Beetle - biology.

Beetle - biology. I INTRODUCTION Beetle, insect belonging to the order Coleoptera, the largest group of animals on Earth. Beetles represent more than a third of all known insect species, and a fourth of all animal species. Scientists have identified about 350,000 species of beetles, but experts estimate that for every known species there are several more species that have not yet been discovered and named. Some experts estimate that there could be more than 8 million species of beetles worldwide. When asked whether his study of nature had provided any insights into the mind of the Creator, British scientist J. B. S. Haldane reportedly responded that God must have "an inordinate fondness for beetles." Beetles have evolved over 230 million years to form one of the most successful groups of insects. They have widely diverse shapes, sizes, and colors and they live in almost all parts of the world except the oceans, Arctic regions, and Antarctica. Beetles are especially successful in tropical habitats, but they can also be found in frigid mountainous habitats as well as in some of the hottest, driest deserts. II CHARACTERISTICS OF BEETLES Coleoptera, the scientific name of the beetle order, comes from the Greek words coleos ("sheath") and pteron ("wing"). The term refers to the characteristic feature of beetles--hardened front wings that form a protective sheath over the hind pair of flying wings. While most beetles can fly, many are clumsy fliers, and some have lost the ability to fly and live primarily on the ground. Most beetle species live on land, but some spend part or all of their lives in water. Others tunnel underground, in wood, or in the carcasses of animals. Some beetles live in the nests of ants and termites, forming a mutually beneficial relationship. The nest protects the beetles from predators, and the ants or termites receive housecleaning services as the beetles consume the waste products of the colony. The beetle diet varies widely. Many beetles feed on plants, and each species usually prefers a particular plant species. Beetles feed on various parts of a plant, anything from the roots to the flowers. Many beetles are scavengers and eat dead plant or animal matter. Others are predatory, preying on insects, snails, or other small invertebrates. About 100 species of beetles are considered some of the most destructive of all insect pests, due to their widespread distribution and varied feeding habits. Worldwide each year beetles cause millions of dollars in damage to plant products, such as food crops or timber, by feeding on them or by transmitting fungi and other agents of disease. One of the best-known beetle pests is the Colorado potato beetle. It became a pest in the middle of the 19th century, when settlers introduced potatoes into the beetle's native range. Farmers find it difficult to control potato beetle infestations because the insects quickly develop resistance to insecticides. Another common pest in gardens and on a wide variety of crops is the Japanese beetle. Accidentally imported from Japan to the United States in 1916, the Japanese beetle feeds on over 400 species of broad-leaved plants. The beetle eats the tissue between the veins of leaves, giving the attacked leaves a lacelike appearance before they wither and die. Another well-known destructive beetle is the boll weevil, which spread into Texas from Central America in 1892. Boll weevils destroy cotton crops in the United States and elsewhere. Many other types of beetles are beneficial to humans. Farmers release certain beetles in their fields to control insect pests. For example, ladybird beetles feed upon aphids and other small sucking insects that injure food crops, and ground beetles feed on crop-damaging potato beetles and caterpillars that destroy trees and shrubs. III BODIES OF BEETLES Among the beetles are found some of the largest, as well as some of the smallest, of all insects. The largest beetle is the massive giant longhorned beetle (Titanus giganteus) of northern South America. Adults can grow 18 cm (7 in) or more in length. One of the smallest beetles is the North American feather-winged beetle (Nanosella fungi), which is less than 0.5 mm (0.02 in) in length. Most beetles range from 1 to 3 cm (0.4 to 1.2 in) in length. As in other insects, the body of the adult beetle has three main parts--the head, which holds an insect's primary sense organs and feeding structures; the thorax, which is the attachment site for the legs and wings; and the abdomen, which contains the organs for digestion and reproduction. A hard outer covering protects the internal organs. A Body Covering The beetle's cuticle, or body covering, provides a tough, waterproof sheath that protects the soft inner organs and provides a rigid framework for the attachment of muscles. Harder and thicker than that of most other insects, the beetle's cuticle is composed mainly of chitin, a strong, flexible compound. The cuticle restricts movement, and some beetles have difficulty righting themselves when turned upside down on a smooth surface. An exception is the click beetle, named for the clicking noise the beetle makes when it springs into the air to right itself. The cuticle is commonly shiny brown or black, often with intricate texture patterns, but it may be brightly colored, or