Butterflies live almost everywhere in the world. Tropical rainforests have the most kinds of butterflies. Other kinds of butterflies live in fields and woodlands. Some butterflies live on cold mountaintops, and others live in hot deserts. Many butterflies travel great distances to spend the winter in a warm climate.
There are about 15,000 to 20,000 species (kinds) of butterflies. The largest butterfly, Queen Alexandra's birdwing of Papua New Guinea, has a wingspread of about 28 centimetres. One of the smallest butterflies is the western pygmy blue of North America. It has a wingspread of about 1 centimetre. Butterflies are every colour imaginable. The colours may be bright, pale, or shimmering and arranged in fantastic patterns. The word butterfly comes from the Old English word buterfleoge, meaning butter and flying creature. Buter probably referred to the butter-yellow colour of some European butterflies.
Butterflies and moths together make up an insect group called Lepidoptera. The name comes from two Greek words: lepis, which means scale; and pteron, which means wing. The name refers to the powdery scales that cover the two pairs of wings of both butterflies and moths. However, butterflies differ from moths in a number of important ways, including the following four. (1) Most butterflies fly during the day. The majority of moths, on the other hand, fly at dusk or at night. (2) Most butterflies have knobs at the ends of their antennae. The antennae of most moths are not knobbed. (3) Most butterflies have slender, hairless bodies. The majority of moths have plump, furry bodies. (4) Most butterflies rest with their wings held upright over their bodies. Most moths rest with their wings spread out flat.
A butterfly begins its life as a tiny egg, which hatches into a caterpillar. The caterpillar spends most of its time eating and growing. But its skin does not grow, and so the caterpillar sheds it and grows a larger one. It repeats this process several times. After the caterpillar reaches its full size, it forms a protective shell. Inside the shell, an amazing change occurs--the wormlike caterpillar becomes a beautiful butterfly. The shell then breaks open, and the adult butterfly comes out. The insect expands its wings and soon flies off to find a mate and produce another generation of butterflies.
Butterfly caterpillars have chewing mouthparts, which they use to eat leaves and other plant parts. Some kinds of caterpillars are pests because they damage crops. One of the worst pests is the caterpillar of the cabbage white butterfly. It feeds on cabbage, cauliflower, and related plants.
Adult butterflies may have sucking mouthparts. The adults feed mainly on nectar and do no harm. In fact, they help pollinate flowers. When a butterfly stops at a flower to drink nectar, grains of pollen cling to its body. Some of the pollen grains rub off on the next blossom the butterfly visits.
Kinds of butterflies
Scientists group the thousands of species of butterflies into families, according to various physical features the insects have in common. The chief families include (1) skippers; (2) blues, coppers, and hairstreaks; (3) brush-footed butterflies; (4) sulphurs and whites; (5) metalmarks; (6) satyrs and wood nymphs; (7) swallowtails; (8) milkweed butterflies; and (9) snout butterflies.
Skippers differ from all other kinds of butterflies in two major ways, and so scientists classify them separately from true butterflies. (1) Skippers have plump, hairy bodies and therefore look more like moths than butterflies. (2) Their antennae have hooked tips, unlike the rounded tips on the antennae of true butterflies.
There are about 3,500 kinds of skippers. Various species live in all parts of the world, except for the extreme polar regions. Skippers get their name from the way they swiftly skip and dart while flying. They range in colour from orangish-brown to dark brown and in many cases have white and yellow markings. Many tropical species are large and iridescent (rainbow coloured, because of light reflections). Skippers include common grassland types, whose caterpillars live concealed in weblike nests. There are also giant New World skippers, whose caterpillars bore into the stems of desert plants such as agaves and yuccas.
Blues, coppers, and hairstreaks account for almost 4,000 species worldwide, and they live in almost every type of environment. They are small butterflies whose names describe their appearance. Blues have a brilliant blue or violet colour. Coppers are a fiery orange-red. Most species of hairstreaks have a hairlike "tail" on each of their hind wings. A number of blues and coppers also have such "tails."
The caterpillars of some species of blues, coppers, and hairstreaks produce a sweet liquid known as honeydew. Certain ants "milk" the honeydew from the caterpillars and also protect the caterpillars from enemies.
