insect

(also called ‘bug‘)

a kind of living organism – there are about a million, 1,000,000, known species at present (estimated to be 20 million, 20,000,000); size:

smallest insect — fairyfly

from (fairyfly) 0.0054 of an inch to (giant weta) 4 inches, not including legs and antennae,

heaviest insect — giant weta

and the heaviest insect weighs 70 grams; feeds on (eats) everything – plant life, flesh and/or blood of other bigger animals, soil/dirt, other insects; found all over the Earth – in the air, on the land, in the soil, in water – everywhere – one kind or the other

Most of the insects have the following physical structure:

an insect must not have any bones; but have a covering of tough material called ‘exoskeleton’; the body is divided into three parts:

body in three parts

head – contains a pair of long or short antennae; two or three, many sided or simple, large or small eyes (some, such as termites, do not have eyes because they do not need eyes in their dark environments); and mouth parts, with teeth or teeth-like growth; thorax – contains 3 pairs of legs, i.e. six (segmented) legs; one or two pairs, i.e. two or four, wings (in winged insects – some insects have no wings, and some others have wings at the first stage of their life and then lose them); abdomen – contains digestive, respiratory, excretory and reproductive organs.

[A group of insects is called a ‘swarm’ or ‘cloud’; and the movement is called ‘fly’, ‘crawl’, ‘creep’, ‘flutter’ and ‘hop’, ‘jump’ or ‘leap’.]

Stages in insect life cycle:

Most insects under go some stages, and change their shape and structure of the body, called ‘metamorphosis’, when passing through the stages, and drop off (shed) the old outer cover and grow a new cover at different stages, called ‘moult’.  The stages are: egg, larva/caterpillar, pupa, and adult, (called ‘imago’). {Some insects may by-pass some of these stages.}

Life span:

Most insects live a very short life; but there are some that live for years.  The longest lived insects, for 25 years (?), some do not move from their nest or home, like the ‘queen ant’, ‘queen termite’, etc.; some keep moving from place to place all the time.  Some insects spend most of their life in the larva or pupa stage, and as adults, they live only for some days, hours, or even minutes: as an adult, the mayfly, for example, lives for 48 hours, but the female of another species of mayfly lives only for 5 minutes!  Some insects spend some 2-3 years in their larval stage in water, and when they become adults, they come out of water, and live long enough to mate with their opposite sex partner to produce eggs, and then die!!

Useful insects & harmful insects:

People tend to talk more about the insects which they see regularly and which are mostly harmful.  Though it is a fact that there are too many insects that are harmful to people, there are certainly some kinds of insects that are very useful to people and other animals, but are never noticed or talked about.

harmful insects:

It is estimated that there are about 10,000 species of insects that are classified as pests: mosquito, fly, cockroach, , louse, tick, bed bug, flea, etc. depend directly on people and other animals, and there are numerous insects that damage the crops or livestock, such as locust, weevils, aphids, tstse fly, etc., there are still some other that damage peoples’ things – structures, furniture, books, clothes, etc., such as wood worm, termites, ants, silverfish, book-worms, cockroach, etc.

useful insects:

There are some insects without which people and other animals cannot survive, or may find it difficult to survive.

There are some kinds of insects that other animals depend on directly – bees, being the best and the commonest example. People eat honey, and other animals, including birds, eat honey and the wax.  In some parts of the world, insects are eaten by people! There are butterflies, bees, wasps (some kinds only) that help people and other animals indirectly by pollinating the plants on which the rest of the animal world lives! There are some others, like the dung beetle, that help us keep our surroundings clean; and, there are the likes of ichneumon fly that keep some kinds of harmful insects under control by eating them up!

distribution:

Insects are found everywhere on the Earth.  Some insects migrate (= to go from one place to another distant place depending on the changes in the weather); some other kinds hibernate (= to go into a deep sleep to avoid the very cold or very hot weather conditions, for example, the butterfly, locusts); yet some others live all their life at one place and just die when the conditions change!

{The scientific study of insects is called ‘entomology’, and the scientist who studies insects scientifically is called an ‘entomologist’.}
For an interesting article showing the difference between a ‘bug’ and an ‘insect, please click here.

For an interesting article on the differences between a ‘spider’ and an ‘insect’, please click here.

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