|Drymarchon couperi, eastern indigo snake|
Fitzinger, 1843 
Drymarchon is a genus of large nonvenomous colubrid snakes, commonly known as indigo snakes or cribos,  found in the Southeastern United States, Central America, and South America. Reaching 3 m (9.8 ft) or more in length, they are among the world's largest colubrid snakes.
Indigo snakes are large, robust snakes which can reach a total length (including tail) of over 3 m (9.8 ft). They have smooth dorsal scales, and several color variations, including a glossy blue-black color.
Indigo snakes are diurnal and actively forage for prey. They feed on a broad variety of small animals such as rodents, birds, lizards, frogs, toads, and other snakes, including rattlesnakes. They are not aggressive snakes and will only bite when threatened. Typical threat display includes hissing and shaking of its tail as a warning.
The genus Drymarchon was formerly considered to be a monotypic taxon formed by subspecies of D. corais. Currently the genus includes six distinct species recognized by ITIS:  One of the species has several subspecies which are recognized as being valid.
- Indigo snake, yellow-tailed indigo snake — Drymarchon corais ( F. Boie, 1827)
- Falcon indigo snake — Drymarchon caudomaculatus Wüster, Yrausquin & Mijares-Urrutia, 2001 
- Eastern indigo snake — Drymarchon couperi ( Holbrook, 1842) 
- Margarita indigo snake — Drymarchon margaritae Roze, 1959
Middle American indigo snake — Drymarchon melanurus (
A.H.A. Duméril, 1854)
- Black-tailed cribo — Drymarchon melanurus melanurus (A.M.C. Duméril, Bibron & A.H.A. Duméril, 1854)
- Texas indigo snake — Drymarchon melanurus erebennus ( Cope, 1860) 
- Orizaba indigo snake — Drymarchon melanurus orizabensis ( Dugès, 1905)
- Mexican red-tailed indigo snake — Drymarchon melanurus rubidus H.M. Smith, 1941
- Unicolor cribo — Drymarchon melanurus unicolor H.M. Smith, 1941
- Fitzinger L (1843). Systema Reptilium, Fasciculus Primus, Amblyglossae. Vienna: Braumüller & Seidel. 106 pp. + indices. (Drymarchon, new genus, p. 26). (in Latin).
- Wright, Albert Hazen; Wright, Anna Allen (1957). Handbook of Snakes of the United States and Canada. Ithaca and London: Comstock Publishing Associates, a division of Cornell University Press. 1,105 pp. (in 2 volumes) (Genus Drymarchon, p. 200).
- "Cribos and Indigo Snakes" (PDF). madisonherps.org. Retrieved 2018-10-21.
- "Drymarchon ". Integrated Taxonomic Information System. Retrieved 2011-02-06.
- Wüster, Wolfgang; Yrausquin, José Luís; Mijares-Urrutia, Abraham (2001). "A new species of indigo snake from north-western Venezuela (Serpentes: Colubridae: Drymarchon)" (PDF). Herpetological Journal. 11: 157–165. Archived from the original (PDF) on 2007-02-05. (Drymarchon caudomaculatus, new species).
- Hammerson GA (2007). "Drymarchon couperi ". The IUCN Red List of Threatened Species. IUCN. 2007: e.T63773A12714602. doi: 10.2305/IUCN.UK.2007.RLTS.T63773A12714602.en. Retrieved 23 December 2017.
- Lee J, Calderón Mandujano R, Lopez-Luna MA, Vasquez Díaz J, Quintero Díaz GE (2007). "Drymarchon melanurus". IUCN Red List of Threatened Species. Version 2010.4. International Union for Conservation of Nature. Retrieved 8 February 2011.CS1 maint: Multiple names: authors list ( link)
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