Unfortunately for the common misunderstanding, "basically" is doing too much heavy lifting there. Most of their cells are replaced or reconfigured during metamorphosis but the central nervous system is not reduced to an unconnected paste. Linking an ancient Reddit thread for an overview and terms to chase down if you're curious. https://www.reddit.com/r/askscience/comments/mpqu2/what_happens_to_a_caterpillars_brain_during/c32x1pc/