Brush-footed butterflies total about 3,500 species. Members of this family live everywhere in the world, except for the polar icecaps and the driest deserts. These butterflies have short front legs, called brush feet, which contain special organs that help the insects locate food. Most species of brush-footed butterflies have bright colours on the upper wing surface and dark colours on the undersurface. When a brush-footed butterfly closes its wings, the dark undersurface helps the insect blend with its surroundings. Brush-footed butterflies include such small butterflies as crescents and such large ones as fritillaries. Some well-known butterflies--the viceroy, the red admiral, the Camberwell beauty, and the two-tailed pasha--belong to this family.
Sulphurs and whites form a family of about 1,000 species. They can be found throughout the world, but most of them live in tropical regions. Sulphurs range in colour from light yellow to orange and are named after the powdery yellow mineral. The wings of most sulphurs have black edges. In orange-tip butterflies, the tips of the front wings have a brilliant orange colouring.
Whites have white wings that may be marked with black, brown, yellow, or red spots. The most common white is the cabbage white butterfly. The caterpillar of this butterfly is a major pest.
Metalmarks form a family of about 1,000 species. These butterflies live throughout the world but are especially common in South America. Their name comes from metallic-looking marks on the wings of most species. Tropical metalmarks are of almost every combination of colours and patterns imaginable. Most North American metalmarks, including the northern metalmark and the little metalmark, range in colour from dull reddish-brown to dark brown.
Satyrs and wood nymphs total about 800 species. Most kinds live in the tropics. However, a few species are found in high mountainous regions and the Arctic. Satyrs and wood nymphs have short front legs and fly close to the ground. Most have brown wings dotted with eyespots (markings that look like eyes). The names of several of these species, including the pearly eye and the eyed brown, refer to their beautiful eyespots.
Swallowtails account for about 600 species of butterflies. They are a worldwide family, though most species are found in the tropics. Swallowtails are among the largest and most beautiful butterflies. They include Queen Alexandra's birdwing, the largest of all butterflies, and the African giant swallowtail, which has a wingspan of up to about 25 centimetres. Most swallowtails have a long extension on each hind wing. The butterflies get their name from these extensions, which resemble the tails of certain swallows.
Most swallowtails are black, brown, and yellow with red and blue spots on their hind wings. One group, the apollos or parnassians, has white or creamy wings with red and black spots. Parnassians do not have "tails."
Milkweed butterflies total about 200 species worldwide. They are large, slow-flying butterflies with very short front legs. Most of these butterflies range in colour from orange to brown. Their wings have black veins and black margins with white spots. Some species that live in Africa and Asia are blue, violet, or white, with brown markings. The caterpillars of this family feed on milkweed plants.
Milkweed butterflies include the famous monarch butterfly of North America, which is one of nature's great travellers. During the late 1800's and the 1900's, it spread across the Pacific Ocean to Australia, where it is known as the wanderer. Its caterpillars feed on the sap of the milkweed plant, which is poisonous to other animals. The striking orange and black of both the caterpillar and the adult warns predators that they are distasteful.
Snout butterflies form a small family of 17 species, most of which live in the tropics. The butterflies get their name from their long, beaklike mouthparts.
The bodies of butterflies
Butterflies have certain body features in common with other insects. For example, a butterfly has a hard, shell-like skin called an exoskeleton (outer skeleton). The exoskeleton supports the body and protects the internal organs. A butterfly's body, also like that of any other insect, has three main parts: (1) the head, (2) the thorax, and (3) the abdomen.
The head is the centre of sensation. It bears a butterfly's (1) eyes, (2) antennae, and (3) mouthparts.
Eyes. On each side of its head, a butterfly has a large compound eye, which consists of thousands of tiny lenses. Each lens provides the insect with an image of part of its surroundings. The brain combines the separate images into a complete view.
Antennae. Two long, slender antennae grow between the eyes. The antennae are organs of smell. A butterfly uses its sense of smell to locate food and to find mates. The antennae probably also serve as hearing and touch organs.
