Red Imported Fire Ants

When we speak of “fire” ants, particularly those of you with personal encounters with them, we generally are speaking of one particular kind, and this is the one called the Red Imported Fire Ant, usually abbreviated as RIFA, which I will do in this article. The fire ants are given this catchy name because when they sting there is an instant, intense, burning pain associated with the injected venom. Of all the species of fire ants in the United States, RIFA is, without a doubt, the absolute worst, and it presents a distinct threat to public health and the health of our environment. Let’s learn how.

There are about a half dozen different species of fire ants in the U.S. Some of them are native species, such as the Southern Fire Ant, which occurs throughout the southern states and into California. While they can sting people, and it hurts a lot, they are not nearly the threat of RIFA. These native species have smaller colonies, they are not as aggressive, and they have evolved to fit properly into their native environment. It is the Red IMPORTED Fire Ant that has invaded new territory, and it came without any natural controls to keep its numbers low and to keep it from spreading.

Fire ants in general can be identified by a couple of visible features. First, they are “two-bump” ants, and this refers to the fact that on the thin waist between their thorax and abdomen you can easily see two small enlarged sections. Most of our common, non-stinging, house-invading black ants have only one “bump” at that point. Fire ants also are dark red with blackish abdomens, and over their entire body they have long, bristly hairs. You will need a good magnifying glass to see these various things.

When did RIFA enter the U.S.?

It is not known exactly when this happened, but somewhere around 1930, probably in soil material with plants being brought in from South America, RIFA managed to hitchhike into Alabama. It found the climate to its liking and it set to work expanding its territory. Within 10 years it had spread to other states and by 1953 it had infested 10 states in the southeast. By 1993 it was infesting an unbroken area from Texas to South Carolina, and in 1997 the first colonies were discovered in California, where it now likely is also a permanent resident.

This fire ant species nests in soil, although it may transport soil into above ground objects and structures and make its nests there. It commonly enters equipment that may then be moved from place to place, furthering the spread of RIFA. It commonly nests in bee hives, and it may have entered California in this manner. It commonly nests in the soil of potted plants, and it was transported from infested California nurseries to Nevada in this manner. It commonly nests in vehicles, and it is believed this was the likely mode of transport for colonies found recently in northern California.

What are some of the problems from RIFA?

The problems are numerous and dramatic, but possibly the two most important are the ability of this ant to cause a huge negative impact on the environment in the United States, and its ability to sting. We will focus our attention on these two areas, but it is worth mentioning some other problems too. One of the characteristics of the RIFA is that it commonly makes mounds of dirt above its underground colonies. These mounds may be as high as 3 feet, and they are composed of hard, compacted soil, that interferes with equipment used in harvesting crops or mowing lawns.

What are some of the problems from RIFA?

Often the ants move their nests into equipment or objects near the ground, and for some strange reason they are particularly attracted to electrical devices of various kinds. This may be in the form of landscape lighting, electrical boxes, circuit breaker and fuse boxes, or even computerized equipment. Within these sensitive sites they will chew on the coverings over the wires, and eventually cause short circuits and equipment failures. As a tropical species the RIFA also is attracted to moisture sources, and these may be sprinkler valves and control boxes that also suffer the damage of the dirt piled within them.

Red Imported Fire Ants also will feed to some degree on plant materials, and in either landscape or agriculture they cause some serious damage to developing fruits or other produce. In a commercial nursery, of course, this can be a huge financial loss, as even a small amount of damage to these plants may make them unmarketable. Another way in which RIFA hurts nurseries is by causing quarantines of nursery materials in any area that the ants are prevalent. Since the ants so commonly infest the soil of the pots in which the product is grown it must be assumed they could be there, and prior to being shipped from that area the soil may need to be treated, adding a great deal of cost for the grower.

Environmental Damage!!

We might not think of ants being harmful to an environment, but RIFA has that potential. Remember, again, that it is an “exotic” animal living in the United States, and it came without any natural controls. Remember too, that it is an extremely aggressive animal which populates an area very quickly. A brand new colony, begun by a single queen, could potentially have up to 100,000 stinging workers in it in just one year, and when it matures within around 7 years there could be over 500,000 workers living in it, each and every one capable of stinging.

