During warm summer nights, firefly insects light up and dart about looking like enchanted fairies. Some flicker on and off rapidly, and others keep their lanterns on longer to create curlicue trails of light. Fireflies flash their lights to attract mates. The light of day transforms fireflies into nothing more than plain beetles. Firefly bodies consist of three main sections: the head supporting the eyes and antennae, the middle thorax, and at last the abdomen. Fireflies have six short legs, heavily veined wings tucked under wing covers, and long antennae. Fireflies are mostly black with some yellow segments on their abdomens. Fireflies do not have lungs and instead use tubes called tracheae for breathing. Female fireflies lay luminescent eggs which hatch into luminescent larva called wireworms. Larvae make oval cells within the earth and morph into luminescent pupae. After ten days, pupae split open and full-grown beetles emerge. As larvae, fireflies are carnivores, consuming other insects, worms, and decaying animal flesh. As adults, fireflies transform into herbivores that mainly feed on nectar and pollen.
Like fireflies, butterflies are insects. The video below shows a black veined, orange-red monarch butterfly. Monarchs are distasteful to birds, and their brilliant colors warn birds of their disagreeable taste. Another butterfly species called the viceroy has taken advantage of the monarch's immunity from bird attack by imitating its colors. Have you ever touched a butterfly's wings and noticed the powder on your fingers? Butterfly wings are covered with scales so tiny, they look like dust. Monarchs migrate in large flocks seasonally, flying south for the winter and back north for the summer. Male monarchs have black spots upon their hind wings called perfume pockets. Perfume pockets are filled with scent scales. These scales give forth an odor which humans cannot perceive, but the lady monarch is attracted by this odor. After mating, female monarchs lay eggs that hatch into caterpillars. Caterpillars eat vegetation to grow larger and spin their chrysalises. Inside their chrysalises, butterflies transform from worms into flying pixies. The process of transforming from caterpillars to winged adult butterflies is called "metamorphosis."
Like fireflies and butterflies, honey bees are insects. Honey bees live in large colonies. There are three types of honey bees - the female worker, the female queen, and the male drone - each type with its own role to play. Worker bees gather nectar and pollen, spread pollen from flower to flower, build honeycomb, and produce honey. Workers have special pollen baskets on their legs for collecting pollen. Workers also have long tubular tongues that enable them to gather nectar from flowers. Workers secrete wax from their abdomens to make honeycomb. Queen bees start as regular worker eggs, but are selected to be housed in special chambers and fed with royal honey after hatching into larvae. Princess larvae weave silken cocoons around themselves and change into pupae. Meanwhile, the workers seal their cells with wax. Upon hatching, a queen cuts a hole in her chamber. Her first real work is to hunt for other queen cells. If she finds another queen cell, she makes a hole in its side and destroys the poor princess within. If she finds another full-grown queen, the two fight until one succumbs. Sometimes the workers will prevent the queen from killing another princess or queen. This causes the spurned queen to depart with an entourage of bees to establish her own colony. The queen rarely uses her sting upon anything or anyone except a rival queen. The queen is larger than the drone and worker and has no pollen basket, for her sole job is reproduction. The only job of drones is to mate with the queen. Drones have no pollen baskets, wax pockets, or stingers for fighting. Drone bees are fed by worker bees until the latter part of the season. When the honey supply runs low, the drones are driven from the hive to die of starvation.
Like fireflies, butterflies, and bees, mosquitoes are insects. The word mosquito means "little fly" in Spanish. Mosquitoes start their lives as eggs nestled together in a boat-shaped egg basket. The larvae, or wrigglers, hatch through the bottom of their eggs into the water. The wrigglers hang to the surface of the water by opening their star-shaped valves and allowing air to fill their breathing tubes and tracheae. The wrigglers sweep decaying vegetation into their jaws with the help of their mouth brushes. When touched, wrigglers close their star-shaped valves and sink into the water to defend themselves. Wrigglers swim with the assistance of finger-like projections and hairs. Wrigglers grow into pupae, developing large heads, and they stay at the surface of the water for long periods of time. Unlike moths and butterflies, whose pupae remain still, mosquito pupae can move. Eventually, pupae split open, adult mosquitoes emerge, and the adults float on their pupa skins while their wings dry. Adult females live a week or two, and adult males survive several days. Only the female mosquitoes sing and bite. Females sing to attract mates by rapidly vibrating their wings. Females use a tube, called a proboscis, to pierce human skin and sip blood. Females need this blood to develop eggs. Males have wide, feathery antennae, which they use for hearing. In contrast to males, females have long, spindly antennae.
