Harvesting bug parts is a big part of the game but some bugs often times never give you what you need. This is not really a fix to an issue, It’s more of a change to a mechanic.
So with so much time spent collecting big parts I think it would be fun to be able to choose which part of the bug you get to harvest.
For instance: You just killed a wolf spider and you are given the option to harvest (essentially pick) which parts of the arachnid that you want to keep before the rest of the body is ruined. So let’s say you’re given 5 picks, you could choose to slice 3 legs off that count as spider chunk, and then slice the fangs off which count as 2 parts. Or slice the body and grab the venom inside (which counts as a harvest) You could then grab 3 venoms an then get 1 fang and one spider chunk for a total of 5 harvested items.
We could go in-depth and make the tier of the weapon dictate how much could be collected from the bug. (More effective weapon > cleaner kill > less ruined body ala. RDR2 hunting mechanic)
Some body parts could be accessible by certain type of weapons like daggers to avoid puncturing boiling glands/venom sacs, hammers to squish spider sacs to extract spider web etc.