Butterflies

Evolution

Development and life cycle

The egg

The caterpillar

The chrysalis

The adult (or imago)

Reproduction

Migration

Vulnerability and defense

Conservation

Resources

Butterflies are insects in the order Lepidoptera, which includes the moths. Butterflies at rest fold their wings vertically over their head, whereas moths hold their wings horizontally. Most butterflies are active during daylight, while moths are mostly nocturnal. Butterflies undergo complete metamorphosis, that is, their egg hatches to a larva (or caterpillar), which pupates in a chrysalis, from which emerges the adult butterfly (or imago).

Evolution

Butterflies probably first evolved about 150 million years ago, appearing at about the same time as the flowering (or angiosperm) plants. Of the 220, 000 species of Lepidoptera, about 45, 000 are butterflies, which probably evolved from moths. Butterflies are found throughout the world, except in Antarctica, and are especially numerous in the tropics. They fall into eight families: Papilionidae (swallowtail butterflies), Pieridae (whites), Danaidae (milkweeds), Satyridae (browns), Morphidae (morphos), Nymphalidae (nymphalids), Lycaenidae (blues), and Hesperidae (skippers).

Development and life cycle

The adult life of butterflies is only one week for some species, but up to 10 months for others. Adult

butterflies spend much of their time courting, mating, and (for females) laying eggs. The females lay eggs on the specific food plant upon which the caterpillar must feed. Eggs are typically laid on leaves, flowers, or stems, but sometimes on treebark or even stones, leaving the newly hatched caterpillars to find their necessary food plant. A few species of butterfly lay their eggs while in flight, the eggs attaching to food plants as they fall.

The egg

By the time most female butterflies emerge from the chrysalis, their eggs are fully mature, permitting immediate fertilization. Minute pores in the egg allow entry of the male sperm for fertilization. Eggs may be laid singly, in rows, in clusters, or in rings around a plant stem. The eggs are highly vulnerable to predators and parasites. Females lay up to 600 eggs at a time. A sticky substance produced during egg laying glues them to the host plant. Most hatch within a few days, although those of some species remain dormant over winter and hatch in the spring.

The caterpillar

The larval stage of butterflies, known as a caterpillar, emerges from the egg fully formed. Caterpillars see by means of groups of tiny eyes on each side of their head. The body of many species is protected by bristly hairs. Caterpillars have as many as eight pairs of appendages. Three pairs are true legs, and become the legs of the adult butterfly. These are located on the thorax behind the head. Another four pairs of appendages occur on the abdomen, and are known as false, or prolegs. There is also a single pair of claspers at the tip of the abdomen, which grip tightly to the food plant. Prolegs and claspers also carry tiny hooks, which catch a silk thread spun by the larva as it moves about its food plant and help keep it from falling. The silk thread is produced as a thick liquid, excreted through glands near the mouth, which is then spun into a thread by a spinneret located behind the jaws.

Caterpillars spend most of their time eating. Their large jaws (the mandibles) move sideways while shredding their plant diet. Caterpillars munch their way through life: first eating their egg shell, from which important nutrients are retrieved, and then continuously consuming its food plants. A very small number of butterfly species have caterpillars that are predators that feed on other insects. Caterpillars typically eat more than twice their own weight each day, pausing only to shed their old skin, in order to grow larger. Skin shedding (molting, or ecdysis) occurs at least four times before the caterpillar is fully grown. Growth rate depends on temperature; it is faster in warm weather, and slower when cool. Caterpillars seek a protected place in which to pupate, forming a protective shell and becoming dormant. Some caterpillars travel rather long distances (330 feet or 100 m) when seeking a sheltered place to pupate.

