My Science School

          Many birds have beautiful colours or feather displays. In many species, it is the males that are brightly coloured, to attract females. Females are duller in colour, for camouflage while nesting. Camouflage is also used by both sexes of some birds to avoid predators, or to hunt more effectively.

          Bee-eaters and kingfishers are small birds, often with jewel-like colours. As their name suggests, bee-eaters feed on bees, wasps and other insects. Before swallowing their prey, they crush the sting by smashing it on a branch. Kingfishers sit on branches over stretches of water, diving in to catch small fish in their beaks.

          The long-legged storks and herons also feed on fish, though some large storks are carrion-eaters. Most storks and herons are wading birds, standing in the shallows and snapping up fish in their long beaks. Their relatives, the flamingos, get their pink colour from the tiny plant and animal material in the water on which they feed.

          Hummingbirds and swifts are excellent flyers. They are small birds with long, pointed wings. Swifts can mate, feed on flying insects, and even sleep on the wing.

          Many members of the cuckoo family lay their eggs in the nest of a different species. After hatching, young cuckoos often kill their “true” nest mates. The hoatzin is probably related to the cuckoos. It nests over Rainforest Rivers. If attacked, the young drop into the water, then climb back up to the nest using sharp claws on their wings.

 

 

          With over 5000 species, the perching birds are the largest group of birds. They range in size from the tiny blue tit or wren to the large raven. They are land-living birds, with four unwebbed toes, three pointing forward and one backward. Most feed on seeds or insects, but some eat fruit or nectar. Many small perching birds fly in a bounding motion to save energy, flapping and closing their wings alternately.

 

 

 

          Most perching birds also belong to a sub-group called the songbirds. Though other birds can make short, simple calls, songbirds have extra muscles in their voice-boxes, allowing them to produce complex patterns of notes. Songs are used by males to establish territories and warn off intruders, as well as to attract females. Each species may have a large number of song variations, with birds from different areas having their own “accents”. Young songbirds learn songs from their parents and other adults.

          Most perching birds construct nests in trees or hedges, where their young will be safe from predators. The young are born naked, blind and helpless. They need to be kept warm and fed by their parents until they are old enough to fledge (leave the nest). Other birds such as ducks, gulls or game-birds, that lay their eggs in more exposed places, hatch out as fully-feathered young that can feed themselves almost straight away.

          Many songbirds, like other groups of birds, migrate to warmer places in the winter when food becomes scarce. They feed heavily before migration, laying down stores of fat for fuel on their long journeys. They return in the spring to breed, when there is a plentiful supply of food for themselves and their young.

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          Over millions of years, the ability to fly has enabled birds to escape from predators, and therefore to increase in number and variety. Every kind of bird has also adapted to survive in a particular habitat. In any one group of birds there may be several different families, all looking quite different from each other.

          The ratites include the ostrich, rhea, emu, cassowary and kiwi. They are all birds that have lost the ability to fly, because of a lack of natural predators, or because they have developed another means of defence. Some ratites are tall, long-necked birds that live in wide open spaces. They use their good eyesight to spot predators, and their long strong legs to run away at top speed. Ostriches can reach 65 kilometres per hour.

          Kiwis are much smaller birds, with hair-like feathers. They live in thick undergrowth, using their excellent senses of smell and hearing to detect predators, and their sharp claws for defence.

 

 

 

        Penguins are also flightless birds. Most live on cold, southern coastlines, such as Antarctica. Clumsy on land, in the water penguins are graceful and fast. Their stiff, flipper-like wings pull them through the water in pursuit of fish and squid. They breed in large colonies on land or on ice.

 

 

 

 

        Waterfowl (ducks, geese and swans) also feed in the water, as do grebes and divers, though these are mostly freshwater birds. They swim along the surface with their feet, which are often webbed. Their feathers are coated with a waterproof substance that traps air and keeps the birds afloat. Ducks tip upside down to feed, while grebes and divers plunge completely underwater. These birds feed on fish, invertebrates and plants.

