Content:
- From the Beginning
- Eating, Smelling and Tasting
- Cells, Growth and Imaginal Discs
- Exoskeleton Molting
- Time to Transform
- Do All Caterpillars Turn into Butterflies?
- What to do if you find a Cocoon?
Often we take the beauty of caterpillars for granted without ever knowing anything about them, other than the fact that they will eventually become butterflies or moths.
But there is so much more to learn about caterpillars, such as how they survive, how long before they go into a cocoon or chrysalis, and when they will emerge as fully grown moths and butterflies. This article starts with the caterpillar anatomy and growth.
From the Beginning
The caterpillar is the larval stage of the moth or butterfly. After it hatches from the egg, it will remain a caterpillar for between two weeks and a month, depending on the species. Incredibly, the caterpillar can grow more than 30,000 times its original size during the larval stage.
The body of the caterpillar is segmented and consists of the head, thorax, and abdomen. Attached to the thorax are three pairs of jointed legs that have hooks, and the abdomen has five pairs of prolegs, which are stumpy versions of legs. The whole purpose of life for the caterpillar is to eat plenty and grow until it is ready to metamorphose into the butterfly or moth.
Eating, Smelling, and Tasting
Each caterpillar spends the majority of its time eating with its powerful jaws, also known as mandibles. These jaws have a sharp cutting surface which enables the caterpillar to easily chew through leaves. The caterpillar bites of parts of a plant and the mandibles tear it into small pieces that are easily digestible.
Beneath the mandible is two maxillae, which are smaller mouthparts. These guide the food into the caterpillar’s mouth. While it is easting, the caterpillar uses its thoracic legs to hold onto the food.
The taste cells are located in the maxillae, and they detect whether or not a food is appropriate to eat. If it is poisonous or otherwise inappropriate food, the maxillae won’t push the food into the caterpillar’s mouth. Near the mouth are tiny antennae, and it is through these that the caterpillar can smell.
Digestion
The choice of food for each caterpillar is fairly limited for many species, and they will only eat the leaves from one particular plant.
To digest the food, the body of the caterpillar is filled with the intestines.
As the caterpillar grows so fast, there has to be the ability to store enough food energy to survive.
Therefore, digestive nourishment is very important.
Cells, Growth and Imaginal Discs
Caterpillars are different from the majority of organisms because the number of cells in the body does not increase. By the time the caterpillar is ready to pupate, the number of cells is exactly the same as when the caterpillar first hatched from the egg.
However, the cells of the caterpillar are not the same cells that become the adult. This is where imaginal discs play an integral part in the development from caterpillar to butterfly or moth. The imaginal discs are a cluster of cells that develop into a variety of adult body parts.
Exoskeleton Molting
The exoskeleton of the caterpillar tightens as the caterpillar grows, so it is necessary for them to molt. After the molting, and while the new skin is soft, the caterpillar swallows lots of air which expands the body.
Then as the skin hardens into the exoskeleton, the caterpillar lets out the swallowed air and the result is that the caterpillar then has room to grow.
Caterpillars generally molt four or five times as they grow to the pupal stage. Each of these stages is called an instar.
Colors of Caterpillas
Caterpillars come in a variety of patterns and colors, and many are colored to camouflage them among the host plant. This enables them to hide from many predators.
Generally, the brighter the color of the caterpillar, the more poisonous they are to predators. It is a way to remind the predator that the caterpillar will be toxic if they try to eat it.
Predator Protection
Because caterpillars are slow-moving and have nice soft bodies, they are a target for a variety of predators including birds, mammals, and wasps.
There are even certain species of caterpillars that will eat fellow caterpillars. So, to protect themselves, the caterpillar can use different methods to be safe from predators.
Eyespots
Some caterpillars have markings called eyespots which make the caterpillar appear more dangerous. The eyespot is a circular marking that resembles an eye.
They are often quite large to fool the predator into thinking it is looking at a much larger creature.
Poison
As mentioned before, some caterpillars are poisonous and the brightly colored species are more dangerous than others.
The color alone warns off a cautious predator.
Two of the caterpillars that are poisonous include the Monarch and the Pipevine Swallowtail.
Camouflage
Because many caterpillars rely on camouflage to protect them from predators, they are often green in color to match the plants they live on.
There are even caterpillars that can resemble unpleasant objects such as bird droppings, so they look unappetizing to the predator.
Hiding Behavior
Often a caterpillar will hide in a folded leaf or in some other type of crevice on the plant so it can’t be easily seen.
Smelly Caterpillars
Another method for protection that some caterpillars employ is that they emit a foul smell. These caterpillars have a gland on their neck that is orange in color, and it is this gland that gives off the smell when the caterpillar feels threatened.
This method is particularly useful in protecting the caterpillar from flies and wasps that may be planning on laying their eggs in the caterpillar.
Caterpillar Legs
The thoracic legs of the caterpillar are used primarily for holding onto food while the caterpillar eats. The prolegs enable the caterpillar to climb, even vertically, and they have small grasping hooks on them.
The last pair of prolegs on the abdomen is called anal prolegs, and these disappear when the caterpillar becomes an adult.
Movement and Motion
If you have ever watched a caterpillar move, you would have noticed the rippling motion. This is due to the contraction of the muscles in the rear segments of the caterpillar, which pushes blood into the forward segments.
This lengthens the front part of the body, then the legs hold the forward position and as the front muscles contract, the rear segment is pulled forward.
How Do Caterpillars Breathe?
Caterpillars have breathing pores called spiracles and these can usually be found on the thorax and abdomen.
Vision
You may be surprised to know that caterpillars have six pairs of eyes. They are very small and although they can detect any changes in light intensity, they cannot form an image of the object.
They are usually positioned in two groups of six on the sides of the caterpillar’s head.
What are the Tiny Hairs for?
The tiny hairs that cover the body of the caterpillar are there to provide a sense of touch.
The hairs are attached to nerve cells that send the sensation information back to the brain.
Time to Transform
When the caterpillar is ready to transform, it chooses a place that is isolated before it begins to create the cocoon. Some caterpillars hang from branches as they build the cocoon, while others bury themselves underground. The cocoons are made from silk that comes from two glands on the caterpillar. It has the consistency of thick glue and hardens as it dries.
The shape and color of the cocoon depend on the caterpillar that is constructing it. Different species will have different cocoons. The same difference applies to the length of time the caterpillar stays in the cocoon as it transforms into a butterfly or moth.
Some may only take seven days to transform, while others can take up to a year. The majority however takes less than a month to transform.
Do All Caterpillars Turn into Butterflies?
A common assumption is that the pretty caterpillars become butterflies and the unattractive ones become moths, but this isn’t necessarily true. Even the most stunning butterfly could come from an ugly caterpillar, and the plainest moth may come from a brightly colored caterpillar. It depends entirely on the species.
Regardless of whether the caterpillar will become a butterfly or a moth, the process of transformation is the same. They both come from eggs, and they both go through the same stages before becoming an adult.
What to Do if You Find a Cocoon?
If you find a cocoon hanging from a branch or a leaf, or attached to anything really, you should just leave it alone. If you touch the cocoon, it could cause harmful and sometimes fatal damage to the transforming creature inside. Although the cocoons may seem hard, they can still be damaged quite easily.
Butterflies and moths play a part in maintaining the environment and they don’t generally cause a great deal of harm. Some may be hazardous to your vege-garden though, and if you can identify those, then do what you must to get rid of them. Otherwise, simply enjoy the wonder of these magnificent creatures evolving from a wriggly caterpillar to a winged beauty.