have colored spots, stripes, or other color patterns. Cuticle color in beetles derives from natural pigments in the animal tissue, which provide the many earth tones exhibited by beetles. In some species, minute surface structures refract light of various wavelengths, producing bright metallic or iridescent shades. B Head The beetle's head bears the antennae, eyes, and mouthparts. The antennae function as feelers, helping the beetle navigate and find food and potential mates. In some species the antennae may serve other purposes as well--for instance, the large antennae of some longhorned beetles help maintain balance. Beetle antennae generally consist of 11 segments, and the segments can take a variety of shapes, including cylindrical, beadlike, sawtoothed, club-shaped, or fan-shaped. Scientists use the shape of a beetle's antennae as one means of classifying or identifying it. Like other insects beetles have compound eyes, which are divided into many six-sided compartments called ommatidia. The ommatidia extend around the sides of the beetle's head, providing a wide field of vision. Compound eyes produce blurred images of distant objects, but they are very sensitive to movement. Recent investigations of the structure of the beetle's compound eye suggest that some beetles can see in color. Beetles have chewing mouthparts that move from side to side rather than up and down in the manner of human chewing. Beetle mouthparts consist of four main components: the labrum (upper lip), a pair of mandibles (front jaws), a pair of jointed maxillae (back jaws), and the labium (lower lip). The shape and size of beetle mouthparts vary from species to species depending on the food preferences of the species. For instance, predatory beetles have extended mandibles that can seize, cut, or crush prey. Beetles that consume nectar from flowers use tubelike mouthparts to suck up nectar like a primitive straw. C Thorax The thorax, the body region behind the head, consists of three segments that provide attachments for the legs and wings. Each segment of the thorax carries a pair of legs. The middle segment also bears the stiff wing sheaths called elytra, and the hind segment holds the membranous hind wings. D Legs Beetles have six jointed legs, each leg with five parts. The fifth part is the foot, or tarsus, which itself has three to five segments known as tarsomeres. The number of tarsomeres present helps scientists identify beetle families. In some species, from one to four of the tarsomeres have an adhesive pad on the bottom, which enables beetles to walk up walls, windows, plant stems, and other vertical surfaces. The last segment of the foot bears a pair of claws. Beetle legs may be modified for various life styles. Swift runners, like the ground beetles, have long and slender legs. Swimming beetles, such as true water beetles, have curved, paddlelike legs, and dung beetles use their broad legs for digging. E Wings Most beetles have two types of wings--elytra and hind wings. Beetles use only their hind wings for flight. The hind wings typically fold to fit under the elytra when not in use. In some beetle species that live on the ground, the hind wings may be missing altogether. The elytra cover the abdomen when the insect is not in flight. The two elytra meet in the middle of the abdomen, forming a characteristic straight line down the abdomen. The elytra protect beetles from drying out, from predators that bite, and from other kinds of damage. Many of the beetles that do not fly have fused elytra that insulate the abdomen and protect the insect from extreme heat or extreme cold. As a beetle prepares to fly, it opens the elytra, unfolds its hind wings, and uses its legs to jump into the air. Muscles embedded in the thorax enable the wings to beat. Some beetles can open their wings and jump into the air from a flat surface. Larger beetle species must climb onto a plant or other platform for takeoff or sit in the sun to warm their thoracic muscles before they are able to take off and fly. Beetles active primarily at night must vibrate their thoracic muscles to help raise the body temperature before flight is possible. F Abdomen Behind the beetle's thorax is its abdomen, which is divided into a number of segments. The elytra cover the top of the abdomen. Along the sides of the abdomen are external openings, known as spiracles, which are part of the respiratory system. The abdomen houses the digestive and reproductive organs. G Sense Organs The antennae function as the beetle's main sense organs, receptive to signals of touch, smell, and taste. Beetles use taste and smell receptors on the antennae to locate food and also to identify pheromones, chemical substances released by other beetles of the same species to attract mates. Beetles also have sense organs on their bodies in the form of setae (bristles) that are sensitive to touch, sound, smell, taste, and light. Most beetles have a very good sense of smell, which they use to locate food. Scarabs use smell to find piles of dung, their primary food source, and plant-feeding beetles, such as leaf beetles, rely mainly on smell to find the particular species of plants that they feed on. Beetles in general have a poorly developed sense of hearing. They can sense air vibrations caused by sound waves, but they are more