Difference between revisions of "Solenopsis invicta"

From Bugwoodwiki
Line 1: Line 1:
''Authors: Espinosa, A. and [[User:Achodges|A.C.  Hodges]] University of Florida''
''Authors: [[User:Adrianae|Espinosa, A.]] and [[User:Achodges|A.C.  Hodges]] University of Florida''
<btaxobox imgnum=5314045/>
<btaxobox imgnum=5314045/>

Latest revision as of 17:31, 1 April 2009

Authors: Espinosa, A. and A.C. Hodges University of Florida

Hexapoda (including Insecta)
S. invicta
Scientific Name
Solenopsis invicta
Common Names
red imported fire ant


Red imported fire ants (RIFA) are native to South America. Apparently these ants arrived into Mobile, Al or Pensacola Fl between 1930’s and 1940’s. These ants have spread throughout the years and are currently found in 15 southern and western states of the US (Collins and Scheffrhan, 2001; USDA).

Distribution and Hosts

Besides South America, where they are native, these ants are also established in the US and Australia (Shattuck and Barnett 2005). It has also been reported in Antiqua and Babuda, Bahamas, British Virgin Islands, Cayman Islands, Hong Kong, Malaysia, Puerto Rico, Singapore, Taiwan, Trinidad and Tobago, Turks and Caicos Islands and US Virgin Islands. As of 2006, New Zealand has eradicated RIFA and China is in the process of erradication (ISSG 2006). Within the US, the following states have established infestations: Alabama, Arkansas, California, Florida, Georgia, Louisiana, Maryland, Mississippi, New Mexico, North Carolina, South Carolina, Oklahoma, Tennessee, Texas, and Virginia. The infestations in Maryland and Virginia are sparse and still not formally recognized on USDA maps. Small, localized populations exist in the San Francisco Bay area (Collins and Scheffrahn, 2001). Fire ants have a preference for oily and greasy foods but they also feed on other insects. Workers usually forage around their mounds in underground tunnels (Apperson and Waldvogel, 2008).

Description of Damage

RIFAs are capable of killing baby animals, and destroying seedling crops such as corn, soybeans citrus, okra, bean, cabbage, cucumber, eggplant, potato, sweet potato, peanut, sorghum, and sunflower among others. They also invade home lawns, school yards, athletic fields, parks, etc. RIFA can cause both medical and environmental harms and overall are a nuisance problem (Collins and Scheffrhan, 2001; Stimac and Alves 1994; USDA) The mounds built by ants can interfere with machinery operations in agricultural fields. The ornamental/sod/landscaping industries have been impacted by regulatory actions pertaining to shipments of potentially infested plant material to new non infested areas. (Apperson and Waldvogel, 2008). Besides the unsightly mounds fire ants form in lawns and yards, if disturbed, their sting is very painful and may cause allergenic reactions to some people (Apperson and Waldvogel, 2008). In southern states, fire ants have been seen not only outdoors, but indoors as well, invading residences, offices, hospitals and nursing homes (Apperson and Waldvogel, 2008).

Identification Characteristics

The appearance of RIFA in the field is similar to many other ant species. Size of RIFA ants varies by castes within the colony: minor workers measure about 1/8 inch long, major workers measure about 1/4 inch long, and winged males, winged females and queens measure about 1/3 inch long. They are reddish-brown to dark brown in color with a black gaster, or posterior portion of the abdomen, where the sting is found. As a member of the order Hymenoptera, ants have a pedicel or waist-like structure between the thorax and the abdomen. The pedicel for RIFA is 2-segmented. RIFA antennae are 10-segmented, and terminate in a 2-segmented clubThey are very aggressive and have characteristic mound-shaped nests. Their mounds vary in size but are proportional to the size of the colony. Mounds constructed in clay tend to have a symmetrical and dome shape where as mounds constructed in sand have a more irregular shape. They get very aggressive when their nests are disrupted and try to bite and sting whatever disturbed them. While attacking their target, they sting repeatedly. The sting contains venom that causes a burning sensation and itching blisters. Only female RIFA are capable of stinging and opposed to honeybees that are only capable of stinging once, these ants are capable of stinging repeatedly. The nests can grow up to 60 cm (2 feet) (Apperson and Waldvogel, 2008; Hedges, 1997; Hedges, 1998; USDA).

