In the early 20th century, the vibrant and iridescent California pipevine swallowtail butterflies filled the skies of San Francisco. However, as urban development expanded, these beautiful creatures began to dwindle in numbers, becoming a rare sight in the city. But thanks to the relentless efforts of Tim Wong, a 28-year-old aquatic biologist at the California Academy of Sciences, this stunning species is making a remarkable comeback, all within the confines of his own backyard.

Renowned for their magnificent wings, butterfly enthusiasts consider the California pipevine swallowtail (Battus philenor hirsuta) as one of North America’s most awe-inspiring species. Starting their life cycle as tiny red eggs, they hatch into large, orange-speckled caterpillars. After a gestation period of up to two years, these caterpillars undergo a transformative metamorphosis, emerging as breathtaking blue butterflies shimmering with oceanic hues.

During his workdays, Wong tends to an array of animals, including albino alligators, Japanese stingrays, and octopuses, as an integral part of his role at the science museum. However, in his free time, he dedicates himself to raising butterflies and meticulously maintaining a garden teeming with the essential flora these delicate creatures depend on. His passion for butterflies blossomed during his childhood, where he spent countless hours in an open meadow near his home, capturing, studying, and nurturing any butterflies he could find.

Wong reminisces, “I was first inspired to raise butterflies when I was in elementary school. We raised painted lady butterflies in the classroom, and I was amazed at the complete metamorphosis from caterpillar to adult.” With this fervor fueling his ambition, Wong embarked on a mission to reintroduce the dwindling California pipevine swallowtail population to San Francisco. To achieve this, he delved into extensive research to understand the species intricately.

He discovered that during its caterpillar stage, the California pipevine swallowtail solely feeds on one plant—the California pipevine (Aristolochia californica). Finding this rare plant within the city proved to be no easy task. “Finally, I was able to locate this plant in the San Francisco Botanical Garden [in Golden Gate Park], and they allowed me to take a few clippings,” Wong shares. Armed with his precious plant clippings and utilizing his self-taught techniques, he transformed his backyard into a sanctuary fit for these butterflies.

“I built a large screen enclosure to protect the butterflies and allow them to mate under outdoor environmental conditions—natural sunlight, airflow, temperature fluctuations,” Wong explains. The specialized enclosure not only shields the butterflies from predators but also provides optimal conditions for mating, while serving as an ideal environment for studying the preferences of female butterflies when selecting their host plants.

Once his butterfly paradise was complete, the next step was to acquire caterpillars. Wong managed to locate a group of 20 caterpillars outside the city, in private residences abundant with vegetation. He carefully brought them back to his backyard, releasing them onto the pipevine plants to feed. “They feed as a little army. They roam around the pipevine plant from leaf to leaf, munching on it as a group,” he describes.

After approximately 3-4 weeks, the caterpillars enter the pupal stage, encasing themselves in an outer shell known as a chrysalis. Inside the chrysalis, the insect undergoes a remarkable transformation, liquefying itself and eventually emerging as a butterfly, which occurs in about two weeks. Alternatively, the butterfly may remain dormant for up to two years in a state known as diapause. Once the butterfly emerges, it graces the skies with its presence, primarily from spring to early autumn. Their lifespan typically ranges from two to five weeks, depending on factors such as temperature, predation, and food availability. During their short lives, female butterflies lay eggs on the pipevine plants, typically in clusters of five to 30. Wong carefully collects and incubates these eggs indoors, shielding them from predators like spiders and earwigs. “From there, the cycle continues,” he adds.

Following the hatching of the eggs, Wong nurtures the caterpillars at home before transporting them to the “California Native” exhibit at the San Francisco Botanical Garden. This routine has been repeated for several years, successfully introducing thousands of caterpillars to the garden. Although other conservationists have managed to repopulate the California pipevine swallowtail in Santa Cruz and Sonoma, Wong’s efforts mark the first successful reintroduction in San Francisco in decades.

Wong attributes his success to the thriving habitat he has cultivated for the caterpillars. Cultivating over 200 California pipevine plants in recent years, he has also planted numerous nectar-filled flowers in the vicinity. As a result, he has been able to reestablish the butterfly population within San Francisco, breathing new life into their delicate existence.

“With each passing year since 2012, we have witnessed more butterflies surviving in the garden, flying around, laying eggs, successfully pupating, and emerging the following year.