Mouthparts. A butterfly caterpillar has chewing mouthparts that consist of two lips and two pairs of jaws. These structures re-form as the caterpillar changes into an adult butterfly. One pair of jaws nearly disappears. The other pair becomes a long sucking tube, called a proboscis, that coils up when not in use. The lips form a sheath for the proboscis.
A butterfly uses its proboscis to suck nectar and other liquids. Muscles in the head help the insect draw fluid up the proboscis and into a cavity in the head. A covering on the end of the proboscis closes and keeps fluid from flowing out. Other muscles force the fluid into the stomach.
The thorax forms the middle section of a butterfly's body. A short, thin neck connects it to the insect's head. Attached to the thorax are (1) the wings and (2) the legs.
Wings. A butterfly has a pair of front wings and a pair of back wings. A network of veins runs through the wings. The veins are mainly filled with air and serve as wing supports. The wings are stiff near the front edges and at the bases. The outer margins of the wings, however, are flexible. They bend when flapped in flight. This bending pushes the air backward and moves the butterfly forward. The front margins of the wings give the insect "lift" as it flies forward.
Butterflies and moths cannot fly if their body temperature is less than 30 °C. At air temperatures below this, they must "warm up" their flight muscles either by sunning their bodies or by shivering their wings. The flight muscles then absorb enough heat to make flight possible.
The size of a butterfly's body and wings determines how the insect flies. For example, milkweed butterflies and swallowtails have small, lightweight bodies and large wings. These butterflies can fly by beating their wings slowly. They are excellent gliders and can fly great distances. On the other hand, skippers have large, heavy bodies and small, pointed wings. They must beat their wings rapidly to stay aloft. Skippers do not soar or glide, but they can fly swiftly for short distances.
A butterfly's wings are covered with tiny, flat scales that overlap. The scales provide colour and form beautiful patterns. Some scales contain pigment (colouring matter). Colours produced by pigment include black, brown, red, white, and yellow. Other kinds of scales produce colour by reflecting light from their surfaces. Shiny, metallic colours--for example, blue and green--are reflected colours.
Legs. Butterflies have three pairs of legs. Each leg has five main segments. Joints between the segments enable a butterfly to move its legs in various directions. Each leg ends in a pair of claws and hairy pads. The insect uses the claws to grip surfaces. The hairs on the pads are taste organs. Butterflies have weak legs and can walk only short distances.
In some species, the front legs are very short. These "brush feet" are useless for walking, but the taste organs on them are highly developed. By brushing or scraping leaves with these feet, brush-footed butterflies can determine whether particular plants are good sources of food or suitable places on which to lay eggs.
The abdomen chiefly contains a butterfly's reproductive organs. It also has organs for digesting food and for getting rid of waste products.
The internal organs of butterflies are grouped into five main systems: (1) circulatory, (2) nervous, (3) respiratory, (4) digestive, and (5) reproductive.
The circulatory system carries blood throughout the body by means of a long tube that lies just under the exoskeleton of the back. The tube extends from the head to the end of the abdomen. The heart, the pumping part of the tube, lies in the thorax. The blood empties out of the tube into the head. It then floods the entire body. The blood reenters the tube through little openings along the sides. A butterfly's blood is yellowish, greenish, or colourless. It carries food, but not oxygen, to the cells of the body.
The nervous system of butterflies consists of a brain, which is located in the head, and two nerve cords that run through the thorax and abdomen. Small bundles of nerve cells along the cords branch out to all parts of the body.
The respiratory system carries oxygen to the cells of the body and takes away carbon dioxide. Oxygen enters the body through tiny holes, called spiracles, located along the sides of the body. Each spiracle connects to a tubelike structure called a trachea. The tracheae branch out to all the cells of the butterfly's body. In this way, the body cells obtain oxygen directly from the air rather than from the blood.
The digestive system is basically a long tube that extends from the mouth to the anus, an opening at the end of the abdomen. After nectar has been sucked up by the proboscis, it passes to the gut, where nourishing substances in the food are absorbed. The remaining waste products pass through the hindgut and out of the body through the anus.
The reproductive system. Butterflies reproduce sexually--that is, a new butterfly can be created only after a sperm (male sex cell) unites with an egg (female sex cell). Female butterflies have a pair of organs, called ovaries, in which eggs develop. Male butterflies have a sperm-producing organ, called the testis. A tube carries the sperm from the testis to a tube that extends to the outside of the insect's abdomen. The male places the sperm into an organ in the female called the copulatory sac. The sperm duct transports the sperm to a tube called the oviduct, where fertilization takes place.
