http://uts.cc.utexas.edu/~gilbert/research/fireants/faqans.html

Fire Ants, Armadillos, and Phorid Flies -
Answers to Frequently Asked Questions*

Selected by the sciLINKS program,
a service of National Science Teachers
Association. Copyright 2001.

 
Larry Gilbert, Director
Brackenridge Field Laboratory
The University of Texas at Austin
 

?????????*If you have a question about fire ants and phorid flies that does not appear below, please submit it to lgilbert@mail.utexas.edu. When your question or similar questions appear on a regular basis, we will answer it or an equivalent on this web page.

1. What is the correct scientific name for the red imported fire ant (RIFA)? Solenopsis invicta or Solenopsis wagneri

As of 1995, the correct name for the red imported fire ant was Solenopsis wagneri. This change is based on the discovery that wagneri was the first name given to the species by a taxonomist (a second taxonomist found this out by sorting through dead ant specimens in museums and discovered that the same ant species had actually been named twice). So the first taxonomist assigned the name S. invicta to this species without having done his homework. By international rules of nomenclature, the earlier name has priority.

In most cases it is usually non-controversial to simply change the name and inform all the academic researchers about the new, correct name. However, this is not such a simple case. Many fire ant biologists believe that because thousands of research publications are referenced by the name "invicta" that common sense and practicality should override technically correct taxonomy. There is a procedure for appealing such bothersome name changes and an appeal is in progress for S. invicta. Also aesthetically, invicta seems the better of the two names. The name "invicta" conjures up "invader," "invincible," "vindictive," and sounds more poetic in songs than "wagneri." A case in point: the lyrics of "Queen Invicta" by environmental troubador, Bill Oliver. Ant taxonomists are not pleased that the change from invicta to wagneri was overturned. The name "invicta" is as difficult to extinguish as the species to which it refers!

2. How, when, and why were fire ants imported to the U.S. and where do they occur at the moment?

First of all, several kinds of fire ants are native to Texas. When people ask this question, they really mean imported fire ant species. Apparently the introductions of pest fire ants were accidental. Perhaps the soil of potted plants or ballast on ships arriving from South America to Mobile, Alabama contained invicta nests. Exactly when is not certain. There were invasions by two pest fire ant species. The first, the black imported fire ant from Argentina (S. richteri), was barely established and spreading when the red imported fire ant (S. invicta) arrived and proceeded to shove aside its cousin (which now survives in Mississippi and western Georgia). The original arrivals were probably in the 1920s or before. Professor E.O. Wilson, the famous ant biologist at Harvard, was first to discover the invasion while he was still a budding high school entomologist in Alabama. See the most recent USDA distribution map (248k) by county and time of arrival.

If you live in the northern U.S. where the ground freezes and you think you might have fire ants, check with a nearby university with a department of entomology. Though fire ants probably will not survive winters in northern states, these ants may have been accidently introduced in potted plants and set up temporary residence during warmer months. Fire ants will locate mounds near heat sources (steam pipes, concrete walls, etc.) and conceivably could survive in colder areas than we expect. With global warming we can anticipate a northward shirt in fire ant populations across the landscape.

They have recently been accidentally exported to Queensland, Australia and are following a spread similar to that encountered in the U.S. http://www.sardi.sa.gov.au/pages/entomolo/fa_surv.htm%3AsectID=863&tempID=8

3. I'm not sure I have fire ants. How can I be sure?

Look at the ants. Fire ants include many opportunistic ant species of the genus Solenopsis. There are native and imported species. Native Texas fire ants are very similar to the imported pest, but actually help retard the spread of the imported species and should be spared if possible. Both native and imported fire ants are small, dark orange/brown ants with workers of various sizes that quickly mobilize and sting en mass when their mound is disturbed . Other than the much larger "red harvester" or "Texas red ant" which has no variation in worker size and is conspicuous on its trails and around it's flat open mound entrance, most other stinging, ground-dwelling ants in Texas are encountered as solitary individuals. ( right: native, large worker)

                      

                

Look at the nests. Fire ants live and do most of their foraging for food through underground tunnels. A nest consists of a network of tunnels and chambers that occupy a vertical column 12-18" in diameter and approximately 36" deep. After cool, rainy, weather in Spring and Fall, the ants clear blocked tunnels and expand chambers to create a conspicuous mound of loose soil above the nest. The colony dwells in this above ground extension when the temperature there is optimal for brood development. Though above-ground mounds harden and persist in some soil types, their absence does not mean fire ants are not present or receding. (right: imported, large worker )

You probably have imported fire ants if the following characteristics of the ants and their mounds are observed:

  • Mounds of loose soil, resembling gopher diggings, are found above ground.
  • Mounds are generally numerous and conspicuous.
  • Worker ants are dark, small, highly variable in size, aggressive, and sting relentlessly.
  • Workers have the same body proportions from the tiniest to the largest. Head width never exceeds the abdomen width, even in the largest workers. (See sidebar to left and illustration on web site http://uts.cc.utexas.edu/~gilbert/research/fireants/gemvsinv.html).
Because not all fire ants are the pest species, distinguishing native from imported is an important first step before proceeding with chemical treatment.

