• Striking blairi-morph alterna from the vicinity of Garcia, NW of Monterrey, Nuevo Leon, México. Live collection of UANL. Photograpy © R. W. Bryson, Jr.

  • This blairi morph alterna was collected from Cerro de la Silla on the outskirts of Monterrey, Nuevo Leon in June 1990. Photo © Joseph S. Forks.
  • This dried partial carcass of an alterna was found in 2007 by Chris Harrison and Michael Price in the Sierra Pedernales, Nuevo Leon, México. This is only the second blairi morph of this species recorded from Mexico. Photo © Chris Harrison.
  • Adult blairi-morph alterna from near Garcia, NW of Monterrey, Nuevo Leon, México. Live collection of UANL. Photograph © R. W. Bryson, Jr.

  • This alterna (UF 24750), collected by Fred G. Thompson in August 1966, was found at 3.5 mi. S San Miguel, Coahuila at an elevation of 5000 ft. Photo © G. T. Salmon.
  • Cuesta La Muralla, Coahuila, collected by Ron Savage, 1975. T. Boyden collection. Photo courtesy of D. G. Barker.
  • This is the first specimen (UANL 459) of alterna collected in Nuevo Leon. It was found in May 1967 at Cerro de las Mitras, just W of Monterrey. Photo © Joseph E. Forks.
  • DOR juvenile alterna, Hwy 57 N of Saltillo, Coahuila, September 1997, collected by Joseph Forks, Gerry Salmon, Javier Banda, and Patrick Morris. This specimen follows a trend of alterna phenotype for specimens from Coahuila. Photo © Joseph E. Forks.

  • Ventral view of DOR juvenile alterna, found on Hwy 57 N of Saltillo, Coahuila, September 1997, by Joseph Forks, Gerry Salmon, Javier Banda, and Patrick Morris. Photo © Joseph E. Forks.

  • Badly smashed DOR, found July 7, 1975 by Henry D. Wallace and Stephen F. Hale, N of Saltillo, Coahuila. Photo courtesy of Henry D. Wallace.

  • DOR near Cuesta La Muralla, Coahuila, found August 25, 1977, by Henry D. Wallace and Bruce Smith. Photo courtesy of Henry D. Wallace.

  • Henry Wallace found this female intermediate-morph alterna on August 11, 1980, at 10:00 a.m. His discovery was made on a cloudy morning under a small rock that was under a very large flat rock on a rocky ridge in the mountain pass known as Cuesta La Muralla, between Saltillo and Monclova on Mex. Hwy 57, Coahuila. Photo courtesy of Henry D. Wallace.
  • Powder-gray alterna phase observed by Paul Lynum in August 2002, Cuatro Cienegas, Coahuila. Photo courtesy of Paul Lynum.

  • This remarkably dark alterna was found near Cuatrocienegas, Coahuila, by T. Greenwood. Photo courtesy of G. T. Salmon.
  • Specimen found near Cuatrocienegas, Coahuila, by Steve Hale. Photo by D. Miller, courtesy of G. T. Salmon.

  • This snake was collected at Cuesta La Muralla, Coahuila, by Ron Savage. Photo courtesy of G. T. Salmon.

  • Cuatrocienegas, Coahuila, July 1988 (UANL 3706). Photo © Joseph S. Forks.

  • Cuesta La Muralla, Sierra La Gavia, Coahuila. Collected by Ron Savage, 1972. Photo courtesy of G. T. Salmon.
  • Cuatrocienegas, Coahuila. Collected by Steve Hale and Tom Boyden. Photo courtesy of G. T. Salmon.

  • Specimen from central Coahuila, 1972. Photo courtesy of G. T. Salmon.

  • Specimen from Coahuila, collected by W. Garstka in June 1975. Photo courtesy of G. T. Salmon.
  • Adult alterna collected from the Sierra de Jimulco, Coahuila, at an elevation of 1709 m, July 2009. This desert range is located ca. 55 km SSE of Torreon near the Coahuila-Durango border. Photo © 2009 by Uri Garcia Vázquez.

  • Cuatro Cienegas, Coahuila. Photo © 2001 Arturo Contreras.

  • Beautiful blue-gray DOR alterna, found by Henry D. Wallace and K. Bruce Smith, August 11, 1980. DOR on Mex. Hwy 57, 2.2 mi S of San Miguel de las Vagas, Coahuila, not far north of Saltillo. Coahuila. Photo courtesy of Henry D. Wallace.
  • Cuatro Cienegas, Coahuila. Photo © 2002 Arturo Contreras.