| 1a. |
Rattle present at end of tail. |
(2) |
| 1b. |
No rattle present. |
(3) |
| |
| 2a. |
Numerous small scales on top of head, maximum total length about 4'. |
Crotalus viridis,
Western (prairie) rattlesnake |
| 2b. |
Head covered by large scales, maximum total length about 2'. |
Sistrurus catenatus,
Massasauga |
| |
| 3a. |
Stripes running the length of the body. |
(4) |
| 3b. |
Body plain, banded, or blotched, but without longitudinal stripes. |
(9) |
| |
| 4a. |
Scales smooth; longitudinal black and white stripes. |
Masticophis taeniatus,
Striped whipsnake |
| 4b. |
Scales keeled. |
(5) |
| |
| 5a. |
Distinct black bars at edge of scales on upper lips. |
(6) |
| 5b. |
Not as above. |
(7) |
| |
| 6a. |
Pale stripe on side of body on 3rd and 4th scale rows above belly scales. |
Thamnophis radix,
Plains garter snake |
| 6b. |
Pair of glossy black blotches behind head; pale stripe on side of body on 2nd and 3rd scale rows above belly scales. |
Thamnophis cyrtopsis,
Blackneck garter snake |
| |
| 7a. |
Red color on sides. |
Thamnophis sirtalis,
Common garter snake |
| 7b. |
No red color on sides. |
(8) |
| |
| 8a. |
Belly with conspicuous double row of half-moon markings. |
Tropidoclonion lineatum,
Lined snake |
| 8b. |
Belly variable, but without half-moon markings. |
Thamnophis elegans,
Western terrestrial garter snake |
| |
| 9a. |
Body with distinctly keeled scales. |
(10) |
| 9b. |
Scales on body smooth or very weakly keeled. |
(12) |
| |
| 10a. |
Nose distinctly upturned. |
Heterodon nasicus,
Western hognose snake |
| 10b. |
Not as above. |
(11) |
| |
| 11a. |
Single anal scale; background color yellowish with brown blotches. |
Pituophis catenifer,
Bullsnake |
| 11b. |
Divided anal scale; brown bands on brown or tan body (pattern may be obscured in old individuals). |
Nerodia sipedon,
Northern water snake |
| |
| 12b. |
Scales on back very weakly keeled; body tan with brown blotches; rectangular marks on belly; dark stripes on underside of tail. |
Elaphe guttata,
Corn snake |
| 12b. |
Scales completely smooth; body pattern variable. |
(13) |
| |
| 13a. |
Body with red, black, and cream (or yellow) pattern. |
(14) |
| 13b. |
Pattern not as above. |
(15) |
| |
| 14a. |
Band pattern on body of cream - black - red - black - cream. |
Lampropeltis triangulum,
Milk snake |
| 14b. |
Pattern of red and black bands with cream speckling. |
Rhinocheilus lecontei,
Longnose snake |
| |
| 15a. |
Pattern of brown blotches on paler background. |
(16) |
| 15b. |
Pattern not as above. |
(17) |
| |
| 16a. |
Single anal scale; length to 56 inches. |
Arizona elegans,
Glossy snake |
| 16b. |
Divided anal scale; vertical pupils; small size (adult length less than 20 inches). |
Hypsiglena torquata,
Night snake |
| |
| 17a. |
Tan body, black head, small size (adults less than 15 inches). |
(18) |
| 17b. |
Not as above. |
(19) |
| |
| 18a. |
Eastern slope. |
Tantilla nigriceps,
Plains blackhead snake |
| 18b. |
Western slope. |
Tantilla hobartsmithi,
Southwestern blackhead snake |
| |
| 19a. |
Pattern of black and white bands or black with white speckling. |
Lampropeltis getula,
Common kingsnake |
| 19b. |
Not as above. |
(20) |
| |
| 20a. |
Tail resembles braided whip; adults large (to 80 inches). |
Masticophis flagellum,
Coachwhip |
| 20b. |
Tail plain, not resembling braided whip. |
(21) |
| |
| 21a. |
Olive body with orange ring around neck. |
Diadophis punctatus,
Ringneck snake |
| 21b. |
Not as above. |
(22) |
| |
| 22a. |
Worm-like appearance, with dorsal and ventral scales about the same size, vestigial eyes. |
Leptotyphlops dulcis,
Texas blind snake |
| 22b. |
Not as above. |
(23) |
| |
| 23a. |
Body variable (orange, brown, or gray), often with dark saddles; maximum total length about 15 inches. |
Sonora semiannulata,
Ground snake |
| 23b. |
Not as above. |
(24) |
| |
| 24a. |
Olive or brownish body with yellow or cream belly; nostril bordered by two separate scales. |
Coluber constrictor,
Racer |
| 24b. |
Body bright grass green; nostril centered in single scale. |
Liochlorophis vernalis,
Smooth green snake |
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