4. Which fire ants are the native species and how can I identify them?

Along the Nexican border of Texas and in West Texas, there exist native fire ants that are difficult to distinguish from their imported cousins. However, if you can see four tiny teeth on the mandible or jaw of a fire ants, it is S. invicta. Native species possess three teeth.

Over East, Central and much of South Texas, the most common native fire ant, S. geminata, can be distinguished without examination of tiny details of anatomy. First disturb a mound by digging, then watch for the largest workers. If the heads of the largest workers are conspicuously wider than the gaster (abdominal segments), you are looking at the native species.

S. invicta (left) versus S. geminata (right)

5. We have large red ants that come out of a hole surrounded by open ground covered in small pebbles. Their sting really hurts! Are these fire ants?

No, you have described the Texas red harvester ant, also known as the Texas red ant or "pogo" (genus Pogonomyrmex). These industrious ants collect grass seeds and store them in underground granaries. In fact, they have been shown to reduce rodent numbers by competing with them for grass seeds. Pogos are eaten by "horny toads" and are so conspicuous that people usually notice them before getting stung. Fire ants tend to eliminate this native Texan.

6. Do fire ants have anything to do with the disappearance of horny toads?

This is another question on the minds of people who, as kids, enjoyed watching these great lizards and now lament their absence. The answer is either "probably yes" or "definitely no" depending on where you are. Horned lizards have definitely disappeared over most of the range now dominated by the red imported fire ant (RIFA). There might be other species of lizards or snakes that have suffered due to the presence of the RIFA, but the loss of the Texas Christian University mascot has certainly been the most conspicuous one. In any case, the disappearance of horny toads in RIFA areas is probably due partly to the direct killing of the young lizard by foraging fire ants and partly to the fact that horny toad food, such as Texas harvester ants, have been decimated by the RIFA. However, horned lizards have also disappeared in many areas outside the range of RIFA. It is probable that the RIFA could still be at least indirectly responsible for the horned lizard demise even where the RIFA does not occur. For instance, the publicity about the RIFA has encouraged overuse of and proliferation of ant baits and poisons, killing all species of native ants they touch as well as the RIFA. Many people erroneously assume that the Texas red ant is the imported fire ant and unnecessarily treat their properties. Aside from thereby causing the demise of horned lizard, they are also removing dozens of native, friendly ants and increasing the opportunity for invasion by RIFA into a vulnerable system with lowered resistance. Agricultural activities such as shredding and other habitat destruction that prevent weeds from producing seed also can rob the Texas red harvester ant of its food source. No seeds = no ants = no lizards.

7. Why are imported fire ants such a pest, while the native Texas fire ants are not?

Both biological wisdom and recent research indicate that fire ants, like other opportunistic organisms, become more "weedlike" and achieve pest status when introduced into regions free of their natural biological enemies, such as parasites and pathogens. A case in point is the fire ant species native to Texas. Our native fire ant species is a is a minor nuisance at home, but a major pest in India where it was inadvertently introduced. Likewise, the pest fire ant from Brazil is "just another ant" there and not a serious pest. Still, the Brazilian name for the ant, "lava pé" (translated "wash feet") reflects its status as a nuisance to those not watching where they stand.

8. I poured a solution of grits and water on my fire ant mounds. Several weeks later they were gone. Why not do research on this?

Out of revenge, desperation, or a hope for quick profits, countless remedies have been used in attempts to eradicate fire ants. Encouraging a few fire ant colonies to abandon mounds in a yard is relatively easy. Even regular watering can cause a colony to move. However, safely and economically eliminating hundreds or thousands of RIFA colonies from parks, farms, and ranches has proved to be nearly impossible. Remedies against fire ants which are effective in a backyard will not solve the overall problem across the countryside because no effective and safe measure has proved to be economically feasible or sustainable on the grander scale.

