Hydrogen Pun Sui-fan, the adviser at Fung Yuen Butterfly Reserve in Tai Po, has witnessed the dramatic, complete metamorphosis from caterpillar to butterfly first-hand at home hundreds of times.
For eight years, he has been nurturing more than 200 species of butterflies native to Hong Kong. With his logbook and camera, he chronicles their lives as they transform from eggs to caterpillars, from pupae to adult butterflies.
"We all know how staggeringly beautiful adult butterflies look," Pun says. "But their beauty does not last, for they die soon after they mate and breed. Yet that's not even half of the story. There are three stages of life before that."
With a licence from the Agriculture, Fisheries and Conservation Department, Pun and his co-workers collected butterfly eggs from Fung Yuen and country parks. At one point, in 2005, Pun and his family shared their flat with 100 caterpillars in separate airtight boxes.
Raising butterflies from eggs is better than starting with week-old caterpillars, as the latter are usually infected by parasitic flies. The parasites feed on the caterpillars' insides, hindering their growth and killing them at the pupal stage. This can be avoided by raising newborns in a controlled environment indoors.
"Parasites - and other natural predators, such as birds, spiders, and bees - attack the butterfly's young. Only one in 10 caterpillars lives until adulthood," Pun says.
An adult Chinese peacock butterfly
Adults find ways to protect their young. Mother butterflies tend to lay eggs on top of their major food source so their young will have lots of food nearby. Pun says there's a family called the gossamer-winged butterflies that only lay eggs in ant territory. "The caterpillars produce sugary juice to feed ants, who will, in turn, fiercely guard them," he says.
Keeping butterflies isn't easy. Caterpillars are voracious but fussy eaters. "They grow up to 500 times bigger from the moment they emerge from the egg to the time they turn into cocoons," says Pun.
Many species feed only on a particular plant - swallowtails prefer goat horns, one of the most poisonous plants in Hong Kong, while silver-spotted skippers favour a type of grass called sheep's fescue.
The fresher the leaves, the higher nutritional value, which is why Pun ventures out every two days to collect their food - much as a mother bird does for its chicks. "Wind and rain wouldn't deter me," he says. "Not even a typhoon signal No 8."
When Pun notices one of his caterpillars is ready to weave itself into a cocoon, he places a twig into its box. At this stage, the creature won't feed nor move. Its tissues completely break down and reorganise within its skin.
It emerges a fully-formed adult, pumping its stubby wings full of bodily fluids and blood - like inflating balloons - while hanging upside down, until the wings become instruments of flight. When the wings are expanded and firm, the butterfly withdraws the liquids to let them dry.
Although the public cannot actively collect eggs from the countryside, Pun says they can plant butterfly-friendly plants such as Michelia and ivy on their windowsills or in school gardens to attract the winged beauties.
Click here to see more stunning photos of butterflies going through stages of metamorphosis