Speyeria idalia

Geographic Range

Historically, the range for regal fritillaries was from Nova Scotia south to western North Carolina, and westward from northern Arkansas to eastern Colorado and Manitoba, Canada. Currently, there are only two known populations remaining east of the Mississippi River. The largest of these occurs in central Pennsylvania and a second, smaller one is found in West Virginia. (Barton, 1993; Pyle, 1995; Williams, 2002)


Regal fritillaries are considered prairie specialists and in the Midwest are known to occur in a variety of grassland habitats including moist tall-grass prairies, wet fields and meadows, virgin grasslands, old fields, and floodplain forest openings and edges. (Pyle, 1995; Nielsen, 1999; Scott, 1986; Swengel, 1996; Barton, 1996; Struttman, ; Swengel and Swengel, )

Physical Description

The upper surface of the forewings of both males and females is deep orange with black marks and white spots along the outer wing margins. The underside is a mirror image of the upper surface. The undersurface of the hindwing is a rich brownish-black with white spots. The upper surface of the hindwings in both sexes has an iridescent blue-black background with two rows of spots. These spot rows are one of two characteristics used to visually differentiate females from males. The females have two rows of cream-colored spots in contrast to an orange outer row and a cream-colored inner row on the males' wings. The second characteristic is size difference, with regal fritillary females larger than males. Their bodies are brownish-black.

Regal fritillary eggs are conical with irregular ridges running from the crown to the base. They are cream colored when first deposited and appear to darken slightly over time. Larvae have been described as being either velvety black with yellowish-orange blotches or yellow to yellowish orange with black blotches. There are six rows of black bristled spines. The larvae have a black middorsal line, two black transverse lines behind the dorsal and subdorsal spines, yellowish middorsal and lateral stripes, dorsal spines silverish at the base, sublateral and lateral spines orange at the base. The head is black with orangish coloration on the top rear portion. (Holland, 1931; Kopper, et al., 2002; Maynard, 1891; Nielsen, 1999; Pyle, 1995; Scott, 1986)

Scott (1986) describes the pupae as light mottled brown with pink tinge, small black spots on the wings and thorax, transverse bands of yellow on the abdomen, and short, dorsal cones. (Scott, 1986)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • Range wingspan
    6.5 to 10.2 cm
    2.56 to 4.02 in


Eggs are laid in the late summer through early fall and hatch about three weeks later. These first instar larvae usually eat their egg chorion before immediately crawling into the leaf litter and entering into diapause, overwintering without feeding on plant material. In early spring the larvae begin feeding on violet leaves. They will go through five molts before entering the pupal stage, which lasts about 17 days. Larval development was followed in 86 captive larvae by Wagner et al. (1997). Each of the first five instars lasted from an average of 3.6 to 6.6 days. The final instar lasted an average of 17.1 days. Males begin emerging in early June with females following ten days to two weeks later. Opler and Krizec (1984) state that emergence continues through late August, however Barton (1996) found a few freshly emerged males in early September. Female emergence appears to end in mid-July. Few males are still flying by August, and females die off by mid-September. (Weed, 1926; Opler and Krizek, 1984; Holland, 1931; Kopper, et al., 2002; Barton, 1996; Wagner, et al., 1997)


Regal fritillaries are univoltine and begin mating soon after the females emerge in mid-June. Males spend most of their time patrolling for females and Kopper (2002) observed three types of flight behavior. The first type was the actual patrolling flight where the male flew upwind from 10 cm to 50 cm above the ground for distances of 5-30 m. There was a second "tack" flight (short, rapid) that was repeated one to several times followed by the third type where the male flew up into the air for 5-10 m and flew 20-50 m downwind in fast flights between 1 and 2 m above the ground. If no females were encountered, they resumed their upwind flight. Barton (1996) observed males flying low over vegetation then dropping down and presumably searching for females around the bases of blueberry bushes Vaccinium spp. and scrub oaks Quercus ilicifolia. When two males come into each other’s' path, they often will spiral up into the air then continue on their patrols. They have also been observed chasing other insects while patrolling, including monarchs Danaus plexippes, black swallowtails Papilio polyxenes asterias, great spangled fritillaries Speyeria cybele and aphrodite fritillaries Speyeria aphrodite ( B.J. Barton, personal observation, Kopper et al. 2001). (Barton, 1996; Kopper, et al., 2001a; Kopper, et al., 2002)