The chrysalis

The protective case surrounding the pupating caterpillar can take many shapes. It is usually brownish green in color, and may be speckled to aid in camouflage. With few exceptions, butterfly larvae pupate above ground, usually attached to a leaf or stem by a silken thread. Inside the chrysalis the pupated caterpillar gradually transforms into a butterfly. The process takes two weeks for some species, and as long as several years for others. When fully developed, the butterfly inside the chrysalis swallows air, inflating its body and splitting the pupal skin. An adult butterfly struggles out shortly after dawn, its moist wings hanging limply from its thorax. Crawling to a place where it can hang by its legs, the newly emerged butterfly pumps up its wings by swallowing air, increasing its internal pressure and forcing blood through tiny veins in the wings. Within several hours the expanded wings dry and harden. At about the same time the butterfly excretes waste products accumulated during pupation. The butterfly is now free to begin the adult part of its life cycle.

The adult (or imago)

Butterflies, like all insects, have an external skeleton (or exoskeleton) to which muscles are attached. The exoskeleton provides the butterfly’s body with support and reduces water loss through evaporation. The respiratory system does not have a pumping mechanism. The sides of the thorax and abdomen have tiny pores (or spiracles) through which air enters and leaves the body via tubes (tracheae). The insect’s blood (hemo-lymph) is pumped as it passes through a long, thin heart, and bathes the organs inside the body cavity.

Two large compound eyes, made up of hundreds of tiny units (ommatidia), cover much of the butterfly’s head and allow a wide field of vision, including partially backwards. However, the eyes cannot distinguish much detail or determine distance, although they can readily identify color and movement, both of which are vital for survival. Colors aid in the identification of flowers, larval food plants, and the opposite sex of the species, while detecting movement may save butterflies from attacks by their predators.

The long, coiled proboscis (tongue) of the butterfly is projected into the center of flowers while searching for nectar (a liquid, sugar-rich food). Above the eyes and on either side of the head are two antennae covered with microscopic sense organs. The antennae are often incorrectly called “feelers,” but “smellers” would be more accurate because it is through these organs that the butterfly sniffs out its favorite foods and potential mate. The antennae can detect pheromones, which are specific chemical signals released by the opposite sex that are detectable over a great distance.

The thorax of a butterfly is divided into three segments, each having one pair of legs. Each leg ends in a claw, enabling the butterfly to hold on while feeding and egg laying. Sensory receptors on the leg just above the claw detect the chemical makeup of appropriate food plants.

The wings are the most spectacular part of the butterfly, and are extremely large compared to its body. The wings attach at the two rear segments of the thorax. Tough veins provide a framework which supports the wing membrane, covered by millions of microscopic scales arranged in rows like shingles on a roof. It is these scales (about 99,000 per square inch [15,000 per sq cm]) which form the color and pattern of the wing. Brown, orange, and black tones are due to the presence of chemical pigments. However, the brilliant, iridescent blues and greens are parts of the light-spectrum separated by tiny facets on the surface of the scales, creating colors in the fashion of a prism. The wing colors provide camouflage against predators and aid in identifying mates of the correct species. Scales also cover the segmented abdomen, in which the digestive and reproductive organs are located.

Reproduction

Reproduction in butterflies begins with courtship, during which the male vigorously flaps its wings, releasing a dust of microscopic scales carrying pheromones above the female’s antennae. These male pheromones act as a sexual stimulant to the female. Some males release additional pheromones from “hair pencils” under the abdomen. Female butterflies that are ready to mate dispense with courtship. Some species, however, perform complicated courtship maneuvers, probably to find a mate strong enough to endure the rigorous rituals, thereby increasing the chance of producing healthy offspring. Males usually must wait one or two days after emerging from the chrysalis before they can mate, but then they may mate many times. Females can mate immediately after emerging, some species mating several times. However, it is the last male to mate that fertilizes the eggs. Females of some species mate once only.

Migration

Most butterfly species live and die within a narrow geographic range, because their brief life span allows little time for wandering. However, the monarch butterfly migrates thousands of miles from southern Canada and northern parts of the United States to Mexico and southern coastal California. The round trip takes two or three generations to complete, because of the short individual life span. Each butterfly must find its own way, having no living guide, yet the species follows the same broad migratory route year after year, century after century. Monarchs and some other butterflies migrate in massive numbers, forming clouds of color sometimes a mile wide and a mile long; millions perish during the journey.

