The Life Cycle of a Monarch Butterfly

Butterflies have four stages of life: egg, larva (the caterpillar stage), pupa (the chrysalis phase) and adult. These four stages are called Metamorphosis. It takes a monarch butterfly about a month (28 to 38 days) to complete the whole life cycle. 

Common Milkweed

Females lay their eggs on milkweed, which is the only plant monarch caterpillars can eat. The eggs are usually laid on the underside of the leaves and usually one at a time. They are white and are really small, smaller than a pinhead. The egg is attached to the leaf by an 'liquid glue' as it is being laid. Four to six days later they will hatch. Monarch caterpillar egg on the underside of a milkweed leaf.

After it hatches, the caterpillar is so small you can barely see it. It grows really fast, eating nothing but milkweed leaves. A Monarch caterpillar can eat enough Milkweed in one day to equal its own body weight. 9 to 14 days after hatching, the caterpillar will be about 2" long and fully grown. 

 

Monarch caterpillars about one day old.

 

The larger caterpillars are eight days old, and the smaller one is six days old.

During the larval stage, a monarch caterpillar will shed its skin five times. A new, larger skin is waiting under the one that is shed.You can see its shed skin left behind each time.

When the caterpillar is full grown it will usually leave the milkweed plant. It crawls (sometimes 20 or 30 feet away from the milkweed) until it finds a safe place to pupate. The caterpillar lays down a silk-like mat and then attaches itself to the mat with its cremaster. Then it will drop and hang there, upside down in a J-shape, for about one full day.

The caterpillar's skin is shed for the last time as it passes from the larval (caterpillar) stage to the pupa (chrysalis) stage of metamorphosis. Under the caterpillar's skin this time is a jade green casing which is called a chrysalis. Inside the inch long chrysalis, is where the real magic begins as the caterpillar transforms into a beautiful butterfly.

At first, the chrysalis will be very soft. Within an hour, it hardens to become a protective shell for the caterpillar. Lots of majaor changes happen inside the chrysalis. The mouth parts change from being those required for chewing milkweed leaves to a straw-like tongue the butterfly will use for sipping nectar from flowers.

9 to 14 days after the chrysalis is formed, the transformation is complete. The green color will disappear and become clear. Through the chrysalis, you can will be able to see the orange and black wings of the monarch butterfly.    When it's time, and without any warning, the chrysalis will suddenly crack open and out comes the monarch butterfly. Its wings will be crumpled and wet. The butterfly will clings and hang on to its empty chrysalis shell as hemolymph, the blood-like substance in insects, is pumped through its body. Once the hemolymph fills the monarch's body and wings, they will enlarge.

About one hour after emerging from its chrysalis, the monarch's wings are full-sized, dry, and ready for flying. A week later, or less, a monarch butterfly is old enough to mate, starting the next generation's life cycle. Pretty amazing! We are in the process of 'raising' our own caterpillars, if you would like to follow us on our journey so far, you can read about it here.