When a female is encountered, males give chase flying a circular pattern behind them. Unreceptive females fly up to 35 m into the air, often with several males in pursuit, then drop rapidly into the vegetation (Barton 1996). Either the female effectively loses the males, or courtship rituals continue. Barton (1996) observed a successful pairing in the Pennsylvania population. A female was observed exhibiting oviposition behavior, and a male flew down and began following her, quivering his wings. She continued with the oviposition behavior for approximately 10 minutes before starting to quiver her wings at a faster rate than the male. The female crawled down into the vegetation and stopped the wing movement, again dipping her abdomen. The male positioned himself next to the female and slowly beat his wings against the female. They both took flight and landed a short distance away, where the male resumed the wing beats. Copulation then occurred and they paired for 1 hr and 43 min. At one point the pair took flight with the male carrying the female. The female was seen exhibiting ovipositing behavior prior to this event, indicating she may have previously mated. This is in contrast to the findings of Kopper et al. (2001) who state that females mate only once. (Barton, 1994; Kopper, et al., 2001b)

Regal fritillaries produce one brood per year (univoltine). Mating begins soon after females emerge and continues through early July. Females enter reproductive diapause near the end of July and become active again in late August when they begin ovipositing. Kopper et al. (2001) studied the reproductive characteristics of females in a northeast Kansas population specifically looking at reproductive diapause. By monitoring hemolymph juvenile hormone titers, ovarian development, and fat body utilization, they determined that females mate only once. Oogenesis (the formation of eggs) and fat body depletion began in late August/early September, indicating the females undergo reproductive diapause in mid-August. Oviposition begins soon after. When females are ready to oviposit, they will drop into the vegetation and walk around probing with their abdomen until the appropriate site is selected. They will then deposit the egg and fly off to find another site. (Kopper, et al., 2001b; Barton, 1996)

  • Breeding interval
    Regal fritillaries are univoltine, breeding once per year.
  • Breeding season
    The breeding season is from July through September.
  • Range eggs per season
    2000 eggs per female in captivity (Wagner 1997) (high)

There is no parental care exhibited by regal fritillaries.

  • Parental Investment
  • no parental involvement


The longest life span recorded in the wild from mark-release-recapture studies in Pennsylvania was at least 69 days (sex unknown) (Barton 1996). A female is known to have lived in captivity for four months (Barton 1993). As the butterflies age, they experience wing wear which eventually hinders their ability to fly. This makes them vulnerable to predators and also makes travel to nectar sources difficult. Their lifespan is most likely limited by the deterioration of their bodies, and in the case of females, loss of nectar resources due to changes in the season. (Barton, 1993; Barton, 1996)

  • Range lifespan
    Status: wild
    69+ (high) days
  • Range lifespan
    Status: captivity
    120+ (high) days
  • Typical lifespan
    Status: wild
    14 to 60 days
  • Typical lifespan
    Status: captivity
    120 (high) days


Regal fritillaries are active within their home range, nectaring and engaging in reproductive activities. They are daytime fliers and will often take cover in the shade during extremely hot weather (Barton, personal communication).

Home Range

Adults of this species can travel considerable distances, but the majority stay close to their birth sites. During a 1993 mark-release-recapture study in Pennsylvania, the average distance traveled by both sexes was 2.14 miles (3.4 km) from their initial points of capture (19% of recaptured males and 5% of recaptured females actually traveled). The longest distance traveled by a male was 6.3 linear miles (10.1 km), and 4.3 linear miles (6.9 km) by a female. (Barton, 1994; Barton, 1993)

Communication and Perception

Regal fritillaries use vision to detect other animals and the world around them. They appear to be sensitive to vibrations as well. Barton (personal communcation) observed regals flushing from vegetation immediately following a loud explosion from artillery. We have no information on the chemical senses of this species, but since other species of Speyeria communicate with pheromones, adults of this species probably do too. Larval fritillaries can taste chemicals that allow them to choose their food plants. The only observed tactile communication was a male beating his wings slowly against a female's body during courtship. (Barton, 1994; Scott, 1986)

Food Habits

Regal fritillary larvae are violet feeders and reported to use Viola pedatifida, V. papilionacea, V. lanceolata, V. pedata, and V. pratincola. In Pennsylvania, larvae are believed to feed only on V. sagittata (Barton 1996). They are considered diurnal herbivores. (Barton, 1993; Barton, 1994; Barton, 1996; Kopper, et al., 2001a; Kopper, et al., 2002; Scott, 1986; Weed, 1926)

