Regal Fritillary Butterfly – Species Profile & Facts

The Regal fritillary (Speyeria idalia) is among the most beautiful butterfly species that you had no idea existed. This butterfly belongs to the Nymphalidae family, which is the largest butterfly family in the world, containing over 6,000 species. Nymphalids display a unique characteristic compared to other families of Lepidoptera – they only use 4 legs in locomotion.

This is atypical behavior since most other butterflies use all 6 legs to stand and move. It turns out that nymphalids’ forelegs have become vestigial, which means that the butterflies no longer use them for locomotion. Instead, they keep them raised up.

These forelegs are also different than the rest in appearance, in the sense that they contain tiny hairs called setae, forming a brush-like structure. It’s unclear why nymphalids have evolved this way, but the leading theory is that they use these forelegs to enhance their sense of smell and communicate with other butterflies.

And this is not the only thing that makes the Regal fritillary butterfly unique in its genre.

How to Recognize a Regal Fritillary Butterfly?

The Regal fritillary butterfly displays a very distinct look, making it almost impossible to mistake it for any other species. Both males and females share the same orange color and overall pattern, with the females coming with darker orange nuances. The 2 genders look almost identical at first glance, but they do present several distinctions.

Both the male and the female display black, white-spotted bands on their forewings’ markings, but the females’ are a lot thicker. They also showcase 2 rows of spots on their black hindwings. The males’ bottom row is yellow, while the females’ is white.

Other than that, the Regal fritillary female is slightly larger than the male. Both genders showcase tooth-like white spots on the underside of their wings.

What Does a Regal Fritillary Butterfly Caterpillar Looks Like?

The Regal fritillary caterpillar displays several unique features, one of them being the bright-red head contrasting with the caterpillar’s brown body. The caterpillar’s head displays 2 bulgy red lobes that look like the eyes of a large fly.

The body is segmented and light brown in color, with darker brown patterns on each segment. The caterpillar’s body is covered with spiked spikes in the sense that each body segment has sharp thorns that they themselves are covered with tiny black needles. Holding the caterpillar is mostly out of the question.

How Big Does Regal Fritillary Butterfly Get?

The adult Regal fritillary can grow up to 4.2 inches, with females being slightly larger than the males. The larvae will begin their life cycle measuring little over 0.6 inches and will reach a maximum size of 1.7.

These values rank the Regal fritillary among medium-sized Lepidoptera.

Where do Regal Fritillary Butterflies Live?

The Regal fritillary only lives in Central and East US. Its main habitat consists of high humidity environments like wet fields, marshes, tallgrass prairies, etc.

This species’ limited habitat places it among the rarest butterflies available, and this is not the only factor contributing to its scarcity. Another one relates to the butterfly’s life cycle and the larvae’s feeding pattern, which we will discuss later in the article.

What do Regal Fritillary Butterflies Eat?

Adult butterflies primarily consume nectar from plants like coneflowers, milkweed, bergamots, goldenrods, clovers, and others. Flower nectar provides the adults will all the nutrients they need to sustain themselves during their search for mating partners.

On the other hand, the larva displays a drastically specialized eating behavior to the point where it actually endangers the species’ existence. The Regal fritillary caterpillars only consume plants in the Viola genus, family Violaceae. These are your typical violets that come in several species across the Globe.

The Regal fritillary caterpillar consumes various species of violets, depending which species grows in its habitat. This makes the caterpillar dependent on only a handful of plant species, placing the butterfly at a high risk of starvation due to habitat destruction.

Due to its specialized feeding behavior, the Regal fritillary can’t really adapt to a different environment.

What Plants Attract Regal Fritillary Butterflies?

The adult butterfly prefers several plants as food, many of which we’ve already mentioned. When it comes to host plants, the female will exclusively look for representatives of the Violaceae family, containing around 1,000 species, spread across 25 genera.

How do Regal Fritillary Butterflies Reproduce?

The butterfly’s reproduction behavior is another key factor that may endanger the species as a whole. There are several factors to discuss in relation to this topic:

  • The Regal fritillary is a univoltine species – The term univoltine characterizes species that produce only one generation per year. If the eggs, larvae, or pupae die, there’s no way for the butterfly to produce another generation the same year. This already places the species on shaky ground.
  • The male-to-female hatching ratio and timing – Males hatch a month earlier than females. Regal fritillary males all hatch in the beginning of June, while females typically hatch towards the same month’s end. This creates an almost 30-day period during which males have nothing else to do than survive and wait for the females to arrive. Many will die to predators and other natural or unnatural causes, diminishing the available sperm pool and, as a direct consequence, the species’ reproductive potential.
  • The adult female diapause – The mating process is rather typical for this species, falling in line with that most Lepidopterans experience. The male patrols open areas, waiting for the females to fly by, pursue them, and mate. The problem is what happens after. The mating process occurs in late June, soon after females hatch. As soon as the mating phase ends, the female enters a diapause state lasting 6 to 8 weeks, during which its ovaries cease their development. Everything will resume in late August when the eggs fertilize, and the female enters oogenesis. This is another 2 months during which the female may die, failing to lay the eggs and contributing to the species’ decline.
  • The larval diapause – The Regal fritillary female prefers violets as host plants for its eggs, but the problem is that the eggs spawn in late September early October. There are no violets at that time. This forces the newly-born caterpillar to seek shelter deep within the leaf litter and enter a hibernation state for the winter. This diapause period renders the larvae vulnerable to insect predators that may stumble upon it. The larvae will resume its activity in the spring, pupate, then turn into an adult and reset its cycle.

