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Fire ants or harvester ants: how to tell which one you found
You may have seen big red ants moving from a bare patch of soil, or found a dirt mound where kids or pets play. In Phoenix, people often call them fire ants, but many yard mounds are made by harvester ants. This page helps you tell the two apart and decide how careful to be.
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- Rounded gravel mound in bare soil
- Open area around the nest
- Seed husks beside the mound
- Large orange, red, brown, or black ants near the mound
- Painful stings after disturbance
If someone was stung or bitten
Call Poison Help at 1-800-222-1222. It's answered around the clock by nurses and pharmacists at Arizona's poison centers, and they'll tell you whether you can stay home.
Call Poison Help: 1-800-222-1222
Call 911 right away for trouble breathing, swallowing or talking, or for a young child with strong symptoms.
Harvester ants are large seed-gathering ants that may be orange, red, brown, or black and can defend their nest with painful stings. Fire ants also live in Arizona, but they are smaller, vary more in size, and often nest in loose sunny soil near moisture. If anyone has been stung, call Poison Help at 1-800-222-1222 or 911 for severe symptoms, then keep people and pets away from the nest.
Harvester ants are native in the western United States and occur across the desert Southwest. In Arizona yards, their nests are often the giveaway. Look for a mound of gravel, small pebbles, or loose dirt with a broad open area around it.
These ants collect seeds from grasses and weeds. Workers often move on clear trails between the nest and food. You may also see a pile of seed husks near the mound, like the University of Arizona photo from Coolidge.
Fire ants behave differently. Southern fire ants in Arizona like bare, sunny soil near moisture, and their nests may look like low loose patches rather than tidy mounds. They may trail to food or water, but they do not make the cleared gravel mounds that harvester ants do.
Finding one mound usually means you found an outdoor colony, not an indoor infestation. Ants indoors are often foraging for food or water. Crumbs, pet food, soda spills, and food containers left out overnight can draw them inside.
- Workers about 1/4 to 1/2 inch long
- Orange, red, brown, or black body color
- Two small waist nodes
- Long hairs under the head
- Clear trails to food sources
- Mound with a center opening
Health risk
Harvester ants and fire ants can sting, so nests in play areas, walkways, dog runs, or patios deserve care. Fire ant venom can cause a burning sting, and people differ in how they react to ant venom. If symptoms worry you after a sting, call Poison Help at 1-800-222-1222 or 911 for severe symptoms.
Arizona fire ants are active in the morning and early evening. Southern fire ants may move indoors for food during warmer months.
What's different in the Phoenix area
In the Phoenix low desert, red imported fire ant is not established, and the dry climate limits that species. Native southern fire ants and harvester ants are the more likely issue. Irrigated turf edges, compacted bare spots, and sunny soil near moisture can make a yard more inviting to southern fire ants.
Often confused with
What you can do today
Step back from the mound
Do not kick, rake, or probe the nest. Harvester ants can defend the mound fast, especially when the nest is disturbed.
Keep kids and pets away
Mark the spot if it is near a play area, patio, or path. Teach children to avoid ant mounds and tell visitors if stinging ants are present.
Check the mound shape
From a safe distance, look for a rounded mound, a clear open area, and seed husks. Take a photo for a technician if you need help with identification.
Remove indoor food sources
Clean up spills, crumbs, pet food, and drink containers before bedtime. This matters most if ants are showing up indoors.
Avoid risky mound remedies
Do not pour fuel, ammonia, chlorine products, or household mixtures on ant mounds. These can harm soil, water, plants, and people.
When to call a pest control company
Call a local pest control company when stinging ant mounds are in high-use parts of the yard, when ants are entering the home, or when you cannot tell fire ants from harvester ants. A technician will look at mound shape, trails, food and water sources, bare soil, turf edges, and entry cracks before choosing a plan.
Not sure what you're dealing with?
Describe it on the phone. The company on the other end handles these calls every day and will know what to ask.
Common questions about harvester ants in Phoenix
Are harvester ants the same as fire ants?
No. Harvester ants are a different group, though both can sting and both may be red. Harvester ants are larger and often have a distinct mound with an open area around it.
Are red imported fire ants in Phoenix?
University of Arizona sources say red imported fire ant is not established in Arizona. Native southern fire ants and desert fire ants are found here.
What does a harvester ant mound look like?
It is often a mound of gravel, pebbles, or loose dirt in a dry bare area. The area around it is commonly cleared of plants, and seed husks may be piled nearby.
Why are ants coming inside?
Fire ants can forage indoors when they find food or water. Pet food, soda spills, crumbs, and food containers left out overnight can attract them.
Should I disturb the mound to see what comes out?
No. Both fire ants and harvester ants can sting when their nest is bothered. Watch from a distance or take a photo without standing on the mound.
Get the harvester ants problem looked at
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