The life cycle of butterflies
The life of an adult butterfly centres on reproduction. The reproductive cycle begins with courtship, in which the butterfly seeks a mate. If the courtship proves successful, mating occurs.
Butterflies use both sight and smell in seeking mates. Either the male or the female may give signals, called cues, of a certain kind or in a particular order. If a butterfly presents the wrong cue, or a series of cues in the wrong sequence, it will be rejected.
In courtship involving visual cues, a butterfly reveals certain colour patterns on its wings in a precise order. Many visual cues involve the reflection of ultraviolet light rays from a butterfly's wing scales. The cues are invisible to the human eye, but butterflies see them clearly. The visual cues help the insects distinguish between males and females and between members of different species.
Usually, a butterfly that presents an appropriate scent will be immediately accepted as a mate. The scent comes from chemicals, called pheromones, that are released from special wing scales. A pheromone may attract a butterfly a great distance away.
In most cases, the male butterfly dies soon after mating. The female goes off in search of a place to lay her eggs. She usually begins laying the eggs within a few hours after mating.
Every butterfly goes through four stages of development: (1) egg, (2) larva, (3) pupa, and (4) adult. This process of development through several forms is called metamorphosis.
The egg. Butterfly eggs vary greatly in size, shape, and colour. Some eggs are almost invisible to the human eye. The largest ones are about 2.5 millimetres in diameter. The eggs may be round, oval, cylindrical, or other shapes. Most are green or yellow. A few species have orange or red eggs. Some eggs are smooth. Others have ridges and grooves.
Most female butterflies lay their eggs on plants that will provide the offspring with an abundant supply of food. Before depositing the eggs, the female may "taste" a plant with special organs on the ends of her front legs to make sure the plant is suitable. Some females lay their eggs near a plant or drop them at random while flying. After hatching, the young must find food themselves.
While laying the eggs, the female fertilizes them with the sperm that she had stored in her body after mating. Each egg has a small hole through which sperm can enter. Depending on the species, a female may lay several dozen eggs or clusters of up to hundreds of eggs. A sticky substance deposited with the eggs helps hold them onto the plant. The eggs of some butterflies hatch in a few days, but others take months. Eggs laid in the autumn may not hatch until the spring.
The larva, or caterpillar, emerges from the egg and immediately begins its main activity--eating. A caterpillar's first meal is usually its own eggshell. It then begins to eat the nearest food. The majority of caterpillars feed on green plants. In one day, a caterpillar may eat many times its weight in food. Much of this food is stored in the body and used to provide energy in later stages of development.
Most caterpillars are solid green or brown. Many others have patterns of yellow, red, or other bright colours. Some caterpillars have smooth skin. Many others have bristly hair, bumps, fleshy knobs, or eyespots. All these features help protect caterpillars from enemies by making them hard to see or so frightening in appearance that enemies avoid them.
A caterpillar's body is made up of 14 segments. The first segment consists of the head, which includes chewing mouthparts and two short, thick antennae. The head also has six small eyes on each side. The eyes cannot form images, but they help the caterpillar distinguish between light and dark.
The next three segments of the caterpillar's body make up the thorax. Each of these segments has two short, jointed legs with a sharp claw at each tip. The remaining 10 segments form the abdomen. Most caterpillars have a pair of false legs, known as prolegs, on the seventh, eighth, ninth, and tenth body segments. At the end of each proleg are tiny hooks. The last segment has a pair of suckerlike legs called anal prolegs or anal claspers. This variety of leg enables the caterpillar to cling to plants and to move about.
A short structure called a spinneret sticks out below the caterpillar's mouth. It releases a sticky liquid that hardens into a silken thread and gives the caterpillar a foothold wherever it goes. The larva, like the adult, breathes through spiracles on the sides of the body.
