Fire Ants


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There are several species of fire ants in the United States. They get their common name from the painful, – and sometimes fatal – sting that the workers deliver when they are disturbed.

Appearance / Identification

What Do They Look Like?
fire ant identification

Fire ants, like all other ants, have a three-segmented body. The fire ant’s first two segments are reddish in color. The third segment is often dark colored, almost black.
The first segment of the fire ant’s body is the head. The large workers of the tropical fire ant, Solenopsis geminata (Fabricius), have heads that are shaped differently from the heads of the small workers.

Fire ants have eyes, but since they live underground, they receive a lot of sensory information through their antennae. Scientists use the size of the antennae to help distinguish one type of ant from another.

Scientists study the jaws, or mandibles of fire ants to help identify the species. Most species of fire ants have something different about the mandibles. The red imported fire ant, Solenopsis invicta (Buren), has four teeth on its mandibles. The southern fire ant, Solenopsis xyloni (McCook), has three teeth. (This ant is also known as the California fire ant.) The tropical fire ant, Solenopsis geminata (Fabricius), has smooth mandibles with no teeth.

The middle section of the fire ant’s body is called the thorax. All three pair of legs are attached to the thorax. In the summer, the fire ant colonies produce winged fire ants. Their wings are also attached to their thorax. The thorax is the segment of the body that provides movement for the ant.

The third segment is called the abdomen. The beginning of the abdomen has several small segments that give the ant the “pinched” waist. The number of small segments helps scientists identify an ant specimen. The large part of the abdomen is called the gaster. This is where the organs of the body and the stinger are located.

The fire ant stinger is different from the stinger of a honeybee. The fire ant stinger has no barb, so the ant can sting over and over. The fire ant venom is very strong and some people are very allergic to it. A few people go into shock after being stung and fire ants cause a few fatalities each year.

Observing from a Safe Distance
Scientists often have to use magnifying glasses or microscopes to study the bodies of fire ants. The various parts are very small and hard to see. Since fire ants sting and bite, most people prefer not to get very close to them. Most people identify fire ants by the mounds of soil that they build and the aggressive way they defend their colony. These are things that can be observed from a safe distance.

Size of Workers vs Queen
In a colony of fire ants, there workers of different sizes. Scientists use the word polymorphic to describe the difference in the size of fire ant workers. Small workers, called minor workers, are usually less than 1/8″ long. The large workers, called major workers, can reach over ¼” in length. The queens are usually larger then the major workers. Fire ant queens can reach half an inch in length.

Nests / Colonies

Fire ants seem to prefer nesting in open, sunny areas. There can be hundreds of colonies of fire ants per acre. Workers will build a mound of soil, especially in cold or rainy weather. It is very common to find fire ant mounds beside sidewalks, driveways, and foundations. Fire ants also make their nests inside of wall voids and in electrical boxes.

They usually swarm in late spring or early summer. The population of one ant colony averages 100,000 to 500,000 ants.

Bites & Stings

The Dangers of Fire Ants
Fire ants are very aggressive. If the mound is disturbed, hundreds of ants will rush out to defend the colony. They climb up onto the legs of the intruder. All of the ants seem to bite at the same time – as if they had heard a signal.

The ant workers can bite and then use their jaws to hang onto the skin of the victim. They rotate their abdomen and sting over and over. Fire ants got their name from these painful stings.

It is common for people to walk over small fire ant mounds without noticing them. This is the cause of many bites and stings. People who live in areas where fire ants are common supervise their children and pets closely when they are outdoors.

Symptoms of a Sting
In fact some people are sensitive to the venom and they become very sick if they are stung. The stings cause small blisters. Some people are allergic to the venom and these ants cause some fatalities every year.

Distribution / Geographic Range

What Parts of the Country do They Live In?
Fire ants seem to thrive in warm climates. There are several species that are native to the United States. There are also some species that were imported from South America.

Little Fire Ant
The little fire ant, Wasmannia auropunctata (Roger) is a native fire ant. It is found in throughout Florida. There have also been reports of this ant in several places in California.

Southern Fire Ant
The southern fire ant, Solenopsis xyloni (McCook), is native to the southern United States. It is found across the Gulf Coastal region. In California people often call it the California fire ant.

Tropical Fire Ant
The tropical fire ant, Solenopsis geminata (F.), is native to the southern states. In Florida this ant often displaces the southern fire ant. However, it has been displaced from areas along the Gulf Coast by the imported fire ant species.

Black Imported Fire Ant
The two imported fire ant species are the black imported fire ant and the red imported fire ant. The black imported fire ant, Solenopsis richteri (Forel) is found in Mississippi, Alabama, and southern Tennessee. The red imported fire ant, Solenopsis invicta (Buren) has spread across the southern half of the United States. It is found from the Carolinas to California. It has been reported as far north as Kansas and Maryland.

Red Imported Fire Ant
The red imported fire ant has become the dominant fire ant species across the southern United States. It has spread in several ways. Existing colonies naturally expand their territory into new areas during the course of the year. During the spring and summer, winged male and female ants swarm. They leave their nests to mate and start new colonies. These flights expand the fire ant territory.

