I've had no luck using the transillumination technique on lacie hatchlings. It's not a size issue, but the presence of an opaque black band covering the exact area of interest. I've yet to try it with a second set of hands, though, so perhaps if I can get someone to give me a hand with the squirming hatchling and light such that absolutely no light escapes around the tail the light may be strong enough to penetrate the black and show something?