I have very little experience with this series, I have only fully seen Fantastic Beasts and bits and pieces of the main films and never read the books, so forgive me if this is a rookie or obvious answer.
So you might be asking, why is he asking this?
Well, I was doing research for items in a game that I will probably never make in trillion years and ran into a Wikipedia page that listed the magical items in the Potterverse. Horcruxes caught my eye as it was stated that whatever was made into one was pretty much invincible barring like a few methods of destruction. It said living things could be made into them.
Let us say you made a mayfly into one, would it not die in a day or so? Could you still smash them with a rolled up newspaper and kill it? If you made it into one before it turned into an adult, would it stay a nymph?
Just curious, as it sounds like an interesting concept.