Female Speyeria are content to usually lay eggs on the interior of a lunch sack if they come in contact with dead violet leaves.  The life history of Speyeria is somewhat unique in that the larval hostplant is tends to be dried up by the time the adults fly.  Females who oviposit look for where the plant was and lay eggs haphazardly around it.  The unfed first instars then diapause until the next spring.  This makes the brown bag method effective for fritillaries.