Vulnerability and defense

The survival of butterflies is influenced by many factors, and their populations may increase or decrease quite rapidly, and from year to year. Brilliantly colored butterflies are often toxic when eaten, so predators learn to leave them alone. Occasionally, a nonpoisonous species evolves that mimics the appearance of a poisonous species, thus being less susceptible to predators. Dark colors, displayed by butterflies in cooler climates (such as alpine or arctic tundra), readily absorb sunlight so the cold-blooded insect can warm up more quickly.

Some butterflies are well camouflaged and almost undetectable among the flowers of their particular food plant. A variety of spots resembling eyes on the outer edges of the wings of certain species may startle or distract predators, drawing the point of attack of a swooping bird away from the butterfly’s soft body. Some butterflies do a 180-degree turn before landing, so the eye-spots on the wings are positioned where a predator may think the head should be. Butterflies surviving bird attacks can often fly well even with a piece of wing missing.

The underpart of the wing is usually duller than the surface, so that when the butterfly assumes its resting position with wings folded above its head, it is cryptically colored, blending into the background on which it lands. Some butterflies use the club on the end of the antennae to knock small predators off their body.

The hairy spines on many caterpillars deter predators, and their colors often blend in with the leaves of their food plant. Some pupae develop hornlike appendages on the head and rear of the chrysalis, which appear to point menacingly at predators. In other cases, a chrysalis hanging from a twig may look like a dead leaf.

Conservation

Habitat loss to agriculture, deforestation, urbanization, draining of wetlands, and other changes in land use is the foremost threat to butterfly populations. Although pollution, pesticides, and specimen collection pose serious threats to some species, none is as damaging as habitat loss. The short life span of butterflies usually makes it impossible for displaced populations to find another appropriate habitat. Although no species is known to have been made extinct through human actions, some subspecies have been rendered extinct, and some rare species are endangered. Protection of habitat is the most effective way to prevent major reductions in populations and endangerment of butterflies, and of other wild animals and plants.

KEY TERMS

Chrysalis— A soft casing, shell, or cocoon protecting the dormant pupa of insects during metamorphosis.

Metamorphosis— A complete change of form, structure, or function in the process of development, shown by insects.

Pheromones— Chemical substances, secreted by most animals, that stimulate a response from others of that species (e.g., sex hormones for mating) or other species (e.g., a predator sensing chemicals produced by its prey’s fear).

Pupa— An insect in the nonfeeding stage during which the larva develops into the adult.

Resources

BOOKS

Eid, A., and M. Viard. Butterflies and Moths of the World. Book Sales Pubs., 1997.

Feltwell, John. The Natural History of Butterflies. New York: Facts on File, 1986.

Pollard, Ernest. Monitoring Butterflies for Ecology and Conservation. London: Chapman & Hall, 1993.

Sbordoni, V. and S. Forestiero. Butterflies of the World. Firefly Books, 1998.

Scott, James A. The Butterflies of North America. Stanford: Stanford University Press, 2001.

Smart, Paul. The Illustrated Encyclopedia of the Butterfly World. New York: Random House, 1996.

PERIODICALS

Barbour, Spider. “Overnight Sensation.” Natural History (May 1989): 24-28.

Boppre, Michael. “Sex, Drugs, and Butterflies.” Natural History (January 1994): 28-33.

OTHER

The Field Museum. “Butterfly Basics: Butterflies vs. Moths” <http://www.fieldmuseum.org/butterfly/bvsm_basic.htm> (accessed November 6, 2006).