Like fireflies, butterflies, bees, and mosquitoes, dragonflies are insects. Dragonflies can be found skimming over still ponds, flowing brooks, and rippling fields of grass. Dragonflies are among the swiftest of all winged creatures, their rapid flight enabling them to catch their prey. Dragonflies feed on wrigglers and adult mosquitoes and help keep the mosquito population down. Most dragonflies love the sun, disappearing when clouds cover the sky. Dragonflies lay their eggs in water. Nymphs hatch from the eggs, strange little creatures that look like stunted crickets with spider-like legs. In the past, people were suspicious of dragonflies, calling them the devil's darning needles, snake doctors, and snake feeders. In reality, dragonflies are harmless and beautiful, more like shimmering blue and green sprites than evil-doers.
Like fireflies, butterflies, bees, mosquitoes, and dragonflies, beetles are insects. One notable type of beetle is the ladybug, (also called lady beetle or ladybird) often known for its bright wing covers and black spots. Ladybugs come in many colors, some are red with black spots, some are black with red spots, others are yellow with black spots, and still others are orange with no spots. There are around 5000 species of ladybugs, and different species of ladybugs have different numbers of spots. Contrary to what some believe, the number of spots on a ladybug does not correspond to age and does not change over time. Ladybugs do not taste good to birds and other predators. Both the bright colors and the spots of ladybugs warn birds of their bad taste. Tucked under the wing covers are a pair of wings, a thorax, an abdomen, and three pairs of short legs. Like other insects, ladybugs use antennae to sense their surroundings. Ladybugs help gardeners and farmers by eating crop pests such as aphids. Ladybugs have the same life cycle stages as butterflies. They start as tiny yellow eggs, hatch into larvae, and grow into pupae. Ladybugs remain dormant as pupae for a couple of days before adult ladybugs emerge from their pupae skins. Ladybugs are often associated with good luck.
Like fireflies, butterflies, bees, mosquitoes, dragonflies, and beetles, grasshoppers are insects. When any creature has unusually strong hind legs, we may be sure it is a jumper, and grasshoppers show this peculiarity at first glance. The front legs are short, the middle legs a trifle longer, and the femur of the hind leg is nearly as long as the entire body. The hind leg contains many powerful muscles which have the appearance of being braided. Each grasshopper foot consists of three segments and a claw. Surrounding the claws are oval pads equipped with microscopic hairs, called tenent hairs, which secrete a sticky fluid and enable grasshoppers to climb vertical surfaces. Grasshoppers feed upon grass and other herbage and are especially fitted for living in grassy fields. Their color protects them from being spotted and eaten by their enemies, the birds. Since so many species of birds feed upon grasshoppers, their leaping power is much needed for escape. However, when grasshoppers make a longer journeys they use their wings. Grasshoppers have some means of defense as well as of escape; they can give a painful nip with their mandibles; and when seized, emit copiously from their mouths a brownish liquid which is acrid and ill smelling. This performance interests children, who are wont to seize grasshoppers by their jumping legs and hold them up, commanding them to "chew tobacco." In some areas of the world, grasshoppers provide a source of food for people. In Mexico, grasshoppers are served with tortillas and chili sauce. Grasshoppers may also be fried into a crunchy snack.
