What Is an Insect?

What Is an Insect? | Smithsonian Video for Kids  

Insects are everywhere. Imagine taking all the animals on Earth, everything from the bees around your school to the elephants on the savannah. If you did that and sorted them, four out of every five animals would be an insect. That means the majority of animals on Earth are insects. In fact, it is estimated that there are around 10 quintillion individual insects alive all over the world. That's a lot of insects! Of those 10 quintillion insects, there are 900,000 species. They are the most diverse animal group on the planet, with different adaptations to move, eat, mate, and live in different environments. Even with so many different kinds of insects, they all share the same basic features, which we'll review in this video.

To get started, insects are part of the group of animals known as arthropods. Arthropods are animals with exoskeletons, which is a hard outer covering and jointed legs. They are an extremely successful group of animals throughout the history of Earth, which means they've been around for over 400 million years.

For an arthropod to be an insect there are certain features it must have. First, all insects have three main body parts: a head, a thorax, and an abdomen. Take a look at this bee for example. It has a head, a thorax, and an abdomen. The next feature is that all insects have six legs. One, two, three, four, five, six. Six legs. An animal like a spider, which has eight legs, is not an insect. The next feature is that all insects have a pair of antennae to sense things. The insects' antennae are attached to its head and it moves them around to sense chemical signals in the air. And finally, the last shared feature is that all insects have zero or two pairs of wings. This one is a little tricky to understand so let's take a look at it closer. Some insects have adapted over time to not have any wings, or just temporarily like ants or fleas. As for insects with two pairs of wings, see the dragonfly, butterfly, housefly, and beetle. Yes, insects like flies and beetles technically have two pairs of wings. It may look like they have one pair at first, but the second pair is actually modified, or looks different, usually to have a different function other than flying. For example, flies have modified pairs of wings called halteres that look like little clubs that help the insect maintain balance and steer while flying. And for beetles, their modified pair of wings is called the elytra — the hard structure that protects the wings underneath. Wings and legs are always attached to the insect's thorax.

Awesome, now you know that all insects have three body parts: a head, a thorax, an abdomen,  they have six legs, they have a pair of antennae, and they have zero or two pairs of wings. Now that we know the features that all insects share let's take a look at some animals and figure out which one is an insect.

Which one is an insect? Let's see if you can make the comparisons on your own.

All right, did you figure out which one is an insect? The correct answer is "B."  This was a little tricky. To be sure an insect is an insect, we have to look at a combination of features. B, the Malaysian stick insect, has three body parts, six legs, wings, and a pair of antennae.

Nice observation skills! You learned about what makes an insect an insect, looked closely at an animal, and applied what you learned to identify insects from other animals. That is the work of scientists!

The incredible diversity and success of insects is because of their body plan that allows them to adapt different environments and roles. Scientists study insects from all over the world, alive and extinct, to understand how insects have changed over time. They examine key features that we learned about today to learn more about these insects and their habitats, behaviors, what they eat, and even what other insects they're related to. 

Insects play an important role in shaping our lives today, from pollinating flowers to being a food source of other animals, and even cleaning up poop! Our world will look so much different if they weren't around. Knowing more about insects helps us understand our world better. So the next time you find an arthropod, be a scientist and take a closer look to figure out whether it is an insect.