Fire Ants
Fire Ants – What they look like, How you get them & How to get rid of them.
Solenopsis xyloni
Facts, Identification & Control
Fire ants are small species of ant with a big reputation. They get their name from their ability to inflict bites and stings that cause a burning sensation. For this reason, fire ants are one of the most important pest species of ants in the US and around the world. Measuring around 1/16 to 1/4 of an inch long (1.6 to 6 mm), these ants are recognizable by the yellowish-red color of their head and thorax. The abdomen, or final body segment of these ants, is usually black.
The Southern fire ant is a native species found in Southern states such as California, Texas, Arizona, South Carolina, and Florida. The red imported fire ant is an invasive species from Brazil that was introduced to the US in the 1930s and has since spread throughout the country. They are now found in 13 states, mostly in the South. However, populations have been found in Oregon, Washington, and into the Pacific Northwest of Canada.
Fire Ant Head Close Up 
Solenopsis xyloni
Identification & Characteristics
- Other Names: RIFA, red fire ant, Californian fire ant, cotton ant
- Odor: None
- Color: yellowish red head and thorax; black abdomen. Winged reproductives are darker in color, and males are black.
- Size: 1/16 to 1/4 of an inch
- Legs: 6
- Antennae: yes, ten segments with a two-segmented club at the end
- Shape: Three distinct body segments with an unevenly rounded thorax’s
Habitat
Fire ants are ground-nesting ants that usually nest outdoors. Though the southern fire ant will sometimes nest in the wood or masonry of buildings, especially if it is in contact with the soil.
Red imported fire ants also usually nest outside, but will often build nests adjacent to foundation walls. Also, they can sometimes be found inside homes in areas with exposed soil, such as crawlspaces and bath traps. As a heat-loving ant, fireplace hearths and furnaces are also attractive to them. Often, red imported fire ants will be brought into a building via potted plants.
When fire ants do get inside, they are often searching for food or for new place to nest. They are attracted to electricity and can often be found in areas such as:
- Electrical junction boxes
- Air conditioners
- Gas and water meters
- Outdoor lights.
Outside the home, fire ant nests can be identified by the large mounds that they build. The mounds of the red imported fire ant are typically rounded, up to 18 inches high and 24 inches in diameter or more. Southern fire ant mounds are flatter and more regular, covering approximately 2 to 4 ft.² each. Both species prefer sandy soil that gets plenty of sun.
Behavior
Southern fire ants are omnivores. They feed on a wide range of food, including sugars, seeds, plants, and other insects. Like many ant species, the honeydew produced by aphids is an important food source for these ants. Southern fire ants have been known to remove insulation from phone and electrical wires, and have even been found chewing on clothing. However, this tends to happen more with clothes that have had food spilled on them. Although fire ants are capable of preying on other insects, they tend to scavenge more than they actively hunt.
Fire ants get their name from their sting. While they usually sting in defense of the nest, they can sting unprovoked. When a fire ant stings, it begins with a bite. Locking its mandibles in place in the skin of its victim, it then curls its body and delivers multiple stings with a stinger located at the tip of its abdomen. While stings can occur anywhere on the body, they are most common on the legs and feet, since most people are standing when they get stung.
Fire ant venom is an alkaloid, and causes a stinging sensation similar to that of a wasp. The burning sensation usually results in a raised bump or pustule and a reddening of the surrounding skin. However, in some people, an allergic reaction to the ant’s venom can cause a much more serious problem. In rare cases, people who are stung may go into anaphylactic shock. This tends to occur with people who’ve been stung by an ant or wasp in the past. In rare cases, anaphylaxis can be life-threatening if not treated quickly. Serious allergic reactions occur in approximately 2% of the population who get stung. It’s also important to note that anaphylaxis can happen even in people who are not allergic to the ants if they get stung enough times.
It’s estimated that around 30 to 60% of people who live in fire ant infested areas of the US are stung each year.
The red imported fire ant is also an aggressive species that will sting to defend its nest. These ants evolved in the rainforests of South America, and so they have a unique reaction to flooding. When water levels get too high, the ants form a raft from their bodies and drift on the water until they find dry land. Because they are outside of the nest, these ants are even more aggressive than usual and inject higher doses of venom when they do sting. This has caused deaths in hospitals and care homes where these aggressive ants enter and deliver multiple stings to bedridden patients.
Reproduction
Southern fire ants reproduce by swarming. Ant larvae fed a special diet become capable of reproduction and can be either male or female. Guided by pheromone signals, these winged ants will take to the air in the afternoon or evening of hot days between May and October. The lifecycle of fire ants is quite an interesting one. Fire ants will mate in the air, after which the males will die. The females will fly off to establish a new colony in the first suitable spot they can find. However, new queens can sometimes be found one to two miles from the nest they emerged from.
Red imported fire ants also reproduce by swarming. However, the colonies can be either monogyne or polygyne, meaning some have a single queen while others have multiple queens. Nests with a single queen reproduce only by swarming and are territorial. Polygyne nests, on the other hand, are not territorial and can reproduce both by swarming and by budding. Budding is a process in which a queen from an established colony will take a small group of workers and move out of the nest to begin a new colony elsewhere.
Once the queen has founded a colony, she will begin laying eggs. A single queen can produce more than 1500 eggs each day. It takes between 22 and 38 days for an egg to become an adult ant. For the first generation of workers, the queen regurgitates oils, lays sterile eggs as food, and even feeds the young her unneeded wing muscles.