Like fireflies, butterflies, bees, mosquitoes, dragonflies, beetles, and grasshoppers, katydids are insects. "Katy did, she didn't, she did," poet James Whitcomb Riley writes, "The katydid is rasping at the silence." The word "rasping" well describes the note played by male katydids by rubbing their wings together. Katydids are beautiful insects, with green, finely veined, leaflike wing covers under which is a pair of wings. As they resemble leaves, katydids hide from predators by living among trees, shrubs, and tall grasses. Due to their effective camouflage, katydids are rarely discovered except by accident. However, when male katydids sing at night, they may be ferreted out with the aid of a flashlight. Like grasshoppers, katydids undergo incomplete metamorphosis and female katydids lay eggs using ovipositors. Newly hatched katydids look like small adults except they do not have wings. Katydids feed on vegetation. When eating, katydids often hold a leaf or flower firmly with their front feet, biting it off like a grazing cow and chewing industriously with their sidewise-working jaws. As they are insects, katydids breathe air through spiracles, expanding and contracting their bodies to open and close the spiracle openings.
Like fireflies, butterflies, bees, mosquitoes, dragonflies, beetles, grasshoppers, and katydids, crickets are insects. Known as the "troubadours of the field," the chirping of crickets conjures up a calm summer evening. The chirp of the cricket is quiet at the beginning of summer and grows louder as fall approaches. Crickets rub their wings together to make their chirps. Only male crickets chirp, and they chirp to attract mates. If two male crickets sing too close together and see each other, they may change their song to a warning and get into a fight. Crickets are black and shiny like patent leather. Crickets use their compound eyes, their simple eyes, their antennae, and their cerci for sensing the world. Crickets live in fields under stones and in burrows. They eat plants such as grass and clover, but especially enjoy sweet, juicy fruits such as apples or melons. Some crickets fly, but others cannot despite having wings. Like katydids and grasshoppers, crickets have long, strong hind legs that make them good jumpers, although it is usually their quick running that helps them to evade predators and disappear into the grass.
Spiders are not insects like the butterfly or the beetle, they are arachnids. You can remember this by knowing spiders have eight legs instead of six. Also unlike insects, spiders have two main body sections rather than three, as the head and thorax are merged into one cephalothorax. In addition, the abdomens of spiders have no segments unlike insects. One of the most fascinating characteristics of spiders is the gossamer thread they spin. Spiders are the civil engineers of the animal world, spinning bridges, airplanes, and balloons. Spiders often spin their sticky webs where walls meet ceilings in our homes. These webs entangle and trap a variety of insect pests such as flies, mosquitoes, and grasshoppers, making spiders beneficial to humans. As soon as an insect becomes entangled in a spider's web, the spider runs to it, seizes it in its jaws, sucks its blood, and then throws away the shell, the wings, and the legs. Spiders reproduce by laying eggs within egg sacs. The eggs hatch into spiderlings, which mature to adults in around a year. Most spiders are entirely harmless to humans; however, the bites of some species are poisonous, including the brown recluse and the black widow. The mouths of spiders are guarded by two mandibles, each ending in a sharp claw, at the tip of which the poison gland opens.
This lesson covers birds and their feathers. Unlike people, birds don't wear clothing to keep themselves warm and dry. Instead, birds grow feathers to protect themselves from the rain, snow, wind, and cold. Bird feathers have three parts: the shaft, barbs, and fluff. The feathers on the backs and chests of birds overlap like shingles, keeping the bird dry by enabling rainwater to easily run off. As birds preen their plumage, they further waterproof themselves by applying a special oil to their feathers.
In the bird world, oftentimes male birds are brightly colored while their female counterparts are drab. Why is this? Male birds are brightly colored to attract their female mates. Some male birds can be show-offs," spreading their tail to the fullest extent and shifting it this way and that to show the exquisite play of colors over the feathers in the sunlight. Male peacocks, in particular, create gorgeous displays of blue, green, and purple plumage. Female birds are often drab colored to blend in with their habitats, especially their hidden nests, to cover and camouflage their eggs and nestlings. Muted colors help female birds and their babies evade the sharp eyes of hungry, high-soaring predators such as hawks.
Birds wings correspond to human arms. Birds fly by using their wings to press down against the air. Birds use their tails as rudders, enabling them to turn and navigate through the air.
