This is a post i left on another forum talking about what the set bonuses do (perhaps tell us somewhere? haha)
"The spider armor set bonus is not speed. Each piece on its own for some reason give a speed bonus. i used stopwatches and the rake handle for consistency. the mite hat, which also has hyperstamina, does not increase speed, but it does exactly what its description says, increases stamina efficiency (like running uses less stamina – the hat is about 20%). The bee pieces (rotten of course) do roughly 30-40% total (10% each maybe?) decreased stamina when running. The aphid slippers (“The Quickness”) give a speed bonus of about 20% while each spider part gives about 10%. so something seems like a bug with the spider gear, whether its the wrong effect name on each (hyperstamina), or maybe the set bonus is accidentally being split between all 3? i dont have grub or spider sets yet. When i get the spider gear in survival, ill check for stamina efficiency, or you could assuming you have it. I tested by running at a 3 long wall or so at just a slight angle. it takes about 25 seconds to deplete stamina from running with no buffs. if it also has better efficiency, i would bet that the set bonus is faster movement, but its been accidentally split and given to all pieces."
TLDR: hyperstamina on mite hat is efficiency, but a single spider piece (which says hyperstamina) gives speed (efficiency is unknown as i dont have them in survival). Is the hunters prowess speed? if so, it has been accidentally applied to individual pieces. or is spider being marked with hyperstamina actually the wrong effect name? i feel like there has to be something wrong here; it cant be right.