Marie L. Thompson

Butterflies

Butterflies are insects in the order Lepidoptera, which also includes the moths . Butterflies at rest fold their wings vertically over their head, whereas moths hold their wings horizontally. Most butterflies are active during daylight, while moths are mostly nocturnal. Butterflies undergo complete metamorphosis , that is, their egg hatches to a larva (or caterpillar), which pupates in a chrysalis, from which emerges the adult butterfly (or imago).

Evolution

Butterflies probably first evolved about 150 million years ago, appearing at about the same time as the flowering (or angiosperm ) plants. Of the 220,000 species of Lepidoptera, about 45,000 species are butterflies, which probably evolved from moths. Butterflies are found throughout the world, except in Antarctica , and are especially numerous in the tropics. They fall into eight families: Papilionidae (swallowtail butterflies), Pieridae (whites), Danaidae (milkweeds ), Satyridae (browns), Morphidae (morphos), Nymphalidae (nymphalids), Lycaenidae (blues), and Hesperidae (skippers).

Development and life cycle

The adult life of butterflies is only one week for some species, but up to 10 months for others. Adult butterflies spend much of their time courting, mating, and (for females) laying eggs. The females lay eggs on the specific food plant upon which the caterpillar must feed. The eggs are typically laid on leaves, flowers, or stems, but sometimes on tree bark or even stones, leaving the newly hatched caterpillars to find their necessary food plant. A few species of butterfly lay their eggs while in flight, the eggs attaching to food plants as they fall.

The egg

By the time most female butterflies emerge from the chrysalis, their eggs are fully mature, permitting immediate fertilization . Minute pores in the egg allow entry of the male sperm for fertilization. Eggs may be laid singly, in rows, in clusters, or in rings around a plant stem. The eggs are highly vulnerable to predators and parasites . Females lay up to 600 eggs at a time. A sticky substance produced during egg laying glues the eggs to the host plant. Most eggs hatch within a few days, although those of some species remain dormant over winter and hatch in the spring.

The caterpillar

The larval stage of butterflies, known as a caterpillar, emerges from the egg fully formed. Caterpillars see by means of groups of tiny eyes on each side of their head. The body of many species is protected by bristly hairs. Caterpillars have as many as eight pairs of appendages. Three pairs are true legs, and become the legs of the adult butterfly. These are located on the thorax behind the head. Another four pairs of appendages occur on the abdomen, and are known as false, or prolegs. There is also a single pair of claspers at the tip of the abdomen, which grip tightly to the food plant. Prolegs and claspers also carry tiny hooks, which catch a silk thread spun by the larva as it moves about its food plant and help keep it from falling. The silk thread is produced as a thick liquid, excreted through glands near the mouth, which is then spun into a thread by a spinneret located behind the jaws.

Caterpillars spend most of their time eating. Their large jaws (the mandibles) move sideways while shredding their plant diet. Caterpillars munch their way through life: first eating their egg shell, from which important nutrients are retrieved, and then continuously consuming its food plants. A very small number of butterfly species have caterpillars that are predators that feed on other insects. Caterpillars typically eat more than twice their own weight each day, pausing only to shed their old skin, in order that they may grow larger. Skin shedding (molting, or ecdysis) occurs at least four times before the caterpillar is fully grown. Growth rate depends on temperature ; it is faster in warm weather, and slower when cool. Caterpillars seek a protected place in which to pupate, forming a protective shell and becoming dormant. Some caterpillars travel rather long distances (330 ft or 100 m) when seeking a sheltered place to pupate.

The chrysalis

The protective case surrounding the pupating caterpillar can take many shapes. It is usually brownish green in color , and may be speckled to aid in camouflage. With few exceptions, butterfly larvae pupate above ground, usually attached to a leaf or stem by a silken thread. Inside the chrysalis the pupated caterpillar gradually transforms into a butterfly. The process takes two weeks for some species, and as long as several years for others. When fully developed, the butterfly inside the chrysalis swallows air, inflating its body and splitting the pupal skin. An adult butterfly struggles out shortly after dawn, its moist wings hanging limply from its thorax. Crawling to a place where it can hang by its legs, the newly emerged butterfly pumps up its wings by swallowing air, increasing its internal pressure and forcing blood through tiny veins in the wings. Within several hours the expanded wings dry and harden. At about the same time the butterfly excretes waste products accumulated during pupation. The butterfly is now free to begin the adult part of its life cycle.

