it makes an active colony obvious from a distance.
Are they the ants in ant farms?
Often, yes — western harvester ants are commonly sold for them, which surprises people given the sting. Kits ship workers only and no queen.
How do I tell one from a fire ant?
Size and behaviour. Harvester ants are larger, all much the same size, slower, and the nest has a cleared ring and a visible hole. Fire ant mounds have no opening on top and erupt when disturbed.
Jonghyun Park · CC-BY