Montana Field Guide

The following is taken from Ferris and Brown 1981, Scott 1986, Opler and Wright 1999, and Glassberg 2001. Regal Fritillary are large butterflies with a wing span of 6.5-10.5 mm (2.5-4.0 inches). Their front wing is orange with black spots and their hind wing is black with white spots. Their large size and distinctive coloration make them one of the most recognized butterflies in the east and central US.

Males emerge before females in early summer (mid-June), they mate, and females lay eggs in the fall. Regal Fritillaries do not migrate, but females are nomadic in late summer (August). Larvae hibernate in prairies with stable resources (Swengel and Swengel 2016) from September to June (Kopper et al. 2001). Interestingly, females do not rely on the presence of their larval host plants, Violets (Viola spp.), to lay eggs. Regal Fritillaries have high fecundity and lay over 2000 eggs on the underside of leaves (Kopper et al. 2000) increasing the chance of some emergent caterpillars locating Violets by laying many eggs across scattered habitats.

Best determined by the large size, body is brownish-black, uppersurface of forewing reddish-orange with ornate black markings, hindwing is velvety black with a postmendian row of white spots and a submarginal row of whitish spots in female, orangish in male, undersurface of hindwing is dark brown with many elongate whitish spots.

Non-migratory. Females are nomadic in late summer.

Found in wet meadows, undisturbed prairie near marshes, dry to mesic tallgrass prairie, shortgrass prairie, and restored prairie (Ferris and Brown 1981, Scott 1986, Debinski and Babbit 1997, Swengel 1997, Opler and Wright 1999, and Glassberg 2001). These butterflies are primarily restricted to midgrass and tall-grass prairies of the central Great Plains (Scott 1986, Opler and Wright 199, Kopper et al. 2000, and Glassberg 2001). Violets (Viola spp.) are the host plant for Regal Fritillary butterflies. Adult Regal Fritillaries prefer high densities of forbs and a diversity of flowering plants (Caven et al. 2017), gravitating towards areas with recent fires because of increased flower production (Ehrenreich and Aikman 1963). These butterflies generally avoid areas with bare ground, instead preferring land with more litter and lower grazing intensities (Caven et al. 2017). Their habitat is predicted to shift north as air temperatures rise (Post van der Burg et al. 2023).

Larval food plants include several species of Viola (Scott 1986, Swengel 1997). Adults feed on flower nectar, including Apocynum, Asclepias, Calyophus, Carduus, Centaurea, Chrysanthemum, Cirsium,
Cornus, Common Crown-vetch, (Coronilla varia), Dianthus, Narrow-leaved Purple Coneflower< (Echinacea), Eryngium, Helianthus, Liatris, Lobelia, Medicago, Beebalm, (Monarda fistulosa), Pycnanthemum, Rhus, Rubus, Rudbeckia, Salvia, Shrankia, Trifolium, Fascicled Ironweed, (Vernonia fasciculata ssp. Corymbose), and Veronica (Kopper et al. 2001a, Tooker et al. 2002, and Scott 2014).

Females lay eggs singly in shaded sites of grass and forbs near the ground, usually on the undersides of dead vegetation, often near larval food plant but never on it. Larvae build no nests. They overwinter (hibernate) as L1 instars (Scott 1986, and Kopper et al. 2000, 2001a). Males patrol low (10-50 cm) above the ground for distances of 5-30 m throughout the day in search of females, circling back 1-2 m above ground and repeating the low upwind flight. Both sexes take the role of flight while copulating. Females mate once, experience a post-mating reproductive diapause before initiating egg-laying (Scott 1986, Kopper et al. 2001a, 2001b).

Regal Fritillary butterflies were petitioned for Endangered Species Act listing on 19 April 2013.On August 6th, 2024 the US Fish and Wildlife Service proposed listing the western subspecies ( A. i. occidentalis ) as Threatened under the Endangered Species Act. Additional information on the species' management can be found on the U.S. Fish and Wildlife Service's Species Account.