Physical Description

Like other insects, butterflies and moths have bodies with three divisions. The head includes the antennae, eyes, and mouth parts. The thorax includes two pairs of wings and three pairs of legs. The abdomen, with eight or nine distinct segments, contains breathing pores and digestive and reproductive organs.

Butterflies and moths have a highly developed sense of smell. The organs of smell are the antennae, which are probably also used for hearing. The adult has two compound eyes; they are made up of thousands of hexagonal (six-sided) lenses and resemble miniature honeycombs.

For butterflies and most moths the principal mouthpart is a long tube called the proboscis, used for sucking nectar from flowers. When not in use, the proboscis curls up under the head. Two groups of moths lack the proboscis; one group has chewing mouthparts and the other has no mouthparts at all.

The legs are long and slender and can be used only for crawling. The two pairs of wings, the fore wings and the hind wings, consist of membranous tissue supported by a network of tiny hollow tubes called veins. The pattern of these veins varies from species to species. In butterflies, the fore and hind wings are held together by an enlargement of the veins at the base of the wings. The wings of moths are held together by a wide array of coupling mechanisms. In many species, a hook on the front part of the hind wing holds the two sets of wings together in flight.

The sometimes brilliant colors of moths and butterflies are caused by red, yellow, black, and white pigments in the wing scales. Blues, greens, and iridescent metallic hues are the result of overlapping scales acting as prisms to break up light rays.

Many butterflies have wings that are brightly colored on top and drab underneath. When these butterflies alight, they expose the drab undersides of the wings, blending with their surroundings and thus escaping notice of their enemies. Several edible species of butterflies have coloring similar to that of inedible species. The edible viceroy butterfly, for example, resembles the monarch—a species that birds avoid because of its unpleasant taste.

What Are the Parts of a Butterfly?

A butterfly has a thin body that might go unnoticed beside its big wings. Like the bodies of other animals, a butterfly body has a brain, stomach, heart, and other organs. And, as in other insects, the body parts of a butterfly are contained in three main regions—the head, thorax (THAWR aks), and abdomen.

On its head, a butterfly has two eyes, two antennae, and a mouth, called the proboscis (proh BOS ihs). The proboscis is a long, curled-up tube. When the butterfly sips nectar—a sweet liquid in flowers—the insect unrolls its proboscis and uses it like a straw.

The butterfly’s legs and wings are attached to the thorax, the middle part of its body. Every butterfly has a pair of front and a pair of back wings. The back pair is partly tucked underneath the front pair.

The abdomen, or hind part of a butterfly’s body, has holes called spiracles (SPY ruh kulz). The butterfly breathes through the spiracles. The abdomen also contains reproductive and digestive organs.

Can Butterflies See, Smell, Hear, Touch and Taste?

Butterflies have sense organs, but they are not the same as human sense organs. If you looked at a butterfly’s head close up, you would see two huge eyes. Butterflies, and many other insects, have compound eyes. That means that each eye is made up of many tiny lenses that form a honeycomb pattern. Scientists think that this type of eye is very good for seeing movement—an important ability for butterflies, which have many predators.

One of a butterfly’s most important sense organs is made up of the two antennae on top of its head. They help a butterfly smell and balance and may help the butterfly hear and touch things, as well.

Which body part does a butterfly use to taste food? Although it seems unlikely, the answer is its feet. A butterfly’s feet have tiny parts called cells that can taste. If a butterfly lands on a flower full of nectar, the cells signal the insect to start sipping. Life History

Butterflies and moths undergo a complete metamorphosis; that is, their life cycle includes four stages—(1) egg; (2) larva, or caterpillar; (3) pupa; and (4) adult.

What Happens as a Butterfly Grows?

A butterfly goes through four stages during its life cycle. It spends the first stage developing within an egg. Then, the egg hatches and releases a hungry caterpillar and the second stage begins.

Soon, the caterpillar grows large. When grown, the caterpillar transforms into a pupa (PYOO puh), the third stage. The pupa forms a shell around itself. This shell is called a chrysalis (KRIHS uh lihs). Inside the chrysalis, the pupa changes and grows. In time, it breaks out of the shell as a butterfly!

The grown butterfly is in its fourth stage of life. Many adult butterflies live only a few weeks. During that time, they lay eggs. Then the four stages of life start all over again.

