Elphinstonia should not be elevated to genus level, especially given that it shows no autapomorphies respective to Euchloe s.s. and should best be within a wider concept of Euchloe. This has been adressed in the bibliography using genetic data and currently unpublished genomic data supports this definition.
check this for reference:
Marabuto, E., Pina-Martins, F., Rebelo, M.T., Paulo, O.S., 2020. Ancient divergence, a crisis of salt and another of ice shaped the evolution of the west Mediterranean butterfly Euchloe tagis. Biological Journal of the Linnean Society 131, 487–504. doi:https://doi.org/10.1093/biolinnean/blaa129