Life Cycle of the Cecropia moth, Hyalophora cecropia

The Cecropia moth is a member of the family Saturniidae that includes many of North America's largest moths. Only the Atlas moth is bigger. The Cecropia ranges across the United States from the East Coast to the Rocky Mountains. It is "univoltine", meaning only one generation is produced per year. The pupae who have spent the winter months in their cocoons emerge in late Spring or early summer, and live for only a few days - enough time to find mates and for the females to lay eggs before they die.

The larvae - caterpillars - feed on a variety of host plants including cherry, maple, lilac and others. They are voracious eaters and molt four times as the get larger and larger. The hatchlings are so small as to be hard to see and emerge from eggs about 2 mm in diameter. But after shedding their skins over a period of about six weeks, the mature caterpillars are bigger than a man's middle finger.

Eggs

Distinguishing features:

About 1-1.5 mm in diameter
Whitish or pale beige in color with darker spots
Attached to leaves or twigs of host plants
Laid in clutches of two to ten or more eggs, in rows or clumps.

Hatch

A 1st-instar caterpillar emerges from the egg by chewing through the eggshell.

Clutches of eggs on lilac leaves and hatchling caterpillars.

Eggs are laid on the surfaces of the leaves and twigs of host plants, including cherry, maple, lilac, and others.

Hatchlings - 1st instar caterpillars

Distinguishing features:

All black integument and scoli. As caterpillars approach molt, they start to look puffy and more brownish as their skin stretches.
Group feeding occurs with several individuals feeding alongside each other on the same leaf.

Hatchling

This hatchling caterpillar has not yet shed its skin for the first time - so it is called a "1st instar" caterpillar.

Team effort

Hatchling caterpillars are often found close together, eating from the same area of a leaf. This behavior continues as they grow, but eventually they tend to feed solitarily.

Defenses

From birth the caterpillars possess "scoli" - the spiky projections on their backs that serve as defensive armor against predators. The will keep the scoli throughout their lives as caterpillars, but the scoli become much more prominent and colorful as the caterpillars mature.

Almost ready to molt the first time

This 1st instar caterpillar has not yet shed its skin for the first time, but looks a bit overinflated - like its whole body is under pressure. It will molt soon, giving it room to continue growing inside a bigger bag of new skin.

First molt and 2nd instar caterpillars

Distinguishing features:

Body yellow with black spots.
All scoli black.

2nd instar typical appearance

This caterpillar has the typical "leopard skin" appearance of a 2nd instar lava - black spots on a yellow background.

Color change

The larva at upper left has already assumed the typical appearance of a 2nd instar caterpillar, while the one at lower right has just molted and its appearance has not yet stabilized.

Just molted to 2nd instar

This caterpillar has just crawled out of its skin. After resting for about an hour, the caterpillar will turn around and devour the cast-off shell. Its appearance will also change as it is exposed to the environment for a few hours.

2nd instar

Another view of a 2nd instar caterpillar.

Second molt to 3rd instar caterpillars

Distinguishing features:

Body yellow with black spots in longitudinal rows between scoli.
Large orange scoli on segments two and three, each bearing eight spikes - seven pointing roughly horizontally around circumference near crown, one pointing vertically.
One row of blue scoli superior laterally, one row of black scoli inferior laterally.
Spiracles white.
Pads of prolegs tinged with blue.

3rd instar caterpillar - typical appearance

Eating its cast off skin

The newly-molted caterpillar, after resting for about an hour, turns around and eats its recently cast-off skin in its entirety.

Before molting

This 2nd instar caterpillar has the puffy appearance typical just before molting occurs. The caterpillars become motionless for about a day before molting.

Just molted to 3rd instar

This caterpillar has just molted from 2nd to 3rd instar.

Third molt from 3rd to 4th instar

Distinguishing features

Body green laterally blending to more bluish dorsally. Black spots between rows of scoli.
Four bright red scoli, one pair on second body segment, one pair on third body segment.
Pairs of yellow scoli dorsally on fourth to eight segments.
Two rows of blue scoli laterally.

Varicolored scoli

The scoli, the spiked projections on the caterpillar's exterior, become very brightly-colored and prominent in the 4th instar.

4th instar caterpillar

Close-up of scoli

Head

In this image some of the structures in the head of this 4th instar caterpillar are visible: the array of simple eyes, the mandibles and the labrum.

Fourth and final molt as a caterpillar - 5th instar

Ready to molt

This is a 4th instar caterpillar just before molting to 5th instar. Notice how the skin has lost a lot of its color, with white wrinkle marks and a saggy appearance.

5th instar after molting

This caterpillar has just completed the molt to 5th instar. Many of the scoli have fewer spikes and are elongate. The spiracles are a very prominent white.

Protecting the head

While resting or when alarmed the caterpillar curls the forward part of its body and pulls its head back into a protected position.

5th instar caterpillar

From right, you can see the caterpillars three pairs of true legs, four pairs of abdominal prolegs, and one pair of anal prolegs.

Caterpillar Development - 1st to 5th instar

4th instar

5th instar - final caterpillar stage

Adults

Comparison

In this split image, an adult raised from eggs from the Long Island area of the United States is on the left, and a wild Colorado adult is on the right. Most striking is the lack of a cinnamon-colored row with the black and white stripes that appear near the middle of the wings about halfway between the wing margin and the body.

Adult Cecropia moth, Hyalophora cecropia - one of North America's largest moths, with a wingspan of around eight inches. — Adult Cecropia moth, *Hyalophora cecropia* - one of North America's largest moths, with a wingspan of around eight inches.