Some observation of strange things that happen in the moth's cave:
I brought two larvae into the cave. There is Beebs and Fluffy.
Then I wait and see Beebs turn into a moth.
But when I look at the squad, I see that the one who actually turned into a moth is Fluffy (so Beebs still a larva).
Then I wait again. Now I see message that Fluffy is turn into a moth (even though it's already happened). Also, just as you can see at the screenshots below, The color of Fluffy's sprite is different from her actually color (the same goes for Beebs).
In the squad menu, the portrait colors are also different from the originals. But in the level up menu, they still match the originals.
There is, however, an easy way to fix this. If we have to take them both to the Dear nurse, then deposit and take them back in squad, their colors will come in the proper form (sprites too).
Oh, I can fix that no problem, thank you for the report!
The solution I've tested seems to be working, do you have a savefile with beebs and fluffy as larvae?