The seasonal travel of birds from place to place is called migration. Migratory birds engage in this seasonal travel, while permanent residents stay in one place all year. Summer residents are those birds which stay in a location in the summer, and winter residents are those who stay in a location in the winter. This means migratory birds are summer residents to people in certain locations, but winter residents to people in other locations. For example, American barn swallows are summer residents for much of the United States, but winter residents for much of Central and South America. Some birds, such as swallows, gather into flocks before taking their migratory journey. Other birds travel solo between their summer and winter residences.
Birds tend to have better vision than mammals such as humans. Birds of prey, such as hawks and owls, have such excellent vision they can spot mice on the ground from high distances up in the air. Birds have irises of many different colors including white, red, blue, yellow, brown, gray, pink, purple, and green. Some birds, such as hens, have their eyes placed on either side of their heads. This means they cannot see the same object at once with both eyes. Hens often look at something with one eye, and then turn their head to view the object with the other eye. Hens have a black pupil and a yellow iris. Owls cannot move their eyes in multiple directions. To see in different directions, owls must swivel their entire heads. We typically cannot see the ears of birds, as they often consist of small holes covered by feathers. Some birds, such as owls, have better hearing than humans. Owls can even use their sense of hearing to locate prey at night.
Birds' beaks serve multiple purposes. First, they act as a pick for digging into soil or bark after insects. They also serve as pliers for grabbing and holding things. Beaks act as scissors for cutting through things, and brushes for cleaning and oiling their feathers. Beaks offer protection, providing a sharp weapon in case of a fight. Finally, birds also use their beaks to turn their eggs. Different types of birds have different types of beaks. Hens have narrow, sharp, and hard beaks which allow them to dig in the hard earth for worms and bugs. Ducks have broad, flat beaks, which allow them to gather aquatic plants and strain the water out the sides like a sieve. Duck beaks are softer, for they do not need to dig through the hard earth like other birds such as hens. Modern birds do not have teeth. Birds swallow food whole and do not require teeth, for their beaks serve to grip the food, and their gizzards 'chew' the food. All birds have gizzards, which are muscular second stomachs which pulverize swallowed food before it reaches the intestines. Birds have nostrils in their beaks. It is believed birds do not smell well, for their nostrils lack the soft tissues found in dogs or humans that aid in detecting scents.
Hens and ducks have very different feet, each type best suited for their owners' different behavior and habitats. Hens have tough claws and scaly skin that enable them to scratch in the hard dirt. While hens spend most of their time on land, ducks spend ample time swimming. To aid in swimming, ducks have a thin membrane, called a web, that stretches between its front toes.
Is it possible to quantify the pleasure received from hearing birds chirping, calling, and singing? The sounds of the robin, red-winged blackbird, and Canadian goose bring cheer to thousands of people every year. Indeed, it would be difficult to find anyone, except perhaps in large cities, who does not notice the arrival of at least some spring birds - the chirping of robins on the lawn, the honk of the wild geese overhead, or the red-winged blackbird as they call from the top of a shrub. Birds are interesting to most people because of their mere presence, including their cheerful songs, their bright colors, their happy hopping, and their inspiring soaring.
Did you know that the English sparrows we see across America are not native to our lands? They were carried over the ocean and introduced to America by people. They soon overran the country, displacing native song birds. English sparrows are considered pests by some as they feed on food crops meant for people, such as grains and fruit. The sparrows aren't all bad, for they help people by feeding on insects considered pests. English sparrows are very clever and sneak food right from under the beaks of other birds, such as robins. English sparrows are also known as house sparrows, and are today found in North and South America, Europe, Asia, Australia, and Africa.
Found across much of North America, the downy woodpecker is the smallest woodpecker within its range. The downy woodpecker uses its beak to drill into bark and excavate the plump grubs, cocoons, and other insects tucked within. The downy woodpecker wears a fine black, gray, and white suit. The male wears a cap of red on the back of its head. The downy woodpecker does not migrate in the winter, for it can extract the grubs and insects wintering within trees.