The ants hatch from the eggs as limbless larvae. The larvae molt as they grow, shedding their skins through four larval stages. At the end of this process, the larvae pupate and emerge as adult ants. The first generation of workers then helps the queen raise the next generation.
Single queen colonies grow slower than multiple queen colonies, but end up being larger. Eighty thousand individual ants is typical for a single queen nest, but there may be as many as 250,000 individuals in the colony.
Colonies take a year or two to become fully mature. At this point, they begin producing reproductive ants of their own. Six to eight mating flights can take place between spring and fall, producing 4500 swarmers in one year.
Danger?
Fire ant stings are common in the areas where these species are active. In the southern US, most fire ant nests have a single queen and are therefore aggressively territorial. Stepping on or bumping into a fire ant mound will trigger an attack from the creatures. Stings are particularly common on children and household pets who don’t know to avoid the mounds.
Fatalities from fire ant stings are extremely rare. It’s estimated that the red imported fire ant has killed around 80 people since it was introduced to the US in the 1930s. Often, deaths occur due to allergic reaction, underlying health conditions, or immobile people being unable to escape from the ants. However, as an invasive species, red imported fire ants have had a severe effect on the populations of native wildlife. Ground-nesting birds are especially vulnerable to these ants, who often kill young birds in the nest.
Signs of a Fire Ant Infestation
In areas with a fire ant population, you may see foraging ants either outside or inside buildings. As colonies become established, visible mounds will start to form, usually in sandy soil outside. While the mounds make the ants potentially dangerous, they also make it easy to locate where ants are nesting. But remember, the ants can also nest in wood within the walls of a building. If you see lots of fire ants indoors, you may need to check your walls to make sure the ants aren’t nesting inside.
Controlling Fire Ants (including recommended product and Outdoor Control options)
Fire ant control can be difficult. Not only will the ants aggressively defend their nests, but reinfestation is always a possibility. While you may be able to remove them from your property for a season, there is a high risk that your property will be re-colonized by one or more queens during the next nuptial flight. For that reason, you may need to perform multiple treatments throughout the year to keep the fire ant population down.
Recommended product: Ortho Orthene Fire Ant Killer
Outdoor Control
There are multiple methods you can use to control fire ants outdoors, and each has their pros and cons. The best strategy is to use a mixture of different methods to achieve maximum control. The methods you can use on fire ants are:
- Direct injection of fire and mounds
- Broadcast application of bait
- Broadcast treatment with a contact pesticide
Directly injecting the mounds is the quickest way to kill fire ants, but make sure you use adequate protection to prevent ants from biting. You’ll also need to do a thorough inspection of your property to make sure you find as many mounds as possible. While larger mounds are easy to spot, you’ll probably miss some of the smaller nests that are mostly underground.
A broadcast application of bait delivers food that the ants will bring back to the colony and feed one another. While this can take longer, it’s a good way to kill off colonies you can’t find. Let the ants bring the poison into the nest for you. You’ll want to wait 7 to 10 days after applying bait before you interfere in any other way with the nests so that the ants have time to spread the poison through the colony.
A broadcast treatment with a contact insecticide will kill foraging ants on contact. However, killing foraging ants will not get rid of a colony by itself. For that reason, broadcast insecticide treatments are better used as a preventative measure to keep your property from being reinvested by reproductive fire ants. Multiple applications per year are usually needed. This is best done after you have already eliminated all the nests you can find on your property.
Best Products to Get Rid of Fire Ants
Inside the House:
The best products to use for treating fire ants indoors are baits. This avoids the need for spraying potentially harmful chemicals in your home. Also, it means that the ants will carry the poison back to the nest themselves, so you can achieve effective control without needing to know where exactly the ants are nesting.
Most bait uses a stomach poison to kill ants. However, there are baits on the market that combine a poison with an insect growth regulator. These powerful chemicals disrupt the lifecycle of the fire ant and sterilize the queen, making reproduction impossible.
Before using any fire ant bait in your home, make sure the label states it can be used indoors.
Recommended Bait Types:
Regular Bait:
Advion Ant Bait Gel
Bait with insect growth regulator:
Extinguish Plus Fire Bait
Ant Bait Stations:
Ant bait can be messy. That’s especially true when it comes to fire ants, since the bait often comes in the form of granules designed more to be spread outdoors than inside. That’s why ant bait stations can be a useful tool to control fire ants inside a building. Bait stations keep the bait in one place and let the ants come and go. This protects the bait from being spread around, and also keeps it safe from family pets or young children.
For more information on ant bait stations click here to see our full Ant Traps and Bait Stations Review.
Recommended Ant Bait Station:
Best Products for Outside the House:
Fire ants are best dealt with outside, since that’s where they are most likely to be. The best strategy for controlling fire ants outdoors is to begin with an outdoor bait. Then, once you’ve given the ants enough time to absorb the bait, target the mounds directly to destroy them with the pesticide application. Then, perform regular broadcast pesticide applications to kill any queens that attempt to recolonize your property.
Best Outdoor Bait:
Best Mound Treatment:
Best Preventative Treatment:
Preventing Fire Ant Infestations
- Regularly inspect your property to quickly detect any mounds that are forming.
- If you discover mounds, bait and then treat them directly with Ortho Ant Killer.
- Regular applications of a preventative treatment such as Ortho Broadcast Granules can help prevent new colonies from forming.
- Keep fire ants from getting inside your home by sealing up any cracks and crevices around air conditioning conduits, electrical sockets, gas and water meters, cracks in the foundation, and any other entrance points. Weatherproof silicone caulking is good for this task.
- Teach children to stay away from fire ant mounds to reduce the risk of them being stung.
