Fritillary life cycle evolved around its host the Violet
Well first of all there are many Fritillary and many violets.
Caterpillars in the field and garden Allen, Brock, Glassberg
A fritillary female lays eggs in late summer but not on the host plant. Instead she lays the eggs into the duff individually and up to about a 1000 of them. The eggs hatch in fall then spend the winter as first instar not needing to eat (not growing) just hunkering down into a safe hiding spot amid the debris. Come the sunshine of longer days and warmer temperatures of spring and our little guy or girl starts looking for food. Once finding a violet it eats quickly then hides in the plant debris or under a leaf until it eats again. Growing quickly and traveling from violet to violet hopefully the caterpillar finds enough food and lives until the time to pupate in early spring. This is also done in the decaying organic materials creating a duff on the surface of the soil, well hidden from predators and most people.
After emerging the fritillary has no need of the violet as many nectar souces will do for the summer until egg laying time rolls around in a few weeks.
So question answered. Leave the violets grow in an undisturb state. Don't do so much clean up or raking in fall. If you do prescribed burns manage carefully or you will burn off the wintering instars.
Do a little reading yourself just google Fritillary life cycle or read from the links below.
Regal Fritillary northern edu
Regal fact sheet