When a caterpillar changes into a butterfly...

??

Transformation

Metamorphosis. Stahp trying to invent words that are already there :D

if you raise caterpillars and stay up late and catch them while they transform

and eat them.
\
you will get their genetic code and live a long time and be able to fly

That's the one I was 'reaching' for.

I actually felt I did this last time I was under the influence of mushrooms. It was intense.

And most likely tortured soon for evil behavior

I was of this assumption as well, just was not sure.

Okay science. We need to make butterflies turn back into caterpillars before they die so that they can spend their last days reminiscing and miserable just like us.