identifying sub-species

Would someone care to elaborate on the definition of sub- species of Drymarchon. I am aware of the scalation differences between erebenus, and couperi, but what, if any, are the differences which define melanarus, and unis{black tails, and unicolors}? I can see that the black tails are obviously darker towards the tail, but my one little uni is somewhat darker towards the tail as well. Although not nearly as much as a true black tail. And will his tail get lighter with age. I ask these questions because it looks to me that these are not truly seperate sub-species, but just color variations within one sub-species, since they come from the same part of the world, and some specimens, upon first glance could go either way. Thanks,
T.

Tony,
I'm not aware of any scalation differences between unicolors and melanurus. I think it's more of a locality thing and as far as the pet trade is concerned, coloration of the tail.
Unfortunately, most of the BT's being offered in the pet trade are actually unicolor / melanurus intergrades or "brown tails". A true BT should have a jet black tail not just a darker brown than the rest of the body.
Depending on the age of your unicolor, it's tail may continue to lighten up as it matures. Black tails and unicolors look very similar as hatchlings but the dark tails of unicolors fade as they mature.
A true unicolor should be essentially one color with very little if any darkening towards the tail. That's why I think it's important to see pics of the parents when purchasing CB uni or BT hatchlings.
I'm not sure what evidence led taxonomists to make unicolors a seperate subspecies instead of just a color phase of melanurus.
Interesting question though....Dean A. may know the answer to that one.

for the info. That's about what I figured. I've been looking at some quote-"black tails", currently being offered for sale as such. But they look to me to be more of an intergrade than a true blacktail. I am wondering this because I am not really sure how neccesary it would be to be careful not to cross the two. In order to maintain genetic integrity of the two subs, if there is any. In other words if the "line" exists in nature, I should be careful not to cross it in captive breeding. But if it does not exist,...
Go tell Drini to drag his carcass over hear and answere this one. We haven't seen him here yet. Sabout time.
T.