Regal Fritillary

The Regal Fritillary is one of the largest and most striking of the greater fritillary butterflies (genus Argynnis, formerly Speyeria), a group within the brush-footed butterfly family Nymphalidae. It was once common across the tallgrass prairies of the central and eastern United States but has become a specialist of high-quality native prairie remnants as much of its original grassland habitat has been converted to agriculture.

Its bold two-toned wing pattern makes it instantly recognizable among North American fritillaries, and it is often held up as a flagship species for prairie conservation efforts. Sightings today are concentrated in the Midwest, with only a few isolated populations remaining east of the Mississippi River.

Adults are strong, sailing fliers that patrol open grassland in search of nectar and, for females, suitable violet patches on which to lay eggs.

• Forewings are bright burnt-orange with black veins and black spots, resembling other fritillaries.
• Hindwings are strikingly different: black or blue-black with two rows of pale spots — cream-white in males, often more washed or bluish in females.
• Large-bodied with a wingspan often exceeding 3.5 inches, noticeably bigger than most other fritillary species.
• Underside of the hindwing shows silvery-white spots on an olive-brown background.
• Lookalikes include the Diana Fritillary and Great Spangled Fritillary, but the Regal's solid dark hindwing (rather than orange with silver spots) is diagnostic.

Restricted almost entirely to native or restored tallgrass and mixed-grass prairie, including wet-to-mesic prairie remnants, prairie potholes, and unplowed hay meadows. Historically ranged from the Great Plains east to the Atlantic coast, but eastern populations have largely disappeared; strongholds now are in Nebraska, Kansas, Iowa, and a few mid-Atlantic sites. Adults fly from late June through September, with peak numbers in July and August.

Adults are powerful, gliding fliers that cruise low over grass tussocks, nectaring at coneflowers, milkweeds, thistles, and other prairie wildflowers. Males patrol for females early in the flight season, while females become reproductively active later and can be seen searching low over the ground for violet plants. The species plays a role as a prairie pollinator and its larvae, in turn, are prey for various invertebrate predators and parasitoids.

Females lay eggs in late summer near — but often not directly on — violets (the sole larval host plant), sometimes on dried grass stems nearby. Eggs hatch in autumn but the tiny first-instar caterpillars do not feed; they overwinter in leaf litter without eating. In spring they seek out fresh violet leaves, feeding and developing through several instars before pupating in a hanging chrysalis. There is one generation per year, with adults emerging in early summer and flying into fall.