The adult (or imago)

Butterflies, like all insects, have an external skeleton (or exoskeleton) to which muscles are attached. The exoskeleton provides the butterfly's body with support and reduces water loss through evaporation . The respiratory system does not have a pumping mechanism. The sides of the thorax and abdomen have tiny pores (or spiracles) through which air enters and leaves the body via tubes (tracheae). The insect's blood (hemolymph) is pumped as it passes through a long, thin heart , and bathes the organs inside the body cavity.

Two large compound eyes, made up of hundreds of tiny units (ommatidia), cover much of the butterfly's head and allow a wide field of vision , including partially backwards. However, the eyes cannot distinguish much detail or determine distance , although they can readily identify color and movement, both of which are vital for survival. Colors aid in the identification of flowers, larval food plants, and the opposite sex of the species, while detecting movement may save butterflies from attacks by their predators.

The long, coiled proboscis (tongue) of the butterfly is projected into the center of flowers while searching for nectar (a liquid, sugar-rich food). Above the eyes and on either side of the head are two antennae covered with microscopic sense organs. The antennae are often incorrectly called "feelers," but "smellers" would be more accurate because it is through these organs that the butterfly sniffs out its favorite foods and potential mate. The antennae can detect pheromones , which are specific chemical signals released by the opposite sex that are detectable over a great distance.

The thorax of a butterfly is divided into three segments, each having one pair of legs. Each leg ends in a claw, enabling the butterfly to hold on while feeding and egg laying. Sensory receptors on the leg just above the claw detect the chemical makeup of appropriate food plants.

The wings are a spectacular part of the butterfly, and are extremely large compared to its body. The wings attach at the two rear segments of the thorax. Tough veins provide a framework which supports the wing membrane , which is covered by millions of microscopic scales arranged in rows like shingles on a roof. It is these scales (about 99,000 per sq in [15,000 per sq cm]) which form the color and pattern of the wing. Brown, orange, and black tones are due to the presence of chemical pigments. However, the brilliant, iridescent blues and greens are parts of the light spectrum separated by tiny facets on the surface of the scales, creating colors in the fashion of a prism . The wing colors provide camouflage against predators and aid in identifying mates of the correct species. Scales also cover the segmented abdomen, in which the digestive and reproductive organs are located.

Reproduction

Reproduction in butterflies begins with courtship , during which the male vigorously flaps its wings, releasing a dust of microscopic scales carrying pheromones above the female's antennae. These male pheromones act as a sexual stimulant to the female. Some males release additional pheromones from "hair pencils" under the abdomen. Female butterflies that are ready to mate dispense with courtship. Some species, however, perform complicated courtship maneuvers, probably to find a mate strong enough to endure the rigorous rituals, thereby by increasing the chance of producing healthy offspring. Males usually must wait one or two days after emerging from the chrysalis before they can mate, but then they may mate many times. Females can mate immediately after emerging, some species mating several times. However, it is the last male to mate that fertilizes the eggs. Females of some species mate once only.

Migration

Most butterfly species live and die within a narrow geographic range, because their brief life span allows little time for wandering. However, the monarch butterfly migrates thousands of miles from southern Canada and northern parts of the United States to Mexico and southern coastal California. The round trip takes two or three generations to complete, because of the short individual life span. Each butterfly must find its own way, having no living guide, yet the species follows the same broad migratory route year after year, century after century. Monarchs and some other butterflies migrate in massive numbers, forming clouds of color sometimes a mile wide and a mile long; millions perish during the journey.