 

 

 

 

 

 

 

          Birds of prey include eagles, falcons, hawks and vultures. They are all meat-eating birds, with sharp, hooked beaks and strong talons. They swoop down through the air, often at very high speeds, on to their prey - small mammals, birds, reptiles, insects or fish. Most birds of prey, especially the vultures, also eat carrion. Birds of prey have excellent long-distance vision, and can spot potential prey from several kilometres away.

 

 

 

 

 

 

          Though they are also hunting birds with strong beaks and talons, owls are a completely separate group to the birds of prey. Owls have flat faces with forward-facing eyes. Many kinds hunt in dim light or darkness. Their disc-like faces “collect” sound and direct it towards the ears, giving them exceptional hearing to locate their prey. Their feathers are soft, allowing them to fly almost completely silently, taking their prey by surprise.

 

 

 

 

 

          Seabirds spend much of their time in or near the water, feeding on fish or squid. Some kinds, such as cormorants or gannets, dive into the water from the air, or from high rocks. Albatrosses skim over the surface, scooping up food. Many seabirds gather together in colonies on cliffs to lay their eggs. Albatrosses and petrels only come on to land to breed. The rest of their lives are spent gliding on currents of air.

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          The ancestors of birds were clearly reptiles - birds still have scaly legs, and they lay hard-shelled eggs. In fact, it is now known that birds are actually the living descendants of the dinosaurs.

          Like the dinosaurs, early birds had teeth, fingers and a long, bony tail, but they also had small wings and a few feathers. They may have used their wings to glide from tree to tree, or to give them extra speed when escaping from predators on the ground. Gradually, their body structures developed so that they could lift themselves into the air and fly.

 

 

          Archaeopteryx emerged in the late Jurassic Period, about 150 million years ago. Following Archaeopteryx came small flying birds such as Sinornis, which had shorter, more bird-like tails than Archaeopteryx. Up until the end of the Cretaceous Period, 65 million years ago, most birds still had teeth. These were useful for feeding on fish and insects, their main prey. Ichthyornis and Hesperornis were among the first marine birds and fed on fish, swooping over the waves like gulls or diving from rocks.

          At the end of the Cretaceous Period, the dinosaurs, along with many other reptiles died out, but many birds and mammals survived. A wide variety of different kinds of birds appeared, and by Eocene times, 50 million years ago, all the bird groups we know today had emerged.

          After the dinosaurs died out, some birds became large predators. Some kinds stood almost three metres tall. They were flightless, their small wings acting only to balance their heavy bodies. Ferocious meat-eaters, such as Andalgalornis and Diatryma, probably crushed mammals such as small, early horses in their powerful jaws. Other birds, such as Argentavis, a vulture with a seven-metre wingspan, were scavengers.

          Some kinds of birds have become extinct quite recently, due to the arrival of humans into their habitats. They were hunted for food, or preyed upon by rats, cats and dogs which the humans brought with them. Two groups of large, flightless birds, the elephant birds of Madagascar and the moas of New Zealand, were completely wiped out within just a few hundred years.

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            There are almost 9000 species of birds in the world today. Birds are warm-blooded, vertebrate animals with four limbs, two of which are adapted into wings. They have a toothless beak and a covering of feathers over their bodies and heads (apart from the bald-headed vultures). The feathers close to the skin are soft and fluffy for warmth, while long, stiff outer feathers help birds to gain height, steer and control speed when flying. Birds have light, hollow bones to reduce their weight in the air.

 

 

 

 

 

 

 

          Birds lay hard-shelled eggs, usually several at a time. After mating, the male and female often work together to build a nest ready to receive the eggs. Nests can be cup-like structures made of mud, grass and twigs, holes in trees, or even burrows underground. One parent usually sits on the eggs to keep them warm, while the other collects food. After hatching, most birds feed and protect their young until they are old enough to leave the nest.

          Because of their ability to fly at speed for long distances, some kinds of birds are able to migrate to warmer climates as winter approaches. They return to their breeding areas in spring, as food becomes plentiful.

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          Lizards are mostly quite small, quick-moving reptiles. They have a thick, scaly, and usually smooth skin. Most lizards have four legs and a tail, though some kinds are legless. They have long tongues that they flick in and out to “taste” the air or ground, to pick up information about their surroundings. Geckos also use their tongues to clean their permanently closed, transparent eyelids, while chameleons shoot theirs out to catch insects.

