Yesterday, Steve and I went to photograph some of the snakes kept at the Okinawa Prefectural Institute of Health and Environment in the care of our long-time collaborator Terada-san. To get a sense of what the snakes look like, you can see my photographs here. The first two individuals are Protobothrops flavoviridis, P. elegans, the Okinawa and Sakishima habus, respectively. The third individual is their hybrid that occurs in Okinawa. Note that it its shape is more similar to Okinawa habu, but its pigmentation, and particularly eye color is more similar to the Sakishima habu.
The Sakishima habu is the one you most often see in Awamori containers; it is smaller than the Okinawa habu, being about half the size, and, I presume, is easier to stuff into a jar. They have escaped and have been spreading through parts of Okinawa, hybridizing with the native speces.