By Carol Davit, Executive Director, Missouri Prairie Foundation
Photo: Regal fritillary on pale purple coneflower by Allen Woodliffe
When visiting original, unplowed prairies in July, you may see this large, beautiful butterfly flying over the landscape and nectaring on wildflowers.
The regal fritillary butterfly (Speyeria idalia) is dependent in Missouri on original, unplowed prairie remnants with violet host plants on which the butterfly’s larvae feed. (The regal fritillary looks similar to the more common great spangled fritillary, which you may see visiting your native plantings and on prairies.)
A candidate for federal listing under the U.S. Endangered Species Act, the nationwide status of this striking large butterfly with white spots on its ventral wings, as shown above, is currently being reviewed. As of 2015, there were 133 known sites for the species in Missouri, and 25 of these had not been surveyed in the last 20 years. According to a NatureServe analysis, Missouri has one of the best chances of having prairie of sufficient quantity and quality to maintain this species in perpetuity anywhere in the U.S.
Every summer, several MDC biologists and MPF’s Director of Prairie Management Jerod Huebner survey for regals on several Missouri prairies to better ascertain its populations. Among the prairies surveyed are MPF’s Denison, Lattner, and Pleasant Run Creek prairies complex in Vernon and Barton counties, where regals remain abundant.
“Almost exclusively, we saw the most regals on the unburned portions of these prairies,” said Huebner after the June 2020 surveys. While this observation is not conclusive, it may indicate that the butterflies, which overwinter as caterpillars, are emerging as adults from the unburned prairie portions, where the males establish territories in June and July. The adults will be visible through the summer; the females lay eggs in September.
The regal fritillary life cycle underscores how important it is to not burn an entire prairie tract in a year. However, no burning is not a solution either, as without fire, growing conditions for the butterfly’s violet host plants will degrade. A careful balance is required. MPF leaves unburned portions of each of its prairie tracts annually. As we learn more about regals, we may adjust our burn regimes even more.
Learn more in this article on regals by Natural History Biologist Steve Buback in the Missouri Prairie Journal, which includes photos of the butterfly’s life cycle.