What do you call every animal that's not six legged?

A non-insect?

Spiders, ticks, mites, scorpions-arachnids.
Crayfish, lobsters-crustaceans
Centipedes, millipedes- myriapods

Millipedes and centipedes belong to Diplopoda

Bugs.

A non-insect, non-vertebrate?.

Spiders are Arachnids

First of all, not everything with six legs is an insect. There are at least three species of hexapod that do not count as insects: proturans, springtails, and two-pronged bristletails. But in any case, just like we don’t have a single word for all liquids that aren’t water, we don’t have a single word for all creatures that aren’t insects (or hexapods).

They are all invertebrates or arthropods, but those words also describe the 6-legged varieties. There is no word that includes only those invertebrates with more or fewer than six legs.

Thanks all.

I keep hearing _*”.....(fill in the blank) is not called an an insect because it is not 6 legged.”
@JeSuisRickSpringfield “First of all, not everything with six legs is an insect.”
What qualifies for the label insect?

@dappled_leaves that makes sense to me. What doesn’t make sense to me is labelling animals just on the basis of how many legs they have. Like birds and humans have 2 legs, yes, they are (bipedals?) but so what? That is what made me ask the question.

@flo People say say “____ is not an insect because it doesn’t have six legs” because having six legs is a requirement for being an insect. In other words, all insects have six legs (anything that doesn’t have six legs isn’t an insect), but not all things that have six legs are insects (just because something has six legs doesn’t mean it automatically is an insect.

Here is an example that might help: a square has four sides, but not everything with four sides is a square. That’s because having four sides is just one requirement for being a square. To be a square, the four sides also have to be equal and they need to meet at right angles.

So back to insects. In scientific classification, “Insecta” is a class. But classes are a lower level (which, in this case, means more specific) level of classification. To belong to the class Insecta, a creature also has to fit the definition of all of the classification levels above it. Insects are invertebrate animals that have a chitinous exoskeleton, a body that is segmented into three parts, three pairs of jointed legs, compound eyes, and one pair of antennae.

Something counts as an insect only if a creature meets all of these specifications.

@flo ” What doesn’t make sense to me is labelling animals just on the basis of how many legs they have. ”

Sure, it does seem strange in some respects. People have been trying to put organisms into groups with common traits for thousands of years. Although we get better at determining what organisms go with what other organisms and why, our language (and many other languages) still retains words that were used when we weren’t very good at it.

@JeSuisRickSpringfield Thank you that was a great answer!
Thanks to all who gave serious answers.