Interesting topic. If you consider the Eastern indigo and yellowtail cribo to be different species than the blacktail cribo and its subspecies, then I guess the common boa would have a larger range. If you consider all of the Drymarchon to be subspecies of yellowtail cribo, their range is larger for that group, even with the unfortunate disappearance of Eastern indigo from parts of the United States. And I'm wondering if the total range for all of the milk snake sub-species is greater than either boa or Drymarchon.