The smallest species of bird in the world is a hummingbird. Hummingbirds get their names from their wings, which flap so fast, they become a blur and make a humming noise. Aided by their fast wings, the maneuverable hummingbird hovers like a helicopter and darts like jet. As they flit from flower to flower in search of nectar and insects, they transmit pollen between flowers to help new flowers grow. The hummingbird is well-adapted for extracting nectar and insects. They have long, narrow beaks that reach deep into the cups and tubes of flower petals. The side edges of their tongues curl up into grooves for sucking nectar. Their tongues also come equipped with tiny brushes to sweep up nectar and insects. Hummingbirds often sport gorgeous iridescent plumage of greens, blues, oranges, pinks, and purples. As with many bird species, male hummingbirds are often particularly bright and beautiful to help them attract mates and to subjugate other males.
The next group of animals for study is the mammal. Mammals are warm-blooded, have hair or fur, are vertebrates (have backbones), give birth to live young, and nurse their babies. Foxes are mammals that are smaller than dogs and have longer legs. Like dogs, foxes growl and make high-pitched yelping sounds as well as smile and wag their tails to express happiness. Their narrow, pointed muzzles and triangular faces give the impression of slyness and great cunning. Fox fur runs from reddish to gray in color. Foxes have beautifully bushy, white-tipped tails, which foxes wrap around themselves like a fur coat on cold days. Unfortunately, their warm tails are both boon and bane. When weighed down with water, snow, and/or ice, tails may slow the fleeing fox and cause it to be captured by predators. Foxes live in dens or burrows and are good diggers. Dens are more open than burrows and may be in an open field or side hill. Foxes line their nests with soft grass for their babies, which are called puppies or cubs. Fox cubs are born in spring. They have gray fur and are very playful. Both fox parents are devoted to their cubs, raising them, feeding them, and caring for them. Foxes tend to be nocturnal and hunt at night, but may be seen by day. Foxes are omnivores who eat mice, rabbits, woodchucks, frogs, snakes, birds, eggs, grasshoppers, and plants. Foxes hunt and eat hens and geese, which can make foxes and farmers enemies. Foxes can also benefit farmers, since they feed on rodents and other pests. Perhaps due to their cleverness, foxes are a successful animal, residing on every continent in the world except Antarctica.
Like foxes, skunks are a type of mammal. Small and fluffy, with thick black and white hair and a delightfully bushy tail, skunks are striking and memorable in appearance. Skunks have pointed heads and narrow snouts, short legs, and shining dark eyes. Their strong forepaws have long claws, used to catch prey and dig its burrow. Their burrows may be abandoned groundhog lairs or spaces under a sheds or barns. Skunks are nocturnal and are rarely seen by day. Skunks are omnivorous and mainly eat fruits, berries, insects, eggs, mice, snakes, and frogs. Skunks can be beneficial to farmers, ridding them of rodents and other pests. In their burrows, skunks make soft nests of leaves and grass, where they hibernate over the winter and have their babies. Skunk babies are called kittens, and they are typically born in May. Upon first look, skunks seem harmless and vulnerable. Skunks might look like an animal you'd like to pet, but beware! Give wild skunks a wide berth or you will regret it. Skunks will lift their tails and spray a horrific smelling liquid at anything that threatens them. The scent is so potent, it can be smelled half a mile away. Skunks produce this liquid with two marble-sized glands near the base of the tail. Skunks are not particularly intelligent creatures, but they have little need for cleverness when they wield such a potent weapon against predators. Skunks parade about, unconcerned that they will be attacked. Consequently, they are often struck by cars on the highway and trains on the railroad tracks. Some people keep skunks as pets, after removing their scent glands.
Like foxes and skunks, raccoons are mammals. Raccoons have a delightfully mischievous appearance, with triangular faces and pointed snouts. They wear a black mask of fur across their eyes, reminding one of a small, furry burglar. Their tails are as distinctive, bushy with rings of black and grey. Their hair is long, coarse, and colored grey, black, and brown. Their eyes are black and beady and shine with intelligence. The hind foot has five short toes and looks a bit like a human foot. The front foot is smaller and looks like a tiny human hand, with four fingers and a thumb. The fingers and toes are equipped with sharp claws. Raccoons are scavengers that will eat almost anything including both plants and animals. They especially enjoy corn and poultry, to the frustration of farmers. They also eat fruits and aquatic animals such as fish, turtle eggs, and crayfish, which they catch with their hands. Like many omnivores, raccoons have both sharp canine teeth and flat grinding teeth. In captivity, raccoons are neat eaters, washing their food in water before eating and washing their hands afterwards. When sleeping, the raccoon covers its face with its paws and tucks its tail round its body, turning into a big ball of fur. Raccoons hibernate in a nest, often in a hollow tree and sometimes in a group of multiple raccoons. Babies are born three-to-six in a litter in April. Babies are born blind and helpless, and both parents care for the babies. Raccoons do make noises, often at night. Their cries are eerie and haunting, especially when fighting.
