Butterflies and Moths
From Media Hex
Butterflies and MothsButterflies and Moths, insects distinguished by four wings covered with tiny, shingle-like scales and by mouthparts that form a hollow, flexible tube like a drinking straw. Most butterflies and moths use their distinctive mouthparts to feed on the nectar of flowers. The insects have proportionately small bodies and large wings, and a pair of antennae on their heads. Butterflies and moths together make up the second largest order of insects, called Lepidoptera (Greek "lepis," scale; "ptera," wing).
Butterflies and moths are similar animalsButterflies and moths are similar animals, but they have some general differences. The main difference is that butterflies have knobs, or clubs, on the tips of their antennae. Moths may have threadlike, feathery, or blunt antennae, but their antennae lack clubs. In addition, most moths tend to fly chiefly at night, while butterflies are active during the day. When at rest, most moths hold their wings folded flat over their backs, while butterflies hold their wings upright over their backs or bask with them spread flat out to the side. Many species of moths have dull gray or brown wings, and butterflies often have wings with colorful patterns. But numerous exceptions exist. For example, many moths fly during the day and are brightly marked, and many butterflies have soft, brown wings.
Throughout historyThroughout history, lepidopteransespecially the colorful butterflieshave been admired for their delicate beauty. They have a prominent place in art and literature as symbols of freedom, creativity, and the beauty of nature. The animals are also crucial parts of the ecosystems in which they live. Their most important ecological role is in pollination, the transfer of pollen from one flower to another, which helps plants to reproduce. Butterflies and moths pollinate many wild plants as well as important crops grown by humans for food.
By far the majority of lepidopterans areBy far the majority of lepidopterans are moths. Scientists have identified some 200,000 species of moths and suspect there may be many more not yet discovered, perhaps amounting to a million or more species. By contrast, the approximately 18,500 known types of butterflies probably account for most of the world`s butterfly species.
Lepidopterans probably arose between 200Lepidopterans probably arose between 200 million and 300 million years ago from insects similar to present-day caddisflies, night-flying insects that live near water. After flowering plants, on which butterflies and moths depend for food, arose about 130 million years ago, the insects developed and diversified rapidly. The earliest known fossils of primitive moths, found in Lebanese amber and Siberian sediments, are 100 million to 130 million years old. The oldest known butterflies in the fossil record date from about 48 million years ago, and many butterfly fossils are found in shale about 38 million years old from the Florissant Fossil Beds of Colorado. Some of these fossil butterflies closely resemble present-day species.
Range and Habitat
Butterflies and moths are native to almostButterflies and moths are native to almost every part of the globe except Antarctica and the oceans. Different biomes, such as forests, grasslands, deserts, and alpine highlands, each support distinctive arrays of butterfly and moth species. Like many groups of animals, lepidopterans reach their greatest diversity in the tropics. More than 6,000 species of butterflies make their home in Peru, a largely tropical nation in South America with a variety of habitats from rain forest to mountain summits, while only 6 types of butterflies live in Greenland`s high arctic environment.
In generalIn general, wooded habitats are more hospitable to moths, while butterflies prefer open, sunny settings. Butterflies may be found in flowery fields, meadows, and hillsides; along stream banks, roadsides, and the edges of woods; and in clearings, glades, and nature reserves of all sorts. Especially large numbers of butterflies can be found in prairies, arctic and alpine tundra, and deserts following spring or summer rains.
Although the best way to see butterfliesAlthough the best way to see butterflies and moths is to visit places where human settlement has not greatly disrupted native habitats, the insects are also present in urban settings such as city parks, gardens, and vacant lots. Some gardeners plant flowers, herbs, and shrubs to attract colorful butterflies of a great variety of species.
As do all insectsAs do all insects, butterflies and moths have a hard outer covering, or exoskeleton, that supports and protects the body. Also typical of insects, lepidopterans possess a body divided into three main partshead, thorax, and abdomenand have three pairs of jointed legs.
The smallThe small, round head protects the lepidopteran`s brain and bears the insect`s sensory organs and mouthparts. Butterflies and moths have a pair of large, oval, compound eyes, each made up of thousands of individual lenses, or ommatidia. In spite of the many lenses, the lepidopteran eye is thought to see a single, reasonably clear image. In addition to the spectrum of colors from red to violet that humans can see, butterflies and moths can perceive ultraviolet wavelengths of light.