sensitive to vibrations in the ground, which they feel through receptors on their legs. Many beetles make peculiar squeaking noises by rubbing parts of the body together, or produce sounds by tapping on hard surfaces. These sound-producing beetles have better hearing than beetles that do not make sounds. Sense receptors also provide beetles with information about body positions, so that a beetle always knows the position of its legs or head in relation to its body. H Internal Organs Like other insects, beetles digest and absorb nutrients from food, expel waste products via an excretory system, and take in oxygen from the air. Digestion occurs in the alimentary canal, a tube extending from the mouth at one end of the body to the anus at the other. The heart lies in the thorax, and pumps blood toward the front of the body. Blood does not circulate through veins and arteries but passes freely between and around the body organs. Like all insects, beetles lack lungs. Air passes directly into the body through spiracles, the openings along the abdomen, and then circulates to the tissues by a system of branching tubes. The nervous system includes a simple brain made up of ganglia (clusters of nerve cells) lying at the front end of the alimentary canal. From the brain a double nerve cord runs back along the bottom of the body. The nerve cord connects a series of ganglia in the thorax and abdomen. From this nerve cord, nerves extend to sensory cells throughout the body. The beetle's reproductive organs lie in the abdomen. The female has a pair of ovaries where eggs develop and tubes called oviducts to carry the eggs away from the ovaries. When she lays her eggs, a tubelike external organ called the ovipositor helps the female position her eggs near food so that hatching larvae will not need to travel far to feed. The male has a pair of testes where sperm is produced and a duct to carry the sperm to the penis. The male's penis stays inside its body except during copulation. IV LIFE CYCLE OF BEETLES Most beetles reproduce sexually--that is, male sperm cells unite with female egg cells. A few species, including some common species of weevil, lay fertile eggs without mating in a method of reproduction known as parthenogenesis. When mating takes place, the male usually deposits enough sperm inside the body of the female to fertilize all of the many hundreds of eggs she may produce during her lifetime. The sperm remain stored in the female body in a structure called the spermatheca while the female's eggs mature in the ovaries. Fertilization, in which sperm unite with eggs, occurs just before the eggs are laid. Beetles, along with flies, moths, wasps, and some other insects, undergo many body changes as they develop into adults. In a process known as complete metamorphosis, beetles develop in four distinct stages: egg, larva, pupa, and adult. The egg, larva, and pupa stages each have a strikingly different appearance from the adult stage. A Egg The female beetle lays her eggs in a protected place near a food supply, such as in wood or under the bark of trees, on leaves, or in carcasses of decaying animals. Depending on the species, a female may lay a single egg or a mass of eggs. Most beetle eggs range in size from microscopic to about 2.5 mm (0.1 in), and they are usually white. After laying her eggs, female beetles leave the eggs to hatch on their own. Hatching typically occurs after several days, and the wormlike larva stage emerges. In some beetle species the mother watches over the developing larvae to protect them from predators. B Larva Beetle larvae, also known as grubs, vary in appearance, but most have well-developed heads with chewing mouthparts and three pairs of legs. Many species have a pair of leglike structures at the end of the body that help the larvae move. As the larva grows, it molts (sheds its skin) several times. Each molt yields a progressively larger and more developed larval stage. Most beetle larvae live on land and can be found in a wide variety of habitats, but some are aquatic. Depending on the species, beetle larvae feed on plants, decaying vegetable or organic matter, or stored food in warehouses. Some prey on other insects or small animals. The adult beetle and the larva differ not only in structure, but often in feeding habits. The larvae of the Japanese beetle, for example, feed on plant roots, whereas the adults feed on foliage and fruits. C Pupa At the end of the larval stage, the larva secretes silky strands to form a cocoon. Inside the cocoon, the larva transforms into the pale, soft pupa. The pupal stage is often referred to as the resting stage of the beetle's life cycle because externally the pupa appears inactive. In fact, a great deal of activity occurs internally during this stage, as larval tissues break down and reform into adult structures. The changes that occur during the pupal stage include the development of the adult legs, wings, antennae, and reproductive system. D Adult When an adult beetle emerges from the pupal stage, its body is soft and pale. The hardening and coloring of the cuticle may not occur for many hours. During this time the hind wings and elytra, which have formed internally, push to the outside of the body. Adult male and female beetles may look quite different from each other. In some species