Type: report

Article abstract: The Hermes copper (Lycaena hermes) is a rare butterfly endemic to San Diego County and northern Baja California. This species is threatened by urbanization, wildfires, and drought throughout its range in the United States. Since most individuals and the single (known) remaining large population are found in the southern portion of San Diego County, one large fire could extirpate the species in this country. Past efforts have contributed to our understanding of the distribution of the Hermes copper, so it is fairly well understood. This includes wildfires in 2003 and 2007 causing several extirpations with few recolonizations, and more recent droughts further restricting the distribution of this butterfly. We conducted widespread surveys in 2018 with the goal of detecting unknown populations; however, conditions were suboptimal due to below average rainfall. Efforts in 2019 and 2020 followed winters with closer to average precipitation. In 2018, one large population (Roberts Ranch South) was discovered to be larger than previously documented. No new populations were documented and there was no evidence of recolonization within the 2003 or 2007 wildfire at selected sites. The objective of this project (2022 surveys) was to further assess the distribution and annual population sizes, possibly with the goal of future translocations of individuals to reestablish populations. We conducted surveys in many of the areas sampled during 2019-2021. The 2022 status of the Hermes copper populations is similar to the last couple years, with the addition of observations at the San Diego Gas and Electric Substation near Bell Bluff Truck Trail. However, the number of butterflies were lower than past counts at this site and at Roberts Ranch South. Sites with fewer than five individuals have been relatively steady over the last few years. Given these patterns, the long-term viability of the species still appears to be highly dependent on the Robert Ranch South population.