Category Plants & Animals

         Scientists have studied more than 800,000 species of insects. Do you know how they reproduce and develop?

          Reproduction in insects is usually sexual, the male inserting sperm into the female’s body. The fertilized eggs are usually not tended by the insects, but they develop near or in a source of nourishment and protection. In some cases, fertilization is external. This means that the female lays the eggs and then the male fertilizes them. Some insects produce eggs which develop into adults without being fertilized. This is a type of asexual reproduction and is known as parthenogenesis.

          As an egg develops, it goes through several stages before becoming an adult. Some primitive insects develop directly from the eggs. Most of them, however, go through several stages of development called metamorphosis. In complete metamorphosis, there are four stages of development: egg, larva, pupa and adult. In incomplete metamorphosis there are three stages: egg, nymph, adult. The nymph is like a small adult. As the insect goes through its development, it moults several times. The entire process of metamorphosis may take a few days or several years depending on species and environmental conditions. Many insects lay eggs which can survive the winter or other unfavourable conditions.

        

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The name ‘rhinoceros’ has Greek origin. In Greek rhino means ‘nose’ and keros means ‘horned’. The animal has one or two curved horns on its long nose. The horns grow throughout its life. Rhinoceros belong to the ‘odd-toed’ group of ungulates. Rhinoceros are found in Africa and South-East Asia.

The animal carries its large body on its four stout, short legs. It has three toes on each foot, each toe ending in separate hoof. Each front foot actually has a fourth toe, too, that is no longer used.

The skin of the rhinoceros is very thick and has little hair. They look as if they are wearing heavy armour plating held together with rivets. The horns are composed entirely of hair like growths set above thickenings of the nasal bones and frontal bones. They are not attached to the skull and may even be torn off in fighting. When this happens, they quickly grow again. The horn may be upto 107 cm in length.

There are five different kinds of rhinoceros existing today — two from Africa and three from Asia. The Sumatran rhinoceros have two horns whereas the other two Asian species — Indian and Javan — have only one. They are all in danger of extinction but the most endangered is the Javan rhinoceros, which survives only in one small reserve.

The largest of all these is the white rhinoceros from Africa. It stands 1.8 m (6 ft) high at the shoulder and can weigh over 3 tons. An interesting difference between the white and the black rhinoceros lies in the shape of their lips. The white rhinoceros has a wider, square-mouth which is very suitable for cropping grass. The black rhinoceros is more of a browser and has a pointed upper lip for grazing and plucking leaves and shoots from shrubs and bushes. The other two-horned species, the Sumatran rhinoceros, is the smallest of all, standing only about 4.5 ft at the shoulder and weighing less than a ton. 

Rhinoceros feeds on grass, twigs and shrubs. They do not hunt other animals for food. During the afternoon heat, the rhinoceros usually buries itself in muddy water. And from here it emerges with a layer of mud on its skin. This dries and forms a protective coating against insect bites.

This huge animal is usually quiet and retiring. But if it is cornered, it can become very fierce and dangerous. A rhinoceros can charge at a speed of 30 miles an hour, and use its strong, pointed horns to attack its enemy. In captivity the rhinoceros may live upto fifty years.

A female bears only one young at a time. The calf is born about eighteen months after the mating season and remains with the mother for several years.

Now unfortunately the rhinoceros is a rare species. Over the centuries they have been hunted by man for their horns. This is because according to an ancient belief, its horn imparted magical properties to its owner. However, now this second largest land mammal is being protected by law to prevent it from becoming extinct.

          The cassowary is the most dangerous bird in the world. Its inner toe has a long dagger-like claw that acts as a weapon and can slash open a man’s stomach!

          The cassowary is found in New Guinea and Northern Australia. It is a secretive forest dweller and is seldom seen, but often heard croaking and bellowing. It cannot fly, but runs at a great speed on its powerful legs. On each foot it has three toes, the inner one having a long straight claw. It can often be seen giving furious kicks at the trunk of trees without any apparent reason. Because of this strange habit the cassowary is regarded as having a very bad temper. In dense forests it can even speed upto 50 km an hour. It can grow upto a height of 6 ft and weigh as much as 180 pounds. When it gets annoyed, it jumps in the air and delivers a vicious kick.

          It is a bony-headed bird. Its naked blue head is protected by a bony helmet. Its body is covered with coarse hair-like feathers. It is the only member of the family casuariidae. Unlike other birds, the male incubates eggs. At a time three to six eggs are laid. The eggs are green in colour and 13 centimetres long. They are incubated for 50 days in a leafy nest and on the ground. The adult provides parental care for the young ones.

          Cassowaries live in family groups or in pairs. They like to be near water, for they swim readily. They are also good fishers.

