I like the idea of more ambient mobs- the overworld, (and other dimensions for that matter) is currently much in the way of... any ambiance at all. It's almost eerily silent without modifications installed for ambient biome noise. While this could be interpreted as an intentional part of the game, I think we could certainly benefit from more smaller creatures. However, while I'd agree with insects of some sort, this does seem a little redundant in regards to bees already being a thing. (No pun intended.)
It's clear this is a pretty heated topic- on the one hand, I like the idea of more ambiance and environments that feel more alive- but on the other hand, anything new would have to fill some sort of gameplay niche, and furthermore, might take away from the existing feel of Minecraft's world.
...Of course, all this is sort of subjective in terms of how you feel about the game's environments. At least in my opinion, there aren't currently too many reasons to explore the actual terrain itself as opposed to structures- aside from hunting for animals, and more recently searching for berries, (Which aren't very effective anyways), the game is currently more centered around farming, mining, and otherwise being efficient. This seems like something as a loss, seeing as how much work has gone into the terrain and biomes. It would certainly be neat if there were some sort of insect mechanic that encouraged players to hunt down rare insects... I like a lot of the ideas for this- they seem like a creature that feels very much alive. However, they are pretty similar to bees, and don't seem to fill any new niche.