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Insects: A basic look at the creepy crawly world of insects

Updated on August 20, 2013


Entomology is the study of insects. According to the Entomological Society of America, there have been over a million different species of insects identified, but there could be as many as 30 million that have not yet been discovered. That’s a lot of different critters. We don’t have nearly enough room in this study guide to go into a lot of detail about insects so we’ll just cover the basics.

The class Insecta, or insects, have three pairs of legs, a segmented body divided into three regions (head, thorax, and abdomen), one pair of antennae and, usually, wings.

Insects are a class in the Phylum Arthropoda. Other Arthropods have more than three pairs of legs and only one or two body regions, and they never have wings. Other common classes of Arthropoda are Crustacea (such as sowbugs, crayfish, crabs), Diplopoda (millipedes), Chilopoda (centipedes), and Arachnida (such as spiders, ticks, mites, scorpions).


Fun Fact

Dr. E.O. Wilson of Harvard University estimates that there are nearly 10,000,000,000,000,000,000 (10 quintillion) insects in the world.

A stack of 10 quintillion pennies would be about 50 miles square and be worth 100 trillion dollars. If you spent $100 a second it would take 31,688 years to spend $100 trillion.


You can see the black stylet of this shield bug
You can see the black stylet of this shield bug | Source

Are insects bugs? Yes and no. Not all insects are bugs, but all bugs are insects.

Bugs are a type of insect. Some common bugs are the boxelder bug, assassin bug, and stink bug.

Bugs have a stylet (a mouth shaped like a straw) that they use to suck juices, mostly from plants. Assassin bugs use their stylets to suck blood from other insects.

Fairyfly wasp


The long and short of insects

Insects come in a wide variety of shapes and sizes. The Titan Beetle lives in the Amazon rain forest and can be as long as six and a half inches.

The walking stick can have a body is 14 inched long. With legs extended they can be over 20 inches long.

The smallest insect is a wasp that eats the eggs of other insects.

The Fairyfly, shown here much larger than it’s real size, is between .1 and .17 millimeters long. That's about as big as the period at the end of this sentence.

Dragonfly nymph exoskeleton


Natures coat of armour

Humans have a skeleton made of bones. Insect skeletons are on the outside of their bodies. This kind of skeleton is called an exoskeleton. It’s a lot like a suit of armor.

The exoskeleton helps protect an insect from injury and can prevent them from drying out.

One of the problems with an exoskeleton is that as insects grow, their skeleton doesn’t. If you outgrew your suit of armor you’d need a new one.

Growing insects periodically shed their exoskeleton. The old one splits and the bigger insect crawls out of it, leaving it behind. If you find what looks like a dried out insect, it’s probably a discarded exoskeleton.

Insects come in all shapes, colors and sizes. Some try to hide, others want to be seen. Some even pretend to be something they are not.

Since there are a lot of predators that eat insects, many use tricks to avoid being eaten. For example, the leaf insect on the right, looks like leaves. This makes it harder for predators to see them. Some insects fly or jump to get away. Others try to fool predators into thinking they are much bigger and meaner than they really are.

This moth usually rests with it’s outer wings closed, covering the spots on its lower wings. When a predator, like a bird, gets close it will hold as still as possible in hopes that its drab color will make it hard to see.

If the bird gets too close. the moth will spread its outer wings, revealing the spots. Sometimes this tricks the bird into thinking the moth is a bigger animal and that the spots are eyes.


What do insects eat?

There are so many different kinds of insects that it makes sense they don’t all eat the same things. Many insects eat plants, but some eat other insects, nectar from plants, blood, and dead animals. Some insects compete with humans for food. Some are destructive and some are very beneficial.

Most insects chew their food, but some, like mosquitoes, use special mouth parts that work like a straw to eat fluids from plants, animals and other insects.


Fun Fact

You will never be bitten by a male mosquito. Only the females bite.

Mosquitoes are attracted by the carbon dioxide that animals exhale when they breathe.

About two million people die each year from diseases carried by mosquitoes.

Honey bee


The good, the bad and the ugly

Many insects are very beneficial to humans. For example, bees, butterflies and other insects carry pollen from one plant to another. This fertilizes the flowers and makes it possible for fruit, vegetables, and other things humans use for food to grow.

Without insects we might not have apples, squash, and other things we like to eat.

Bees also use nectar they gather from flowers to make honey.



Mole cricket


The bad

Some insects are not as well liked as the honey bee. Some species reproduce very rapidly and can generate such large numbers of offspring that they become very destructive.

Army ants, termites, grasshoppers and crickets are some of the insects that can destroy food supplies and even homes.

Fortunately there are other insects, like the Lady Bugs and Praying Mantis that eat insects and help keep their numbers under control.

The Ugly

Although many insects, such as butterflies, are very beautiful, some others are considered to be ugly, like this mole cricket. Many of the not so attractive insects are those that can be very useful.

Most people get creeped out about maggots. These squirmy critters are really baby flies and they provide a great service.

They eat mostly dead animals and if they weren’t around we’d have lots of smelly dead things lying around to make our world a lot less pleasant

Activity: Go on an insect safari

With the help of your parent, teacher, or other adult go on an insect safari. You’ll probably see some critters that aren’t really insects, too. Remember that insects have three main body parts and six legs.

Unless your adult friend says it’s OK, don’t touch any of the critters you find. Some of them might bite or sting. If it’s OK with them, they can help you make an insect collection.

Common places to find insects

Insects inhabit every place on our planet except the ocean. Look for insects in these places:

•Under boards and rocks – Look for ants, crickets, beetles, termites.

•In or around water – Look for mayflies, dragonflies, aquatic beetles, true bugs, flies.

•Under loose bark, in logs and stumps – Look for termites, ants and beetles.

•On crops and in gardens – Look for grasshoppers, beetles, flies, aphids, leafhoppers.

•In the air – Look for butterflies, moths, flies, bees, wasps, beetles, leafhoppers.

•Around outdoor lights – Look for moths, beetles, true bugs, mosquitoes.

•In, around or on flowers and ornamental plants – Look for beetles, bees, wasps, ants, aphids, walking sticks, butterflies, moths.



Be careful

Some insects have powerful bites or painful stings. Most of these have bright of contrasting colors, like this wasp. This way, once a predator learns that the insect can hurt them, they will avoid any future contact with anything that looks the same.

Some insects use this trick to protect themselves. The hornet moth, shown below, doesn’t have a stinger, but it’s resemblance to the real wasp can keep predators away.

Always be careful when handling insects. Don’t touch them unless you know they are safe to handle.

Hornet moth



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