For most people, the terms “bugs” and “insects” are used interchangeably to refer to any itsy-bitsy critter flying through the air or crawling on the countertop. But etymologically, there are a few small, yet notable distinctions that differentiate the two words. So when is it appropriate to call something a bug vs. an insect? To understand this debate, let’s travel back to a middle school science class lesson.
Scientists classify living organisms using a seven-tiered taxonomy scale: kingdom, phylum, class, order, family, genus, and species. (A common mnemonic to help remember this order is: King Phillip Came Over For Good Soup.) These distinct groups range from the most general at the top (kingdom) down to the most specific (species). Within the kingdom Animalia, you’ll find a vast array of living creatures that includes humans, birds, baboons, and beetles, just to name a few. But once you drop down a level to phylum, you begin to see significant differences both biologically and etymologically.
The phylum Arthropoda includes pretty much all the critters that we’d refer to as “bugs” — beetles, spiders, moths, centipedes, ticks, ladybugs, you name it. However, it also includes crabs, lobsters, shrimp, and any other creatures with an exoskeleton, a segmented body, and jointed appendages. The specific term “bug” originated in Middle English as the word “bugge,” referring to a “frightening scarecrow.” Over time, its use was expanded to include anything that induced fright, such as creepy-crawlies.
The term “insect,” meanwhile, is derived from the class Insecta, which is a more specific grouping further down the taxonomic scale. By their literal definition, all insects have an exoskeleton, head, thorax, abdomen, three pairs of jointed legs, and a pair of antennae. This means that the term can be used to describe ants, beetles, butterflies, cockroaches, grasshoppers, fleas, termites, and many more creatures. At the same time, it would be inaccurate to refer to centipedes or spiders as “insects” since they lack all those features. (Centipedes are in the class Chilopoda, and spiders are in the class Arachnida.) When it comes to nomenclature, using the term “bug” for a crawly critter is almost always correct, as it’s a far more general term than “insect.”