Practical decisions on what research topics to explore are based on 1) systematic analysis of past research into the biology of fire ants and 2) an assessment of the economic and ecological consequences of various approaches. Qualified scientific personnel and/or the time they have available is a very limited resource for effective fire ant research. Therefore it is not possible or desirable to pursue every line of research suggested at the expense of carefully considered and ongoing investigations.

9. Are imported fire ants problem pests in their homelands, Brazil and Argentina?

Fire ants of the species S. invicta and its closely-related species of ants are not generally viewed as important pests in Brazil and Argentina. Occasional local outbreaks, which could result from temporary escape from normal controls due to habitat disruptions, have been reported in recently settled towns in the Amazon region. It is safe to say that fire ants native to South America are no more pests there than are native fire ants pests in North America.

10. How can I avoid being stung by fire ants?

Being aware of your surroundings at all times is the way to avoid everything from car wrecks to rattlesnake bites. If fire ants do crawl onto your skin, they first bite with their mandibles in order to anchor for the thrust of the sting. As soon as you feel this pinching sensation, quickly sweep the ants off before they actually sting and you can avoid most of the damage! If you must work in proximity to fire ants, wear rubber boots and gloves powdered with talc.

11. How do fire ants affect quail and other wildlife?

You might have seen pictures of massed fire ants killing hatchling quail chicks or stinging the noses and eyes of newborn deer. Without question RIFA can kill young birds, small mammals, and reptiles. However, in the case of quail, it could be that a more important impact on populations is the removal of insect food that would normally be available to quail chicks. Because quail populations fluctuate widely due to climatic changes, it is hard to pinpoint the extent to which RIFA might trigger populatioin-wide collapse. Certainly if climatic conditions are unfavorable, the depredations by fire ants could become a major factor in affecting the survival of certain species of wildlife.

12. Why are fire ants attracted to electrical circuit boxes and electric motors? Is that dangerous?

One of the greatest economic impacts and dangers posed by RIFA results from short circuits and fires in electrical systems after fire ants move into circuit breakers, relays, motors, and other electrical devices. Why the ants are drawn to them is still something of a mystery, but researchers at Texas Tech are close to providing some methods for protecting electrical systems from these problem ants. See their web site at http://www.ttu.edu/agriculturaltechnologytransfer/rifa2/index.htm

13. Why do we find piles of dead fire ants?

When fire ants die, workers remove the bodies and body parts from nests. Nest hygiene is a key to disease prevention in social insects such as bees and ants. Trash piles, called middens, accumulate in underground chambers during weather that inhibits above-ground activity, and are then moved to the surface after spring and summer rains when ants rebuild galleries and clean house. Midden piles might increase in size and conspicuousness after a colony has had a territorial dispute with another colony of ants, after application of pesticides, or when a colony is experiencing higher rates of disease or parasitism. We suspect that phorid fly infected ant heads are tossed into these middens so that the first view of the world by a newly emerged adult phorid would resemble the garbage dump in Star Wars!

14. What are the safest and most effective chemical controls for fire ants in yards and pastures? I don't want to expose my family and pets to dangerous chemicals.

First, put small pieces of hot dog as bait around the yard.  Visually match up ants that come to bait with fire ants that you see by disturbing the mounds. If you have an area dominated by ants other than fire ants, avoid treating that. If you do have fire ants, use Amdro, Award, Logic or similar granule bait preparations.  These don't kill instantly but give the workers a chance to take the bait back to the mound as food where its pesticides disrupt reproduction by hormonal control over queen ants. Fire ants forage out of underground tunnels that lead all around within 100' of a mound.  Therefore use a broadcast spreader to evenly distribute the bait over your yard.

Pick a mild day on which you first determine that the ants will swarm a piece of hot dog.  That means they will efficiently harvest the bait. Broadcast these granules all over the infested area on a nice day so that the fire ants get all of the bait. The worker ants will take the granules into the mound. Be patient because these baits take about 6 weeks to take effect; the mound will die. You should have control for many months and additional spot applications of the granule baits when you see small mounds restarting should keep things tolerable (or with just a mound or two, boiling water poured on the mound when it comes up after a rain is very effective).

If you coordinate with neighbors and use the same treatment area-wide on the same week, you will reduce the rate of re-invasion.  We find that native ants increase after such treatments and that's good because they serve useful functions including helping to resist fire ant invasion.  Imported fire ants are often the worst where native ants have been disrupted by soil disturbances that accompany home and road construction, or exterminated by broad spectrum pesticides.