          According to zoologists, the cassowary’s ancestors were able to fly. But in the process of evolution, it became flightless. It has adapted itself to make the most efficient use of its environment. Emu, kiwi weka and takahe are also flightless birds. Most of the flightless birds are found in Australia and New Zealand. 

          

    A woodpecker is a bird which gets its name as it pecks the wood of trees, looking for insects to eat. The woodpecker is a great help to the trees because quite often, the insects and worms are harmful for the trees. These grubs and insects remain hidden deep in the crevices of the bark of trees. The woodpecker can find them instinctively even when they cannot be seen outside. Then he drills a deep hole and straight gets down to them. Sometimes woodpeckers make two openings, like a front and back door. This is to enable them to get away if an enemy shows up.

           The woodpecker has a chisel-like beak which can drill holes into dead or unhealthy trees. The structure of the head and neck of a woodpecker is adapted for driving its beak powerfully forward into the tree bark and absorbing the shock of the blow. It then uses its long tongue to capture and eat worms and insects. They can bore holes in the trees. Most woodpeckers nest in large holes that they dig in the branches or tree trunks. 

 

             

 

 A woodpecker is a member of the family picidae. There are 24 species of wood-peckers found in North America. These include the flickers and sapsuckers. The downy woodpecker can grow upto a length of 14 cm. The pileated woodpecker, found in the Eastern and North-Western United States and in parts of Canada, often reaches a length of 34 cm. The pileated woodpecker chisels large, deep, oblong holes into tree trunks.

               The European green woodpecker is green with red crown and yellow rump. The greater and lesser spotted woodpeckers are the British species. They have black, red and white plumage. There are about 210 species of woodpeckers worldwide except in Australia.

 

 

               Most insects live only for a short span of time compared to other living creatures on earth. Do you know which insects have the longest lifespan? 

The longest living insects are the Splendour Beetles (Buprestidae), some of which remain in the larva stage for more than 30 years. They pass through a complete metamorphosis. In the young larval forms they are very varied and include some of the largest and smallest of all insects. The largest is ‘Hercules Beetle’ of South Africa which is 15 cm long. The smallest is only 0.05 cm. Queen Termites (lsoptera) previously thought to live 50 years or more, are now known to have a maximum lifespan of 15 years.

Apart from these two insects, there is one insect called cicada that actually lives for 17 years. Its lifecycle is very interesting. The female cicada lays eggs on the twigs of trees. When the young one (nymph) hatches, it drops down to the ground. Then it burrows itself into the ground and attaches itself to the roots of plants and trees. Here it remains motionless for about 17 years, sucking at the sap of the roots. After this long burial, it is driven by some mysterious instinct towards light. It climbs the tree trunks and its skin splits open and the mature cicada emerges.

For about five weeks, it leads an active life in the sunlight. After this it just dies. So it takes 17 years to develop for just five weeks of active life.

The male cicada makes a shrill sound which can be heard in the countryside. It is well known for the monotonous, whining songs of males. This sound is probably a mating call. According to scientists, the noise-producing organ of the cicada is probably the most complicated musical organ to be found in nature. The male cicacta has little drum-like plates which constantly vibrate by muscles that never seem to get tired.

There are more than 800 species of cicada and 100 of these are found in North America. But the 17-year cicada is found only in the United States. Most of the other species live only for two years.

          A peacock displaying its feathers provides one of the most spectacular sights. Do you know the reason behind it? 

          Peacock has a beautiful train of feathers which he displays during the breeding season. It usually attracts several females by such display, but as soon as any of them approaches, it turns its back. The reason for this peculiar behaviour is not clear. But it is certain that this is done to woo the female. In Greek mythology the pattern of the peacock’s tail feathers represents the eyes of Argus – a giant with 100 eyes.

          Peacock is the national bird of India. It belongs to the family phasianidae. Strictly speaking, the male is a peacock and the female is a peahen. Both are together known as peafowl. There are two species of peafowl. One is found in India and Sri Lanka and is blue in colour. The other species is found in South-East Asia which is green in colour. In fact, peacock is a native of Asia and the East Indies, from where it has been brought to other parts of the world.

          The male of both species has a 75 cm long body and 150 cm long tail. The female is smaller than the male. The tail is made up of beautiful feathers. In display, the peacock lifts its tail, brings it forward, enveloping his body as he struts and quivers, audibly rattling the quills and uttering loud screams. Generally, a peacock has a train of upto 150 tail feathers, which are erected by it in display to form a showy fan.

          The blue peacock’s body is metallic blue green. The green peacock has a green and bronze body. The hens of both species are green and brown. They do not have the train of feathers or ‘crown’ on them.

          In the wild, they live in open lowland forests, flocking by day and roosting high in trees. The male usually has a harem of one to five hens each of which lays four to eight buffy or white eggs. Peafowls are omnivorous, i.e. they eat both plants and animals. They can eat young snakes.