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Western Regal Fritillary
This colorful butterfly is a subspecies of the regal fritillary.
About This Species
As a grassland butterfly, it depends on periodic, natural fires that maintain a high-quality habitat of grasses and forbs. This species is known for having a regular population boom-and-bust cycle. This allows it to take advantage of favorable years and expand across the landscape, but populations will crash in years with poor conditions, so much that it can become locally extinct, disappearing from specific parts of its range. Populations can grow and expand across the landscape very quickly, so planting high-quality, nectar-bearing plants is a productive way to support this species.
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Physical Characteristics
The western regal fritillary is a large butterfly. The upper sides of the forewings are orange, while the upper sides of the hindwings are dark purple with rows of orange and white spots in the male but only white spots in the female. The undersides of the forewings are orange with black spots, while undersides of hindwings have large white spots and a copper background.
Range
The western regal fritillary can be found in native grasslands in the central and northern Great Plains. Eastern Colorado is the southwestern limit of its range. It’s thought that sightings in Colorado are not individuals that went through a complete life cycle here, but dispersered from other states in the late season; much of the short-grass prairie habitat is too dry to support large or persistent populations.
Habitat
The western regal fritillary requires habitats with abundant violets (host plants for the caterpillars) and nectar-bearing flowers (food for the adult butterflies). A grassland butterfly, it depends on periodic, natural fires that maintain a high-quality habitat of grasses and forbs
Diet
Violets (species in the genus Viola) are the obligate host plants of western regal fritillary caterpillars — these caterpillars are specifically adapted to this plant and no other. Adults require high-quality nectar-bearing flowers, such as milkweed, coneflowers, blazing star flowers, bee balms and verbenas.
Reproduction
The western regal fritillary has one annual generation, which means it is born, matures, reproduces and dies within one year. Females lay eggs in the later summer and fall. Before building a chrysalis, caterpillars go through multiple stages of growth, called instar stages. Each instar stage is separated by a molt, when the caterpillar sheds its exoskeleton. Eventually, they pupate, forming a chrysalis and developing into an adult butterfly. Caterpillars in the first instar stage undergo diapause (insect hibernation) for the winter in grass litter, waking in the spring to seek out violets as host plants. This species has six instars (five molts) before they pupate and emerge as adults in late May through mid July. Males emerge before females and typically have a shorter lifespan. Females live eight to 12 weeks. After emergence, females will mate and then enter a brief reproductive diapause before laying eggs in September and October. A single female can lay thousands of eggs.
Threats to Species
Habitat loss from agriculture, urbanization and altered pasture is a key threat to this species. Additional threats include the encroachment by woody vegetation and habitat invasion by non-native plants.