Ok but “bug” has multiple meanings, and almost nobody means “hemiptera” when they say it. More commonly, it’s any terrestrial arthropod. Arachnids are bugs. Centipedes are definitely bugs.

Heck, there’s a broader definition that basically includes all arthropods. “Moreton bay bugs” are a popular food this time of year. And they’re a kind of lobster.

uh, slugs are bugs! any non-vertibrate animal is a bug

uh, slugs are bugs

I’mma be honest, I would not instinctively agree with this.

I suggest “bug” applies exclusively to chitinous invertebrates.

I’m trying to square my instinct that

  • snails aren’t bugs (because they’re squishy without the shell) with the feeling that
  • crabs are bugs (because they’d go tap-tap if you tapped on their exoskeleton with a finger) but
  • hermit crabs aren’t bugs if they’re in a shell but are bugs if they’re naked
  • Snail shells aren’t chitinous.

    Crab shells are chitinous.

    Hermit crabs are only partly chitinous, and the shells they use are not chitinous.

    Hope that helps