Here's the suggestion:  3/4 lb. hydramethylnon in baited granules (under trade names "Amdro" or "Siege")   mixed with  3/4 lb s-methoprene in baited granules (under trade name "Extinguish") broadcast applied per acre. A report published on trials with this mix is on the web: Amdro/Siege, a metabolic inhibitor, takes 3-6 weeks after ants consume it to show an effect and the effect lasts for several months until a re-invasion occurs.  Extinguish is a growth regulator that takes longer to show an impact, but then can last a year or more.  Since these things are not instantly toxic, workers can distribute each of them throughout the colony long before effects set in. While these compounds or breakdown products definitely  would not be good for frogs or fish, if application occurs during a period when no run-off rains are anticipated,  all of the active material will be taken into fire ant mounds within 30 minutes.  Persistence in the environment is relatively short for both.

The answers to this question change frequently. Consult the TAMU extension service web site at http://fireant.tamu.edu/.

15. Why not bring back Mirex?

For those who don't know about Mirex, it was in many ways a highly effective product that, when mixed with ant bait and applied aerially, reduced fire ant populations. The problem was that it was not specific and therefore killed other ants and insects that consumed the bait. Mirex is thought to have helped spread fire ants even faster by wiping out pockets of native ant resistance to the RIFA invasion. It also produced a toxic and persistent byproduct, dioxin, which accumulated in ecological systems. Chemical treatments for fire ants today are much more specific to the target pest, but they are not perfect. Therefore, it is necessary to identify the ant species, and whether treatment is even warranted.

16. What should I do if I have native ants in my yard?

If you still have native ants, keep doing what you have been doing (or not doing). If you see an invading fire ant mound in an otherwise RIFA-free area, verify that it is not the native species before attempting to kill it. If you do treat such a RIFA mound, be sure to confine treatment to that mound or its immediate surroundings.

17. Armadillos eat fire ants and some people think this might control the RIFA. Is this a real possibility for controlling the RIFA?

Many observant folks notice that armadillos dig into fire ant mounds and correctly assume that they are eating the ants. Armadillos also dig into mounds in droughts when more favored foods are hard to find. Actually they do this when the colony inhabits the uppermost parts of the mound, the portion of the approximate 3 ft deep nest that offers the best temperature for developing brood. Developing brood is what armadillos eat. So yes, armadillos probably do have an effect on fire ants in Texas as well as in in Brazil, where they are also found. Research should be carried out to assess the effect predation by armadillos has by comparing fire ant densities in areas with and without them. However, if armadillos alone could stem the tide of RIFA, these ants would not have become a problem. Actually, since some phorid flies attack fire ants when mounds are disturbed, armadillos and phorid flies could be a winning combination. Until we examine that idea more carefully, we should all avoid running over these little fire ant munchers.

18. Why not import anteaters?

Although anteaters are terrific ant predators, their cousin, the armadillo, is already in Texas, but has had little effect on RIFA populations. Good biocontrol agents are 1) highly host specific, 2) limited by their host availability, and 3) able to survive in the climate where they are introduced to control the pest species.

Anteaters consume a wide range of ants, not just fire ants and, except for the giant anteater, live in trees and usually eat ants that nest in trees. Because the RIFA does not usually inhabit trees, the anteater wouldn't have much of a chance to eat RIFAs. Also, anteaters are tropical and would not survive cold weather as well as fire ants do. Importing anteaters as biocontrol agents of the RIFA is an idea based on comic strips, not scientific observations.

19. What do phorid flies do to fire ants?

Female phorid flies are attracted to fire ants swarming over a disturbed mound or foraging along a trail to food. They hover over ants looking for a preferred individual. (Each phorid species has a particular size range of fire ant workers which it prefers.) When the hapless victim is chosen, the phorid darts in, injects an egg into the ant's body, and explodes away at warp speed. The attack takes a fraction of a second and leaves the ant partly paralyzed and disoriented for a minute or so before she staggers off to join her sisters! (right: last abdominal segment of phorid with "harpoon" ovipositor extended) The stinger is a modified egg-laying device.  That's why males of ants, wasps, and bees can't sting.

The injected egg develops in the ant's thorax until after about ten days the ant dies as the larva moves into the ant's head. The head falls off and the larva eventually pupates in the safety of the hard chitin shell that once housed the ant's jaw muscles and brain. Ant pieces are tossed on ant trash piles or middens and adult flies emerge from pupae about 45 days after the original attack. That's the direct effect of mortality that these decapitating flies impose on ants.