males are smaller than females, while in other species the reverse is true. The males and females of many species have different colors, suggesting that beetles of these species use color vision to find mates. Other structures that help scientists differentiate males from females in various species include the antennae, mouthparts, abdomen, and elytra. In some species, the proportion of males to females may be unequal. For instance, there may be as many as 60 female bark beetles for every one male. Beetles spend more time in the larval and adult stages than most insects do. Wireworms (click beetle larvae) may remain at least 12 years in the larval stage before pupating. The larvae of an Indian species of longhorned beetle have been known to live for ten years in captivity, but the adults are short-lived. The adults of a large species of darkling beetles have been kept alive in a laboratory for nine years. Witnesses have observed one species of jewel beetle (Cypriacis aurulenta), common in the forests of western North America, emerge from a piece of wood furniture built 35 years earlier. V KINDS OF BEETLES Entomologists (scientists that study insects) have identified about 170 different families of beetles. This section discusses principal characteristics of some of the larger families in order of their size. Most of the families discussed are distinctive enough to have well-recognized common names. The Latin family names, recognizable by the ending -idae, appear in parentheses after the common names. A Weevils (Curculionidae) Weevils constitute the largest family in the entire animal kingdom, with over 50,000 species identified. Weevils are sometimes called snout beetles for their distinctive long snout. In some species this snout may extend more than three times the length of the body. Female weevils generally have longer snouts than males. Some female weevils, such as the female acorn weevil, use the mouthparts at the tip of the snout to drill holes in plant seeds, where they lay eggs and their larvae develop. To distinguish weevils from other beetles with snouts, scientists look at the antennae. Weevil antennae have club-shaped tips and bend forward at an elbow. Many weevils are a drab brown or black, but some have brilliant metallic colors, and some have a covering of colored scales similar to the scales of butterfly wings. Adults average 7.6 mm (0.3 in) in length. All weevils are plant eaters and many are serious agricultural pests. Weevil larvae feed on all parts of plants, and adults feed on leaves, flowers, and developing fruit. Some species of weevils reproduce by parthenogenesis; no males of these species have been discovered. B Rove Beetles (Staphylinidae) Rove beetles, numbering more than 46,000 species, are probably named for their habit of roving through a wide variety of habitats searching for insects to eat. Various species search under stones and other objects, along shores of streams and lakes, onto flowers and carrion, into manure, and inside ant and termite nests. Some species gather in large numbers around lights that attract them. Others collect to prey on insects feeding on animal waste products or carcasses. Typically brown or black, rove beetles range from 2 to 20 mm (0.08 to 0.8 in) in length. They have shortened elytra that expose most or all of the abdomen. Rove beetles are excellent fliers. They have a distinctive gait, sometimes moving with the tip of the abdomen raised, which may fool predators into thinking that the beetle has a defensive sting. Large abdominal glands found in some adults and larvae secrete chemicals that defend against predators. C Ground Beetles (Carabidae) Scientists have identified around 40,000 species of ground beetles, making them one of the larger families of beetles. As their name suggests, most ground beetles are found in or on the ground, especially in gravelly areas near streams and rivers, under logs or bark, and in rotting wood. Many ground beetles do not fly and these species lack hind wings and have fused elytra. Some species, however, never touch the ground and spend their entire lives hunting for food in trees. Ground beetles range in size from 4 to 75 mm (0.2 to 3 in) or longer. Usually black or brown in color, some can have metallic green or blue hues. They often have a grooved pattern on the elytra. In most ground beetles, both the larvae and adult are predatory, feeding extensively on other insects and snails, as well as on insects and larvae that feed on dead animals and other organic debris. Tiger beetles, named for their predatory habit of pouncing on their prey suddenly, use their long, sharp mandibles (akin to the piercing canine teeth of tigers) to kill prey. Some farmers use ground beetles that feed on cutworms (moth larvae), caterpillars (butterfly larvae), grubs (beetle larvae), or maggots (fly larvae) to control crop pests. Many ground beetles protect themselves by secreting foul-smelling fluids from the hind end of the body. Bombardier beetles release a chemical compound as a vapor, which appears as a puff of smoke that temporarily blinds or repels predators. The release of the vapor makes a distinct popping sound. D Leaf Beetles (Chrysomelidae) Leaf beetles constitute another large family of beetles, numbering over 35,000 species. As their name suggests, the adults eat