Thanks for the additional info. I was looking for something for identifying colubrids - I have only worked with microcips for dogs and they are quite large to use on neonatal or even young corns or milks. I really like the idea of microchips for larger or adult snakes as a means of permanent identification - aside from the problems of chip migration.
I was hoping for something that would be visible externally and last the lifetime of the herp, rather than having to rely on a scanner to read a chip code. Are their chips available that can be used for smaller species?