          Lizards have a special receptor on their heads that is sensitive to light. This is connected to the brain, and may act as a “third eye”, giving the lizard information about the patterns of day and night.

          Lizards are mostly land-dwellers, living all over the world except in Polar Regions. Some are burrowing animals, while many live in trees. Chameleons and some iguanas have prehensile tails to help them climb. Geckos have tiny ridges on their toes and can even walk upside down. Some lizards, such as skinks, are good swimmers, and will dive into the water to escape from predators.

          Almost all lizards are meat-eaters, feeding on insects, birds, small mammals and other reptiles. The largest lizard, the Komodo dragon, can reach three metres in length. It is a powerful predator, and can kill large mammals such as cattle. It has even been known to attack and kill humans.

          Lizards lay their eggs in warm, damp holes. Most female lizards take no interest in their eggs after laying them, but a few kinds guard the eggs until they hatch.

          The smaller lizards have many predators. They defend themselves with camouflage, or by running away, climbing trees or even playing dead. Several species are able to break off their own tails, to confuse an attacker while they run away. The tail has a special “weak point” that can be snapped without harming the lizard. A new tail will grow in its place.

          Snakes are a group of reptiles that have long, narrow bodies and tails, and no limbs. Their ancestors, however, were four-legged, lizard-like creatures. Some snakes have two tiny lumps on their bodies - the remains of the hind legs of these ancestors. Snakes have no eyelids. Instead, their eyes have a permanent, transparent covering.

          Snakes have many more bones in their spines than other animals. They move by flexing their belly muscles, which are attached to their many ribs. As they move, most snakes curve their bodies into a series of S-shapes, giving them greater speed.

          Most snakes lay eggs, and a few kinds will guard them from predators until they hatch. There are some snakes, such as sea snakes that give birth to live young. Young snakes are left to survive on their own.

          All snakes are carnivores. Some kinds eat small animals such as snails or worms, but many feed on large prey such as frogs, birds and mammals. Snakes have special loosely hinged jaws that can open extremely wide to take large prey. Their skin can also stretch. They swallow their prey whole, using their sharp teeth to pull it into the throat, and their muscles to squeeze it into the stomach. A snake may need to hunt and feed only every few weeks or even months.

          Some snakes have good vision, but most rely on special senses to hunt their prey. Like lizards, snakes are able to collect “tastes” from the air or ground by flicking out their forked tongues. Some kinds of snakes also have heat sensors on their heads that help them to locate live prey accurately, even at night.

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          The main characteristic that sets turtles and tortoises apart from other reptiles is their shell. It is made of bone fused to the skeleton, and covers both the back and belly. For extra protection, the shell is covered with thick, horny scales. If threatened, most turtles and tortoises are able to draw their heads and necks backwards into their shells.

          Turtles and tortoises do not have teeth. Instead they have a sharp, horny, beak-like mouth. They are mostly plant-eaters, but some kinds also feed on insects, fish, snails and even small mammals and birds.

         Tortoises are found on land. They have stumpy, scaly legs with short toes. Tortoises move slowly, relying on their high-domed, heavy shells to protect them from predator. Turtles live in the water, some in the oceans and others in freshwater rivers and ponds. Most have webbed feet, but some ocean turtles spend so much time in the water that they have developed paddle-like flippers that allow them to swim at speed.

         All turtles and tortoises breed and lay eggs on land. Some large sea turtles can lay over 100 eggs at once, returning to the same beaches every year. They dig holes in the sand, lay their eggs and then cover them over. Then they return to the water. After hatching, the young must dig their way to the surface. Many newly-hatched turtles are killed by predators as they make their way from the beach to the sea.

 

 

          Crocodilians are meat-eating reptiles that spend much of their time in water. They include crocodiles and alligators, and also the gharial, which has a long, narrow snout. Crocodilians use their long tails to swim, but can also run at speed on land. Most species live in freshwater rivers and lakes, especially tropical swamps. A few, such as the saltwater crocodile, live in sea estuaries.

