Red Imported Fire Ants vs. Southern Fire Ants

Close-Up Of Fire Ants On String And Cable

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As if Arizonians didn't have enough critters to be worried about--scorpions, rattlesnakes, killer bees, and black widow spiders--a new natural enemy has surfaced, and it is no laughing matter. The fire ant has been a hot topic of conversation since a napping three-month-old baby in the Phoenix area was killed by hundreds of stings from fire ants in 2003.

This is an unusual case, and neither the Arizona Department of Agriculture nor Arizona State University entomologists have been able to explain why the fire ants swarmed in this particular situation. Since this type of occurrence is rare, it is best not to panic if you see a few fire ants. It is prudent, though, to be aware of them.

Types of Fire Ants

Fire ants include a large group of reddish-brown to black ants. There are two types of fire ants we need to be concerned about. There are the Red Imported Fire Ants (Solenopsis invicta) and Southern Fire Ants (Solenopsis xyloni). In the case mentioned above, the culprits were the Southern Fire Ants, which are native to Arizona.

To be honest, it is difficult for someone who isn't an ant expert to distinguish between the critters. Red Imported Fire Ants have been targeted for extinction by the U.S. government, and it has been trying for years to stop their migration across the country with limited success. We know there have been Red Imported Fire Ants documented in Arizona. According to The Arizona Department of Agriculture, our state has been successful, so far, at eradicating the highly aggressive Red Imported Fire Ant when it has been identified.

Although Southern Fire Ants are common here, and not as aggressive as their Red Imported relatives, as non-experts in the study of ants we should probably treat them all with caution. After all, it can take many samples for even experts to tell which ant is which!

Characteristics of Southern Fire Ants

  • Fire ants are between 1/16 to 1/4-inch in length. The biggest will be "soldier" ants, while the smaller ones are the "minor" ants.
  • Fire ants are reddish-brown to black in color.
  • Fire ant mounds or nests may be constructed under stones, boards, or other objects.
  • Fire ants also nest in wood or the masonry of houses, especially around heat sources such as fireplaces.
  • Fire ants enjoy warm climates.
  • It is common for fire ants to sting children, typically on the lower extremities.

Characteristics of Red Imported Fire Ants

  • Red Imported Fire Ants are very aggressive, readily attacking anything that disturbs them.
  • Red Imported Fire Ants have a painful sting, causing blistering. The Southern Fire Ant typically has a relatively minor sting. Of course, just like bee stings, people can have allergic reactions to ant stings that may be more severe.
  • Red Imported Fire Ant mounds are often large and easy to spot. A mound might be 18 inches high and 24 inches in diameter. They are dome-shaped. They do not have one central opening into the colony. An extensive tunneling system is present within the mound. Southern Fire Ant nest mounds are usually much smaller. There may even be no mound at all, but rather just a series of small dirt piles.

In Arizona, if you come across some fire ants, it is more likely that they will not be the more aggressive and dangerous Red Imported Fire Ants. They are probably the Southern Fire Ant that in most cases, won't cause much harm. Fire ants build mounds in sunny, open areas such as lawns, playgrounds, ball fields, parks, golf courses, and along road shoulders. When it becomes very hot (or very cold) they may move indoors. If they concern you, your local exterminator can easily handle them.

There is some good news about fire ants: they are considered beneficial insects because they feed on other unwanted pests such as fleas, filth-breeding flies, horn flies, boll weevils, sugarcane borer, ticks, and cockroaches.

If You Are Stung By Fire Ants

If you notice blistering occurring after being stung or after stepping on an ant mound, seek out medical advice. Some people experience an allergic reaction to a fire ant sting. Symptoms may include sweating, slurred speech, chest pain, shortness of breath, hives, swelling, nausea, vomiting, and/or shock. People exhibiting these symptoms after being stung by fire ants should get medical attention immediately. For more information, you can contact the Arizona Poison and Drug Information Center at 1-800-222-1222 or 520-626-6016.

The death of the infant, in this case, was a tragic aberration. There's no reason at this time to believe that there is an epidemic or infestation of deadly fire ants in the Phoenix area.

Special thanks to Dale Ward of Tucson (Ants of Arizona)for his assistance with this feature.

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