Ecological Overview

Regal Fritillary Butterfly

This brush-footed butterfly (Nymphalidae) is part of the long wing and fritillary subfamily that is spread across North America and abundant throughout the tropics. The Regal Fritillary (Speyeria idalia) is a unique butterfly in that it is a specialist (fits into a narrow range of habitat) that is endemic to a specific type of tallgrass prairie. The Crane Trust is on the western edge of the range, and the historic range would have been throughout the continuous prairie that reached all the way to New York and Pennsylvania. However, it is likely that the populations of Regal Fritillary were only locally abundant in appropriate habitat. Firstly, the butterfly requires a good density of its host plant, or the plant it eats as a caterpillar. The Regal relies on violets (Viola spp.), but a single violet cannot provide enough for even a single caterpillar to reach metamorphosis so the caterpillars much explore the prairie floor to find what it needs. To complicate this further eggs are laid in the fall, with no idea where violets may grow in the spring, so after hibernating over winter the caterpillar must meander in search of violets. Another important factor is a thatch over story which seems to be extremely important for caterpillars and when the female enters diapause (a hibernation-like pause where biological function slows) before they lay their eggs. The thatch may be sheltering caterpillars from the hot dry sun which can dry out the creatures, and also can provide cover from predators. Females in diapause need shade and shelter to survive from late July to early September in the grass, likely to decrease energy consumption, and protect their wings from wind, rain, and even hail.

The Crane Trust is currently investigating long-term trends for this and other butterflies of conservation concern. Additionally, because of the unique habitat requirements for this species we carefully plan out management to increase habitat connectivity and ensure there is appropriate habitat for caterpillars each fall and spring. Currently, the fritillary is under review as a candidate species for the Endangered Species Act and has been recommended by an expert in butterfly biology to be listed as Threatened. We hope that the Fish and Wildlife Service will be able to announce the official opinion by the end of 2019. However, many organizations, institutions, and individuals have been working on how to properly protect and manage prairies where Regals currently inhabit as well as beginning attempts at vital human-assisted re-introductions. These re-introductions or transportation will be necessary to promote genetic diversity, and allow the butterflies to cross the desert of agriculture which is impenetrable for this species unlike many generalist butterflies such as the Monarch, Painted Lady, or Orange Sulphur.

KC King and Josh Wiese