leaves of many plants. Females lay their eggs on the underside of leaves so that the larvae can feed on the leaves when they hatch. Scientists suspect that most broad-leaved plants have at least one species of leaf beetle that normally lives on that plant. The beetle's eating habits can be highly destructive. The elm-leaf beetle and its larvae can eat their way through the foliage of elm trees, while the Colorado potato beetle and its larvae threaten potato foliage and plants. Cucumber beetle larvae bore their way into the stems and roots of cucumber, squash, and pumpkin plants. Leaf beetles appear in so many diverse forms that scientists find it difficult to characterize their appearance. Beetles in this family range in length from 1 to 16 mm (0.04 to 0.63 in). Many leaf beetles are brightly colored in yellows, reds, or greens, sometimes in metallic hues; others are brown or black. In some species large spots or lengthwise stripes appear on the elytra. Species of leaf beetles known as flea beetles take their name from their remarkable jumping ability. The strong hind legs of these shiny beetles enable them to jump a distance of many times their own length. Some species of leaf beetles resemble ladybird beetles so closely that scientists often need to count the number of segments in the feet to distinguish a leaf beetle (five segments) from a ladybird (three segments). E Scarab Beetles (Scarabaeidae) There are nearly 31,000 species of scarabs, thickset beetles with dull brown or black colors or metallic green or blue hues. Some have interesting patterns of stripes, spots, or other markings. Scarabs range in size from tiny--2 mm (0.08 in)--to massive; the Eastern Hercules beetle (Dynastes tityus) reaches 152 mm (6 in) in length. Scarabs can be recognized by their lamellate (layered) antennae, which unfurl like a fan and give these beetles a well-developed sense of smell. Dung beetles, a group of scarab beetles that feed on animal dung, use their keen sense of smell to locate food. The dung beetle prepares a ball of dung in which to lay its eggs. Holding the ball between its hind legs and traveling backward, the beetle rolls the ball until it finds loose soil or sand good for burying the ball. The female then lays her eggs in the dung ball on which the larvae will feed. By digesting and disposing of dung, dung beetles speed the recycling of nutrients in the environment. Some Indian scarab species make very large balls of dung that they coat with clay before burying. Archaeologists have found these dung balls in semi-fossilized condition and mistaken them for ancient stone cannonballs. Early Egyptians were so impressed by the food-gathering ability of dung-rolling scarabs that they regarded them as sacred and believed that the Sun was rolled across the sky by a scarab. At least six different species of scarabs have been identified among ancient Egyptian drawings and images. Chafers are plant-eating members of the scarab family. The rose chafer, for example, feeds on the flowers and leaves of rose bushes, and its larvae feed on the roots. Another destructive, plant-eating chafer is the Japanese beetle, which eats the foliage and fruit of a variety of plants. June bugs, or June beetles, are common chafers in the United States. They are known as May beetles or May bugs in the Southern United States. Related species are known as Christmas beetles in Australia or southern Africa, because they are active in the summer months of the Southern Hemisphere, around Christmas time. F Longhorned Beetles (Cerambycidae) There are more than 20,000 species of longhorned beetles, which derive their name from their elongated antennae that may be several times the length of their body. These long antennae increase the beetle's sensory powers, helping it find food. Females use their antennae to locate a place near food to lay their eggs. The antennae may also help the beetles maintain their balance. Closely related to leaf beetles, longhorned beetles generally have a longer and narrower body. Some tropical species of longhorned beetles are bright green and blue, with a metallic luster, while others have colored stripes that enable them to hide on colorful tropical plants. Longhorned beetles can grow more than 18 cm (7 in) in length, excluding antennae. All longhorned beetles are plant eaters. Many only feed on dead or dying trees, and these species help recycle wood tissue back into the soil. Some longhorned beetles feed on live trees and cause significant damage: an infestation can kill a tree and destroy timber. Larvae bore deep into wood to feed, tunnel into bark to pupate, and the adult beetles chew their way out. In the process the beetles can create holes larger than the diameter of a pencil in the heartwood, piercing the tissues that carry water from the tree's roots to its leaves and eventually killing the tree. Because the life cycle of some longhorned beetles lasts several years, adult beetles may emerge years later after lumber from the tree has been used in building construction. A species of longhorned beetle native to India commonly lives in the wood used for making pianos. As the larvae tunnel through the wood, they sometimes cause the piano strings to sound at night, leading to tales of ghosts. Asian longhorned beetles made their way to the United States in