I mostly use Illustrator for black and white quilt patterns, and have never before tried vectorizing a raster image. After considerable trial and error, I eventually stumbled on how to convert my bug's 6 layers of .tifs into a vector image. I'm using CS5, so maybe that's why there's a lot of weird little artifacts in the final result? (2nd image, the white and light slivers along edges). I didn't get so many artifacts when live tracing a one-layer .tif of the same bug (3rd image). Is this why you recommend doing the initial layers in greys and then add color later in Illustrator? (I added all color in Procreate.)

I used Live Trace preset Color 6, but maybe there's a better choice?  Some advice on a good preset would be appreciated!  

Seems like a lot of work to individually trace numerous layers of a drawing to still end up with stray little rubbish to clean up, when a trace of a single layer is somewhat cleaner.  I feel I must be missing a few key points.... Maybe it's because I'm using CS5, but I'm too stubborn (and cheap!) to pony up for the perpetual Adobe subscription plan, lol.

Anyway, I'm very glad to have learned something new - thank you!