How two butterflies became one

During the American Revolution, some North American lepidopterists focused on butterflies, discovering two new species: the White Admiral and the Red Spotted Purple. These butterflies have distinct survival strategies; the White Admiral uses camouflage, while the Red Spotted Purple mimics a poisonous species. Near the US-Canada border, these butterflies interbreed, leading to hybrids with mixed traits. Despite their visual differences, they are genetically similar, prompting scientists to classify them as one species. This case highlights how appearances can be deceiving in species classification.

What led scientists to classify the Red Spotted Purple and White Admiral as the same species?

Explain the concept of cross-border species and provide examples from the text.