Two antennae protrude from the head. TheTwo antennae protrude from the head. The antennae are covered with many small pits that serve as smelling organs, enabling the butterfly or moth to locate food sources by scent. Scent also plays a role in lepidopteran mating. The antennae of many male moths, equipped with elaborate side bristles, resemble feathers or ferns and are thought to give the moths a particularly sharp sense of smell, enabling them to locate females from several kilometers away. The function of the knobs on the ends of butterfly antennae is not fully understood. But butterflies lacking one antenna tend to fly in circles, which suggests that the knobs may play a role in orientation.
The lepidopteran`s mouth is located betweenThe lepidopteran`s mouth is located between its eyes. When it is not feeding, the butterfly or moth keeps its tongue, or proboscis, curled up below its face. The animal can uncoil the proboscis, which functions like a drinking straw, and insert it into flowers and other food sources. The proboscis may vary in length from a fraction of an inch to a foot or more. A few moths, such as the giant silk moths, have no functional mouthparts, and one family of tiny moths has jawlike structures called mandibles instead of a proboscis. These moths use their mandibles for chewing pollen grains.
The thoraxThe thorax, or middle body part, of a butterfly or moth is the thickest of the body segments. It contains the powerful flight muscles and bears the legs and wings. The six legs are attached to the underside of the thorax. Each lepidopteran foot bears a pair of claws, used for clinging to perches, and hairlike structures responsible (along with the proboscis) for the sense of taste. If the front feet of a butterfly are touched with a small brush dipped in a very weak sugar solution, the butterfly will uncoil its proboscis and attempt to feed because the tasting hairs on its feet sense food.
The wingstwo forewings and two hindThe wingstwo forewings and two hind wingsoriginate from the sides of the thorax. A lepidopteran`s wings are large in proportion to its body and very thin. The wings are made of two membranes with a network of stiff veins between the layers. The scales covering the wings give butterflies and moths their distinctive colors and patterns. Scales may contain pigments like those found in skin or fabric that give them their color. Ridges and furrows on the scales may also diffract light like a prism, producing metallic and iridescent hues called structural colors. The scales rub off easily when a lepidopteran`s wings are touched.
The third body partThe third body part, the abdomen, is tubelike in shape and usually consists of ten segments. Inside the abdomen are the lepidopteran`s heart, respiratory and digestive systems, and reproductive organs. The heart, a muscular tube that runs the length of the abdomen, pumps blood toward the front of the body. Oxygen enters the body through six to seven pairs of breathing holes known as spiracles, located on the sides of the abdomen. The spiracles are connected to a network of tubules called tracheae, which deliver oxygen to the tissues. In females, the reproductive organs take up most of the abdomen. Their abdomens tend to be fuller and blunter than those of the males because of the large number of eggs inside.
The smallest butterflies are certain bluesThe smallest butterflies are certain blues that have wingspans of a mere 0.7 cm (0.25 in). The largest are the female giant birdwings of Papua New Guinea, which measure up to 30 cm (12 in) across. Moths range in size from tiny Microlepidoptera, several groups of small moths with wings no more than 0.16 cm (0.06 in) across, to giant silk moths, such as the atlas moth, which may exceed 30 cm (12 in) in wingspan.
Reproduction and Life Cycle
Butterflies locate potential mates by sightButterflies locate potential mates by sight, identifying the wing colors and patterns characteristic of their species. In some types of butterflies, males and females display different patterns on their wings. In other species, the wing markings look the same to the human eye. But either the males or females often have scales on their wings that reflect ultraviolet light, producing patterns that enable the butterflies to distinguish one sex from the other. During the breeding season the males of some species stake out territories, where they perch and watch for females.
Once a male and female butterfly locate
Once a male and female butterfly locate each other, the male initiates a courtship dance. Scientists believe that this ritual exposes the female to pheromones, chemical signals released by the male that induce the female to mate. Males of many species have patches of specialized scales called androconia on their wings, thorax, or abdomen that release pheromones. Females also release pheromones from their abdomens. The butterflies sense each other`s pheromones with the smelling organs on their antennae. During the courtship ritual, the male may flutter around the female or bump her with his wings or body. The pair may also alight on a plant or other perch and stroke each other with their antennae. In some species the courtship ritual is elaborate, but in most it is simple and brief.
