It's Very Simple. Those Caterpillars That Reconstituted Themselves Into Something Useful After Dissolving Into A Slurry Went On To Reproduce.

And the ones that didn't, didn't. And that's where we got butterflies. You'd have to be retarded not to see it. Or probably a Republican.

Interesting post and discussion at Uncommon Descent, in response to a very lame argument made by an evolutionary scientist, which amounts to something along the lines of "because cars sometimes crash, they weren't designed."

See also this interesting page of quotes and counter quotes.