Solenopsis invicta was introduced from South America into Alabama in 1918, and has been gradually spreading throughout the Southeast ever since. The species is highly aggressive when a nest is disturbed, pouring out of every orifice of the colony.  They inflict a painful sting, inducing welts on the skin; further South the colonies can be enormous and this species has become a major pest.  In our area their nests look like broad mounds of loose soil raised a few inches aboveground.  Numerous colonies can be seen along the sidewalks of Circuit Drive and Science Drive on the Duke Campus.