Fritillaries love nectaring on Asclepias purpurascens, but it isn't a host plant for their caterpillars. Monarch butterflies nectar on such mikweed and also lay eggs on them so that their caterpillars can eat the foliage and make chrysalises nearby and grow into adult monarchs

Please click on image to ENLARGE view of Great-Spangled fritillary on purple milkweed on June 3, 2011, in south Fayetteville, Arkansas. Click on enlargement to enlarge view of the Speyeria cybele on Asclepias purpurascens even more.