Have you ever wondered how does a caterpillar turn into a butterfly? Do you know about the four stages of the butterfly’s metamorphosis? Let’s take a look at how a caterpillar turns into a butterfly and what this means for the little caterpillar, because the question should really be “how does a butterfly become a butterfly?”
How Does a Caterpillar Turn Into a Butterfly?
First, not all caterpillars turn into butterflies. Some turn into moths instead. No matter what, all caterpillars go through the same four stages: egg, larva, pupa and adult. Each stage has different goals and time lengths. For example, the monarch butterfly completely changes in about one month.
These transformations are also called metamorphosis, which is Greek for “transformation” or “change in shape.” There are actually two types of metamorphosis for insects: incomplete and complete.
Incomplete metamorphosis is when the young insect looks like a small version of the adult insect. You often see this with cockroaches, crickets, dragonflies, grasshoppers and termites. Complete metamorphosis is when the young insect looks different from the adult insect and must change drastically to look like the adult. Bees, beetles, butterflies, moths and flies undergo complete metamorphosis.
Stage 1: Egg
The butterfly’s life starts in a small, round or oval egg. The shape varies depending on the butterfly type. Most butterflies lay their many eggs on leaves. The eggs attach to the leaves with an adhesive fluid.
A mother butterfly can lay hundreds of eggs at one time, as many will not make it to the final stage of metamorphosis.
Stage 2: Larva
Once the butterfly hatches from the egg, it becomes a larva. However, this larva stage is actually when the butterfly is in caterpillar form. The tiny caterpillar has small eyes and short legs and antennae. It also has bundles of cells called imaginal discs that are waiting to turn into butterfly features, including long antennae and legs, as well as wings. However, the imaginal discs are prevented from growing by a constant source of juvenile hormones. These hormones will eventually trigger the third stage.
The caterpillar spends most of this time eating, including the leaf it was born on. In fact, caterpillars can be quite picky when it comes to what leaf to eat. This is why it is vital that the butterfly lays the eggs on a leaf the caterpillar will eat. For example, monarch caterpillars only eat milkweed.
Once the caterpillar eats, it grows – about 100 times more than when they first hatched. Some internal organs begin to change, though the imaginal discs continue to stay dormant. Monarch caterpillars reach full growth after about two weeks of eating.
Since their exoskeletons don’t stretch, they grow by molting, or shedding their skin, several times, like a snake. The hormone ecdysone causes the molting.
Stage 3: Pupa
During this third stage, the caterpillar is now ready for the next stage. Once the caterpillar is done eating and growing, there is a lack of the juvenile hormones, which causes the caterpillar to form a silk cocoon or shiny chrysalis around itself and begin radically transforming into a gorgeous butterfly. The cocoon is often hidden under branches, in a bunch of leaves or even underground.
This transformation is called complete metamorphosis, which we discussed above. From the outside, nothing appears to be happening, but inside is completely different.
The caterpillar dissolves into a soup-like substance using enzymes triggered by hormones. Its tissues, limbs, organs and imaginal discs then begin changing. The discs move to their correct positions, and the caterpillar starts taking a new shape as a butterfly.
It sprouts new colors, wings, long legs and antennae, better, larger eyes and other adult butterfly features. The mouth changes from a chewing mouth into a proboscis that sips nectar, as butterflies don’t eat solid food.
The metamorphosis takes place over a few weeks or months, and the caterpillar transforms into a completely new-looking insect.
Stage 4: Adult
The finished product and final stage end with a butterfly. The newly turned butterfly will break free from its cocoon. It will take some time to stretch its long legs and antennae and pump hemolymph (the blood-like substance of insects) into its wings so it can fly. The butterfly must also wait for the wings to dry and grow to their full size.
Once that happens, the butterfly will fly off and find a new mate to start the process all over again. Some butterflies only live a few weeks while others can last for months.