[Marika (OP)]

Jack wants to know:

Why do caterpillars go through all the faff of metamorphosis just to become a butterfly to reproduce, lay eggs and start all over again?  Seems like an awful lot of energy expenditure and hard work!  I am guessing there must be some evolutionary advantages somewhere to make it all worthwhile.

What do you think?

[evan_au]

...start all over again?  Seems like an awful lot of energy expenditure and hard work!

From a very high level, the main goal of life is to spread forth and multiply. Laying eggs and starting a new generation fulfills that imperative (at least, for an insect, a fish, bird or reptile).

In the process, life does consume energy faster than non-living things, so you could say that a byproduct of life is to hasten the heat death of the universe.
See: https://en.wikipedia.org/wiki/Heat_death_of_the_universe