          Crocodilians feed on a wide range of prey, including fish, turtles, birds, and mammals. The largest crocodiles, which can grow to more than seven metres long, will even kill deer and cattle. They lie in the water, waiting for their prey to come down to the water to drink. Then they lunge out with their powerful jaws, dragging their prey into the water to drown.

          Crocodilians can lie with their bodies almost completely hidden underwater, because their eyes and nostrils are on top of their heads. They also have a transparent “third eyelid” which closes to protect their eyes when they submerge. They can close off part of their throat to avoid swallowing water while feeding.

          Like all reptiles, crocodiles and alligators lay their eggs on land. Some kinds, such as the Nile crocodile, dig holes into which they lay their eggs, covering them over with soil to keep them warm. Others build nests of plant material. They will guard their eggs and defend their young.

 

          The tuatara is the only member of an ancient group of reptiles that lived on Earth even before the dinosaurs. Lizard-like in shape, the tuatara lives in burrows on small islands off New Zealand. It basks in the sun during the day, and feeds at night, hunting insects, worms and small lizards.

          Like turtles and tortoises, the tuatara is very long-lived. It becomes an adult at 20 years old, and may live for over 120 years.

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          Reptiles are cold-blooded, vertebrate animals that have a dry, scaly skin. The skin is made of one continuous sheet, rather than individual scales as in fish. Water cannot pass out through their skin, unlike that of amphibians. This means that reptiles do not need to keep their skin moist. Reptiles moult regularly, shedding their skin when a new one has grown underneath.

          Because they are cold-blooded animals, reptiles need to bask in the sun to raise their body temperature before they are able to move about in search of food. However, they do not need to eat as much food as the warm-blooded birds and mammals, so are able to survive more easily in harsh desert environments. Most reptiles lay eggs, either soft and leathery, or hard-shelled. Some give birth to live young. Reptiles do not care for their young after hatching or birth.

          Reptiles are descended from the early amphibians. The first reptiles were probably small, lizard-like creatures. Unlike the amphibians, they did not have to stay close to water to keep moist and lay their eggs. They were able to live more easily on land. The lizards, turtles and tortoises and the crocodilians (crocodiles and alligators), appeared during the Triassic Period, about 250 million years ago. Snakes evolved later, about 135 million years ago. Some modern-day reptiles have hardly changed since the time of the dinosaurs.

 

THE AGE OF DINOSAURS

          The period from 250 million to 65 million years ago is known as the Mesozoic Era. During this time, a new group of reptiles, the dinosaurs, emerged. They held their legs straight beneath their bodies, rather than sprawling out to the sides like other reptiles.

          For about 150 million years the dinosaurs were the only large land animals. They ranged in size from the chicken-sized Compsognathus to the 14-metre-tall Brachiosaurus. Some were slow, four-legged plant-eaters, while others ran swiftly on two legs. A few kinds were terrifying predators. Many of the plant-eaters lived in herds like modern-day cattle or horses, while the smaller predators hunted in packs, as hyenas and wild dogs do today.

          The dinosaurs all died out quite suddenly, but no-one knows why. Perhaps a huge asteroid hit the Earth, and a dust cloud plunged the Earth into cold darkness.

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          Amphibians are a small group of cold-blooded, vertebrate animals. They include two main groups: the salamanders and newts, and the frogs and toads. The word “amphibian” means “double life”. Most amphibians spend the first part of their lives underwater, taking in oxygen from the water through gills, like fish. Their adult lives, however, are spent on land, breathing air through lungs. They return to the water to lay their eggs.

          Most amphibians have four limbs. Only the salamanders and newts have tails. All amphibians have moist skin, through which they can “breathe in” oxygen in the water. They can also take in or lose water from their bodies through their skin. Because they need to keep their skin moist, most amphibians spend much of their time in cool, damp conditions. Many live in or near water, even as adults.

          Amphibians undergo metamorphosis, a change in the body from young to adult. The most obvious change in salamanders and newts is that they lose their feathery gills and develop lungs. Frogs and toads change from plant-eating tadpoles with gills, a tail and no legs, to carnivorous, tail-less adults with lungs and long legs.

