What Are Insects?
Insects are the largest group of Arthropods. Over 90% of the different types of animail on earth are insects. You
can find insects almost everywhere. They have a hard external skeleton that protects their body and a three-part body which consists of the head, thorax and abdomen.
The Atlas Moth is not the world’s biggest insect, but it is the world’s biggest moth They have three pairs of jointed legs, two antennae and a pair of compound eyes. Compound eyes are different from human eyes which have a single lens for each eye. Compound eyes have many lenses for each eye. For example, the fly has about 4,000 lenses in a single eye. That is why they can see very well. Compound eyes possess a very large view angle, and can detect fast movement.Compound eyes are common in arthropods.
How Many Types of Insect are There?
Insects are the most diverse group of animals on the planet. For example, there are about 2,200 species of praying mantis, 5,000 types of dragonfly, 20,000 types of grasshopper, 82,000 species of bug, 120,000 species of fly, 110000 species of bee, wasp, ant and sawfly , 170,000 types of butterfly and moth and 360,000 different beetles. Insects have two or four wings depending on their species. The different types of insects alive today include
- The Bristltails – these wingless insects have not been studied well. There are about 350 different species, some even living in the cold of the Arctic!
- Silverfish are flat insects that eat starchy food such as cereal or paper. There are over 200 species.
- The Mayflies are famous for having very short lifespans – some live for only half an hour as adults! Mayflies are very sensitive to pollution. There are about 2500 species.
- The Dragonflies and Damselflies are a group of relatively large insects. Dragonfly larvae live in the water, and are predators. Their prey includes mosquito larvae.
- The Stoneflies are rather long, simple insects. There are over 1700 species, with more being discovered regularly.
- Webspinners live in tube-shaped tunnels that they line with silk. Most of the 300 types of webspinner live in the tropics.
- The 34 types of Angel Insects live in small colonies under rotting wood, eating mold spores and mites.
- The Earwigs have a longish body with a pair of pincers at the tail. There are about 1800 types of earwig. All are harmless – the pincers are not poisonous, and earwigs don’t carry any disease.
- The Crickets, Grasshoppers and Locusts include about 12000 species of insect. The Little Barrier Island Giant Weta from New Zealand, probably the
world’s largest insect, belongs to this group.
- Stick Insects disguise themselves as twigs or sticks to hide from their enemies. There are over 3000 different species. The world’s longest insect is one of them.
- There are about 30 different species of Notoptera, called ice-crawlers or gladiators.
- Of the 4000 types of Cockroach, only 30 live in houses. What’s more, the 4000 types of Termite are now considered by scientists to be a special kind of cockroach, making a total of 8000 different species in this group.
- The Mantises include another 2200 species of well camouflaged, predatory insects.
- The Booklice and Barklice include over 5500 species of winged insects that eat lichens or the paste in book bindings. Additionally, the 3500 species of Lice, including the 3 species that
are parasites on humans, belong to this group.
- Thrips are tiny insects that eat mites or suck sap from plants. There are over 5000 different types.
- True Bugs, Aphids and Cicadas are grouped together into another group, with 80000 species, called Hemiptera. The largest grow up to 15 cm long (6 inches)
- Ants, Bees, Wasps and Hornets are grouped together into the second most diverse group of insects. Over 120,000 different types have been named, and there may be as many as 300,000.
- Beetles are the most diverse group of animals on the planet, with over 350,000 known beetles, and millions yet to be discovered. One in every four known type of animal is a beetle. The Goliath Beetle larva is the heaviest insect of all.
- The “Twisted-Wing Parasites” are little-known parasitic insects that attack, mainly, other insects.
- Snakeflies are common in Europe and Asia with large compound eyes. The eggs hatch in tree bark or rotting wood. There are about 150 different species.
- The 300 or so species of Alderflies, Dobsonflies and Fishflies belong to a group of insects called Megaloptera, so named because their wings are large. They are not well known, because the adults don’t live very long.
- Lacewings, Antlions and so forth make up another 4000 species of insect.
- The Scorpionflies have, at their tails, something that looks like the tail of a scorpion, but is harmless. There are about 550 different types.
- Fleas have no wings, and need to suck blood to survive. In the past, some terrible diseases have been passed from human to human by biting fleas. There are about 2000 known species of flea.
- Flies, Mosquitoes and Midges are grouped together into a large group of 240,000 or so different types. True flies have only a single pair of wings. Some members of this group, especially some mosquitoes, are responsible for transmitting some terrible diseases. For example, Malaria makes 350 million people sick each year, killing 1.5 million of them.
- Caddisflies have hairy wings
- Lepidoptera contains the 180000 or so species of moth and butterfly. The largest flying insects belong to this group.
An Insect’s Body Structure
The thorax contains the legs for walking, swimming, jumping or digging. Most insects use six legs for walking and they can walk rapidly and steadily. For example, cockroaches – cockroaches are amongst the fastest insect runners. Water beetles and water bugs have legs like paddles to help them to swim. In fact some can even walk on the surface of the water like water spiders. Insects are the only group of invertebrates that can fly. Their abdomen has all their vital organs – their heart, digestive system, respiratory organs, as well as the organs for eliminating waste products and more. Most insects must moult in order to grow. During moulting, the insect will cast off the outer layer of its body. This either at specific times of year, or at certain points in its life-cycle.
The Wetapunga, or Little Barrier Island Giant Weta, is the World’s Heaviest Insect
Insects and People
Many insects are pests to us. For example, mosquitoes, flies and cockroaches spread diseases, termites damage houses, some aphids, beetles and caterpillars destroy our food crops. On the hand, there are also insects which help us – pollinating flowering plants (bees, flies, butterflies and mosquitoes), producing honey (bees) or silk (the silkworm moth), eating other insect pests (ladybirds), or cleaning up (ants). Plants can’t reproduce without pollination, and many types of plants depend on insects to do this job. They make flowers to attract insects. As bees get nectar from flowers, they get the flowers’ pollen all over their bodies, and carry it to other flowers.
What is the World’s Largest Insect?
There are several contenders for the title of world’s largest insect. The heaviest ever weighed was a Little Barrier Island Giant Weta from New Zealand – which looks like a big ugly cricket. A close contender is the Goliath Beetle, which is certainly heavier as a larva. Scientists are not yet exactly sure which of these grows bigger in general. The longest insect ever measured is a kind of stick insect from Borneo, about which very little is known – only three specimens have been found, the longest of which was 56 cm long (22 inches), and is now on display in the British Museum.