The short version: you can't. There are no diagnostic characters reliably separating "Elaphe slowinskii" from either "E. guttata" or "E. emoryi".

That said, Burbrink gives the following distinctions:

Body and tail blotches:
emoryi: 48-65, mean 58
slowinskii: 42-56, mean 48
guttata: 34-47, mean 38

Width of dorsal blotches at midbody, in scales:
emoryi: 9-15, mean 12
slowinskii: 10.5-15, mean 13
guttata: 13-19, mean 16

Length of dorsal blotches at midbody, in scales:
emoryi: 2.5-5.5, mean 4
slowinskii: 3-5, mean 4
guttata: 5-7, mean 6

As you will notice, in these characters slowinskii always overlaps with both emoryi and guttata.

It is also worth mentioning that Burbrink's sample sizes for each "species" range from 17 to 19 individuals, and in the cases of emoryi and guttata include a fairly small subset of the geographic ranges of each. As a result, the ranges he gives for each character are almost certainly underestimates.

Patrick Alexander

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