How one man repopulated a rare butterfly species in his backyard

Though the California pipevine butterfly had nearly disappeared in San Francisco, it was still common outside the city, in places with more vegetation. With permission, Wong was able to source an initial group of 20 caterpillars from private residences.

He carefully transported them to his backyard and set them loose on the plants to feed.

"They feed as a little army," he says. "They roam around the pipevine plant from leaf to leaf, munching on it as a group."