User blog comment:Lord Loss/Discussion of the Week: Neopterons/@comment-6050823-20140418004021/@comment-1011548-20140418165823

Yeah, centipedes/milipedes are myriapods, spiders/scorpions are arachnids, all the six-legged things are insects, and insects, arachnids and myriapods are all in the Arthropod phylum.

Neoptera are a sub-group composing of a few winged insect species and Chelicerata are basically the arachnids + horseshoe crabs and an extinct branch of seascorpions. Obviously Capcom picked them for their cool sounding names, and doesn't stick strictly to their real-world definitions.

There's a few more sub groups and things, but that's a general gist of it. And it's easier if you draw a diagram. ;-)