 

 

 

SALAMANDERS AND NEWTS

          Salamanders and newts are long-bodied amphibians with long tails. They are often nocturnal, and are all carnivorous. They feed on insects, worms, slugs and snails, and the young also prey on frog tadpoles. Some salamanders live in water all the time, and several even keep their gills into adulthood. Others live on land but return to the water to lay their eggs. Newts will travel several kilometres to return to the breeding ponds where they grew up.

 

 

 

 

 

FROGS AND TOADS

          Frogs and toads have short, tail-less bodies and long hind legs. Frogs are usually smooth-skinned. They spend most of their time in water. Their very long legs and streamlined bodies mean that they can make huge leaps and swim quickly. Toads have shorter legs, fatter bodies and lumpier skin. They live mostly on land, in dark, damp places to keep their skins moist and cool. Toads crawl or hop rather than leap.

          Both frogs and toads usually lay their jelly-like eggs (spawn) in water, often returning to the same pond or lake year after year to breed. Some tree frogs lay their eggs inside a foam “nest” on an overhanging branch, so that when the tadpoles hatch, they will fall into the water. Many frogs and toads leave their eggs to hatch on their own. Others carry them on their backs to keep them safe. Mouth-brooding frogs hold their tadpoles in a throat sac, until they jump out as tiny frogs.

          Frog and toad tadpoles mostly feed on water plants or filter algae from the water. As adults, however, they are carnivorous, feeding on insects, snails or worms. The larger frogs and toads will also eat fish, other frogs, and even small mammals.

          In hot climates, toads and frogs burrow underground to avoid the heat of the day. Frogs that live in colder climates often spend winter in hibernation at the bottom of ponds, breathing through their skin.

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          Forming a much larger group than the cartilaginous fish, bony fish have skeletons made of bone. Their bodies are usually covered with overlapping scales. They also have gas-filled swim bladders inside their bodies that allow them to stay afloat even when they are not moving.

          Some bony fish live in fresh water (rivers and lakes), while others live in the seas and oceans. Many feed on plant material, but some are carnivorous. Among the largest predators are the barracudas, which strike at great speed with their powerful jaws. Even larger is the blue marlin, which can be over four metres in length. Probably the most extraordinary of the large bony fish is the ocean sunfish, or mola mola. Its round body can be as large as a small car, and it “rows” itself through the water using its fins.

          Most bony fish have good eyesight, and can see in colour. Their eyes are on the sides of their heads, giving them a wide field of vision. Some kinds of bottom-dwelling fish have eyes that point upwards, to spot predators or prey above them. Fish such as salmon, which are preyed upon by many other animals, swim in large groups for protection in the same way as some animals, for example, cattle, herd together on land.

          Seahorses rely on camouflage to keep themselves safe, while angelfish stay near clumps of seaweed or rocks. Some fish hide in the stinging tentacles of sea anemones.

 

 

          Several kinds of fish have protective armour made of fused scales, while others have sharp spines. Bright colours are often a warning signal to predators. The markings of the lionfish warn that its long, sharp spines are poisonous. Other fish inflate their bodies suddenly to startle an attacker.

          Most fish have a familiar streamlined body shape, but several kinds look very different. Eels have long bodies with narrow dorsal fins that do not stick out from their bodies like those of other fish. Seahorses live in shallow waters and swim upright. They grasp on to seaweed with their tails to avoid being swept away by the current.

          Many ocean-living fish are found close to the surface, where there is warmth and light and tiny plants, called plankton, to eat. Small plankton-eating fish may be prey for larger fish.

          Fewer fish live in the deeper, darker waters. The oarfish lives between 300 and 600 metres down. With its ribbon-like body and red “mane”, it may be the sea monster described in old sea legends. Some deep-living fish travel up through the water to hunt, while others feed on scraps of food that drift down from the surface. Some deep-living fish are able to make their own small lights to attract prey towards their gaping mouths.

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          Fish are vertebrates (animals with backbones). They live in water all the time. Most kinds cannot survive out of water, because they do not have lungs to breathe air. Instead, they take in oxygen from the water using gills in their heads.

          Fish have hairless, streamlined bodies with fins and a tail. Many have a protective layer of overlapping scales. Fish are cold-blooded animals, so their body temperature depends on their surroundings. Some species have a special substance in their blood to stop them freezing in cold waters.

