Solenopsis invicta is native to Southwestern Brazil, Paraguay and Northern Argentina (Sutherst and Maywald 2005). In these particular areas, the Red Imported Fire Ant thrives in moist, protected areas, either embedded in soil, underneath logs, or buried within the nests of other organisms like termites (Taber 2000). What makes these ants “invasive” is not only their ability to dominate but actually thrive in altered habitats such as “cleared” areas brought on by humans, an adaption that similar species are incapable of attaining. The RIFA also do exceptionally well in extreme habitats like, for instance, the South American rain forest (Taber 2000).
         The intrusion of these ants to the United States was likely due to human transport. They were unintentionally introduced into this country over the past century as stowaways in cargo shipped from their homeland of South America and have rapidly been spreading throughout the southern United States ever since (Ascunce et al. 2011). Recently there has been cases where it seems that this invasive species has been introduced to new regions like California and other areas around the globe too. They are said to be one of the most successfRed Imported Fire Ant infestation map courtesy of the United State Department of Agriculture http://www.ars.usda.gov/sites/fireants/Imported.htmul and most hated invasive species of ants (Cumberland and Kirkman 2012). Models of future range expansions of the Red Imported Fire Ant are based largely on historical temperature and precipitation data. These models show the potential for this species to eventually become established in over almost half of terrestrial land masses which goes to show the versatility of the S. invicta (Ascunce et al. 2011).
            Added to that, their adaptability is seen in the other unique habitats in which they can be found. For instance, they are capable of nesting indoors within drawers, boxes, walls, and underneath rugs, bringing soil with them in all these cases (Taber 2000). On the other hand, outdoors they are more inclined to dominate open and disturbed areas, particularly soil disturbances created by human actions. Areas such as roadsides, cultivated fields, and lawns make great homes for these ants (Cumberland and Kirkman 2012). Pastures are a favorite target for newly mated RIFA queens. In fact, pastures in Georgia average about 27 colonies per acre of land (Taber 2000).
            OnRIFA mound, photo credit to Alexander Wild http://www.alexanderwild.com/Ants/Taxonomic-List-of-Ant-Genera/Solenopsis/e of their most distinguishing features is their nest which begins with mated RIFA queens who begin by digging a vertical tunnel in the soil to a depth of about three inches. Within about one day, the entrance will close from the inside and the queen(s) will start laying their eggs in isolation. Surprisingly, in about three years mounds can grow to about one foot high and two feet wide at the base. Most nests contain a mound that is the above ground portion of the nest that allows each offspring to be moved about in order to track temperature and humidity suitable for their development. The size, the shape, and the internal framework habitually depend upon the soil type and the vegetation in the surrounding area. Over time, a hard outer crust will encase the structure and tunnels and passageways will occupy more than half of the total volume of the mound. Certain colonies are called “polydomic” or “polycalic” because they have more than one mound (monodomic). Each RIFA mound will have several main, horizontal tunnels diverging about one hundred feet into the surrounding area. Each main, horizontal branch will divide into smaller side branches with openings reaching the soil surface. Vertical tunnels are found inside as well, some of which extend about six feet or more into the water table. In general, mounds in the United States are built on a smaller scale, one fourth of which are found to be abandoned. In Brazil, mounds tend to be smaller in the dry season and larger in the wet season. Often if the heat is too intense, the temperature too high, mounds can be entirely absent because ant are able to cool off by retreating to the depths of the soil underneath. By doing this, they are unable to maintain the structure (Taber 2000).
            Red Imported Fire Ant mounds courtesy of the United State Department of Agriculture http://www.ars.usda.gov/sites/fireants/Imported.htm

       The amazing resilience of this species of ants makes them a very unique species to learn about. S. invicta have evolved many adaptations that have helped them become a versatile species. To learn more about these modifications check out our adaptations page. 

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