These two belong to the genus Speyeria, the greater fritillaries. Whether they are great spangled fritillaries (Speyeria cybele) or Aphrodite fritillaries (Speyeria aphrodite), I don’t have the lepidopteristical-if-that’s-even-a-word chops to say. They are spectacular, though, and obligingly stayed in one place for several shots, until I inched closer and dropped my pannier to the ground with a thud. Oops.
Speyeria are named for 19th century German entomologist Adolf Speyer, about whom I am able to find frustratingly little just by futzing about on the Internet. He does not even have a German Wikipedia page! The Biodiversity Heritage Library, though, courtesy of the Smithsonian, has his book Deutsche Schmetterlingskunde für Anfänger (German Butterfly Lore for Beginners) scanned. I read passable German, but it is printed in Fraktur, which I find hard going; all the same the spectacular Victorian cover is worth a look.