What’s the Difference Between Bugs and Insects?

The difference between bugs and insects comes down to more than just semantics—both terms have scientific definitions.
Spoiler alert: This ladybug isn’t actually a bug.
Spoiler alert: This ladybug isn’t actually a bug. / AFP Contributor/GettyImages

When summer arrives, you can expect to see critters that fly, bite, and scuttle making the most of the warm weather. But whether you tolerate these creepy crawlies or you'd be happy to never see one again, you may ask yourself: Which are bugs and which are insects?

Bugs and insects aren’t necessarily the same thing. The two words are used interchangeably, with insects appearing mostly in scientific contexts and bugs being used more casually, but the difference between the terms comes down to more than just semantics. They both describe groups in the animal kingdom recognized by science.

The boundary around insects is clearer than it is around bugs. Insects are a class in the phylum Arthropoda, which also includes arachnids like spiders, myriapods like centipedes, and crustaceans like crawfish. Insects, along with all arthropods, have segmented legs and hard outer layers called exoskeletons. Unlike some other arthropods, insects typically have six legs, two antennae, and a body segmented into three sections (head, thorax, and abdomen). Insects comprise a lot of the creatures you tend to think of as bugs. Ants, grasshoppers, bees, and flies are all insects.

All bugs are insects, but under the technical definition, not all insects are bugs. True bugs belong to an order of insects called Hemiptera. There are a few characteristics that distinguish bugs from other insects: Most bugs have a straw-shaped mouth, or stylet, that they use to either sap juice from plants or blood from animals. They also tend to have long, segmented antennae and wings that are tough and dark where they meet the body and are thin and translucent at the ends. True bugs include stink bugs, bed bugs, water striders, and cicadas. Confusingly, some insects with bug in their name aren't actually true bugs, like ladybugs and June bugs (they're both beetles).

When viewed from a linguistic perspective, the line between bugs and insects gets fuzzy. Most people think of bugs as any small, non-sea creature with more than four legs, which covers everything from spiders to beetles to millipedes. That’s why entomologists refer to members of the order Hemiptera as true bugs and not just bugs, because even scientists are guilty of using the term in a general way.

A version of this story ran in 2019; it has been updated for 2023.