The other thing that phorids "do" to ants is probably the most significant from the standpoint of biocontrol. As phorids fly above ants looking for victims, the ants respond by hiding, pilling on top of one another, retreating into the nest, and posturing in various odd ways. This fly harassment disrupts the economy of provisioning the nest with food and protecting home and territory. Native ant species can then take advantage of the RIFA's distraction and reclaim lost territory. This more indirect and subtle effect has only recently been identified as the mechanism by which phorids might reduce the impact of fire ants. The idea was posed originally by a UT graduate student, Don Feener, in the late 1970s. At Brackenridge Field Laboratory, he observed phorids that attacked one of our native ants. Dr. Feener, now a professor, continues important studies of phorids at the University of Utah.

20. Why don't you just release the phorid flies now?

Actually phorid flies are being released in selected experimental sites, the ant populations of which were assessed before release so that comparisons can be made post-release. Currently, there are too few phorids being bred in research laboratories to provide enough for mass releases in more than a few carefully-selected areas. But even if there were enough phorids to "go around," only two species, Pseudacteon tricuspis and P. curvatus, arecurrently available in substantial numbers. Further research is required to assess the most effective methods for breeding and releasing up to 15 additional phorid species, some of which could be more effective than the ones now available.

21. Now that phorid flies are being released, when will they eradicate fire ants?

Unfortunately the answer is never. Imported fire ants are now permanent residents in the U.S. Eradication is possible from pesticides only temporarily and only at a local scale, but not at a regional level. However, we can hope for eradication of the pest status of the ant, assuming that we can find and successfully introduce effective biological control agents. Even assuming the best results with phorids, it could take years to reverse seven decades of spread and growth of RIFA populations. Although we expect phorids to be detrimental to populations of the RIFA, don't overreact to the media hype about phorids and expect an overnight solution.

22. My property is available for this project. Why don't you release phorid flies on my back yard, farm, ranch?

In addition to those considerations, this experimental release/research phase is limited by availability of flies and researchers. Our laboratory's procedure is to conduct initial release experiments in areas where extensive previous baseline data on the ant fauna and its boundary with imported fire ants has been studied. The good news is that naturalized phorids have now been documented to have spread up to 15 miles from release sites in Texas, and in Central Texas occupy more than 100,000 acres (est.).

23. How big are phorid flies? Will they be a nuisance too?

The phorid flies that attack fire ants are tiny. Compare the end of Lincoln's nose and top of his lip on a U.S. penny to the length of this Pseudacteon phorid which attacks S. invicta. Only fire ants and a few dedicated biologists are likely to see phorids in action. They are not attracted to people as are some small flies, like gnats and mosquitoes.

The species of phorid flies that attack fire ants are specialists; some even attack only single species of fire ants. For example, our native Texas fire ants have their own phorid fly and it will not attack the imported fire ant - that's why we have to bring the specific phorid fly that attacks the imported fire ant from the countries from which they were imported.

There are over 20,000 species of phorid flies. Most phorid flies are scavengers and some utilize corpses and are useful in forensics (the so-called coffin flies). Phorids that show up in houses typically breed in the sludge in sink drains but could be coming up from animal remains under the house (e.g. dead rats). Phorids that parasitize ants are a highly specialized minority that do nothing except attack and consume ants. The vast majority of people will never knowingly see one of these inconspicuous creatures.

24. What are the possible negative effects of phorid flies introduced to control imported fire ants? What will they eat after they kill off all the fire ants?

Phorid flies of the genus Pseudacteon permitted for release have been through careful screening to identify those species most specific to the imported pest fire ant. Prior to the decision to release target-specific phorids, USDA APHIS produced an Environmental Assessment (EA) http://uts.cc.utexas.edu/~gilbert/research/fireants/envassess.html. This document contains a review of the biological qualities in fire ant-attacking phorids and assesses the potential benefits vs costs of releasing these exotic insects in North America. Aside from a small amount of nectar-feeding by adults, Pseudacteon flies are completely dependent on ants. Indeed, most species of flies under consideration for release as biocontrol agents of the RIFA are restricted to a single species or species group of fire ants. For example, native phorid species attack our native fire ants, S. geminata and S. xyloni. The fact that in over seven decades, no switch by native phorids to the invading S. invicta has occurred is strong evidence of how extremely host-specific these flies are.

25. Why should we be concerned about studying our native species of ant-attacking phorid flies?

Studies of flies, genus Pseudacteon, that live, reproduce, and thrive on host fire ants in North America can reveal much about details of phorid natural history. Understanding the biology of these temperate-zone phorids could provide important guidance for developing optimum methods for introducing phorids from South America which would attack the pest fire ant species.