A mothA moth goes from egg, to caterpillar, to pupa, to adult.
The Egg

Female butterflies and moths lay their eggs singly or in groups, generally on leaves or stems. The eggs of some species are coated with a protective covering. The size, shape, and color of the eggs vary, as does the time it takes them to hatch. Many butterfly and moth eggs are eaten by spiders, wasps, and ants.

The Caterpillar

The caterpillar, which hatches from the egg, is a wormlike creature with a body divided into a head, thorax, and abdomen; it has no wings. The head has six pairs of simple eyes, called ocelli, and the thorax has three pairs of walking legs. These have five joints apiece and a claw at the end. There are five pairs of fleshy, jointless legs called prolegs on the underside of the abdominal segments. The caterpillar's body may be hairy, covered with spines, or bare. Caterpillars have biting jaws. Most caterpillars feed on plants; some feed on animal products (such as wool); and a few feed on other insects.

As the caterpillar grows, it becomes too large for its skin, which it then sheds, or molts. The number of times that a caterpillar molts varies from species to species, ranging from 3 to 10 times. Many caterpillars change in color and pattern with each molt.

Why Does a Caterpillar Eat All the Time?

A caterpillar’s first day starts when it hatches out of its egg. Right away the hungry animal eats its own eggshell. Then it searches for green plants to eat. But, chances are it won’t need to search for long, because its mother probably laid her eggs near a good source of food.

The caterpillar starts eating and never stops. That’s its job—to eat and eat. It is storing up energy to use in the next stages of its life.

With all its eating, the caterpillar soon becomes too big for its own skin. Then the caterpillar molts. That means its skin splits wide open. The caterpillar sheds its old skin like taking off a coat. (It had already formed a new skin beneath the skin it molted.) A caterpillar will molt several times as it grows.

The Pupa

After several weeks as a caterpillar, the insect enters the pupal stage. During this stage, the pupa appears to be inactive, but major structural changes take place. The pupa of a moth is usually enclosed in a silken case called a cocoon, while a butterfly pupa is usually protected by a tough skin called a chrysalis. At first, a pupa is light in color and soft, but with exposure to air, it darkens and hardens. Moth pupae are brownish and relatively smooth; butterfly pupae may have a variety of colors and frequently an irregular shape. After a period ranging from weeks to months, the cocoon or chrysalis breaks apart and the adult comes out, usually head first. The wings are wrinkled but soon unfold and spread out to their full span. There is no further growth.

A cocoonA cocoon is spun by the larva of butterflies and moths for protection during the pupa stage.
What Happens Inside a Chrysalis?

Many people think that butterflies emerge from silky cocoons. This, however, is rarely the case. Only moths and a few species of butterfly do that. Most butterflies develop within a chrysalis.

When a caterpillar has finished eating and growing, it is time to form a chrysalis. First, the caterpillar finds a sheltered spot where it deposits a silky substance from which it will hang. Then the caterpillar molts one more time to become a pupa. Soon, the outer shell of the pupa hardens and the chrysalis is complete.

If someone found a chrysalis on a branch or stem, he or she might think the animal inside was dead. Nothing could be further from the truth. The caterpillar is very busy. It is turning into a butterfly. This entire process is called metamorphosis (MEHT uh MAWR fuh sihs).

Is It Magic?

The alteration a pupa undergoes may seem magical, but, of course, no magic is involved. Scientists are able to explain the changes that happen within a chrysalis.

Researchers have found that certain chemicals produced by the pupa actually break down many of the pupa’s body structures. This material is recycled and used to develop the new body parts needed by the adult butterfly.

When development is complete, the grown-up butterfly begins to separate itself from its chrysalis. The butterfly works hard to free itself. Out of the dead-looking chrysalis comes a beautiful butterfly!

The new butterfly has important work to do. It uses its front legs to “zip up” its proboscis, which was in two parts when the butterfly emerged. And, the insect pumps its folded-up wings full of air and blood, allowing them to spread out wide and to dry. Now the butterfly can take off.

The Adult

Most adult butterflies and moths live on flower nectar, but some moths—those that lack mouthparts—do not feed in the adult stage. Many types of butterflies and moths spend the winter as pupae or eggs. Of those that are in adult form during winter, some hibernate while others migrate. The normal lifespan of an adult butterfly or moth ranges from about a week to several months. Non-feeding moths, however, generally live only a few days.