Life History

The lifetime of RIFA depends on the workers size. The smaller workers live between 30 and 60 days, the medium sized workers may live between 60 and 90 days, the larger workers live between 90 and 180 days and queens may live between 2 and 6 years. From egg to adult it may take them between 22 to 38 days (Hedges, 1997). Mating occurs during flight and it is the primary means of colony propagation. After one year of the colony establishment, reproductive alates are produced. Alates are the winged reproductive insects that in the case of ants are destined to become queens. About six to eight mating flights that may contain up to 4500 alates occur between the spring and fall (Vinson and Sorenson, 1986). According to Hedges (1997) mating flights usually occur at noon on warm sunny days after rain (>74o F/ 24oC). Soon after mating males die. Mated queens tend to cluster together under some kind of shelter. These helps in establishing a colony, but as the colony develops all but one queen are killed in monogyne colonies (single queen colonies), where as in polygyne colonies (colonies with multiple queens) queens are not killed (Vinson and Sorenson, 1986). Once females are mated, they break their wings at the basal suture and find a suitable spot to begin a new colony (Holldobler, 1990). The mated queen excavates and forms a small chamber in the ground to lay her eggs; as the colony continues to grow the mound is formed. Within 24 hours, she would have laid about 10 or 15 eggs that will hatch within 10 days. By the time her eggs have hatched, the queen will have laid between 75 and 125 more eggs. The larval stage usually lasts between 6 and 12 days and the pupal stage would last nine to sixteen days. The queen will stop laying eggs until the first group of workers mature which will take between 2 weeks to one month. The queen will feed the first set of young larvae with oils regurgitated from her crop, trophic eggs which are unfertilized eggs that are not laid for reproduction but for nutrition of their offspring’s and/or or secretion from her salivary glands will feed the first set of young larvae. Also, the queen’s wing muscles break down to provide nutrients for the larvae (Vinson and Sorenson, 1986). This first group of emerged workers tends to be smaller due to the limited amount of food that the queen can provide them. These workers are called “minims”. Minims will begin seeking for food to feed the queen and the larvae and also start constructing the new mound. Within six months, the colonies may contain several thousand workers. Within a colony the queen is the single egg producer and may produce up to 1500 eggs per day. A typical colony contains about 80000 workers but may contain as many as 240000 workers (Vinson and Sorenson, 1986). Multiple queen colonies differ from single queen colonies in that the mounds are closer together and present in higher numbers per acre of land, the colonies tend to have smaller workers, workers are not aggressive with neighboring colonies and queens produce less eggs than single queens. Overall the number of eggs produced in a single queen colony is less than in a multiple queen colony (Hedges, 1998; Vinson and Sorenson 1986).


Because fire ants spend most of their time foraging for food, good sanitation is highly recommended. It is important to keep outdoor trashcans and the area around the trashcans clean. Leaving trash in trashcans outdoors overnight should be avoided. Dumpsters and grease bins and the area around them at food service facilities should also be kept clean to avoid fire ant infestations. It is also very important to keep the areas around buildings clean and to keep shrubs to keep them pruned. Shrubs and debris can serve as a shelter for RIFA (Apperson and Waldvogel, 2008).

If you find red imported fire ants on your property, it is highly recommended to contact your local extension agent prior to taking action.


Both single mound treatments and wide broadcast applications may help manage RIFA. There are six different methods for individual mound treatment:

1. Drench mounds with either insecticides or hot water. This method might not reach the queen, therefore making it difficult to eliminate the colony. Best control occurs during the spring and fall when temperatures are between 70 and 86oF because under hot summer days ants will remain deeper within their mounds. If treating in the summer it is best to do it early in the morning or in the evening when temperatures are cooler.

2. Use a granular or dust insecticide and apply it over the mound and then water it in. This method is similar to the use of drenches.

3. Inject insecticides at high pressure. This is a more effective but more expensive method.

4. The use of baits is a very effective control method, but it will take longer to control.

5. There are some mechanical and electrical devices to control RIFA in the market but there is no documentation about their efficacy.

There are few products available for broadcasting, within these, the use of granular insecticides or baits are common. The main problem with this is that it may be dropped where ants cannot find it, well fed colonies will not need to feed on baits, some baits might me light sensitive and degrade quickly and that baits are not specific for fire ants (Vinson and Sorenson 1986). There are several biological control agents that are being investigated for RIFA management, among these are the pathogens Thelohania solenopsae and Beauveria bassiana; the decapitating parasitic flies Pseudacteon tricuspis and Pseudacteon curvatus and the parasitic ant Solenopsis daguerri that invades RIFA colonies and take over the queens to control the colonies (Collins and Scheffrhan, 2001).

For additional information about fire ants please refer to Imported Fire Ants Community Page at: http://www.extension.org/pages/Imported_Fire_Ants_Community_Page

This is an Extension site to which about 150 members from land-grant universities and agencies such as USDA-APHIS, USDA-ARS and state and county governments belong. The goal is to collaborate with information to get a better understanding of the history, biology and behavior of fire ants and to provide tools to help manage fire ants in an economically and environmentally sound manner.

Image Gallery



  • Stimac JL, Alves SB. 1994. Pest Management in the Subtropics: Biological Control A Florida Perspective. (Rosen D, Bennett FD, Capinera JL, Editors) pp. 353-380. Intercept Limited, Andover, Hants SP10 1 YG, UK. In: Collins, L. and R.H. Scheffrahn. 2001. Red Imported Fire Ant. Solenopsis invicta Buren. Found at: http://creatures.ifas.ufl.edu/urban/ants/red_imported_fire_ant.htm

Additional Links