Adult regal fritillaries have a long proboscis that is used for inserting into flowers to obtain nectar. They feed on a variety of nectar plants, most commonly butterflyweed Asclepias tuberosa, ironweed Vernonia baldwinii, purple coneflower Echinacaea augustafolia, blazing star Liatrus spp., thistles Cirsium spp., and other milkweeds Asclepias spp. Other recorded nectar sources include Deptford pink Dianthus armeria, mountain mint Pycnanthemum spp., Joe-pye weed Eupatorium perfoliatum, boneset E. maculatum, goldenrod Solidago spp., Calyophus serulatus, Carduus nutans, Schrankia nuttalli, Liatris squarrosa, L. aspera, yarrow Achillea millefolium, dogbane Apocynum cannabinum, Centaurea maculosa, Chrysanthemum leucanthemum, and black-eyed Susaun Rudbeckia serotina. (Barton, 1993; Barton, 1994; Barton, 1996; Kopper, et al., 2002; Scott, 1986; Weed, 1926)

  • Plant Foods
  • leaves
  • nectar


There is no information available on anti-predator adaptations by regal fritillaries. Adults are susceptable to predation by birds, spiders, and possibly robber flies. Known predators include the eastern kingbird Tyranus tyranus, crab spiders (family Thomisidae), and black widow spiders Latrodectus mactans. (Barton, 1996)

Common predators of lepidopteran larvae include parasitic wasps, ants, and spiders.

Ecosystem Roles

Regal fritillaries serve as hosts for parasitic wasps and flies, and as food for birds and spiders. They may also serve as pollinators.

  • Ecosystem Impact
  • pollinates

Economic Importance for Humans: Positive

Regal fritillaries attract ecotourists who are interested in viewing this rare species, thus bringing economic benefit to the nearby communities. The conservation efforts of groups preserving the prairie habitats where regal fritillaries occur provide places for people to visit to enjoy a snapshot of what the midwest once looked like. Research activities have enhanced our knowledge of prairie ecosystems.

  • Positive Impacts
  • ecotourism
  • research and education

Economic Importance for Humans: Negative

There are no known adverse affects of regal fritillaries on humans.

Conservation Status

Regal fritillaries are not currently on the IUCN Red List, CITES, or the US Endangered Species list; however, they are listed as endangered, threatened, or extirpated by several state governments. They are listed as endangered in the state of Michigan. In the eastern U.S. where the species is most imperiled, efforts have been underway by the Pennsylvania Air National Guard and various private organizations to protect the habitat of the population in Pennsylvania. Other conservation groups such as The Nature Conservancy are actively protecting many known sites (Barton, personal communication).

Other Comments

Regal fritillaries have been known by several common names, including regal silverspot butterfly, regal silverwing, and silver Argynne. Scientific names have changed as well and are as follows: Papilio idalia (Drury) 1773, Argynnis astarte (Fisher) 1858, A. ashtaroth (Fisher) 1859, A. infumata (Oberthur) 1912, A. dolli (Gunder) 1927, and A. pallida (Eisner) 1942. (Maynard, 1891; Miller, 1992)

Williams (2002) believes that ecological differentiation may exist between Midwestern populations and those in the east. The larvae in the Pennsylvania population eat Viola sagittata, a plant not used anywhere else in their range. Habitat differences exist as well, with mesic conditions found in the east and xeric in the west. Williams speculates that glaciers extending into southern Indiana and Ohio during the Pleistocene may have divided regals into eastern and western populations. The results of mtDNA sequencing analysis suggest the Pennsylvania population is a distinct lineage, and that they may have separated from the midwestern population about 400,000 years ago. (Williams, 2002)


Matthew Wund (editor), University of Michigan-Ann Arbor.

Barb Barton (author), Special Contributors.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.

  1. active during the day, 2. lasting for one day.

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


an animal that mainly eats leaves.


An animal that eats mainly plants or parts of plants.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

internal fertilization

fertilization takes place within the female's body


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


an animal that mainly eats nectar from flowers


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


chemicals released into air or water that are detected by and responded to by other animals of the same species


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season


remains in the same area


offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


movements of a hard surface that are produced by animals as signals to others


uses sight to communicate


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