Vulnerability and defense

The survival of butterflies is influenced by many factors, and their populations may increase or decrease quite rapidly, and from year to year. Brilliantly colored butterflies are often toxic when eaten, so predators learn to leave them alone. Occasionally, a non-poisonous species evolves that mimics the appearance of a poisonous species, thus being less susceptible to predators. Dark colors, displayed by butterflies in cooler climates (such as alpine or arctic tundra ), readily absorb sunlight so the cold-blooded insect can warm up more quickly.

Some butterflies are well camouflaged and almost undetectable among the flowers of their particular food plant. A variety of spots resembling eyes on the outer edges of the wings of certain species may startle or distract predators, drawing the point of attack of a swooping bird away from the butterfly's soft body. Some butterflies do a 180-degree turn before landing, so the eye-spots on the wings are positioned where a predator may think the head should be. Butterflies surviving bird attacks can often fly well even with a piece of wing missing.

The underpart of the wing is usually duller than the surface, so that when the butterfly assumes its resting position with wings folded above its head, it is cryptically colored, blending into the background on which it lands. Some butterflies use the club on the end of the antennae to knock small predators off their body.

The hairy spines on many caterpillars deter predators, and their colors often blend in with the leaves of their food plant. Some pupae develop hornlike appendages on the head and rear of the chrysalis, which appear to point menacingly at predators. In other cases, a chrysalis hanging from a twig may look like a dead leaf.

Conservation

Habitat loss to agriculture, deforestation , urbanization, draining of wetlands , and other changes in land-use is the foremost threat to butterfly populations. Although pollution , pesticides , and specimen collection pose serious threats to some species, none of these is as damaging as habitat loss. The short life span of butterflies usually makes it impossible for displaced populations to find another appropriate habitat. Although no species of butterfly is known to have been made extinct through human actions, some subspecies have been rendered extinct, and some rare species are endangered. Protection of habitat is the most effective way to prevent major reductions in populations and endangerment of butterflies, and of other wild animals and plants.

Resources

books

Eid, A., and M. Viard. Butterflies and Moths of the World. Book Sales Pubs., 1997.

Feltwell, John. The Natural History of Butterflies. New York: Facts on File, 1986.

Pollard, Ernest. Monitoring Butterflies for Ecology and Conservation. London: Chapman & Hall, 1993.

Sbordoni, V., and S. Forestiero. Butterflies of the World. Firefly Books, 1998.

Scott, James A. The Butterflies of North America. Stanford: Stanford University Press, 2001.

Smart, Paul. The Illustrated Encyclopedia of the ButterflyWorld. New York: Random House, 1996.

Periodicals

Barbour, Spider. "Overnight Sensation." Natural History (May 1989): 24-28.

Boppre, Michael. "Sex, Drugs, and Butterflies." Natural History (January 1994): 28-33.

Marie L. Thompson

KEY TERMS

Chrysalis

—A soft casing, shell, or cocoon protecting the dormant pupa of insects during metamorphosis.

Metamorphosis

—A complete change of form, structure, or function in the process of development, shown by insects.

Pheromones

—Chemical substances, secreted by most animals, that stimulate a response from others of that species (e.g., sex hormones for mating) or other species (e.g., a predator sensing chemicals produced by its prey's fear).

Pupa

—An insect in the nonfeeding stage during which the larva develops into the adult.

Butterflies

Butterflies are popular, well-known insects with large, colorful wings covered with tiny scales. Together with moths, butterflies make up the order Lepidoptera, which contains over 150,000 species or kinds. Scientists estimate that about 15,000 butterfly species exist worldwide. During its life cycle, a butterfly undergoes a complete metamorphosis (pronounced met-uh-MORE-fuhsiss) during which it changes from a leaf-eating caterpillar to a nectar-sipping butterfly.

