Claim: In South East France, Zerynthia rumina (a butterfly belonging to the family Papilionidae) can be confused with the Southern Festoon (Zerynthia polyxena), but the two can be told apart by the presence of blue on the hindwing of the southern festoon.
Evidence: Zerynthia rumina, the Spanish festoon, is a butterfly belonging to the family Papilionidae. 
In south east France it can be confused with the southern festoon (Zerynthia polyxena). 
The two can be told apart by the presence of blue on the hindwing of the southern festoon.