What Is an Insect

A ladybug, a mosquito, and a giant stick bug that grows longer than your arm all have one thing in common: they are all insects! In fact, scientists have named over 1 million different kinds of insects, more than every other animal on Earth put together. But a spider is NOT an insect, and neither is a worm or a snail. So what makes something an insect? It comes down to counting body parts.

- The three body parts every insect has: head, thorax, and abdomen - Why insects always have exactly 6 legs - How to tell an insect apart from a spider or other bug - Where insects live and what most of them eat

Every single insect, no matter how big or small, has exactly three body parts. The head holds the eyes, mouth, and two antennae for smelling and feeling. The thorax is the middle part, and that's where the wings and all six legs attach. The abdomen is the back part, and it's where the insect breathes and digests its food. Next time you see a bug, look for these three sections. If you can count three clear parts, you might be looking at an insect!

The easiest way to check if something is an insect is to count its legs. Insects always have exactly 6 legs, no more, no less. A spider has 8 legs, so a spider is NOT an insect, it's an arachnid, a totally different animal group. A pill bug, sometimes called a roly-poly, has 14 legs, so it isn't an insect either, it's actually related to shrimp and crabs! So remember: 6 legs means insect. Any other number, and it's something else.

Insects live almost everywhere on Earth: in your backyard, deep in caves, high on mountains, and even in freezing cold Antarctica. Different insects eat very different things. Butterflies sip nectar from flowers through a long straw-like mouthpart called a proboscis. Ants eat tiny bits of almost anything, from crumbs to other insects. Ladybugs are great garden helpers because they eat aphids, tiny bugs that damage plants, sometimes gobbling up 50 aphids in a single day!