The gnats are in east shroud, between the hawthornes hut aetheryte and the friendly sylphs - they congregate around that one tree stump and south of there near the edge of the forrest.
Ok, this simplifies things some. So technically im not sure if someone else playing your account violates any rules, so i wont recommend that(im not saying dont do it, but certainly dont make a point to talk about it). Back to some specifics. It occurred to me that i skipped a couple bug types when i made that list yesterday(antlions, buzz flies, chocobo fleas, grasshoppers, silk worms), but your description makes it sound like these probly wont be much of an issue. When i say butterfly type enemies, im referring to something like this. When i say ant, it looks like this. And when i say worm, they typically look like this guy. Of those, the butterfly type is fairly uncommon and only appears in one or two zones and dungeons. The ant type is mostly just cutters cry and a small bit of the overworld in north-western central thanalan. The worm type is the open desert of southern thanalan, but it appears a few times as a mid-dungeon boss. Im going to move on assuming that all these other bugs arent the issue, though we can revisit if needed.
Mentioning separately, the gnath(mentioned above from the dravanian region) are actually a beast tribe. Theyre kinda like beetle-people but with a hive mind. Being anthropomorphized a bit, im not sure if that would make them better or worse. The story will have you defeat their god Ravana eventually.
Ok, bees etc are the main culprit. I wont include any screenshots here as im sure i dont need to. The game primarily seems to use 3 models for these types of enemies, and two can be found in east shroud. There are some smaller "traditional" bee types near the honey yard on the west side of the map, and you met what ill refer to as the gnat type on the east side of the map. The third type is kinda a hybrid of the two(and likely would be the worst of both worlds), and ill refer to this as a hawk type. So the traditional type shows up in a few dungeons as trash/add enemies. These often have a killer finishing move called final sting, and traditional strategy is to kill them first and quickest. They appear as adds during a boss fight in Qarn(optional dungeon at level 35, the story makes you clear it once at 50). They appear again as "adds" during a boss fight on your required trip up Sohm Al(in this particular fight the plant boss is using pollen to attract them - they ignore you and approach him and he eats them for a buff so killing them reduces his damage but they never attack you). They can also be found in optional dungeons Neverreep, Hullbreaker Isle... and i think thats it. They can also appear on some of the floors of Palace of the Dead. The gnat type is mostly relegated to the east shroud so you wont run into many of those once you leave.
Which leaves the hawk type(which someone commenting on 14db described as "this creature is seriously from my nightmares!" - so you arent alone). These are mostly overworld enemies, and you wont run into any until well after 50. Dravanian Hinterlands has a set youll need to bypass to get to the settlement of Idyllshire. They inhabit the upper portion of the last forest in the Fringes close to Castrum Oriens. They can appear as an enemy set in Aquapolis(these are randomized so they might not). The boss of the beehive section of the Arboretum is actually a hawk model. And to clarify one thing, the Arboretum is just that - an arboretum. Its been ignored for years(in the storyline), so all the plants are overgrown. You mostly fight plant enemies in there, but after the first boss you need to move through an overgrown beehive to get to the end. This includes smashing through honeycomb walls, riding a honey slide, and a boss fight with a large hawk-style queen bee. Once you beat her and exit the other side of the hive, its back to plants. But yeah, the 5-8 mins that part of the dungeon takes(synced, unsync you can run through it much quicker) would probly be a bit too intense for you im guessing. And im going to give a special call out to the A rank hunt Erle in the fringes. Erle is a giant hawk model. As an A rank he can spawn randomly almost anywhere in that zone(though once defeated he stays down for like 4 hours), and being an A rank means that he is agressive if you get in range. When you eventually get there(level 61ish), hes something to be on the lookout for and to give a wide berth to.
I dont think im forgetting anything, but im doing this mostly from memory so its possible i am. Best of luck!