The Mission Blue Butterfly (Icaricia icarioides) can only be found in a few places along the Pacific coast in the area of San Francisco. They depend on just 3 species of lupine flowers, so as development removes these flowers and the coastal scrub environment, these butterflies no longer have anywhere to live. Their numbers are dwindling and they becoming restricted to just a few park areas. I haven't heard an estimate of their population number exactly, but researchers say the population is decreasing. You can check out more about them at: this site