Accidentally introduced into the US in the 1930s from its native S America, the red imported fire ant (RIFA) is an invasive ant species that has since spread to Asia and Australia. These resilient, aggressive pests possess a painful sting and build mounds that can destroy crops. US officials estimate that the ants cause more than $5 billion in damages annually. While RIFA stings are rarely life-threatening to humans, the insects are responsible for at least 80 deaths. What causes them to swarm? Discuss
Source: The Free Dictionary