Interactions

     Because Solenopsis invicta is an “invasive” species, it is implied that this is a harmful or disruptive species.  Indeed, these ants do have quite a large negative impact on many other organisms.  Although conducting experiments to discover long term impacts on different species on a large scale is difficult, small scale observational studies can be very informative (Allen et al. 2004).            
    Small animals are at high risk for being negatively affected by S. invicta, especially ground nesting organisms (Smithsonian Marine Station 2007). Reptiles are prime examples, because the adults do not provide proper care to their young if their nests have been infiltrated by RIFAs (Allen et al. 2004).  Snake and amphibians are also in this same situation, although much attention has been focused on sea turtles.  According to a study performed in 2009, Loggerhead sea turtle eggs are especially susceptible to being breached by foraging ants (Diffie et al. 2010).   RIFAs will sting and eat hatchlings, which overall devastates sea turtle populations (Allen et al. 2004).  Birds, such as doves, terns, and northern bobwhites have also been found in lower numbers in invaded areas, and small mammals are also profoundly impacted. These mammals have far lower species richness in infested areas than their counterparts in unaffected regions (Allen et al. 2004).
    Red Imported Fire Ants also affect native ant species.  Areas with small populations of RIFAs and higher diversity of other ant species show that competition may occur, although studies also show native ant species and RIFAs can coexist (Cumberland and Kirkman 2012). Human involvement in the eradication of S. invicta has actually caused greater strife between native and invasive species than actually occurs in nature.  Air sprayed with pesticides in the southeast United States was an attempt to kill off the invasive RIFAs, but also killed off native ants. The harmful pesticides actually caused more devastating distresses (Encyclopedia of Life 2013). The RIFAs, being more efficient at reproduction and colonization, recovered faster than native species, therefore becoming more dominant and worsening the problem (Gordon 2010). The native ants did recover, but human contribution did not help the situation which is still a struggle to this day.
    Humans have been working towards getting rid of the pesky Red Imported Fire Ants across the globe, especially in the United States since they were accidentally introduced from South America about a hundred years ago (Encyclopedia of Life 2013).  However, most attempts have been futile.  RIFAs have been responsible for substantial crop damage. The Department of Agriculture has estimated that these ants have cost about 6.5 billion dollars between damages and control of population (Smithsonian Marine Station 2007). To learn more about the economic impact of S. invicta, please visit http://entoplp.okstate.edu/ddd/insects/rifa.htm.
    Besides crop damage, RIFAs are simply an annoyance.  The venom of Solenopsis invicta unique in that fact that is contains 95% alkaloid and only a small amount of protein, while most other ant and wasp venoms contain little to no alkaloid.  This toxic special property of the venom causes a very unpleasant reaction in victims (Taber 2000). Even slight contact of skin with a nest will lead to a plethora of stings, which are very painful (Gordon 2010). The pustules that form are necrotic, causing cells to die, due to the poisonous venom which the ant releases when it stings (Klotz et al. 2008).
    However, Red Imported Fire Ants aren't solely pests.  Some colonies actually have a mutualistic association with plants.  The plant provides space for a nest to form as well as nutritious nectar, while the ants protect the plant from herbivores (Gordon 2010).  As mentioned in The Southwestern Naturalist, specifically there is facultative mutualism between RIFAs and a particular type of legume, Senna occidentalis (Fleet and Young 2000).  Large colony size and large individual ants may provide an even better form of protection for these legumes (Fleet and Young 2000).
    Within colonies, RIFAs interact and communicate via chemicals known as pheromones (Taber 2000).  Ants also use “recruitment” pheromones as a trail for other ants to follow in order to find a food source (Taber 2000).  RIFAs are foragers and predators, feasting upon anything from seeds, to termites and miniscule invertebrates, and scavenging on dead organisms (Asano and Cassill 2012).  The image to the right clearly depicts how aggressive RIFAs can be when hunting for food. To view even more photographs of the fascinating S. invicta , click here to visit the gallery.

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