Now, there are many kinds of ants in the country, most native but some exotic, and most of them feed on the same kinds of foods – other insects, sugary liquids, etc. Therefore, they are competing with each other for the available food supply, and RIFA is particularly unsociable in this respect. A colony of RIFA will quickly kill off colonies of other ant species when it enters a new area, and this change in the fauna of our environment definitely is not a good thing. It also aggressively attacks and kills any other kind of insect for its food, and it can have a serious impact on the beneficial bugs in an area.

In addition to insects, RIFA will attack larger animals, such as baby birds or baby mice that are too small and helpless to flee or fly away. RIFA has a unique style for subduing these larger prey. When a large food source is discovered the word gets out to the colony, and hundreds or thousands of workers will swarm onto the animal. They do not begin stinging right away, but instinctively know to wait until large numbers of them are in place, at which time a chemical signal is emitted and the stinging begins all at once. This allows for a larger dose of venom to be administered, increasing the chances of subduing that large prey. The RIFA may use this same tactic in defense, such as when an unfortunate person stumbles upon a mound, and within seconds is covered with thousands of ants, resulting in terrible stings and injury.

The Sting!!

So, this leads us to the threat that most of us already perceive, when it comes to the Red Imported Fire Ant. The venom of RIFA is a little different from that of most other stinging insects. Their venom is a protein that causes small blisters to form within about a day after the stinging episode. These little pustules can cover the skin of the person who was the recipient of hundreds of stings, and potentially can become infected to cause even more severe damage. It is recommended that the blisters NOT be broken, but instead a first aid recommendation is to wash the area carefully with soap and water, apply cold compresses to reduce swelling, elevate the affected area, and GO TO A PHYSICIAN. Some people have serious immune system reactions to insect venom, and you should not take chances that it will not become a worse problem.

Our wildlife is also at risk of stings, and native deer as well as livestock get stung badly around their faces, as they poke into the mounds or graze in an infested area. The wild animals in North America have no experience with RIFA, and therefore they have no instinct to avoid the mounds. Ground nesting birds such as quail, bobwhite, or killdeer, are particularly at risk. In some areas of Texas and the Southeast it is not uncommon to find over a hundred mounds on a single acre of ground, and as many as 1000 mounds on an acre have been found. The odds of wildlife having an encounter are pretty high.

RIFA is well adapted for stinging effectively. They can sting repeatedly, and may continue to do so for almost 30 seconds, and long after they have run out of venom. Before they begin stinging they grip our skin with their jaws, and then rotate around this point stinging over and over, leaving little circles of sting marks. This also makes it much more difficult for us to brush them off quickly.

Some Interesting RIFA Biology

While we definitely can hate this ant we might also reflect with admiration over just how effective a survivor it is, and how readily it populates an area. Colonies are started in two ways:

  • Swarming flights of males and females, where mating takes place hundreds of feet in the air. Males then die and the females fly back to the earth to dig into the soil and begin a new colony.
  • “Budding”, a process by which a queen simply walks away from a colony with a small contingent of workers, and starts a new colony nearby. There may be hundreds of queens within a single RIFA colony, so they have some to spare.

The workers in a RIFA colony are of many different sizes, a phenomenon we call “polymorphic”. There are large “majors”, medium sized “medias”, and small “minors”. Their jobs are assigned based on how old they are, and a typical RIFA worker will live only about 5 weeks. The youngest ants care for the brood of eggs, larvae, and pupae, and even spray their venom on them as a disinfectant, to keep the colony free and clear of germs. The older workers forage for food, which they bring back to the middle-aged workers, who then feed it to the larvae.

Through all of this the queen – or queens – just continue with their role of laying eggs, and it behooves the queen to do a good job of it. A RIFA queen which becomes unable to produce eggs will be killed by the workers, and a new queen installed in her place. Nature can be ruthless, but the fire ant colony works as a single entity, and the survival and continuance of the species is all that matters. The primary queen that began a colony has the potential to lay up to 1500 eggs each day, so you can see why the colony grows so quickly.