The larval stage lasts at least two weeks. During that time, the caterpillar grows rapidly. Its exoskeleton, however, does not grow. When the skin becomes too tight, it splits lengthwise along the back. But before the exoskeleton splits, the larva forms a new skin under the old one. It then crawls out of the old skin. The new exoskeleton is soft, and the larva stretches it to provide growing room. The larva then lies motionless for a few hours as the new exoskeleton hardens. Most caterpillars moult--that is, shed their exoskeletons--four or five times.
The pupa. After a caterpillar reaches its full size, it is ready to become a pupa. In preparation for this stage, most moth larvae spin silken cocoons around themselves. However, only a few butterfly species spin cocoons. Instead, the typical butterfly caterpillar finds a sheltered spot, usually high on a twig or leaf, and deposits sticky liquid from its spinneret. The liquid quickly hardens into a silklike pad. The exoskeleton then begins to split near the head, and the pupa starts to emerge. As the exoskeleton falls from the tail, the pupa thrusts its cremaster--a many-clawed structure at the end of the abdomen--into the pad. This procedure is dangerous. If it does not grasp at the pad fast enough, the pupa may fall to the ground and die.
Many pupae hang head downward, supported only by the cremaster hooked into the silken pad. Other pupae are positioned head upward. Such a pupa has an additional support of silken thread spun around the thorax and the twig or leaf to which it is anchored.
The pupa is soft at first, but a hard shell immediately begins to form over it. Some shells have unusual shapes and colourful patterns. In some cases, the shell has a golden shimmer, and so scientists call the pupa a chrysalis. This word comes from the Greek word chrysos, which means gold.
The pupa is motionless and is often called a "resting stage." However, much activity occurs within the shell. Larval structures are being broken down and re-formed into those of an adult butterfly. Only the internal organs remain basically the same.
The pupal period ranges from a few days to more than a year, according to the species and the time the pupal stage begins. Many species spend the winter as pupae and emerge as adults in the spring.
The adult. After the adult butterfly has formed, its body gives off a fluid that loosens it from the pupal shell. The thorax swells and cracks the shell. The head and thorax then emerge. Next, the butterfly pushes its legs out and pulls the rest of its body free. The entire process may take only a few minutes.
The exoskeleton of the newly emerged butterfly is soft. The wings are damp and crumpled. The proboscis is split in half lengthwise. The butterfly uses its muscles to pump air and blood through its body and wings. Its exoskeleton hardens, and the legs and other body parts become firm. The wings flatten and expand. Using its front legs, the butterfly joins the halves of its proboscis together. About an hour after leaving the pupal shell, the adult butterfly may be ready to fly.
Most adult butterflies live only a week or two, but some species may live up to 18 months. Most butterflies feed only on nectar, which provides quick energy but does not contain life-prolonging proteins. Certain species of butterflies obtain proteins by feeding on moist, decaying animal matter. Some other species obtain proteins from pollen, which they pick up while feeding on nectar. A number of butterflies do not feed on anything. Instead, these butterflies live on food they have stored during the larval stage.
How butterflies protect themselves
Butterflies have many enemies, including other insects and birds. To escape their enemies, butterflies have developed various means of self-defence.
Many butterflies and caterpillars escape harm because they blend with their surroundings. This form of defence is known as protective coloration. Butterflies may look like bark or other vegetation. Most caterpillars are green or brown. Green ones blend with the plants they eat. Brown ones look like dead leaves or twigs.
Many butterflies have chemical defences. Among certain swallowtails, the caterpillar has an organ just behind the head that gives off an unpleasant odour when the caterpillar is disturbed. Some butterflies are protected as both larvae and adults because they taste bad to enemies. During the larval stage, many of these butterflies eat plants that have bitter or poisonous juices. The juices are stored in the tissues, making the insects distasteful to predators. Most such butterflies, such as the adult monarch butterfly and its larva, have bright colours and so advertise that they taste unpleasant. This form of protection is called warning coloration. An animal that has eaten one of these butterflies will probably avoid eating another butterfly with that coloration.
Some nonprotected butterflies resemble, or mimic, distasteful species. Predators cannot tell them apart and so leave both alone. In North America, the viceroy butterfly mimics the monarch butterfly. Enemies avoid the viceroy because the monarch tastes unpleasant. Some protected butterflies even resemble other protected ones. By mimicking each other, these insects gain extra protection.
