What a nice game! Even though it's not finished I had a nice time playing it. Obviously would love some audio and more puzzles.
Controlling the bug and the plant feels alright but switching between the two is awkward IMHO. I'd rather toggle the controls entirely instead of having to keep a button pressed. Some graphical feedback on what you're currently controlling would also be great (you still have two colours to play with, maybe a subtle highlighting of the bug/plant would be enough).
I had a hard time figuring out the plant could grow in diagonal and the bug could walk on the stem. But maybe I'm just a bit dense.
Anyway, would love to see this one refined and expanded on. Well done!