Beauty with a purpose

Butterflies are one of our very favorite insects. The fact that they do not sting or bite, are brightly colored, and do not become pests in people's homes has something to do with why most people enjoy seeing them fly around and would seldom think of killing one (as one might do with other insects thought of only as "bugs"). Most people think that butterflies simply make the world a prettier place. However, like other life forms in the world, they have a place and serve a purpose. For the plant world, butterflies pollinate or carry pollen from plant to plant, helping fruits, vegetables, and flowers to produce new seeds. From the animal point of view, butterflies are near the bottom of the food chain and provide food (especially in their caterpillar stage) for birds, mammals, and other insects.

It is thought that the word butterfly may have originated in England when people started calling the yellow Brimstone or the English sulfur a "butter-colored fly" because the pretty insect reminded them of the color of butter. Eventually it was shortened to "butterfly." The scientific name of its order, Lepidoptera, means "scaly wings" in Latin. This is a correct description since their wings and their bodies are covered with tiny scales. Butterflies and moths are the only insects that have scales. Moths and butterflies are mainly different in their appearance and activities. Moths fly mostly at night and usually have a dull color. Butterflies are active during the day and are brightly colored. Their bodies are thin and hairless, while most moths have plump and furry bodies.

Words to Know

Chrysalis: A soft casing, shell, or cocoon protecting the dormant pupa of insects during metamorphosis.

Metamorphosis: A complete change of form, structure, or function in the process of development.

Pupa: An insect in the nonfeeding stage during which the larva develops into the adult.

Butterflies are everywhere

Butterflies are found nearly everywhere in the world except Antarctica. They have lived on Earth for at least 150 million years and range in size from the Western Pygmy Blue, which is smaller than a dime and found in North America, to the Queen Alexandra's Birdwing of Papua New Guinea, which has a wingspan of up to 11 inches (28 centimeters). Although some tropical butterflies can live up to one year, the average life span of a butterfly is at most two months. Butterflies display every color of the rainbow in their wings, and no two butterflies are exactly alike. This coloring serves many purposes: from attracting a mate, to blending in with its surroundings, to warning its enemies that it is poisonous and should be avoided.

Unique life cycle

One of the most interesting things about butterflies is their unique life cycle. When a butterfly changes from a slow-moving, fat caterpillar to a colorfully winged, beautiful flying insect, one of nature's most magical events occurs. This metamorphosis happens to most insects, but not as dramatically as it does to a butterfly (the word metamorphosis is Greek for "change in form"). There are four stages in a butterfly's metamorphosis. Every butterfly begins life as an egg. After mating, the female lays her eggs (she actually "glues" them) in small clusters on the leaves of a certain plant. Each species selects its own plant, and the eggs of each are different in shape and markings. In many species, the female dies shortly after doing this. When the egg hatches, the larva emerges. Actually a tiny caterpillar eats its way out the egg, and then proceeds to eat the eggshell. This caterpillar is a true eating machine, and it continues to eat the leaves of the plant where its mother laid her eggs. Caterpillars have one goal—to eat as much as possible—and in their short lifetimes they may eat as much as twenty times their own weight. Caterpillars naturally grow quickly with all this eating, and since their skin cannot stretch, it splits and is shed. This is called molting and it happens several times as the caterpillar gets fatter and fatter. It is at this slow-moving stage that many a caterpillar is devoured by a hungry bird. Still, many protect themselves by using their colors to blend in with their environment. Other have sharp spines or prickly hairs on their bodies to deter predators, while still others have circles or spots on their skin that trick their predators into thinking that the caterpillar is really a larger animal than it is.

Caterpillar to chrysalis to butterfly

If the caterpillar survives and reaches its full size, it attaches itself to a stem from which it hangs upside down. It then sheds its skin one last time, and the old skin hardens almost immediately and becomes a tough shell called a chrysalis (pronounced KRIS-uh-liss). The caterpillar has now become a pupa (pronounced PEW-puh) inside a chrysalis, and its body parts are broken down into a thick liquid that will feed special, pre-programmed cells that have lain dormant in the caterpillar. These cell clusters start to form specialized body parts, like wings, legs, and eyes of a new creature. This process goes on for days, weeks, and sometimes months, according to the type of butterfly that will emerge. The final stage occurs when an adult butterfly finally pushes itself out of its chrysalis, looking nothing like the caterpillar that it was. When the butterfly breaks through the now-soft shell, its wings are wet and crumpled and it must rest while it expands its wings and pumps them full of blood. Continued flapping makes them strong, and soon the adult butterfly is ready to fly away and begin this cycle all over again by looking for a mate.

