Insect vs. Bug: What’s the Difference?

Contrary to popular belief, bugs and insects are not the same thing. They are two classifications with many physical differences.

Oct 13, 2023By Colt Dodd
insect vs bug difference

Imagine an aphid and a butterfly side-by-side. At first glance, these are both bugs––a common term for any creepy crawly of the six-legged variety. However, in the scientific community, there’s a stark difference between insects and bugs. As the saying goes, all bugs are insects, but not all insects are bugs. It’s like saying all cats are animals, but not all animals are cats.

The difference between insects and bugs boils down to their evolutionary design and characteristics. Here, budding entomologists can learn more.

Bugs and Insects Are Classified Differently

Bugs and Insects
Image Credit: Wikimedia Commons

Since the 1700s, scientists have classified living things into categories based on their physical appearance, evolutionary origins, and behaviors. This is called taxonomy. Making distinctions between seemingly similar creatures lets scientists learn more about their roles in nature and how they co-exist.

When thinking about bugs versus insects:

  • True bugs generally belong to the Hemiptera order. Hemiptera comes from the Greek meaning “half-winged.” This classification contains more than 80,000 types of bugs. They generally have hard wings and proboscis, a straw-like tongue used for eating.
  • Insects are in the Insecta class. This is a much larger classification than the Hemiptera category. Insects generally have three body parts and three pairs of legs. They also undergo more life stages (typically three or four) than true bugs.

Types of Bugs

Green bug
Image Credit: Wikimedia Commons

Per the Smithsonian Institution, bugs have a hypodermic-needle-like mouthpart that allows them to suck blood and other fluids. For instance, (as the name suggests), bed bugs are true bugs. They have a proboscis that lets them suck the blood of sleeping hosts.

Other true bugs include:

  • Stinkbugs
  • Common milkweed bugs
  • Assassin bugs
  • Backswimmers
  • Coreid bugs
  • Creeping water bugs
  • Damsel bugs

Don’t be fooled by the suffix -bug. For instance, ladybugs are not true bugs. They’re actually beetles, and they belong to the Coleoptera order alongside fireflies, weevils, and scarab beetles.

Types of Insects

praying mantis against a blue background
Image Credit: Wikimedia Commons

The Insecta group is one of the largest taxonomic classifications. Sometimes called “Hexapoda” (meaning six legs), these critters include:

  • Wasps
  • Bees
  • Butterflies
  • Moths
  • Beetles
  • Fleas

These insects’ bodies typically comprise three parts: a head, thorax, and abdomen. The head includes a set of compound eyes and an antenna. They also use mandibles (a set of jaws) to eat rather than a proboscis.

Both Bugs and Insects Are Arthropods

Wikimedia Commons
Image Credit: Wikimedia Commons

Both bugs and insects are classified as arthropods. To belong to this category, an animal must:

  • Have an exoskeleton. Both bugs and insects have a hard exterior called “chitin.” As they grow, they shed their exterior when it becomes too confining. How often they shed their skin depends on many factors. For example, younger tarantulas typically molt once a month, while older spiders might molt once or twice a year.
  • Have a segmented body. Both bugs and insects generally have three or four segmented body parts, each with its own specific function.
  • Have jointed legs. Arthropods have multiple legs that allow them to bend, move, and hide in tight spaces.

Bugs and insects aren’t the only creatures in the arthropods category. Others include spiders, lobsters, and horseshoe crabs. Just like bugs and insets, they rely on segmented bodies and have hard exteriors.

How to Tell Bugs and Insects Apart

a spider on a white surface
Image Credit: Wikimedia Commons

You’re on a walking trail when you spot a caterpillar resting on some milkweed. Is this striped beauty a bug or an insect? To tell the difference, ask yourself some questions, like:

  • Does this critter have six legs? All insects have six legs, but not all bugs do.
  • What does this critter eat? Most insects would have a proboscis for sucking nectar and liquid, while many bugs would have mandibles for capturing live prey.
  • Does this animal have mandibles or a proboscis? This is a tricky one because some insects have mandibles as juveniles, but then shed this feature in favor of a proboscis. Yet, for the sake of “Is this caterpillar a bug or what?” it has mandibles, just like many insects.
  • Does this critter have a segmented body? At first glance, a caterpillar just looks like a decorative worm. However, upon closer inspection, it has three thoracic segments and 10 abdominal segments.
  • Is it an arthropod? Sometimes, it helps to think about bugs and insects in a bigger context alongside other species. Remember: arthropods have hard shells, multiple legs, and molt throughout their lifetimes.

When in doubt, there are many apps online that allow for the easy identification of bugs and insects. Simply take a picture of the mystery maggot and wait for the results. Google Lens (which comes with the Google app) also has this feature.

Are Snails Bugs or Insects?

a snail on a sidewalk
Image Credit: Wikimedia Commons

Despite having a hard shell and antennae, snails (and slugs, for that matter) are not bugs or insects. They belong to an entirely different classification altogether. While some argue that they are distant relatives of insects and bugs, they’re more closely related to mollusks, such as octopuses and squid.

Like arthropods, mollusks have their own characteristics, including:

  • A specialized “foot” that allows for creeping, digging, and grasping
  • A mantle (a piece of soft flesh) that protects the internal organs
  • A radula, a tiny structure with teeth that lets mollusks feed

Snails eat just about anything they can digest, and that includes bugs and insects. On the other side of the coin, it’s not uncommon for an ant colony to carry off a helpless snail and chow down.

Bugs and Insects Have Their Own Niche

Image Credit: Wikimedia Commons

Nature is fascinating. Even the smallest garden can host thousands of different species, each having carved out its own space. While there are many differences between bugs and insects, to some extent, they both rely on each other for survival. For more information on bugs, insects, and all things creepy-crawly, the online resources are limitless.

Colt Dodd
By Colt Dodd

Colt Dodd is a sighthound enthusiast with three years of freelance writing experience. He has an Italian greyhound/Shetland sheepdog mix named Homer. In his spare time, he enjoys going to dog parks and writing fiction.