Type: report

Article abstract: This report summarizes our butterfly survey efforts of 2024. Larval surveys for this project/task are planned for winter of 2024/2025. The Harbison’s dun skipper (Euphyes vestris harbisoni) has a very restricted distribution in southern California and northern Mexico and entomologists have expressed concern that threats will lead to the extirpation of populations. The larvae of this skipper feed only on San Diego sedge (Carex spissa) and are generally associated with riparian oak woodlands. In 2024, surveys for Harbison’s dun skipper adults were conducted to assess the annual adult population size. Surveys started in a relatively small geographic area where skippers were observed in past years, but expanded to surrounding areas if skippers were not detected. Due to the relatively consistent numbers of adults through the month of June, each site was surveys two times. A total of 22 males and 11 females were counted, with adults detected at 7 of 18 sites. The higher number of skippers observed in 2024 compared to 2023 was likely due to San Diego sedge plants becoming established following the heavy rains and streambed scouring during the 2022 – 2023 winter. To facilitate a shift to using larval surveys to monitor annual population sizes, larval surveys will be conducted during the winter of 2024-2025 to compare adult and larval counts. This process is planned to be repeated one more time, with adult surveys in 2025 and larval surveys in the winter of 2025-2026.