Monarch Life Cycle

Stage 1: Egg

The first step in the life cycle of the monarch butterfly is the egg. In order for this to occur, a female monarch butterfly must find a mate in order to be able to fertilize her eggs. Her eggs have already developed. When a female monarch butterfly spots an attractive male monarch butterfly to mate with, they both mate, as shown in the image above. During this process, the female monarch butterfly's eggs are fertilized by the male, as his sperm pass through the selectively permeable membrane of the egg covered with micropyles. This fertilization allows for the development of larvae in the eggs inside the female's body (The Monarch Joint Venture).

After mating, the female monarch butterfly will fly to a nearby milkweed plant source. She will lay her eggs on the leaves of these milkweed sources, usually about one egg per leaf. Each egg has a height of approximately 1.2 mm and a width of approximately 0.9 mm, no bigger than the tip of a pushpin, and a female doesn't just lay only one egg! She can lay up to about 300-500 eggs in about two to five weeks of her egg-laying period, securing each egg laid with a strong adhesive substance. Young monarch butterfly larvae will typically hatch out of their eggs after 3-5 days. You can tell if a monarch caterpillar may hatch out of its egg if you see a black head on the tip of the egg: that is the young caterpillar's head. The female monarch butterfly does not care for her offspring, although she does ensure they are laid on their appropriate host plant: milkweed (The Monarch Joint Venture).

Stage 2: Caterpillar

A monarch caterpillar molts five times in its larval stage. The fifth molt transitions it from the larvae to the pupal stage. The first four molts cause it to grow about 10 times in size. From Monarch Watch.

When a monarch caterpillar hatches out of its egg, it starts off as an extremely tiny caterpillar no more than 2-6 mm! They first eat the outside of their egg shell, the chorion, consuming nutritious protein - an essential source for growth! Then, they start chomping down on the milkweed that they were laid on. Soon after they eat enough milkweed, the monarch caterpillar molts for its first time, meaning that it has shed its skin to become bigger. Now the caterpillar is about 6-9 mm. (It's getting there). And what does it do next? It continues to chomp on more and more milkweed molts for a second time! This time, the monarch caterpillar is about 10-14 mm in size. But it does not stop there. The monarch caterpillar eats more and more milkweed, consuming more milkweed. Because its mouth is bigger from its increasing size, it can take bigger bites of milkweed than it did when it was a baby. Soon the caterpillar continues to grow in size, doubling to about 13-25 mm! But it will persist - it will keep on eating more and more milkweed until it becomes a plump monarch butterfly larvae about 25-45 cm in length (Monarch Watch). In about two weeks from its hatching, a monarch butterfly larvae had eaten enough milkweed to grow 10 times its original size!

What does our plump monarch caterpillar do next? There's no more room for milkweed. See what happens by scrolling down to Step 3 below on this page!

Stage 3: Pupa

Our friend the plump monarch caterpillar will molt again. And this will be the final molt: the fifth molt that a monarch caterpillar undertakes. It will hang in a "J" position and dangle - probably from a branch, the top of a building roof, or maybe even your backyard fence! The monarch caterpillar hanging in this position was able to dangle in this position by creating a sticky silky surface near their hind legs (Monarch Joint Venture). This provides them with an adhesion between their legs and the surface that they choose to dangle on.

To further secure its position on the surface the monarch caterpillar is hanging from, it produces a small black stem that pierces its adhesive silky mat. This little black stem is known as the cremaster (Monarch Joint Venture). After molting to produce a green casing, this, the chrysalis, forms. The mush of butterfly larvae attempts to knock its molted skin off the chrysalis, letting it drop to the ground. The chrysalis then hardens.

Within the chrysalis, the mush of cells begin to reform the caterpillar into a monarch butterfly. However, this does not happen overnight. This natural transformation of complete metamorphosis happens for about 2-3 weeks!

Stage 4: Butterfly

After about 2-3 weeks, the monarch butterfly in the chrysalis slowly changes from solid green to the color of a developing monarch butterfly: black, orange, and white. Once the monarch caterpillar has completely transformed into the monarch butterfly, it hatches again - but this time out of its chrysalis. Instead of the shell of the chrysalis being supplied as a source of protein for monarch butterflies, the monarch butterfly uses the shell for support when it emerges from a chrysalis.

Why does it need this immediate support (as you can see from the video)? Well, a monarch butterfly immediately hatching out of its egg cannot fly yet. It's abdomen is huge and its wings are tiny and wet. To acclimate to its new surrounding environment, monarch butterflies circulate their hemolymph (their version of blood) throughout their wings, allowing their abdomen to slowly shrink to normal size and for its wings to spread and grow. Plus, its wings also are in the process of drying. This takes about several hours. It is very important for nothing to disturb this process, as the wings could dry incorrectly for a monarch butterfly, leading to a deformed, flightless butterfly with a significantly low chance for survival.

Once the butterfly flies off, it searches for potential mates. They usually do this after about 3-8 days from hatching out of their chrysalis. Mating can last up to about 2/3 of the entire day, and monarch butterflies can mate multiple times. After mating, a female monarch butterfly lays her eggs to prosper the next generation of monarch butterflies...and the life cycle repeats again (Monarch Joint Venture).

If a monarch butterfly hatches near the August and September months, it has an extra vital task unique to monarch butterflies: it has to migrate to its winter refuges in southwest California or Mexico. They get an extra bonus to their lifespan - these monarchs can live up to almost three-quarters of a year (Monarch Joint Venture)!