Almost every fig species has exactly one wasp species that alone can pollinate it
Fig trees and fig wasps have co-evolved in pairs for tens of millions of years: a female wasp squeezes into a fig so tight she often loses her wings and antennae getting in, pollinates the flowers hidden inside, lays her eggs, and dies without ever leaving. Her offspring hatch, mate, and the fertilized females fly off to find the one fig species their line is matched to.