A large nymphalid butterfly, Speyeria idalia, found chiefly in the prairies of east-central United States, having deep orange forewings and distinctive blue-black hindwings with pale spots; also called regal silverspot, Idalia.
Origin
Late 19th century; earliest use found in Psyche.
Definition of regal fritillary in US English:
regal fritillary
noun
A large nymphalid butterfly, Speyeria idalia, found chiefly in the prairies of east-central United States, having deep orange forewings and distinctive blue-black hindwings with pale spots; also called regal silverspot, Idalia.