There is only 1 achievement for catching bugs. I've caught 2 but don't have that achievement yet. How do you get it, besides catching bugs obviously.

You get it by catching 30 bugs, and showing them all to Chimalma
By "showing them all to Chimalma" you mean have all 30 in my inventory and going over to her page?

I think it just means over time you need to show her all 30, it tracks what you've done even if it doesn't show it in the tiers. The bird catching achievement was the same way.
Great, thanks for reminding me about those birds. I collected them as long as they were available then fragged all but 1 of each. Now I remember how it went. Kind of glad I won't be having to dig all those bugs out!

Considering she is asking to see one bug per day, having all 30 in your inventory will not work.
It's an achievement that you get by showing her 1 bug per day for 30 days.
Or you have to show her all 30 of the different bugs that are available to be found, at least that's how I first interpreted. Unless there are less than 30 different ones, I haven't actually counted them from the item directory.
I know, I'm saying that it may mean that over time you have to find and show her all 30 of them, not all at once. Like how the bird watching one was for finding birds from 8 different lands.
For the birdwatching achievement, you got a different bird each day until you got them all, then you got the achievement. Bugs should work the same way