What is an insect?

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Many people use the word “insect” to refer to any one of many little crawling critters, like ants, spiders, dragonflies, beetles, and more. In truth, the word “insect” technically refers to just some bugs, and not all of them.

What we generally think of as bugs are animals in a scientific group called “arthropods.” Within arthropods are further groups of bugs, including insects and arachnids. Insects include bugs like beetles, flies, ants, bees, and butterflies. Arachnids include bugs like spiders, scorpions, and ticks.

A lot of the differences between insects and other arthropods have to do with physical features. Insects have three body segments (head, thorax, abdomen), six legs, and one or more pair of antennae. Other arthropods do not have these same features; arachnids like spiders, for example, have eight legs!

A big group of little critters!

Insects may be small in size, but as a group, they’re actually huge! Insects actually make up about three-quarters of all the animals on Earth, and there are about a million known species of insects. (And it’s very likely there are even more still unknown!)

Why do you think there are so many kinds of bugs on Earth? Do you think that being small helps them to survive? What else would make life as an arthropod easier or harder??

What kinds of bugs do you know about, and how are they helpful? For example, bees are helpful for making honey, while butterflies are helpful for pollinating flowers! What other helpful arthropod friends do you know about?