Due to the nature of my work, I'm around disturbed earth quite a lot, and I've noticed that wasps seem to like it; there always seem to be plenty around anyway, at least in summer and early autumn (not now the weather is colder), and they seem pretty curious about whatever is going on nearby.
This got me thinking about the possibilities for gaming, tunnels and whatnot (including fresh digging) being an important part of the setting of D&D. Killer Bees are of course a well-established monster, but what about giant Mine Wasps? They'd hang around Dwarven and Gnomish tunnels and disrupt the activities going on there, I'd suspect. I can imagine big wasps being a problem for Gnomes. Halflings too like burrowing in the earth, so perhaps their settlements would be plagued by these things. Or maybe, Halflings settle where there are no giant wasps. Maybe that's why Halflings stay close to home? In the Wild, there is too much change of encountering Mine (or Burrow) Wasps. It's a serious business, I guess, establishing a new Halfling community (or even setting foot out of your door, as Bilbo reminds Frodo).
Perhaps there are even Grave Wasps, that have some affinity with freshly-dug graves. These would naturally be good animals for Necromancers and certain evil clerics to have domesticated, to use as both scouts and guards (and wasps as we all know being made of pure evil anyway).
Giant Spiders (such as in Mirkwood, Shelob, Ungoliant) are part of the lore of fantasy worlds. Other arthropods too - Sam is plagued by 'neekerbreekers' in the Midgewater Marshes, and 'Hummerhorns' (giant flying insects) are at least referred to in Hobbit songs (if not necessarily as real creatures... but they could be).
I was also bitten (I should say nipped really) some time ago by a kind of green shiny bug. I don't know what it was but there seemed to be a lot of them where I was. They were very small (only a few millimetres long) but I definitely felt the nip. A scaled-up version would be at least as fierce I think, like a bright green Tiger Beetle perhaps; I decided that it should be called a Dragon Beetle.
A couple of years ago I was working at a place called 'Dragonfly Mews'. That got me wondering about who would need to keep dragonflies in a special housing, presumably using them to hunt. Some elven Court, perhaps? Maybe they use giant dragonflies the way humans hunt with hawks. In that case, what would they be hunting?
Perhaps it's Halflings who use them - probably, slightly smaller ones than theoretical Elven hawk-insects. Or perhaps the dragonflies are kept by some insane lord for hunting the Halflings. That would be pretty sinister. Perhaps these things are even the Hummerhorns of Hobbit folklore. I still haven't decided, but these questions will be bugging me for some time to come I'm sure.