Another interesting feature of RIFA biology is that the adult workers cannot eat solid food themselves. They can ingest liquids, such as the honeydew drippings from aphids, but when they bring back solid food to the colony it is fed to the older larvae. These members chew up the food and liquefy it, and then they regurgitate this material back to the workers for their sustenance. It’s disgusting, but it works. It also is one reason that controlling RIFA is so difficult, because any toxic bait products offered to the ants must be:

  • Non-repellent – if it tastes bad they just won’t eat it.
  • Slow-acting – if it kills the workers too quickly they cannot get it to the rest of the colony.

Controlling Red Imported Fire Ants

This leads us nicely to the question of how we can control this menace. The principal goal of control is to kill the entire colony of the ants, and their nests may go as deep as six feet into the soil. Just spraying some chemical onto the top of the mound, or dusting a little into the top of the colony, probably will not work. Instead, RIFA abatement professionals are relying heavily on Bait – essentially, toxic food that is offered to the foraging worker ants, in the hopes they will find it, like the taste of it, and feed it around to all the members of the colony.

RIFA is very fond of oils, particularly peanut and soybean oil, and this food ingredient is mixed with either a toxic stomach poison or a growth regulator, placed onto corn cob granules, and sprinkled over areas the ants are foraging in. The oil must be fresh, as rancid oil really turns them off and they will avoid it. The materials work slowly to kill the colony, with the stomach poisons taking about a week to kill it if all goes well, and the growth regulators taking many weeks longer, as they affect the larvae only, keeping them from becoming adult ants. If no new workers are being produced the original workers eventually die without any replacements to keep the colony going.

How About some Natural Controls?

Well, actually there are some biological entities that are being investigated for controlling RIFA, and if they work they may be a better long-term solution for keeping the populations of the ant low. One of these is a tiny fly called a Phorid Fly, and it is a parasite of the ants. The larva of the fly feeds inside the worker ant until it kills it, at which time other workers toss the dead ant onto the bone-pile outside and the new fly emerges. These flies are native to South America, so intense study of the flies is necessary before releasing them into this country, to ensure they themselves cannot become an environmental nightmare.

There also are some micro-organisms that infect the ants, and studies are continuing to see if these could be produced in large batches for release into RIFA infested areas. The same concerns exist for these control agents too, as the introduction of ANY exotic organism into the U.S. is a cause for worry, and it needs to be known that they won’t affect other, natural organisms.

Even some of the chemical growth regulators that are being used in the fire ant baits are basically “natural”, in that they are chemically identical to growth chemicals present in the ants, but just introduced to them in doses large enough to mess up their proper growth.

What does NOT work to control RIFA?

Let me just give a quick list:

  • flame throwers made from household aerosols
  • stomping the mound flat with your feet (not a good idea)
  • household cleaning products poured into the nest
  • flooding with a garden hose (actually makes them relocate, maybe into your house)
  • auto exhaust (just gives them a nice nap)
  • anteaters and armadillos (they eat ants, but not enough of them)
  • ultrasonic repelling devices

Home remedies may give you a moment of satisfaction, thinking you have really caused the ants to have a bad day, but it won’t kill the colony. I’d like to elaborate just a moment on the last one listed – the Ultrasonic Repelling devices – which I tend to pontificate on quite a bit. These devices claim to repel all sort of nasty vermin, but somehow have never stood the test of efficacy when tested by independent universities. In fact, one study testing them for effectiveness against RIFA found the ants not only NOT eliminated, but now nesting comfortably within the vibrating box, even as it continued to work in the manner it is supposed to.

It is very likely that we in the United States will never be rid of the Red Imported Fire Ant. There are hopes it can be completely eradicated from California and some of the other states where it recently has popped up in isolated spots. However, the 11 states in the Southeast, where it is so firmly entrenched, will probably have to endure it forever. For areas where RIFA is not yet prevalent it would be an excellent idea for you to have any suspicious ant mounds, and stinging ants, properly identified. You could take them to a local pest control company or the Department of Agriculture office in your area for this. We are relying heavily on the eyes and ears of the American public to watch out for the spread of this terrible pest.