Insects live all over the world. they are by far the most numerous of all animal species. More than 850,000 different kinds of all insexcts are known.
Roughly eight out of ten of all the Earth’s animals are insects!
Insects range in size from tiny fleas which can be seen only through a microscope to beetles as big as your hand. Many have interesting life stories or cycles. Some insects, such as the desert locust of Africa are destructive pest. But many others are helpful. without bees and other flying insects, flowering plants would not be pollinated and fruit trees would not bear fruit.
Among the most fascinating insects are the social insects, which live in highly organised communities or colonies.
These include ants, bees and termites. Many insects make regular journeys. Some butterflies, beetles and dragonflies migrate at certain times every year.
Helpful insects such as bees can pollinate flowering plants plants and also give us honey. The silkworm (the larva of the silk moth) is reared for the silk it spins when turning into a pupa. Ladybirds are the garderner’s friend because they prey on the aphids which attack roses and other plants. Insects such as the icheumon wasp prey on the other insects, controlling pest.
Scavenging insects, such as bury beetles, feed on dead matter and help to make the soil fertile.
Harmful insects are those that carry disease and destroy food grown by the farmers. The mosquito (which carries malaria) and the tsetse fly (which spreads disease in people and cattle) are pest. Flies, lice, fleas and cockroaches live close to people, often inside houses, damaging food and spreading disease. The Colorado beetle destroy potato crops. Locusts are feared by farmers in Africa because they swarm in suck vast numbers that they blacken the skies. The locust eat every plant in their path. The locusts also can travel long distances in destructive swarms.
All insects have a similar body plan. AN insect’s body is in three parts; a head, thorax and abdomen. The head has eyes, jaws and feelers (antennae). The middle part of the thorax, carries three pairs of jointed legs and sometimes wings. The abdomen contains the stomach, reproductive organs, and breathing tubes called spiracles.
All insects start life as eggs. In the most advanced insects, there are four stages in the life cycle. The egg hatches into a larva or grub. This larva grows by shedding its skin and finally turns in a pupa or chrysalis. The Pupa looks lifeless, but inside many changes are taking place. The pupa finally splits apart and a fully-formed adult insects emerges
Some insects, such as grasshoppers, hatch from eggs not as larvae, but as nymphs. Grasshopper nymphs do not yet have wings, but otherwise look much like their parents. Nymphs grow by moulting their skins. The most primitive insects, such as silverfish, hatch from the egg looking exactly like adults, only smaller, and shed their skins may times as they grow.