The next mammal under study is the cheerful chipmunk. Smaller than squirrels and less adept at climbing, chipmunks can climb trees, but are more likely to be seen scampering along the ground. They are mainly brown, tan, and white with prominent black and white stripes stretching along their backs. One marvelous thing about chipmunks is their large cheek capacity. Chipmunks cram their cheek pouches full of nuts and other tasty treats. They use their cheeks as buckets to carry out dirt when excavating their burrows. Chipmunks dig burrows in dry earth, making narrow entrances and exits with wider, well-cushioned nesting areas. Chipmunks hibernate in these burrows during the cold winters, although they may briefly awaken on mild, sunny winter days for a snack.
Groundhogs, also known as woodchucks, dig tunnels and burrows under the earth. Groundhogs are mammals like chipmunks, but are larger, plumper, and have dark brown shaggy fur. Groundhogs are rodents and considered large squirrels. Groundhogs keep mostly to the ground, but are adept swimmers and can climb trees to reach fruit or escape predators. Groundhogs engineer their burrows so that they don't flood in times of rain. Groundhogs accomplish this flood-proofing by digging down with their sharp claws and then slanting back upwards before hollowing out their burrows and lining them with soft grasses. Groundhogs also make sure to dig multiple backdoors to their burrow for easy escape. Groundhogs love to eat grasses, clover, fruit, and crops. They eat early and late in the day and take a nice siesta during midday. People, foxes, and dogs are groundhog predators. When encountering predators, groundhogs run straight for their burrows and disappear into the earth. Groundhogs are rumored to enjoy music, even joining in with the singing on occasion. Baby woodchucks, called 'chucklings' are born in spring, between March and May.
Like foxes, skunks, chipmunks, and groundhogs, muskrats are mammals. Muskrats have small but plump bodies covered in brown, gray, and white fur. Their long, scaly tails look like big brown earthworms. Muskrats sport an overcoat of coarse hairs and a waterproof undercoat of fine fur. Muskrats' scaly brown tails are used in the water both as oars to propel the muskrats and as rudders to turn the muskrats. Their front paws have claws and are used for grasping things and digging. Their back paws are larger, have claws, and are webbed for swimming. Muskrats have very short legs, making them slow runners, but they are far more agile in the water. Muskrats have small ears, tucked down among the fur, and eyes that shine like round black buttons. Muskrats have an apt name, as they mark their territory with a musky smell. Muskrats live near water, especially streams, marshes, and ponds. Muskrat tracks can be seen in the mud around water sources. The tracks show small clawed front feet, larger clawed hind feet, and a narrow, hairless tail. Tracks can also be seen in the snow on mild days in February and March, when muskrats venture out for food.
Although bats have wings and fly, they are not birds. Bats are the only mammals that truly fly. Bats are highly skilled flyers, executing quick turns and darting through masses of branches untouched. Bat wings consist of very long fingers and a rubbery membrane stretched between the fingers and ankles. Bats use these wing membranes like nets to scoop up insects. A hook projects from each wing, which bats use to drag themselves along the ground, to scratch themselves, and to aid in hanging upside down. Bats use their tiny clawed feet to hang upside down when they are sleeping. Bats have soft brown fur and clean themselves like cats, using their wings to rub themselves and then licking their wings clean. Bats make a high-pitched squeaky noise to communicate with other bats or to express alarm. Bat babies are born in July as twins. As bats are mammals, bat babies nurse from their mothers. Like human children piggybacking on their parents, bat babies often soar through the air on their mothers' backs. In cold climates, some bats hibernate over the winter in a cave or hollow tree. Bats have a bad reputation among humans. Some people believe bats will attack them or write stories where bats turn into vampires. Bats are actually beneficial to humans, controlling insect populations including the mosquito.
