More Than It Racemes: Understanding Adult Butterfly Nutrition in Icaricia icarioides blackmorei

by Hanna Brush

mentor: Elizabeth Crone, Biology; funding source: Provost’s Office

Understanding how species interact with their environment is crucial to conservation and protection of vulnerable ecosystems. One such ecosystem is the rapidly disappearing network of prairies in the South Puget Sound of Washington state. These unique prairies are home to many species found nowhere else, including the Puget blue butterfly (Icaricia icarioides blackmorei). However, little is known about this butterfly’s life history or how it interacts with its environment. One major facet of these interactions is adult nutrition and nectaring. Female adult nutrition is crucial to the success of butterflies and their offspring, but little is yet known about what they eat or what species and resources they prefer. For my Summer Scholars project, I studied adult female nectaring behavior, asking three novel questions about their feeding: what flowers do they feed on, are they opportunistic feeders, and do available floral nutrients drive feeding patterns. To answer these questions, I conducted field observations of nectaring behavior, and determined availability of nectar species via sugar and amino acid content, and floral abundance. A normal field day consisted of capturing and observing female butterflies and counting flowers at different spots on the prairie. I found that female Puget blue butterflies nectar on eight species of flowers, notably spending nearly half their nectaring time feeding on the closed racemes of their larval host plant, lupine. The butterflies did not feed in direct proportion to the availability of flowers on the prairie, meaning they are not opportunistic feeders. They did not feed in proportion to either sugars or amino acids in the nectar, meaning these nutrients likely do not drive foraging preference. These results tell us that we must conserve the complete prairie ecosystem to preserve the butterflies’ selective feeding and highlight the importance of lupine throughout all life stages of the Puget blue butterfly.