How Do They Spread?
The most significant way for fire ants to expand their territory is by human transportation. Scientists discovered that red imported fire ants were being transported in truckloads of sod, bales of hay, and in potted nursery plants. Fire ants have also been transported in shipments of cargo and in the household items of relocating families. Many states have quarantines and conduct thorough inspections of incoming shipments to prevent fire ants from being introduced.


Ways to Get Rid of Them

People who find fire ants in their yards want them eliminated FAST. They also hope that after the treatment the ants will never return. So the ideal fire ant killer would be fast acting and it would also be long lasting. In order to accomplish both objectives, most people find they have to combine treatment methods.

Liquid Treatment / Sprays
There have been a lot of methods suggested for fire ant control. A few of them worked, but most of them did not work. Many people have tried to get rid of fire ants by spraying their yards with liquid insecticides.

Most of the time the ants came back. Sometimes the ants simply moved, and a few times the ants stayed right where they were and ignored the spray.

There are several things about fire ants that make them hard to eliminate. Their mounds are very sturdy. Most sprays hit the mound and run off. The mounds have no entrances on the outside. The ants come and go through tunnels under the mound. Insecticide sprayers usually don’t deliver enough liquid to reach the inside of the mound, let alone reach deep into the underground tunnels and kill thousands of ants.

Many insecticides can be applied directly to a fire ant mound. The insecticide label will have directions for drenching fire ant mounds. This will kill many ants, so it will provide immediate relief for mounds that are threats to people and pets. It will usually cause the surviving ants to relocate to a new nest site. Be sure to follow label directions for mixing and applying insecticide. Be careful — do not allow the ants to attack while doing this treatment!

Bait application
Bait is an effective tool for fire ant control. Most fire ant bait is made with a food attractant with an active ingredient mixed in. The ant workers take the bait back to the nest and share it with all of the other ants in the colony. If all of the ants eat a dose of the bait, the colony will begin to die. If the queen eats some of the bait, she will die and there will be no replacement ants produced.

Ant baits are made with several types of active ingredients. Several brands contain an insecticide as the active ingredient. When an ant eats a dose of this bait, it dies. Every ant has to eat a dose of bait or receive a dose from another ant. It usually takes time for this type of bait to work. A few brands of insecticide bait can eliminate a fire and colony in a few days. However, Most ant bait that contains insecticide takes a few weeks to get complete control.

Some brands of ant bait contain an insect growth regulator (IGR) as the active ingredient. The most commonly used IGR works by killing the eggs that the queen produces. When there are no new ants produced, the colony starts to die. This type of bait usually takes time to work. Some people use this type of fire ant bait as a preventive treatment.

The bait package label will have important directions. The label will specify how much bait should be applied. The label often prescribes the amount of bait to apply for every one thousand square feet. It is often easier to treat very large yards in sections. Multiply the length by the width to find the number of square feet in each section.

Fire ants forage for food near sunset and in the early morning. They do not look for food on the mound, so apply the bait in the grass away from the mound. Bait that goes on top of the mound will usually be wasted because the ants will not eat it. Some types of ant bait can spoil if they get wet, so be sure to read the label and watch the weather.

When the yard is fire ant free, the ants from the neighbor’s yard ill try to invade. The bait package label will have directions that explain when to re-apply the bait.

Perimeter application
If fire ants have made mounds next to the foundation, the workers might start coming inside to find food. The liquid insecticide label should have directions for a perimeter application. This can help discourage the ants from getting close to the house. Treat the foundation and a small band of soil next to the foundation. Follow the label directions.

Unfortunately, no insecticide treatment lasts forever. Sunshine and rain cause insecticides to breakdown. New ant colonies ill try top invade from the neighbor’s yard. The insecticide labels will have directions for re-applications.

Ineffective Methods

Do It Yourself Techniques That You Should Avoid
People have tried a lot of tricks in hopes of getting rid of fire ants.

Boiling Water
Many people pour boiling water on the fire ant mound. It may kill a few ants that are near the top of the mound. Since the tunnels extend deep into the soil, most of the water probably soaks in without accomplishing much. Most people who try this are disappointed with the results. The boiling water injures a few people in the process.

Some people have tried pouring gasoline or diesel fuel on the mounds. This is really harmful to the grass and to the environment. It is also risky to the person pouring the gas. The ants usually move their nest a few feet and continue their activities. This treatment is REALLY not recommended.

People have also tried feeding instant grits to the fire ants. Some say the ants will eat the grits and explode. Others say the ants will eat the grits and choke. In fact, adult ants can only digest liquids so they could not eat the grits. If ants find solid food, they take it back to the nest and give it to the immature ants, called larvae. The adults need sweets for their nourishment. The larvae require protein food, so the grits might help the larvae grow into strong, healthy adult ants. People who try this treatment have been disappointed with the results too.

Club Soda
There have been reports that pouring club soda into the mound would suffocate the ants with carbon dioxide. Scientists do not think this will work. It would take an enormous bottle of club soda to fill all of the tunnels with carbon dioxide. Many of the ants would escape during the treatment.