26. Who funds fire ant/phorid fly research at The University of Texas

Before 1986, work on the fire ant invasion was carried out by students as part of undergraduate honors projects and graduate thesis and dissertation research. Between 1986-1994, we were funded by the Texas Department of Agriculture, American Farm Bureau Research Foundation, and USDA Competitive Grants program. From 1994-1997, we received funds from the following foundations and agencies: Dougherty Foundation, Ewing Halsell Foundation, Fondren Foundation, Houston Livestock Show & Rodeo, Robert J. Kleberg, Jr. and Helen C. Kleberg Foundation, National Science Foundation, and Texas Parks and Wildlife Department. From 1997-2004, our major funding has been through the Texas Imported Fire Ant Research and Management Project that supports research efforts of Texas A&M University, Texas Tech University, The University of Texas, the Texas Department of Agriculture, and others and is administered by the Texas Extension Station (TES). During this time, foundatoins supporting our effort included The Robert J. Kleberg, Jr. and Helen C. Kleberg Foundation, The Lee and Ramona Bass Foundation, and Worthington Charitable Fund. This is the nation's most innovative cooperative effort to eliminate the pest status of an exotic organism. For further information contact Bastiaan Drees (b-drees@tamu.edu).

27. How do you communicate your project goals and results to the general public?

Interviews to newspaper, magazine, radio, and TV reporters are given when requested by the media or when we have a breakthrough to announce. Scientific presentations are made at local and national conferences and articles submitted to professional journals.

28. I am very allergic to fire ant stings. Is it possible to have successful immunotherapy as a protective measure?

Though there have been no controlled trials of IFA immunotherapy, a reasonable support for the current clinical approach is Dr. Ted M. Freeman's "IFA Immunotherapy: Effectiveness of Whole Body Extracts", Journal of Allergy and Clinical Immunology, Vol 90 pgs 2150 ff, 1992. Conducted at the Wilford Hall Medical Center (Air Force hospital) allergy clinic in San Antonio, the study reports that 11 patients with IFA sensitivity refused immunotherapy. Six of the 11 received subsequent field stings and all six suffered anaphylaxis. However in the more than 60 people who had received immunotherapy, about 47 suffered field stings and only one reported a mild anaphylaxis. The p value for immunotherapy providing protection from subsequent sting reaction was <0.0001. Though not perfect, the results suggest that immunization can protect against anaphylaxis. During sting challenges of some 30 patients on maintenance doses of immunotherapy, only one person reacted to an IFA sting. He believes that pure venom would make a much better research tool than WBE (whole body extract). Unfortunately there is no commercial product available and extraction of venom to do medical research is tedious.

29. a. What do fire ant stings look like?

This high resolution photograph (194K) illustrates the pustules that may result the day after being stung. Each pustule represents a separate sting.

b. What causes the pustules?

Freeman article (28. below) describes two components of imported fire ant (IFA) venom: proteins and alkaloids. The immune response, especially IgE (an antibody, "immunoglobulin E"), is generally to the protein component of foreign substances - 4 in Solenopsis invicta (the red IFA) and 3 in Solenopsis richteri (the black IFA). There is evidence that people who are sensitive to IFA have IgE to the venom proteins. Freeman is unaware that anyone has demonstrated IgE to the alkaloids. He feels the alkaloids are responsible for the local cell necrosis that produces the fairly typical and nearly pathognomonic (i.e., distinctively characteristic of a particular disease) "psuedo-pustule" of the IFA sting. This is psuedo because a true pustule is composed of an active neutrophilic infiltration fighting an infection. In the case of the IFA reactions, the infiltrate is just dead cells and there is no infection.

30. How can I treat fire ant stings?

Immediately after being stung, wash off the area with alcohol, try not to scratch it so it doesn't get infected . Sometimes a white pustule will form the second day, but it will eventually be resorbed. Commercial preparations such as StingEze, etc will numb the area for a while. A thick paste of baking soda and water can also help right after the sting. Careful application of ice will help decrease pain, but can burn the skin if left on too long. Meat tenderizer can also burn the skin. If the pustule becomes infected, apply an antibiotic and see your doctor. OTC Benedryl may help with local reactions: burning and itching. Follow label instructions carefully.

If other reactions occur soon after the stings, i.e., difficulty breathing, itchy rash, loss of consciousness, etc., get the person to an emergency room immediately. About 1% of the population have the potential for serious and dangerous reaction to fire ants. A physician can prescribe an EpiPen (single dose epinephrine auto injector device) to carry with you in case of subsequent ant stings and anaphylactic reaction.

