“Bugs” not only includes insects and spiders, it also includes millipedes, centipedes, worms, and terrestrial isopods (“pill bugs”) – none of which are insects. It’s basically any small terrestrial/freshwater arthropod that isn’t obviously a crab/crayfish.

adventuresinchemistry:

so it’s even more non specific than i thought!

but yeah, as like a 10yo i really only knew about the insects and spiders thing and boy did it piss me off

True bugs are members of the order Hemiptera, all of which are insects having piercing, sucking mouthparts. Stinkbugs are examples. 

“Bugs”, colloquially, are any sort of crawly thing that aren’t obviously crabs, crayfish, or lobsters.