Thanks for playing my game and your feedback :).
Also thanks for your suggestions. I think it might be my favourite too, to just make the moth, egg, etc. a bit brighter when hovered. It's not too flashy and easy to implement. Thanks :), I'll probably go with this
About the bug: Did you click the caterpillar multiple times? It's sadly not clear from the current game yet but you gotta click on each state a bit more than on the last. For the egg 1 click is enough, then 3 for the caterpillar, then 5 for the pupa and then 10 for the moth. So maybe that was the reason? I didn't encounter a bug for that so I'm not sure, but I'll make sure to play again. It would be interesting to know where you placed the egg though :).