If you are really struggling with wolf spiders I have a simple, yet effective strategy for you to use to unlock this achievement along with the accompanying mutation. There are several places where wolf spiders spawn. In this video below, it demonstrates how easy it is to kill them with venom arrows from a distance. I made a "wolf spider play pen" with palisade walls and added spike traps inside to help soften them up. All you have to do is shoot them from up top. If you're lucky, under the oak tree you have 1-3 wolf spiders in there at any given time. This video shows 3 wolf spiders trapped for easy farming of spider fangs.
Same concept, but with no defenses. You can also just beat them with a mint mace and block well. If you are lucky, you can lure one out and go ham. See below video.