What you are objecting to, Weelittledrummer, in your "earwig" example is the most primitive form of reincarnation belief imaginable...and a form that is held by a minority of people who believe in reincarnation these days.

It would be comparable to the most primitive forms of Christian or Islamic fundamentalism.

Basically, spiritual evolution is thought to work quite similarly to the natural evolution of species....in fact the one would be the extension or reflection of the other. They would work hand in hand.

Which is to say: less complex forms (and consciousnesses) tend to evolve over time into more complex forms (and consciousnesses). They do not devolve. So...you would only be likely to come back as an earwig if you were already as limited in consciousness as an earwig is.

You may actually BE that limited in consciousness, of course. ;-) Who am I to say? But I seriously doubt it.