a 1996 shipment from China with wood packing materials. Because these beetles are so destructive and have no natural predators in the United States, the U.S. Department of Agriculture placed under quarantine areas in which the beetles were found. The quarantine prohibits the removal of infected wood from the area, to prevent the spread of the beetles. G Darkling Beetles (Tenebrionidae) There are about 19,000 species of darkling beetles, so named because most species are dark brown or black and many are active after dark. They range in length from 13 to 50 mm (0.5 to 2 in). Many species have spiny projections on the body. Their most recognizable feature is a ridge along the head, beneath which the eyes lie. Many species of darkling beetles live in or on the ground, in rotting wood, under logs and stones, or in ant and termite nests. Some species are common in deserts and other dry areas. Their fused front wings prevent them from flying and also protect them from drying out. Most darkling beetles are scavengers, feeding on decaying vegetation, dung, and seeds. A few, such as the flour beetle, are pests of cereal products in storage. Many darkling beetles emit a dark-colored, foul-smelling fluid when threatened by predators. Pet stores commonly sell darkling beetle larvae as food for pet reptiles. H Metallic Wood Borers (Buprestidae) There are nearly 15,000 species of metallic wood borers, also known as jewel beetles. Most species have a distinctive metallic copper, green, blue, or black color, which makes jewel beetles among the most beautiful of all insects. This bright, shiny coloring helps them escape detection among the flora of humid, tropical habitats. The males and females of many species are different colors. The range of size within this family is quite incredible. The largest tropical wood-boring species grows up to 12 cm (5 in) long, whereas a small, triangular leaf-mining species reaches only a few millimeters in length. All metallic wood borer larvae feed on plants. Most of these larvae have a flattened head and thorax that helps them bore beneath bark and tunnel through the wood of dead and dying trees. The adults of some species have special sensory structures that perceive infrared light, and these beetles are attracted to wildfires, laying their eggs in burned trees. In Australia, many species feed on the nectar of plants in the Eucalyptus family and have mouthparts modified into a primitive siphon for that purpose. Some metallic wood borers can cause extensive damage to the lumber industry, particularly when foreign species are introduced into new areas where they lack natural predators. In 2002 scientists discovered that a metallic wood borer from Asia had been introduced in Michigan. Known as the emerald ash borer (Agrilus planipennis), the beetle attacks ash trees and forestry experts are concerned that the beetle may become a serious pest. I Click Beetles (Elateridae) The 10,000 species of click beetles derive their name from the clicking noise produced by a hingelike structure on their elytra. When the beetle falls on its back, it arches and quickly straightens its hinged back, producing the clicking sound and pushing itself into the air to right itself. Most click beetles range in length from 5 to 50 mm (0.2 to 2 in). They are brown, black, or metallic green in color, with grooves along the elytra. Their antennae have saw-toothed segments. Adult click beetles feed on the foliage of trees and bushes, and sometimes under bark or in rotten wood. The yellow or brown larvae live in clay and sandy soils where they eat roots, underground stems, and bulbs. Click beetle larvae are known as wireworms. In some species, wireworms are a significant agricultural pest, causing extensive damage to tobacco, cotton, potatoes, corn, and beans. Unusual click beetles found in tropical regions of North and South America emit a bright light from organs on each side of their thorax. Even their eggs and larvae emit light. These beetles, which belong to the genus Pyrophorus ("firebearer"), are sometimes called fireflies. But the fireflies most commonly seen in North America are members of the family Lampyridae. J Ladybird Beetles (Coccinellidae) Ladybird beetles, also known as ladybugs, are some of the best recognized and most beneficial of all beetles. The adults and larvae of most species prey on common agricultural pests, including scale insects, aphids, other insect eggs and larvae, and mites, and farmers often use these beetles to control crop damage from such pests. There are more than 6,000 species of ladybird beetles. Adult ladybird beetles are broad, rounded insects, ranging in length from 2.5 to 13 mm (0.1 to 0.5 in). Many of them have red or orange elytra with black spots, and antennae that are slightly club-shaped. Ladybird larvae are usually black with spots or bands of red or yellow. When ladybird larvae pupate, they hang head downward on their host plants. K Predacious Diving Beetles (Dytiscidae) Aquatic both as larvae and as adults, the 4,000 species of predacious diving beetles live in small, shallow bodies of water with little or no current, such as small ponds and edges of lakes and streams. Adult diving beetles have a smoothly rounded, streamlined form suited for diving and swimming. The adults are active in daytime and spend most of