I have been proceeding through the ranks of Bug Stomper and Animal Control (rank 2 out of 3 in each case) and it seems I already do quite a lot of melee and guns damage vs. mutated animals and insects at melee 80 and guns 79. When I reach rank 3, I understand that I will get a 10% damage bonuse vs. mutated insects and mutated animals respectively.

Is it worthwhile to spend a one of the precious few perk slots on Entomologist or Hunter? It would seem these perks would only be helpful with Cazadores (Entomologist) or Night Stalkers (Hunter), as those are the only insects and mutated animals I have come across that are still a bit problematic and require more than one sneak critical hit to take down at this point (level 21). Are deathclaws considered mutated animals?

I wouldn't waste perk points on them, it seems rather counterproductive

I guess if you want to do an unnecessarily silly amount of damage to a particular group, yes.

http://fallout.wikia.com/wiki/Abominable Along with Nightstalkers and anything else covered by http://fallout.wikia.com/wiki/Purifier_(perk).

What's the "Vs" thing? You can have all that stuff with little trouble. Rank three of Bug Stomper + Entomologist really cuts Cazadors down to size.

This alone makes purifier worth it for me, because it covers a good 50% of the tougher enemies in the game: super mutant masters, nightkin masters, deathclaws.

Everything but praetorians/NCR heavy troopers/BoS Paladin and Cazidore.

Well at level 21 with 79 guns, I would expect you could kill weaker insects and animals fairly quickly since they are weaker enemies. Other than Cazadores, I have Bug Stomper, and they are still tough.

perhaps this is because i have light armor and low endurance, but the Cazadores have been the most difficult creature in the entire game for me. sentrybots, deathclaws, nightkin, most other tough enemies, even bosses, I can knock down with superslam and hack them to bits with the supersledge as they try to stand, but cazadores only need one good hit and I'm dead, even though i'm regenerating +8HP/sec due to rad child at deadly rad poisoning level. their flight pattern also makes them extremely hard to hit from a distance without using VATS.

Sniper rifle shots to their wings (with handloaded .308) stops Cazadores cold. Of course, if 4 or 5 are swarming you....

Animal Hunter is probably not as useful. Toughest opponents in animal category are lakelurks and firegeckos. Also note that perk bonus damage apply only on criticals. But then, there are few useful perks on level 2 so you might take it if you have survival of 30.

Entomologist on the other hand covers giant radscorpions and casadores, one of the toughest opponents out there. Bonus damage also apply to any hit so I'll say, this perk is pretty useful.

Level 21 with 79 guns? How?! I always max out my weapon skill first.

And what do you do with skill books later in the game?

All those perks I consider useless.

I'd imagine that the effects of the perks earned from challenges stack with normal perks, so if you want to do absurd damage to "insects" (Qoutation mark used because scorpions are arachnids, not insects, yet the game would have us think otherwise.) and animals, I guess you could take the perks, I wouldn't do so myself, though, since there don't seem to be too many really powerful enemies in either catagory, the only enemies in the insect catagory that I could see being worth spending a perk to kill more quickly are giant radscorpions and cazadores, cazadores could be really dangerous if you let them get close enough to attack, and giant radscorpions sometimes just make me want to shout "Why won't you die?" As far as Hunter goes, deathclaws and nightstalkers don't count as animals, then I wouldn't bother with it, I might consider Entomologist, though. But really, I'd agree that Purifier sounds like the most useful perk that gives bonus damage against a certain type of non-human enemy, seeing as it covers supermutants, nightstalkers and deathclaws... especially deathclaws.

There's a thread around here about your Fallout OCD moments... Mine is, I always took Etymologist and Robotics Expert in F3 and damned if I'm not doing it again in FNV. No reason, really.

OT: I love that you can stomp those little mantises.