When an invading insect threatens an ant colony' s territory or food sources, the ants will vigorously swarm over the invader, biting or stinging it. This defensive tactic can effectively deter even aggressive flying insects, such as wasps. Ants do not attack all insects within their territory, however. For example, riodinid caterpillars commonly live harmoniously among South American ants. These caterpillars, which are a favorite prey of wasps, produce secretions the ants consume as food.
The statement "Among insect species that inhabit South America, wasps are the only kinds of organism other than ants that use riodinid caterpillars as a source of food" is most strongly supported by the information above.