          Fish move by flexing the muscles along their bodies in a wave-like motion. The fins help to balance and steer the fish while the tail can be used for propulsion. The streamlined shape of most fish, as well as a coating of slimy mucus on their bodies, helps them to swim easily through the water.

          Most fish lay vast numbers of eggs at once, which they leave to hatch out on their own. Newly-hatched fish are perfect, tiny replicas of their parents. A few kinds of fish, such as sharks, carry their eggs inside their bodies, and give birth to live young.

          Fish were the first vertebrates to evolve, millions of years ago. One of the oldest types alive today is the coelacanth, fossils of which date back 90 million years.

          There are two main groups of fish, the cartilaginous fish and the bony fish. Cartilaginous fish include sharks, rays and chimaeras. Most are found only in the seas and oceans. Cartilaginous fish have skeletons made of soft cartilage. Instead of flat, overlapping scales, they have tiny, pointed, tooth-like scales. Their gills can be opened and closed, but, unlike the bony fish, usually do not have protective flaps covering them. Cartilaginous fish must keep moving all the time, to stay afloat in the water.

 

 

 

          Sharks are mostly predators, although the largest kinds of all, the whale shark and the basking shark, feed only on plankton, which they filter from the water using a part of their gills. Unlike bony fish, most of which have good vision, sharks rely on smell to hunt their prey. Sharks can detect a single drop of blood in a huge volume of water. They also have sensors on their bodies that can pick up tiny electrical signals produced by the movements of their prey.

 

 

          Sharks have large, razor-sharp teeth, which arc set in rows. If the shark loses a tooth during feeding, a new one comes forward in the mouth to take its place. Most sharks feed on fish or squid, but the larger sharks, such as the great white, also eat turtles and large mammals such as seals. They slam into their prey, tearing out huge chunks of flesh. Despite their fearsome reputation, only the largest of the predatory sharks, such as the tiger shark or the great white shark, are dangerous to humans.

 

 

          Rays, and their relatives the skates, are cartilaginous fish with flat bodies and often long, narrow tails. Their gills and mouths are on their undersides. They have large, wing-like fins that they flap as they swim, making them look as if they are flying through the water. Rays feed on fish and shellfish near the sea bed. Sometimes they hide in the sand to ambush passing prey.

          Like sharks, a few kinds of rays can be dangerous. Torpedo rays can give off a powerful electric shock, while a jab from the venomous spine on a stingray’s tail can kill a human. Unlike sharks, however, rays do not see humans as prey.

          Chimaeras are a group of cartilaginous fish with long bodies and tails. They include the rabbit fish, a bottom-dwelling fish with large eyes and a venomous spine on its dorsal fin.

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          Spiders and scorpions are arachnids. They differ from insects because they have two, rather than three, body sections, eight legs instead of six and no antennae or wings. Most arachnids also have eight simple eyes and no compound eyes. They rely more on sound than sight. Most have bristles on their legs that are sensitive to vibrations in the air or through the ground.

          Arachnids feed by piercing their prey with their sharp fangs, paralyzing or killing it. Their saliva turns the body tissues of the prey into liquid that can then be sucked up.

 

          Spiders are carnivores, feeding mainly on insects and other spiders. Many spiders use webs to catch their prey. Any insect that flies into a web is caught in the strands, which are often sticky. As the insect struggles to free itself, the spider, sitting at the edge of the web, feels the vibrations and comes to claim its prey. It avoids becoming caught in the threads itself by walking on the claw-like tips of its feet.

 

 

 

 

          Silk is used by the spider for many other purposes besides forming webs. It can be a safety line when jumping, be woven into a sac by a female to hold her eggs, or used to wrap up prey before feeding.

           All spiders have poisonous venom, which they use to paralyze or kill their prey. Some, such as the black widow spider, are so poisonous that they can kill humans.

 

 

 

SCORPIONS

          Scorpions have a sharp sting on the end of their tail-like abdomen that injects poison into their prey. It is also used for defence. Like other arachnids, scorpions have an extra pair of “limbs” either side of their jaws. These form large pincers for the scorpion to grasp its prey. After hatching, young scorpions climb up their mother’s pincers on to her back, where they are carried until they shed their skins for the first time and become independent.