The only thing balancing things out is the female’s ability to lay between 1,000 and 2,000 eggs during the oogenesis period. This egg-laying proficiency takes away some of the species’ problems, ensuring it remains on the floating line.

Where do Regal Fritillary Butterflies Lay Their Eggs?

Most species of Lepidoptera will lay their eggs on the larvae’s host plants. They do so to provide the larvae with immediate access to food without having to look for it. Such a strategy minimizes the time the caterpillar needs to grow and pupate.

The problem is that the Regal fritillary’s life cycle doesn’t allow for that comfort. Since the female undergoes diapause and can only lay the eggs end August, host plants are usually not available. At this point, the female’s goal is to lay the eggs in a secluded and safe location, typically on the leaf bed in areas where violets will grow.

The larvae will seek cover under the leaf bed immediately upon hatching, preparing for the overwintering phase. This means that the Regal fritillary female needs to consider the larvae’s safety when looking for a viable place to lay the eggs.

Are Regal Fritillary Butterflies Rare?

Regal fritillary butterflies are rare and in decline. Their habitat destruction, combined with their intricate and volatile life cycle, has pushed the butterfly to the brink. Efforts are being made to preserve the Regal fritillary’s habitat and allow the population to grow and rebalance itself, but the journey is anything but smooth.

One of the main problems is the reduction in violets across the butterfly’s native territory due to housing expansion, row crops, business development, and gravel mining, among other things. These issues have already drastically diminished the Regal fritillary’s habitable zone from 18 states to only 3 since the 1960s.

Is the Regal Fritillary Butterfly Endangered?

Yes, the Regal fritillary ranks as an endangered species in some areas and vulnerable in others. One of the main problems that make this species so vulnerable is its lack of mobility and specialized habitat.

The Regal fritillary butterflies prefer to live in tallgrass prairies and cannot adapt to the altered habitat surrounding their native environment. Row crops, human-developed areas, or non-native pasture are all incompatible with the butterfly’s life cycle.

It’s also worth noting that Regal fritillary butterflies don’t migrate, so they have to deal with their present conditions, however hostile. And, since they only produce one generation of offspring per year, the species cannot heal any population losses it might suffer in any given year.

How Long do Regal Fritillary Butterflies Live?

The adult may live as little as 14 days and as long as 60 days depending on the environmental conditions. This is because the adult butterfly can withstand bad weather when necessary. However, you will most typically see females reaching the 60-day mark more often than males due to their diapause phase.

This phase occurs immediately after mating, during which the female waits for its ovaries to mature. Only then will it be able to fertilize its eggs with the male’s sperm and prepare for oogenesis.

What is the Meaning of Regal Fritillary Butterfly?

There is no meaning behind the butterfly’s name. Or, at least, none that I’m aware of.

Is the Regal Fritillary Butterfly Poisonous?

The Regal fritillary butterfly isn’t poisonous or toxic despite its bright coloring. This would’ve made the species more vulnerable to predators if it weren’t for the larvae’s adaptable behavior. The Regal fritillary caterpillars will look for hiding immediately upon hatching, rendering itself invisible under dead leaves, plants, and wood.

This will protect the caterpillar from any birds or other predators that may spot and hunt it down. The caterpillar will remain there throughout the cold season and come back to life in spring when it pupates and turns into an adult butterfly.

It also helps that the caterpillar is spiky and nearly impossible to chew.


Regal fritillary butterflies are very rare today, listed as endangered in many states and protected under the law. This species is unique in terms of life cycle, feeding pattern, and reproductive behavior, but it’s currently heading towards extinction due to human interactions and habitat destruction.

Fortunately, efforts are being made to restore its environment and preserve the natural conditions that the species needs to thrive.

Butterflies   Updated: February 3, 2022
avatar Welcome to Insectic, a blog to learn about insects and bugs. I'm Richard, and I've created this website to share my experience, knowledge, and passion with others.

Richard I’ve been wondering if the regal fritillary or any other endangered butterfly could be successfully raised outside of the natural habitat ( ie in a carefully constructed, climate controlled habitat). I would assume that this has been attempted.

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