It is very hard to give differences!
From literature:
Here are the summary of differences in head markings out of a paper by mine, printed at the end of this year or early 2013:
Hierophis gemonensis (following HENLE, 1993):
- between the eyes a "yellow", in the center broken line.
- at the back side of the Parietalia a "yellow" band, the collar is bordered by "yellow" lines = 3 lines on caudal side of head/neck.
Hierophis viridiflavus (following HEIMES, 1993):
- crossband between the eyes.
- yellow spot on each parietale.
- on caudal side of head/neck 3 light crossbands.
Therefore the only difference should be these two light spots on parietalia, but see this:
- Baby gemonensis with two spots on Parietalia. From Ulcinj/Montenegro. Far outside of the range of H. viridiflavus
I dont believe in these differences!
Its the overall appearance, the small white spots on the dorsal scales (lower and upper edge of each scale) in gemonensis. Also the dorsal central blotches are much wider in viridiflavus.
And real babies, like yours, in viridiflavus the color is much more dull, the blotches are not so strong in contrast to the body color.
If you really want to know, you have to count the ventrals, but there´s a overlap too
Mario