>>40050899
modern bugs have well defined ancestry going back to the cambrian, most of the rly famous cambrian animals like anomalocaris & opabinia are part of a broader overarching lineage that also included the ancestors of today's spiders insects crustaceans etc as well as what would become the tardigrades & velvet worms of today
where that diversity in the cambrian came from isnt really clear but prior to the cambrian explosion the common ancestor of the groups that would later diversify into bugs, vertebrates, and most other animals wouldve been a simple tiny worm thing with a mouth in front and an anus in the back. this basic body plan is the essential template for most animal life on earth and all the more complicated forms are really just tacking things on to the underlying worm shape, whether its exoskeletons and antennae or skin and bones