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.
First instar caterpillar 6 days after hatching. Skin is stretched, giving the caterpillar the appearance of a spikey hotdog.
Second instar after skin has dried and colors have stabilized 16 days after hatching.
Third instar caterpillar feeding on a lilac leaf, 26 days after hatching.
Nine days after hatching, this caterpillar has shed its skin and is now called a "second instar" caterpillar.
This caterpillar has just shed its skin and become a third instar, 18 days after hatching, The caterpillars typically turn around and eat their cast-off skins within an hour or so of moulting.
Close-up of the colorful tubercles that serve as defensive weapons against potential predators.
Twenty-six day-old third instar caterpillar.
Thirty-one days after hatching, this caterpillar has just become fourth instar. The area surrounding the spiracles on the sides through which the caterpillar respires have turned white and there are other subtle changes in color and appearance.
A third-instar caterpillar of the Cecropia moth, Hyalophora cecropia, sheds its skin.
A close-up from the side reveals the single hooks on each of the six "true" legs [these will become the legs of the adult moth], and rippled edges of the blue pads at the bottom of the thick prolegs. At left just under the green plant stem can be seen the caterpillar's head and the notched labrum whose inverted "V" shape guides the caterpillar's mouth along the edge of a leaf as it eats.