PROTECTION STATUS: Not listed
PETITIONED: 1991 (San Diego Biodiversity Project); 2004 (Center for Biological Diversity)
RANGE: A small area on Otay Mountain in southern San Diego County
THREATS: Overly frequent wildfire and prescribed fire, Department of Homeland Security activities, habitat fragmentation, and global climate change
POPULATION TREND: Prior to the Mine fire in 2003, biologists estimated that about 400 Thorne's hairstreak butterflies remained in about eight populations. After the fire, surveys turned up fewer than 100 individual butterflies. Only five very small populations exist, all within an area of a few square miles on Otay Mountain.