When a nontoxic viceroy butterfly has come to resemble the distasteful monarch butterfly the relationship can best be called?

The relationship can best be called Batesian mimicry. In this form of mimicry, a harmless species, like the viceroy butterfly, evolves to resemble a harmful or distasteful species, such as the monarch butterfly, to avoid predation. This adaptive trait helps the viceroy survive, as predators may learn to avoid both butterflies based on the unpleasant experience associated with the monarch.