Congratulations on your beautiful pictures! I'm actually from Brazil, but never saw snails like those.
Regarding your flash, may I ask how you used it? Personally, I use an off camera flash for small things, hand held at a different angle (sort of 45° to the upper left), with something in front of it to smooth the hard light (a peace of translucent paper or the "built in wide lens adapter" present in my SB600).
The ladybug was pictured using this technique, and notice that the light was so "on the spot", that you can see the translucence of the bug without too many excessively illuminated points (mainly on it's upper/left side).
Would like very much to hear about your results with different settings.