Red Imported Fire Ant (RIFA)

These ants are named after the sting they deliver, which can feel like 'fire'! They can also damage crops by feeding on flowers, stems, and fruit, as well as by protecting other sap-sucking pests.  Laura Wilkins is keeping her eyes peeled for the dirt mounds, or nests, they make in the ground.  Watch your step!

Printable Field Guide: PDF

  • Closeup of a red imported fire ant (Solenopsis invicta) worker. RIFA workers are dark red to brown in color and vary in size a lot, but are usually between 3 and 6 mm long.  Photo Credit: April Noble, Antweb.org, Bugwood.org

  • Red imported fire ants live in colonies. Worker ants within the colonies vary greatly in size in order to perform different tasks. These ants are foraging for food.  Photo Credit: USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org

  • Red imported fire ants are very aggressive and will readily swarm and attack anything that disturbs their nest or food sources.  Photo Credit: USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org

  • Red imported fire ants may be small, but they make up for it with their large numbers and venomous stings.  Photo Credit: Scott Bauer, USDA Agricultural Research Service, Bugwood.org

  • Egg, larval stages, pupa, and adult of the red imported fire ant (Solenopsis invicta).  Photo Credit: USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org

  • With the exception of winged males like this one, all of the ants in a red imported fire ant colony are female. Male ants and females with wings are only produced at certain times of the year, most commonly in spring and fall after rainy periods. The purpose of these ants with wings is to mate and begin new colonies elsewhere.  Photo Credit: April Noble, Antweb.org, Bugwood.org

  • Red imported fire ants mate while flying. After mating, new fire ant queens lose their wings and begin laying eggs to start a new colony.  Photo Credit: USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org

  • Red imported fire ant queens (left) lay thousands of eggs in their lifetimes and are mothers to all of the other ants in the colony! The queen is larger than the worker ants she produces (right).  Photo Credit: B. M. Drees, www.bugmugs.org

  • The brown mounds in this pasture are red imported fire ant nests. The ants can attack and sting the livestock and may even kill baby animals.  Photo Credit: USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org

  • Red imported fire ant mounds near electrical equipment.  Photo Credit: Jake Farnum, Bugwood.org

  • Fire ants sometimes build their nests underneath buildings, which makes them more likely to come indoors.  Photo Credit: Bart Drees, www.bugmugs.org

  • Red imported fire ants survive floods by forming "rafts" by joining their bodies together with their queen at the center and floating to higher ground.  Photo Credit: Bart Drees, www.bugmugs.org

  • Red imported fire ants like to make their nests in crevices, such as this one between a curb and lawn.  Photo Credit: Jake Farnum, Bugwood.org

  • Red imported fire ants feed on flowers and fruits of many common crop plants, such as soybean, corn, bean, cabbage, potato, and peanut, among others. Here, the ants are feeding on a cotton flower.  Photo Credit: John Ruberson, Kansas State University, Bugwood.org

  • Red imported fire ants feeding on a cracked pecan. These ants are very attracted the the oily nut and other greasy foods. They damage crops by feeding on flowers and seeds and threaten workers during harvest.  Photo Credit: Bill Ree, www.bugmugs.org

  • Fire ants sometimes lend a helping hand to to other bad bugs on crops! Here, they are protecting mealy bugs, which damage plants by sucking out their sap, on a pecan tree.  Photo Credit: Bill Ree, www.bugmugs.org

  • Red imported fire ants can build their nests at the bases of orchard trees and damage their roots and trunks.  Photo Credit: Bart Drees, www.bugmugs.org

  • Red imported fire ants will eat just about anything. They feed on plants, seeds, insects, ground-nesting reptiles, mammals and birds, and human food waste. Here, fire ants attack a grub.  Photo Credit: Herbert A. 'Joe' Pase III, Bugwood.org

  • Red imported fire ants attack ground-nesting bird chicks as they try to peck their way out of their eggs.  Photo Credit: Brad Dabbert, www.bugmugs.org

  • An adult bobwhite quail (Colinus virginianus), a species heavily impacted in areas infested with red imported fire ant.  Photo Credit: Casey Sanders, Bugwood.org

  • Unable to escape vicious fire ant stings, hatching alligators are especially vulnerable to attack.  Photo Credit: Daniel Wojcik, USDA-ARS, http://www.ars.usda.gov/is/graphics/photos/sep99/k8575-28.htm

  • Attacking fire ant workers both bite AND sting! Unlike bees, which can sting only once, fire ants can sting many times. OUCH!  Photo Credit: Nadeer Youssef, www.bugmugs.org

  • This person was stung over 250 times by red imported fire ants in just ten seconds. After three days the characteristic blisters of fire ant stings have formed.  Photo Credit: Daniel Wojcik, USDA-ARS, http://www.ars.usda.gov/is/graphics/photos/sep99/k8575-31.htm 

