Key to Snakes of Washington

1A. Deep pit between nostril and eye; rattle on tail tip .....Western Rattlesnake, Crotalus viridis
1B. No deep pit or rattle .....2

2A. No enlarged chin shields; blunt tail .....Rubber Boa, Charina bottae
2B. Two pairs of enlarged chin shields; tail long and pointed (unless broken off) .....3

3A. Some or all dorsal scales keeled .....4
3B. All dorsal scales smooth .....7

4A. Four prefrontals; body with large blotches .....Gopher Snake, Pituophis catenifer
4B. Two prefrontals; body striped or with small spots .....5

5A. Eight upper labials; conspicuous checkered pattern .....Western Terrestrial Garter Snake, Thamnophis elegans
5B. Seven upper labials; never with conspicuous checkered pattern, although sometimes with dots .....6

6A. 17 scale rows at midbody; usually a dark postocular stripe contrasting with paler head color; pattern very variable (dorsal stripe may be lacking, ground color may be pale) .....Northwestern Garter Snake, Thamnophis ordinoides
6B. 19 scale rows at midbody; head usually all dark above; always dark with light stripes above .....Common Garter Snake, Thamnophis sirtalis

7A. Anal plate entire; body brightly banded .....California Mountain Kingsnake, Lampropeltis zonata
7B. Anal plate divided; not brightly banded .....8

8A. Spine on tip of tail; belly finely barred with black .....Sharptail Snake, Contia tenuis
8B. No spine on tail tip; belly colored otherwise .....9

9A. Orange belly and ring around neck .....Ringneck Snake, Diadophis punctatus
9B. No neck ring; belly colored otherwise .....10

10A. Pupil vertical; spotted above, with large blotches on neck .....Night Snake, Hypsiglena torquata
10B. Pupil round; unicolor, striped or spotted, no large blotches on neck .....11

11A. Finely striped above Striped Whipsnake, Masticophis taeniatus
11B. Unicolor (adults) or finely spotted or banded above (young) .....Racer, Coluber constrictor

Adapted by Dennis Paulson from key in Nussbaum, R. A., E. D. Brodie, Jr., and R. M. Storm. 1983. Amphibians & Reptiles of the Pacific Northwest. Univ. Press of Idaho, Moscow.