One specimen from La Palma on the Mexican Plateau (KU 29275) has the top of the head an olive-color, the entire dorsum black, the chin and ventrals 1-42 a cream-color, remainder of venter black, and all of the labials heavily barred with black. A juvenile from Capirio in the Tepalcatepec Valley (UMMZ 114627) is black above and has pale olive-colored flecks on the anterior one-third of the body; the top of the head is dark olive-brown, and the sides of the head are somewhat paler. Anteriorly the belly is a cream-color; posteriorly it is black.
The specimens from the Tepalcatepec Valley are typical of Drymarchon corais rubidus. Those from the coastal lowlands differ in having large areas of brown or red pigment on the dorsum, a condition not mentioned by Smith in his description of the subspecies. The specimen from La Palma, like many others from various localities on the Mexican Plateau, resembles in certain characters D. corais orizabensis (Smith, op. cit.: 477). Our knowledge of the geographical variation in coloration in this species is incomplete; many populations have been assigned to subspecific rank without justification.
In Michoacán this species is found from sea level to 1350 meters in the Sierra de Coalcomán and to 1300 meters at La Palma on Lago de Chapala. It has been collected in scrub forest, semi-deciduous broad-leafed forest, and oak forest.
Drymobius margaritiferus fistulosus Smith
Drymobius margaritiferus fistulosus Smith, Proc. U. S. Natl. Mus., 92:383, November 5, 1942.—Miramar, Nayarit, México.
Apatzingán (3); Coahuayana; Coalcomán (3); El Sabino (3); El Ticuiz; 12 km. S of Tzitzio.
This snake is abundant in the lowlands of the state; the few specimens listed above are indicative not of the rarity, but rather of the speed and agility, of this diurnal snake. It most frequently is found near water, where there is a dense growth of vegetation. One individual was observed in a large pool inhabited by several small Rana pipiens, and another was seen along the bank of a hyacinth-choked river channel. A third individual was captured while it was in pursuit of a Cnemidophorus.
This species has been collected on the coastal lowlands and seaward foothills of the Sierra de Coalcomán and in the Tepalcatepec Valley to elevations of 1150 meters.
Elaphe triaspis intermedia (Boettger)
Pityophis intermedius Boettger, Ber. Offen. Vereins. Naturk., 22:148, 1883.—México. Type locality restricted to Hacienda El Sabino, Michoacán, México, by Dowling (1960:74).