31. What has your research with phorid flies produced so far?

Over the last few years, we have studied about a dozen species of Pseudacteon phorid flies in Brazil and Argentina which attack fire ants in their homeland. With colleagues in those countries and in coordination with colleagues at USDA in Gainesville, FL, we have learned about the life history, behavior, and host specificity of most of these phorid species and have identified several as high priority for application in biological control.

Two species of Pseudacteon phorids have been introduced successfully to Texas. One, P. tricuspis, has now spread up to 15 miles from release sites around Austin, TX and now occupies approximately 100,00 acres. The second species has established and is beginning its spread.

Introductions in South Texas have not been as successful and we are now working in Texas-like areas of Argentina in order to find phorid species already adapted to climatic conditions to be encountered south of San Antonio. We have identified several Argentinean species "of interest" and are working to develop laboratory cultures.

32. Do fire ants destroy plants?

Fire ants probably don't kill plants but they can diminish their health and vigor by tending aphids and mealy bugs on stems and roots.

33. How much money do fire ants cost us?

According to a study at Texas A&M University, fire ants cost the economy of Texas over $1 billion per year.

34. How can we introduce phorid flies in our county?

We have recently began a pilot program to assist local extension agents and private interest groups to participate in acquiring their own phorid "infections." Fire ants are collected in the area to be treated with phorids according to our instructions. Ants are separated from soil at Brackenridge Field Laboratory. We show participants where to place out trays of ants in phorid fly "hot spots." The flies will arrive and attack the fire ant workers. These phorid fly-infected ants are then transported back to their home colony and reintroduced. Establishment of phorid populations will require multiple replicates of this process over 6 weeks.

35. I was stung by an ant that is fairly large (1.5cm) red with white rings around the tail-end. They can "hiss" and seem to travel alone. What kind of ant is this?
We have large ants that are furry with an orange furry back with a black belly.
Are either of these fire ants?   

These are not ants, but rather a wingless solitary (non-social) female wasp in the family Multillidae. Females are wingless and typically colorful; males have wings. The common name for the group is "velvet ants." Here in Central Texas we have about 40 species of velvet ants, some small and some big. The "hiss" is called "stridulation" and is caused by washboard-textured body segments rubbing rapidly against one another. That and the coloration are warning signals to potential predators. Some species could be described as furry.

As a kid I made the mistake of handling one in south Texas called "cow killer."  I've had great respect for these critters ever since. They mind their own business if not bothered.  Most are very beautiful and neat to have around.  Their color is a warning not to get too close. For information and a photo, see http://www.sdnhm.org/fieldguide/inverts/dasymutilla.html

36. Why do we have so many imported fire ants in Texas?

First, Texas possesses extensive open grassland and pasture habitats favored by Solenopsis invicta. But also, in Texas we have the multi-queen variety of fire ant which may have up to 100 reproductive queens per mound.  Multiple-queen or polygyne S. invicta do not display the territorial conflict that promotes spacing between colonies in the single queen or monogyne form found in South America and in the SE United States. In Texas therefore, mound densities can be much higher than in regions dominated by the monogyne form.

37. When the ground is dry, fire ant mounds disappear. Are the mounds dead?

Fire ant brood (babies) are sensitive to temperature and humidity. Worker ants move the brood up high when it is wet. That's why you see tall mounds after rains. When conditions are dry, they move the brood deeper to more humid chambers and you may see no mounds at all. Mounds can extend as much four feet below the surface.

38. Can you describe the life cycle of fire ants?

Here is a thumbnail outline:

1. egg laid by queen 2. larva hatches and grows through 4 larval developmental stages or instars between which molts of larval skin occur 3. at 4th molt a pupa is produced 4. pupa hatched into adult ant.

There are two basic types of eggs.

  • 1. unfertilized eggs — become males with wings whose only function is to mate with queens
  • 2. fertilized eggs — become females which are either
    • a. winged virgin queens or
    • b. various castes of sterile workers.

How the colony feeds and cares for female larvae determines their caste; i.e., whether they behave as workers (all are sterile females) or queens. Male ants develop from unfertilized eggs and therefore possess only one set of chromosomes; i.e. they are haploid. Thus male ants have no father (but they have a grandfather). Females develop from fertilized eggs and are typical diploids. This type of life cycle occurs in other so-called eusocial insects including wasps, bees, and ants and is called "haplo-diploidy." Eusocial insects possess sterile castes that help queens by raising other siblings. Why some individuals give up the option to reproduce has been an interesting evolutionary dilemma since the time of Darwin but the work of people like the late W.D. Hamilton has largely solved the problem.

