Evolution and butterflies: a question

[George Reiswig]

Hello, all.
	I hope you dont mind my asking an amateurs question.  A friend
of mine and I are having an ongoing discussion about evolution.  His
contention is that evolution could not possibly explain the diversity of
species, that the leaps which evolution makes are of the meter variety,
when what is needed is more of the mile variety.
	As an exercise, he wants me to try to come up with an example or
a plausible scenario for the evolution of metamorphosis in butterflies.
I can think of one possible scenario, but I dont know if it really holds
water or not.  Im not aware of any intermediate steps such as that
hes looking for, either living or in the fossil record.
	The scenario I had in mind involves an ancestor which basically
developed via instars, like the Chinch Bug does.  It seems plausible to
me that the stages of the instars could have become more specialized over
time.  For example, perhaps the first stage was put in a position where
it needed to become more of an eating machine...short growing season or
something.  So, it lengthened its abdomen, and increased its capacity.
 Aft-legs evolved to help cart around this giant stomach.  The pupal
stage became necessary to help the insect winter, and to enable the
rather dramatic change from a caterpillar to a winged adult.  (Why the
species clung so tenaciously to being a winged adult is a little tough to
explain.)
	Anyway, Im wondering if any of you have thoughts on this.  Does
anyone know what the true evolution of butterflies was?  Are there living
or fossilized examples of intermediate stages?
	Thanks in advance for any help.

GR