Hibernation and migration
Butterflies cannot live actively in cold weather. They must either hibernate or migrate to warmer areas.
Hibernation. Many species of butterflies survive the winter by hibernating in a sheltered place. Butterflies may hibernate in the egg, larval, pupal, or adult stage. But each species usually hibernates in only one stage, and it is as pupae in most cases.
Just before hibernation, the blood of a larva, pupa, or adult produces substances called glycols. These substances are related to the antifreeze used in cars. Scientists believe the production of glycols may be triggered by the decreasing daylight that occurs as winter approaches. The presence of glycols enables the insect to survive even the severest cold. After warm weather returns, the glycols are gradually replaced by normal blood substances.
Migration. A few kinds of butterflies escape the winter by migrating to a warmer region. One species, the monarch, is a long-distance champion. Dense clouds of monarchs may travel more than 3,000 kilometres from Canada and the Northern United States to the southern U.S. states of California and Florida, and even Mexico.
The butterflies spend the winter resting and conserving energy for their return flight in the spring. Few adults live long enough to complete the return trip. Female monarchs lay eggs on the way back. The offspring, after maturing, continue the northward journey. Other migrating butterflies include the painted lady and the red admiral, which travel between Europe and North Africa.
How to collect butterflies
Collecting butterflies can be a fascinating hobby. The equipment you need to collect butterflies includes a long-handled net, a poisoning jar with an airtight lid, and a poison called ethyl acetate. You also need cotton, a pair of tweezers, mounting pins, mounting boards, and display boxes. All the equipment can be purchased at a hobby or craft shop. But many of the items can be made from materials at home.
Capture the butterflies with the net and place them in the poisoning jar, which contains cotton soaked with ethyl acetate. Fumes from the poison will kill the butterflies. Use the tweezers to remove the dead butterflies from the jar. Place the body of each insect in the groove in the mounting board and insert a pin through the thorax. Spread the wings fully and pin threads or thin strips of paper over the wings to hold them in place. After the specimens have dried, remove them from the board and mount them on cardboard or some other material. Label each butterfly specimen with its name and where and when it was captured. Then put the butterflies in a glasscovered box to protect them from moisture and other damage.
Butterfly conservation
Some butterflies have become rare through overcollecting. But most species are threatened by the loss of their native habitats. Many swallowtail butterflies are endangered. For example, the cream-banded swallowtail of Central Africa has become rare because of the destruction of forest for timber trees such as mahogany. In Jamaica, plantations of coffee and pine trees have replaced native forests, causing the decline of the beautiful homerus swallowtail. In Papua New Guinea, the Queen Alexandra's birdwing (the largest, and one of the rarest, species) is becoming rarer because of the cultivation of large palm oil plantations.
In Papua New Guinea, the commoner birdwing butterflies are farmed. Adult butterflies are attracted from the forest into gardens where nectar plants and caterpillar food-plants are grown. The adults lay their eggs in the gardens. They then fly off, and eventually the caterpillars are collected and reared in cages. The adults that emerge are mostly killed and preserved for the specialist trade. But some are released to maintain the wild population.
Scientific Classification. Butterflies belong to the order Lepidoptera, which also includes moths. Skippers make up the superfamily Hesperioidea, as well as the family Hesperiidae. All other butterflies are true butterflies and belong to the superfamily Papilionoidea. True butterflies include the following families: blues, coppers, and hairstreaks (Lycaenidae); brush-footed butterflies (Nymphalidae); sulphurs and whites (Pieridae); metalmarks (Riodinidae); satyrs and wood nymphs (Satyridae); swallowtails (Papilionidae); milkweed butterflies (Danaidae); and snout butterflies (Libytheidae).
Questions
How do most butterflies that taste bad to their enemies advertise their unpleasant taste?
Why must a caterpillar shed its skin to grow?
How do skippers differ from all other butterflies?
What change occurs in a butterfly's blood that enables the insect to hibernate during the winter?
How do butterflies find mates?
What equipment does a person need to collect butterflies?
How long do most butterflies live?
What are "brush feet"? How do butterflies use them?
What are the four stages of development in butterflies?
How do butterflies differ from moths?