39. How do fire ants spread?

Fire ants reproduce opportunistically when conditions are wet and warm. They are found in all types of soil, but they do better in open pastures and sunny, grassy places than in thick shaded woods. Grassy medians of freeway and mowed pipeline and powerline rights of ways provide prime "freeways" for the ants too.

Polygyne colonies (those with multiple queens/mound) can reproduce by budding off new colonies and spread by walking a few meters per year. Colony establishment by winged queens can occur miles beyond source populations. This mode of spread may be promoted by prevailing winds and is the only way that monogyne or single queen colonies reproduce. Judging from the spread across Texas, natural dispersal was on the order of 10-20 miles/year. Of course transport in nursery products spread the ants beyond the boundary of natural dispersal. Though fire ants may arrive in the NE U.S. and Canada via nursery products, nests in RVs, cars, vans, etc., they are not likely to become a problem because of the cold conditions in fall spring and winter.

40. What can I use to kill fire ants indoors? I don't want to expose my family and pets to dangerous chemicals.

If you can avoid pets and kids you could consider making these same baits available in the house as well. Don't bradcast there but put baits in corners under, appliances and in closets. Indoors, I've also used boric acid (15% by volume) in peanut butter placed in bottle lids where ants have trails. Boric acid works in similar fashion, killing slowly after distribution among colony members (it also kills cockroaches when mixed with cornmeal and sugar). It will take about 2 weeks to completely control them, but is very effective. Treating the inside alone will never work since ants killed there are quickly replaced by a large population outdoors.

41. Why not kill all the ants in my yard just to be sure I kill the fire ants?

Other ants compete for food with fire ants and help keep them under control. If you kill all ants in your yard, you create an "ant vacuum" and after the next rain, it will be fire ant queens that land in your "safe" yard to begin new mounds unopposed by any other ants. Fire ants are better at colonizing and dominating newly disturbed habitat than the average ant species.

If native ants are not harming you but simply sharing their habitatwith you, I would suggest leaving them alone.  Often when one removes a native element of the ecosystem, something much worse fills the void.  In Texas, our worst fire ant problems are in areas where people blasted the native system with pesticides and made invasion by introduced pests more likely.

42. Why are phorid flies better than pesticides in controlling fire ants?

Phorid flies may not be better than pesticides in many local, short-term circumstances, so there will always be role for some careful use of pesticides. However, over an entire region and over decades, biological control agents like phorid flies are likely to be a more economic and safe way to reduce the pest status of imported fire ants.

43. Do fire ants sting or bite? Why didn't I feel any ants on me until I was stung multiple times?

Fire ants bite and then sting! One feels a prickly sensation as the ants bite the skin's surface with their mandibles to get a grip. The bite does not inject venom, rather this gives them a solid anchor at the head end, while they jab the stinger (a hypodermic-like device modified from the ovipositor, the egg laying structure) into the victim, injecting a toxic alkaloid venom from a special gland and at the same time releasing an alarm pheromone (chemical signal) that excites additional attackers. Fire ants do not inject formic acid, as in the case in many ants. (Not all ants sting, but fire ants do and it is the venom injected by the sting that people react to. Some other ants that don't sting do bite and then squirt venom onto the area of the bite.)

Note: strychnine, nicotine, morphine, and caffeine are also alkaloids.

44. Someone suggested that pouring gasoline on fire mounds was a certain way to kill them. What do you think?

Gasoline is as dangerous to the applicator as it is to a fire ant colony. That's a common, but inefficient and ill-advised, approach. Gasoline would be a very expensive, environmentally harmful method if applied on the scale of acres rather than one or two mounds.

45. I heard that if fire ants get into the walls of a house, they can do an much damage as termites. Is there some ant that does this and if so should we be concerned about them in Texas?

Carpenter ants (genus Campanotus) are termite predators and move into old termite galleries or into wood softened by fungus. As a result they are accused, perhaps  unjustly, of creating serious structural damage. I view them as a symptom rather than a cause. Fire ants will eat both Campanotus larvae and termites, but not wood. Fire ants also transport dirt into walls, circuit boxes, etc. but do not damage wood structures directly.

Return to: Gilbert Lab Conservation/Fireant Research Frequently Asked Questions

17-Dec -2004
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For further information, contact: lgilbert@mail.utexas.edu