Last week, the Star ran a story about the U.S. Fish and Wildlife Service deciding not to list the Sonoran Desert tortoise as endangered and instead put it on the candidate list. That's a kind of imperiled species limbo-land for plants and animals considered in trouble but not in enough trouble to put on the endangered list because so many other species are in worse trouble and the service doesn't have the money to protect them all. About 250 species sit on the candidate list today.

Now, the Center for Biological Diversity has sent out a story about what it considers a poster child for the plight of candidate species. The subject is a rare butterfly living near Key West, Fla. -- the Miami blue butterfly. According to the article from a Key West paper, the butterfly could be down to as little as one remaining population, in the unpopulated Marquesas islands, within the Key West National Wildlife Refuge, about midway between Key West and the Dry Tortugas. Another population, discovered about a decade ago at Bahia Honda State Park in the Keys, has now apparently vanished, according to the article.

In an email, center director Kieran Suckling said the butterfly is "on the knife edge of extinction.

"It is slipping into the void before our eyes, yet neither the Bush nor the Obama administrations have lifted a finger to save it. You expect that kind of denial from Bush, but seeing the Obama administration do the same thing is incredibly disappointing and infuriating. Historians may well look back and see the appointment of Ken Salazar as Interior Secretary as the final nail in the Miami blue butterfly's coffin."

The butterfly was put on the candidate list in the 1980s, taken off years later and put on a second time 2005. Had the butterfly been listed, federal and state officials would have spent much more money conserving it, would have found more and better sites to reintroduce it and and would have acted to keep iguanas from eating existing populations, Suckling said.

Ken Warren, a service spokesman in Vero Beach, Fla., said it's difficult to say if listing this species would have prevented it from apparently disappearing from Bahia Honda State Park. The service is now reviewing another petition for an emergency listing for this butterfly, he said.

"We're extremely concerned about the status of the Miami blue butterfly.  Based on current information, there appears to be only one, possibly two small populations of this species left in the extreme southern portion of the historical range," Warren said. "In that regard, we're evaluating all available information that could lead to an emergency listing and are actively involved in conservation efforts."