  • Imported fire ants are attracted to sources of electricity, like this electrical switch. When they contact the electricity, they get shocked and die, releasing chemical signals (pheromones) that attract more ants. As more ants are shocked and killed, they accumulate in the electrical equipment and make it stop working.  Photo Credit: Bart Drees, www.bugmugs.org

  • Red imported fire ants in the United States have escaped their natural enemies. Scientists have brought some of their enemies, such as this tiny fly, to the US in hopes of controlling their numbers.  Photo Credit: Sanford D. Porter, USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology, Bugwood.org 

  • Biocontrol: This tiny fly (Pseudacteon sp.) (only about 1mm long) lays an egg inside the ant, which develops into a larva that eventually eats the ant's brain! When the larva turns into an adult fly, it causes the ant's head to pop off its body so that it can emerge. Photo Credit: Sanford Porter, USDA-ARS, http://www.ars.usda.gov/is/graphics/photos/jan11/d2023-1.htm

  • An ant that has been killed by a biocontrol fly in the genus Pseudacteon.  Photo Credit: Sanford Porter, USDA, www.bugmugs.org

  • It is important to control red imported fire ants in agricultural fields and pasture because they can damage crops, attack field workers, and harm livestock. Here, a tractor is being used to treat a field for fire ants.  Photo Credit: USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org

Scientific Name: Solenopsis invicta

 

Description:  Red imported fire ants are reddish-black and about 3mm long.  They are very aggressive and are known for their painful bites and poisonous stings that feel like your skin is on “fire!”  They live in large underground colonies of up to 240,000 ants.

 

Native Range:  The RIFA is native to central South America.

 

Introduced Range:  RIFA was brought to the continental United States sometime between 1933 and 1945.  It probably hitchhiked in a load of dirt from Brazil that was used to balance a ship that visited a port in Mobile, Alabama.  Since then, RIFA has spread to the rest of Alabama, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, New Mexico, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia and Puerto Rico.

 

RIFA was found in New Zealand, but it was contained before it spread out of control.  RIFA has also been reported in several areas of China, Antigua and Barbuda, the Bahamas, the British and U.S. Virgin Islands, Cayman Islands, Hong Kong, Malaysia, Singapore, Taiwan, Trinidad and Tobago, and the Turks and Caicos Islands.

 

Habitat:  RIFA is a big problem not only in cities, but also on farmland and in natural areas. Fire ants usually build their nests underground.  Often their nests look like hills of dirt about the size of a dinner plate and several inches high.  They are crafty with the placement of their nests, and they burrow under sidewalks or roads, in open areas such as farm fields, playgrounds, or yards, or in woods and fields in natural areas.  Sometimes, especially when the ground is very dry or floods have occurred, RIFA colonies may nest in the walls of houses or office buildings.

 

Distribution:

 

RIFA Distribution

Map Courtesy of USDA APHIS

Impacts:  Red imported fire ants are a HUGE problem wherever they are found.  They can make new colonies and spread very quickly.  Imagine if these stinging bad guys built their nest in the middle of your favorite sports field or playground!  Their speedy attacks and painful stings often injure people and make these areas unusable.  They are also very attracted to electrical equipment, like outdoor power boxes and air conditioning units, and can cause great damage to these expensive devices.  Obviously, RIFA in cities don’t play well with people, but it is very expensive and time-consuming to get rid of RIFA once they have invaded an area.

 

Unfortunately, RIFA doesn’t just stick to living in cities. On farms, RIFA in pastures may attack and harm farm animals, especially the babies.  They can also damage young crop plants and the machines used for harvesting.  They cause farmers to lose money and threaten workers in crop fields.  In natural areas, fire ants attack and kill ground-nesting insects, reptiles, birds, and mammals, and reduce the amount of food available for other insect-eaters in the area.  They also destroy young native plants and seeds.  Because fire ants impact so many other species when they are present in an area, they are listed as one of the “100 World’s Worst Invasive Species” by the Global Invasive Species Database.

 

The Facts:  Red imported fire ants are classified as “omnivores,” meaning that they eat both plant and animal materials…in short, just about anything!  Worker ants are responsible for collecting food for the colony, and will attack a variety of animals and plants for food.  Workers also aggressively protect the queen (a larger female ant that produces all of the new offspring for the colony) and her “brood,” or the young ants that have been produced by the queen.

 

These ants can survive even if the ground where their nest has been built becomes flooded.  The workers join their bodies together to form a living “raft” with their queen at the center, and float to higher ground where they can begin a new nest.  Talk about a SUPER pest.

 

Fortunately, scientists are hard at work identifying natural enemies of RIFA that can help us control them.  One tiny fly that shows promise lays eggs in the worker ants, which grow into larvae and eventually make the ants’ heads pop off!  This strategy is called biological control.