Hans Christian Andersen's well-known tale, "The Ugly Duckling", is the story of an ugly juvenile bird that matures into a beautiful swan. But the transformation of moths and butterflies from caterpillars to adults is a much more dramatic and complex change than the development of a swan from "duckling" to adult.
To this in about 7 weeks:
This metamorphosis from a tiny black hatchling to such a big canvas of pastel-colored green and blue is almost as amazing as what happens next in its life: after over-wintering for about 8 months in its cocoon, what emerges bears no resemblance at all to what came before. This caterpillar has grown from a tiny hatchling barely 3/8" long, shedding its skin four times to become larger than an adult's forefinger. From here, it will spin a cocoon, shed its skin inside the cocoon to become a pupa, and overwinter before emerging as an adult next summer.
And when it does emerge, it will be as a stunning beauty with startling eye spots, and a feathery/furry coat with colors from rose to gray to creme to cinnamon:
But what is most amazing is how complex and thorough are the changes these animals undergo from egg to adult. It takes more than a year to develop from a tiny egg, through five molts as a caterpillar, overwintering as a pupa inside its cocoon, and finally emerging as an adult moth. The adults exist to breed and produce eggs, and have no functional mouthparts for feeding. Having lived into their second summer, their lifespan as adults is only about a week after emerging from their cocoons.
From eggs 2 or 3 mm in diameter to caterpillars the size of your forefinger in 6 weeks, the growth of the large silk moths is prodigious. The changes in size and coloration of the caterpillars are remarkable, but nothing as completely transformative as their progression from caterpillar, to dormant pupa, to a moth bigger than your hand.
These are images of the development of the Cecropia moth, Hyalophora cecropia, North America's largest.
From eggs that were laid on 19 May, these tiny beings emerged:
Feeding on nothing but lilac leaves, they have gone through three molts and have increased in size by a factor of about 40 in about a month.