The Monarch Butterfly Life Cycle

There are four stages in the life cycle of a butterfly. The stages include, egg, larva, pupa, and adult. The entire process is called complete metamorphosis and is one of two ways insects develop from an egg to an adult. The other type of insect development is called incomplete metamorphosis.

Egg

 

A monarch begins life as a single cream-colored egg attached to the underside of a milkweed leaf.

 

Illustration of a monarch butterfly egg. Notice this egg surface is not like a chicken or bird egg.

The worm-like larva grows inside the egg. When it is ready, the larva chews a small hole in the egg shell and wriggles its way into the world. After a few minutes, the newly hatched larva has its first meal -- the remains of its egg. Female monarchs lay one to three eggs on the underside of milkweed leaves. This process is repeated until the female has laid hundreds of eggs. |top|

Larva

 

After eating the shell, the larva begins to eat milkweed leaves. Milkweed is the only plant that monarch larvae will eat. The larva eats and grows, grows and eats. The larva grows so much that it outgrows its skin, much like outgrowing old clothes.

In order for the larva to keep growing, molting must occur. The old skin splits, revealing the new skin underneath. The larva wriggles free of the too-tight skin. After freeing itself, the molted larva often eats its old skin before moving on to more milkweed leaves. |top|

 

After shedding their skins, monarch larvae continue to grow and will have to molt four more times. The last molt is much different than the others. The larva crawls away from its milkweed plant, searching for a suitable place. Some larvae will travel longer distances than others. When the larva has found a suitable place, it weaves a silk mat with a "button" in the center. Once the mat and button are ready, the larva grabs the silk with its legs and hangs upside down. The front part of its body will curve to make a "J-shape." |top|

 

Once in the "J", the larva molts for the last time. The skin splits behind the head, and the larva wiggles while it hangs upside down to remove the old skin. This final molt is the trickiest, because the larva must shed its old skin and still hang onto the silk button. Once the larva embeds a hook-like structure at its rear end into the button, the rest of the skin can slip off. |top|

 Pupa

 

When the skin fall off, the larva becomes a pupa. The monarch has no eyes and no antennae. It has no legs, and it cannot move. All of the major changes in body shape, size, and arrangement happen. In monarchs, this stage can last as long as a week. At the end of this stage, an adult butterfly will emerge from the chrysalis. |top|

Adult

 

A newly emerged butterfly will wait two or more hours before it can fly. New wings are small and shriveled, so the butterfly pumps body fluid through its wing veins in order to make them get bigger. Then, the monarch has to wait for air to replace some of the fluid. Until this happens, the monarch cannot fly, and its wings are easily damaged. |top|

 

After the wings have hardened, the butterfly flies away to find its first meal. From this point on, the monarch drinks all of its food. The butterfly will visit several different kinds of flowers to get its nectar dinner. |top|

A monarch butterfly caterpillar eating a Swan plant leaf. Image by Pseudopanax via Wikimedia Commons.

Food

Part of the life cycle of the butterfly is their change in diet during different stages of development. Monarch larvae only eat the leaves of the milkweed plants. Once they become an adult they switch to feeding on the nectar of different plants including milkweed.

Not only do adult monarchs need to drink nectar, but like other butterflies they also need to drink water. You can sometimes see them on damp ground where they can get water from the soil. This is called mud-puddling, or puddling.

Mating

A monarch butterfly uses its long proboscis to drink nectar from a flower. Image by CJ Kazilek.

Adult monarchs begin mating in the spring, before they return to their summer range. Female monarchs will generally lay one to as many as three eggs on the underside of milkweed leaves. She does this many times until she has laid hundreds of eggs. These eggs will hatch into larva, pupate, and become adults in the summer. These new adults will also mate. The new females will lay eggs as they fly northward. This cycle repeats throughout the summer.

Finally, in September, mating stops. The last generation of the summer is the one that will migrate to the overwintering grounds.

Additional images via Wikimedia Commons. Butterfly egg picture by forehand.jay.