 

 

 

MYRIAPODS

          Myriapods are a group of arthropods that includes centipedes and millipedes. Myriapods have long bodies made up of segments, and as many as 200 pairs of legs. They must live in dark, damp places because their bodies easily dry out.

          Millipedes have short, strong legs for burrowing through soil or dead leaves. Most feed on plant material, chewing with their strong jaws. Centipedes are carnivorous predators. Most have longer legs than the millipedes, and can scuttle at great speed after their prey. They use the large “poison-claws” on their heads to capture and paralyze their prey before eating it.

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            Like termites, ants live in large colonies with a winged queen and king, wingless workers, and sometimes soldier ants. Their nests have separate chambers for eggs, larvae and sometimes even food stores.

 

 

 

 

 

          Bees nest underground or in hollow trees and other small spaces. They feed on pollen and nectar which they collect from flowers using their long tongues.

 

 

 

 

          Wasps are carnivores. Some solitary-living wasps lay their eggs on or inside hosts, often butterfly or moth caterpillars. The larvae feed on the host as they grow, usually killing it in the process. Other wasps build nests from mud, or paper nests made out of chewed-up wood. These kinds of wasps bring their insect prey to the nest to be fed to the grub-like larvae.

            Unlike a queen bee, which always has workers in attendance, a queen wasp finds a nest site by herself and raises the first brood of workers. The workers then continue the nest-building and other tasks.

          The black and yellow stripes of bees and wasps are a warning sign to predators. Both bees and wasps have a sharp, pointed sting on their abdomen which injects painful venom into an attacker’s skin. Honeybees defending their nests are able to sting only once, as the act of stinging also kills them.

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          The largest and most successful groups of insects are the beetles. All beetles have two pairs of wings, but only the back pairs are used for flying. The front wings, called the elytra, form a hard, protective case. This fold over the fragile back wings when the beetle is on the ground. As the beetle takes off, the elytra open. Some beetles do not fly at all, so their elytra are fused together.

          The hard elytra are good protection against predators. Many beetles also have other methods of defence, such as squirting poisonous chemicals at their attackers, or startling them with loud noises.

          Beetles hatch from their eggs as grub-like larvae. They grow and then pupate, emerging as fully-grown adults. Some plant-eating beetle larvae are legless grubs, while predatory beetle larvae have large jaws and legs which they use to catch their prey.

 

 

 

          Fleas live on or near the bodies of animals, feeding on their blood and so often spreading diseases from one animal to another. Fleas carried on the bodies of rats were responsible for the plague in the 14th century, known as the Black Death. Fleas have a powerful “trigger” in their hind legs that allows them to travel over 100 times their own length in a single leap.

 

 

 

 

          Some flies also feed on blood, biting animals and humans and spreading disease. However, most flies are very useful insects. Many help to pollinate flowers by feeding on nectar and pollen, while others are scavengers. They actually help to keep our environment clean and healthy, by feeding on dung or rotting material such as dead plants and animals.

 

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          There are more kinds of insects in the world than all other animals put together. They live in every environment apart from the oceans. Some are pests, eating crops or spreading diseases, while others are vital to the survival of plants and animals. Many insects spread pollen between plants, helping them to reproduce. They are also prey for many animals, so are an important part of the food chain.

          Insects can run at speed, jump incredible distances, swim and fly. Dragonflies are among the best flyers. They are able to fly at speeds of over 50 kilometres per hour, carry out split-second changes of pace and direction, hover and even fly backwards. Dragonflies feed on other insects, chasing them through the air and catching them with their legs, or plucking them off plants.

          Dragonflies live near rivers, streams and ponds. Males patrol their territory and chase rivals away. Dragonfly young (nymphs) live in the water, feeding on tiny fish, tadpoles and other insects. They climb out of the water just before they shed their skin for the last time to become adults.

 

 

 

          Cockroaches are extremely adaptable insects. They can live almost anywhere and many will eat any kind of food they can find. Some are tree-dwellers and have wings, while other, wingless kinds burrow into the ground or hide in small spaces, coming out to feed. Some kinds are found in houses, where they eat our food and spread germs and diseases.

