By Eric Simons, Bay Nature
The Mission blue butterfly takes its name from San Francisco — the original population was discovered on Twin Peaks, at the time considered part of the Mission — and is the city’s only endangered butterfly. It probably never was widespread, but in the modern era it is incredibly rare. When the Endangered Species Act became law in 1974, there were a lot of creatures that everyone already knew were endangered, and the Mission blue was one of them. It went onto the list in the first big batch of insect listing in 1976. It has declined since then.
When the the U.S. Fish and Wildlife Service created its recovery plan for the butterfly in 1984, the agency declared that for it to come off the list it would need a “self-sustaining” and “secure” population on Twin Peaks.
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