their time under water. They breathe air that they trap beneath their elytra before diving. Ranging in length from 1 to 50 mm (0.04 to 2 in), predacious diving beetles are black or dark brown in color, sometimes with yellow or light markings. Adults and larvae feed on dragonfly and damselfly nymphs (larvae) and other aquatic animals. Larvae of diving beetles also prey on tadpoles and small fish. The larvae insert their hollow mandibles into their prey and inject digestive fluids to liquefy the prey's tissues. They then suck the digested tissue back through the mandibles. Most species of predacious diving beetle can fly and tend to fly toward light. When they migrate in search of new watering holes, they locate water by moonlight reflected off it. Artificial street lighting can confuse these beetles, causing them to congregate in large numbers on city sidewalks at night. They soon fly on to find water. L Fireflies (Lampyridae) There are about 2,000 species of fireflies, which are also known as lightning bugs and glowworm beetles. These insects are named for their light-producing ability. Luminous organs in the adult beetle's abdomen emit flashing lights that play a role in courtship. Each species has a distinctive pattern of flashes. At night a male will flash in flight and look for answering flashes from a female of his species on the ground. Some firefly species flash weakly or not at all. These beetles are more active during the day. Some female fireflies mimic the flashing pattern of other species and then prey on the unsuspecting beetles attracted to the flashes. Adult fireflies have elongated, relatively soft bodies that grow as long as 2.5 cm (1 in). Most adult female fireflies resemble the males, but some females, known as glowworms, have short wings or none at all and look like larvae. Firefly larvae have hollow mandibles that they use to inject digestive chemicals into prey, mostly snails. They then suck up the liquefied body parts of the prey through their mandibles. M Hide Beetles (Dermestidae) There are about 700 species of hide beetles, named for their habit of consuming hides, skins, and other soft animal remains, as well as carpets, silk, dried meats, dead insects, stuffed animal specimens, and other animal products. Adults of some hide beetle species, such as carpet beetles, even infest and destroy insect collections that are not safeguarded with protective chemicals. Most hide beetle larvae live on rotting animal carcasses, but the larvae of some species can cause extensive damage to food in pantries, carpets, furs, skins, and woolen clothing. These larvae molt frequently, and piles of molted skin often provide the first sign of their presence. Most hide beetles are relatively small, rarely growing beyond 12 mm (0.5 in). Scales of different colors--typically brown, black, white, or orange--give many species a mottled appearance. The short, clubbed antennae may be withdrawn into grooves in the body. N Whirligig Beetles (Gyrinidae) Scientists have identified about 700 species of whirligig beetles. Also known as waltzing beetles or scuttle bugs, whirligig beetles are so named because adults rapidly whirl or gyrate on the water's surface at the edges of rivers and lakes. Their hind legs beat up to 60 times per second to propel them across the water's surface or underneath the surface in search of prey. Whirligig beetles are also skillful divers. After they submerge, they breathe a bubble of air trapped under the elytra. Oval-shaped with flattened bodies, whirligig beetles resemble the black seeds of apples and range in length from 3 to 15 mm (0.1 to 0.6 in). They are the only beetles to use the surface tension of water for support to stay afloat. Whirligig beetles have an interesting adaptation to aquatic life. They have two pairs of eyes--one pair of eyes can see above the surface of the water, and the other pair can see underwater, enabling them to watch for predators and for prey both above and below the surface of the water. Adults scavenge on decaying plants and animals, while larvae prey on other aquatic insect larvae. Whirligig beetles often congregate in groups in sheltered areas. Most fly and migrate from one body of water to another, usually in the fall. O Carrion Beetles (Silphidae) Scientists have described about 175 species of carrion beetles. As their name implies, the adults feed on decaying animal matter or on the maggots that feed on carrion. Most carrion beetle larvae feed on dead animals, but some also feed on plants, such as spinach and beets, causing crop damage. Among the best-known members of this family are the large black and orange beetles of the genus Nicrophorus, sometimes known as sexton beetles. Sexton beetles lay their eggs on the carcasses of small vertebrate animals, such as mice, which they then bury. Burial prevents the carcass from drying out before the larvae have consumed it. Carrion beetles range in length from 3 to 38 mm (0.1 to 1.5 in). Unlike the conspicuous sexton beetles, most species in this family are dull black with a rough surface. Some species live in ant nests; others lack eyes and live in caves. Scientific classification: Beetles are classified in the phylum Arthropoda, class Insecta, order Coleoptera. Reviewed By: Charles L. Bellamy Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.