This lesson moves on from insects, birds, and mammals to introduce a new group of animals called fish. Fish are cold-blooded animals with backbones (vertebrates). Fish maneuver through the water by waving their fins. Fish do not have legs, although some fish "walk" on land using their fins. Fish are covered in either smooth skin or armored scales, and are coated with a layer of slippery slime to help them slide through the water. Most fish lack lungs like birds or mammals, and instead use gills for breathing. One exception is the lungfish, which uses its lung sacs for breathing air. Fish have nostrils which are used for smelling and moveable eyes with no eyelids.
This lesson advances from insects, birds, mammals, and fish to introduce a new group of cold-blooded vertebrate animals called amphibians. The word 'amphibian' is derived from the Greek 'amphibios,' meaning 'double life.' Amphibians include frogs, toads, newts, and salamanders. Amphibians start their lives breathing with gills in water and transform into animals that live on land and breathe air. Amphibians that live this double life include frogs and toads, which start their lives as aquatic tadpoles. Tadpoles hatch from eggs laid in the water by toads or frogs. When they hatch, tadpoles look like tiny fish. They breathe with gills and have fins. As tadpoles mature, they absorb their tails, develop lungs, grow legs, and develop into frogs, toads, or other amphibians.
With their slippery, moist skin, frogs are amphibians and spend most of their lives near the water. When compared to their cousins, the toads, frogs are slimmer, not covered in bumps, and tend to be brighter in color. Frogs escape their predators, including snakes, lizards, birds, and skunks, by virtue of their slick skin and powerful jumping legs. Several types of frogs also evade predation by changing their color to blend in with their environments. Frogs are adept swimmers and many have webbed feet. Frogs have nictitating membranes that slide up to cover their bulging eyes. Frogs have grayish, round ears and small nostrils which they close under the water. Frogs hibernate in the winter by burrowing deep into mud to escape freezing.
So far, these lessons have covered insects, birds, fish, mammals, and amphibians. This lesson introduces snakes, which fall into a new group of animals called reptiles. Reptiles are cold-blooded and have dry skin covered in bony plates or scales. Reptiles include snakes, lizards, turtles, crocodiles, and alligators. Some reptiles live near water, and others live in deserts. This lesson focuses on the snake, a type of reptile whose species range from those that can swim to those that live in dry deserts. Snakes are well known for their forked, flickering tongues, the translucent skins they shed, their sharp fangs, and their tubular bodies. Snakes have neither legs nor fins for moving. Instead, snakes make their graceful, silent motions by moving their ribs, connected to crosswise plates covering snakes' undersides. Snakes have no eyelids, cannot blink, and sleep with their eyes open. However, they do have a protective scale that covers and protects the eye. Snakes come in a rainbow of colors including green, blue, black, and red. Snakes eat insects, eggs, fish, birds, frogs, lizards, and small mammals and are the only animals that can swallow prey larger than themselves. Some snakes even eat large mammals such as pigs and deer. The bite of some snakes is poisonous, but others render a harmless bite. Snakes kill their prey either by their bite or by crushing their prey to death. Snakes can be beneficial to humans, preying on animals such as rodents.
This lesson introduces turtles, which like snakes are reptiles. Turtles are found in a variety of habitats including lakes and oceans. Like snakes, turtles are found on every continent except for Antarctica. The turtle carries with it not just a house, but a shell fortress that protects its soft body from the sharp teeth of predators, such as sharks, whales, dogs, raccoons, skunks, foxes, and even people. In times of safety, a turtle will stretch out its neck and head and its legs and tail will emerge from its shell. The turtle has an upper shell, connected to its backbone, and a lower shell, connected to its breastbone. Turtles enjoy eating insects, worms, small fish, and other turtles. Some turtles also consume certain vegetables and fruit. Turtles do not have teeth, instead they have beaks. Watch out for snapping turtles in lakes. They have very strong, sharp beaks and may bite people. A turtle is different than a tortoise. Tortoises spend their time on land, whereas turtles spend part or most of their time in the water.