 

 

 

 

 

 

 

        Some kinds of grasshoppers, known as locusts, are also pests. They mass together and can eat whole crop-fields. Most grasshoppers and crickets, however, are better known for their loud, chirping songs. These are usually made by the males to attract females, and are produced by rubbing both wings, or a leg and a wing, together.

 

 

 

 

 

 

           Some insects are plant-eaters; others are carnivorous, feeding on other insects or small animals. The mantis is a formidable predator. It sits, camouflaged and completely motionless, waiting for its prey to approach. Then the mantis strikes, grasping the prey between its sharp, spiny front legs before bringing it up to its jaws.

 

 

 

 

 

 

 

          Stick and leaf insects are also masters of disguise, although their camouflage is used to hide from predators rather than for hunting. They live in trees, feeding on vegetation. They are coloured green or brown, and look very similar to twigs or leaves. They even sway from side to side if the tree is moved by the breeze.

 

 

 

 

 

 

 

          Bugs differ from other insects because they have long, beak-like mouthparts instead of biting jaws. They use them to pierce their food and suck up the liquid contents. Most feed on plant juices, but some hunt and feed on other animals.

          Carnivorous bugs either suck the blood of their victims or inject saliva into their bodies, liquefying the insides so they can be sucked out. Many live in water, either underwater or skipping across the thin film of the surface on their long legs. They grasp their prey with their forelegs in a similar way to a mantis.

 

 

 

 

          Termites live in colonies that may number several million. They build large, complex nests underground or in dead trees. In hot, dry climates, termites build hollow mounds over the nest, allowing cool air to circulate. Inside the nest lie the large king and even larger queen, her swollen body full of eggs (inset). Soldier termites protect the colony from attack by enemy ants. Worker termites find food, feed the others and look after the young.

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          Insects are invertebrates, animals that do not have backbones. Insects belong to a large group of invertebrates known as arthropods. Other members of this group include centipedes, spiders and scorpions, woodlice, crabs and shrimps. Instead of having an internal skeleton, arthropods have a hard outer skeleton. This is made of a light, strong material called chitin that supports and protects their soft inner parts.

          All insects have six legs and a body divided into three sections: the head, thorax and abdomen. The chitin covering the legs is jointed to allow the insect to move easily. Insects have a pair of antennae on their heads which they use to smell, touch and pick up sound vibrations. Most insects also have one or two pairs of wings.

          Insects have two kinds of eyes: simple eyes that detect changes in light, and compound eyes. The compound eyes are made up of thousands of tiny units, each of which sends an image to the insect’s brain.

          This means that insects have good, all-round vision, and are able to sense movements and judge distances very accurately.

          After mating, a female insect lays her eggs. The young are usually left to hatch and fend for themselves. Some insects, such as bugs or grasshoppers, look like tiny adults when they hatch. As they grow, they shed their hard outer skeleton several times, after a new one has grown underneath.

          Other insects, such as butterflies or bees, hatch out as larvae (caterpillars or grubs). They shed their skin several times as they grow. Then they develop a protective coating inside which they pupate (change into their adult form).

 

 

 

 

 

BUTTERFLIES AND MOTHS

          Butterflies and moths are a group of flying insects, with wings that are covered with tiny, overlapping scales. These scales give butterflies and moths their bright colours and striking markings. Most butterflies and moths have coloured scales. Others have scales that reflect the light to give an impression of colour.

          The colours and patterns of butterflies and moths are used to attract mates, for camouflage, and also to deter predators. Large spots that look like the eyes of a large animal, or bright colours to warn that the butterfly or moth is poisonous, help these insects to avoid being eaten.

 

 

 

 

 

 

         Butterflies generally fly during the daytime. They are usually more brightly-coloured than moths and have club-like antennae. Most moths are night-flyers, and have feathery antennae. Adult butterflies and moths have a long, hollow tongue called a proboscis. They use it to probe inside flowers and suck up nectar.

          Butterfly and moth larvae are called caterpillars. They feed on leaves until they have grown large enough to pupate. Then they spin a protective cocoon of silk around their bodies, inside which they completely change their structure, and finally emerge as adults. Some may migrate to warmer climates when winter comes, returning to breed and lay eggs.