MothsMoths, creatures that are often drab in color and active at night, rely primarily on smell to find mates. In many moth species the female releases pheromones, and the chemicals become plumes of scent on the wind that advertise her presence. When a male detects a female`s pheromones with his sensitive antennae, he responds by flying directly upwind toward the source of the scent. Some silk moths are able to detect the scent of the females from 10 to 20 km (6 to 12 mi) or more away.
Lepidopterans mate by perching and bringingLepidopterans mate by perching and bringing the tips of their abdomens together. The male holds the female tightly with handlike structures on his abdomen called claspers, and if threatened the pair can fly away while still maintaining their embrace. Mating lasts from several minutes to several hours, depending on the species. The male uses his penis to pass to the female a spermatophore, a package containing sperm (male sex cells) and nutrients. The spermatophore`s weight may be up to 10 percent of the male`s body weight. The generous supply of nutrients it contains helps sustain the female as she lays her eggs.
After matingAfter mating, sperm are stored in the female`s reproductive tract. Fertilization, or union of the sperm and egg, takes place just before each egg is laid. Female butterflies and moths usually lay their eggs on or near plants suitable for the young to eat. Many species deposit their eggs singly on the plant`s leaves. Others, such as tiger moths and checkerspot butterflies, lay their eggs in large clusters, often ringing the stem. Most eggs hatch from two or three days to a month or more after they are laid. Some eggs laid in the fall do not hatch until the next spring.
The egg hatches into a larva called a caterpillarThe egg hatches into a larva called a caterpillar, which has a cylindrical body and mouthparts designed for chewing. Like an adult lepidopteran, a caterpillar has three pairs of legs on its front segments. Most types also have five pairs of leglike structures called prolegs on the rear segments. After hatching, the caterpillar usually consumes its eggshell and then begins feeding on the leaves, buds, or flowers of its host plant. Some species have more unusual habits, boring into the stems or roots of plants or feeding on stored grain. A few types of caterpillars eat other insects, especially aphids or ant larvae. Some caterpillars are tended and protected by ants, and in return provide the ants with honeydew, a sweet, nutritious substance that the ants use as food. Caterpillars are voracious eaters and grow rapidly. Most types molt, or shed their skin, four or five times as they grow. Each time they molt they enter a new growth phase, called an instar.
When a caterpillar reaches its full sizeWhen a caterpillar reaches its full size, it prepares to complete its metamorphosis, the radical change in body form that turns a caterpillar into a butterfly. Metamorphosis takes place inside the pupa, or chrysalis, a hard, sometimes thorny, oval structure. Most caterpillars pupate by attaching themselves to a twig or other support. To anchor themselves to the support they spin a button of silk from their mouthparts, then grasp the silk button with the cremaster, a clawlike structure at the end of the abdomen. Hanging from the twig, the caterpillar sheds its skin to reveal the pupa underneath. Most moth caterpillars spin a cocoon of silk around their bodies before becoming a pupa. The cocoon helps protect the pupa from predators and from drying out.
Within the pupaWithin the pupa, the tissues and organs of the caterpillar break down into a soupy liquid, and then reassemble into the tissues and organs of the adult butterfly. Groups of cells known as the imaginal discs remain complete, and the adult butterfly`s structure takes shape as directed by these cells. The imaginal discs work in tandem with hormones, chemical messengers that carry information between different parts of the body, to program the insect`s development, much as silicon chips direct the operation of a computer. The pupal stage may last anywhere from one week to several years, depending on the species and the weather.
When its development is completeWhen its development is complete, the adult butterfly or moth splits the pupal shell and crawls out. It unfolds its wings and pumps blood into the veins, then holds the wings spread out like a kite until they dry and harden. The animal is then ready to fly off, feed, and mate. Most adult butterflies and moths live just one or two weeks. A few types, such as anglewings and the migratory generation of monarchs, may live six months or more.
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