This lesson introduces crayfish, which are in a new group of animals called crustaceans. Crayfish are notable for the magnificent pair of nippers on each of the front legs. Like a thumb and finger, the thumb joint can move back and forth freely. The nippers are edged with saw teeth and armed with a sharp claw at the tip for capturing prey and fighting. Crayfish have five pairs of legs. The second and third pairs have nippers like the first, and the fourth and fifth pairs have only a single claw. Crayfish have two compound eyes set on extendable stalks that can be swiveled in any direction to look for danger. Crayfish breathe oxygen from water using the gills on their legs. Crayfish have long, segmented antennae that are thick at their base and thin at the threadlike tips. Above the antennae on each side is a pair of shorter ones called antennules. The antennae and antennules are used for sensing the environment around the crayfish. Crayfish have a cephalothorax, six abdominal segments, and a flaring tail. The tail can be opened and closed like a fan; it can be lifted up or curled beneath. The abdomen has some very beautiful feather-like organs called swimmerets that, along with the tail, help propel the crayfish through the water. In the spring, the mother crayfish covers the swimmerets with glue and plasters on the grapelike clusters of eggs she lays. Even after the little ones hatch, they remain clinging to the maternal swimmerets until they are large enough to scuttle around on the brook bottom and look out for themselves. Crayfish haunt ponds and still pools along brooks and rivers. There they hide beneath sticks and stones, or in caves of their own making. Crayfish are omnivorous, eating both plants and small animals such as worms and fish.
This lesson introduces earthworms, which are in a new group of animals called annelids. Annelids are also called the 'ringed worms' or 'segmented worms' and also include leeches. Earthworms are very beneficial to humans, known as Earth's original farmers, plowing the land, fertilizing the land, and adding tunnels in the soil for drainage. Earthworms dig anywhere from mere inches to eight feet under the soil's surface, breaking up the soil with the sand and gravel in their gizzards. Earthworms plow the land by bringing soil to the surface and dragging organic matter such as seeds, leaves, flowers, and animal bones under the surface. Earthworm stomachs add lime to fertilize the soil, just like human gardeners. For clinging and crawling, earthworms use tiny bristles on the undersides of their bodies called setae. Their muscles also aid in movement, which earthworms contract and expand. Earthworms can feel vibrations, but cannot hear. They can sense light and darkness, but have no eyes. They cannot smell much, but their senses of taste and touch are well-developed. Earthworms dig tunnels which end in a larger chamber, where they hibernate during the winter. Earthworms are nocturnal, not appearing by day unless they are rained out of their burrows. Earthworms are omnivores, eating earth, leaves, flowers, meat, and even fellow earthworms. An earthworm begins life as a yellow-brown football-shaped cocoon containing between one to five worms. Tiny white worms hatch from these cocoons and grow into reproducing adults in around six weeks.
This lesson introduces snails, which are in a new group of animals called mollusks. In addition to snails, the mollusk group includes marine animals such as clams, scallops, oysters, octopuses, and squid. Snails hatch from soft-shelled eggs that are the size of peas. Baby snails hatch already possessing shells with single spirals. As the babies grow, they add layer after layer to the opening rims of their shells, adding on additional spirals. Snails are best known for carrying these houses with them wherever they go and for their slow pace of travel. Each snail travels using their single foot, which secretes an adhesive substance that helps them cling, even when upside-down. This substance leaves a shining trail of ooze behind the snail. Snails have two stalks on their heads, each bearing an eye. These eye stalks are retractable and can be extended around corners or over edges. In the event of danger, the snail can pull its eyes inward for protection. Below the eyes are two feelers which are also retractable. The snail breathes through an opening called a breathing pore. The snail opens and closes the breathing pore to suck air into the shell, where it bathes the snail's lung and is forced out again. Snails have a set of brown upper teeth for chewing and a round tongue. Most land snails are herbivores, eating vegetation such as leaves, vegetables, and fruits. A few species of snail are omnivores or carnivores. Snails live on average two to three years, but some larger species can live for up to ten years.
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