Every adult butterfly is covered with millions of tiny scales that help it to control its body temperature. They also can help it escape from a predator's grip since they rub off easily. It is these scales that give but terflies their beautiful colors. A butterfly's body is made up of three parts: head, thorax, and abdomen. On its head are two long antennae, which it uses as feelers to touch and to smell things. They also have two large compound eyes, which means that each is really thousands of eyes formed together. This allows a butterfly to see in all directions at once. They also have a long hollow tube called a proboscis (pronounced pro-BOSS-siss), which they use like a straw to sip the energy-rich, sugary liquid called nectar produced by flowering plants.

Amazing fliers

A butterfly's wings are its most important part since they enable it to move about for food, shelter, a mate, and all the other things it needs. Its wings are very strong, and they are supported and shaped by a network of veins, just like those in a leaf. Different species have different-shaped wings that make each fly in a different manner. Those with large wings flap and make long glides, while those with wide wings flutter and flit or move with short bursts. Those with long, thin wings fly the fastest, and those with short, triangular wings can zigzag and dart about quickly. No matter how they move about, butterflies are incredible fliers, and some migrate over 3,000 miles (4,800 kilometers) to spend the winter in a warmer place. The well-known Monarch butterfly flies to Mexico from North America before the autumn chill arrives. Those living east of the Rocky Mountains fly the longest, traveling over 2,000 miles (3,200 kilometers) to get to the same spot in Central America. Some scientists believe that they find their way by using the position of the Sun as a compass, while others think that they are able to detect changes in light waves that are filtered through the clouds. However they do it, millions make the journey south every year, and their offspring make their way north again the following spring.

The ancient Greeks are said to have believed that when people die, their souls leave their bodies in the form of a butterfly. Their symbol for the soul was a young girl named Psyche who had butterfly wings. Today, we know that real butterflies are extremely sensitive to changes in their environment. More and more, as their habitats are being destroyed and endangered by pollution, pesticides, and other human activity, butterflies are threatened. Some rare species may have already become extinct.

[See also Insects; Invertebrates ]

but·ter·fly / ˈbətərˌflī/ • n. (pl. -flies) an insect (superfamilies Papilionoidea and Hesperioidea, order Lepidoptera) with two pairs of large wings that are covered with tiny scales, usually brightly colored, and typically held erect when at rest. Butterflies fly by day, have clubbed or dilated antennae, and usually feed on nectar. ∎  a showy or frivolous person: a social butterfly. ∎  (butterflies) inf. a fluttering and nauseated sensation felt in the stomach when one is nervous. ∎  (in full butterfly stroke) [in sing.] a stroke in swimming in which both arms are raised out of the water and lifted forward together. ∎  [as adj.] having a two-lobed shape resembling the spread wings of a butterfly: a butterfly clip.• v. (-flies, -flied) [tr.] split (a piece of meat) almost in two and spread it out flat.

butterfly often taken as the type of a fragile and ephemeral creature (as in break of Chancery).
butterfly effect the effect of a very small change in the initial conditions of a system which makes a significant difference to the outcome; the term derives from the title of a paper (1979) by the American meteorologist Edward Lorenz (1917– ), ‘Predictability: Does the flap of a butterfly's wings in Brazil set off a tornado in Texas?’
float like a butterfly, sting like a bee the summary of the boxing strategy of Muhammad Ali (1942– , born Cassius Clay), probably originated by his aide Drew ‘ Bundini’ Brown.

See also break of Chancery.