I have to say I thoroughly enjoyed that post, Aviatrix!

I figured out what my mystery bug was, and believe it or not, I actually found 2 of them today. I think your post brought them out.

Ginnygirl,
If it's the worm you're missing, I found them when it rained. I had already caught all of my bugs when it started raining, so I closed and reopened the game, then I found 2 of them next to the river.