‘Bugs’ is a word used by many people to describe creepy crawlies, but it is also a proper biological term used to describe a group of insects known scientifically as Hemiptera. So shield bugs are bugs, waterboatmen are bugs, bedbugs are bugs but beetles are not bugs,nor are ladybirds, flies, wasps or bees. Certainly spiders are not bugs nor slugs nor snails.
I have tried to name the various insects but I am not an expert, so if you can be more specific or you think I have made a mistake then let me know. Just so you appreciate the problem of identification, in the group properly called bugs, ie the Hemiptera, there are about 1,630 species in Britain alone.