A Review of the Frogs of the Hyla bistincta Group

by William Edward Duellman

Variation.—There is little variation in structure. The total number of vomerine teeth varies from 6 to 14. In some individuals the supratympanic fold covers the upper part of the tympanum, but at least the lower part of the tympanum is always visible. The extent of the webbing between the toes varies from three-fourths to two-thirds complete. Usually the web extends to some point on the antepenultimate phalanx of the fourth toe, but in some specimens the web extends to the base of the penultimate phalanx.

In the large series of specimens from Uruapan, Michoacán, the coloration of the flanks and anterior surfaces of the thighs varies from nearly uniform creamy yellow with only fine dark reticulations to bold reticulations enclosing yellow spots. Some specimens from Oaxaca and Veracruz have slightly different markings on the flanks; in these the dark pigment is in the form of irregular spots or dashes, instead of reticulations.

There is considerable variation in color in the living frogs. The dorsum varies from greenish tan and pale yellowish tan to reddish brown, and some individuals are dark chocolate brown.

Remarks.—Shannon (1951:470) named Hyla bistincta labeculata on the basis of a single male from San Lucas Camotlán, Oaxaca; he diagnosed the subspecies as differing from Hyla bistincta bistincta by having "the gray reticulation of the sides entirely broken up into elongate black blotches; tarsal fold moderately elevated." The condition of the tarsal fold is characteristic of the species. The dispersion of dark pigment on the flanks is variable. The type of Hyla bistincta labeculata (USNM 123689) is extreme in the development of dark dashes on the flanks, but this condition is approached in several specimes from Oaxaca and Veracruz. For example, in some specimens from Cumbres de Acultzingo, Veracruz, the mottling on the flanks is bold; in others the flanks are reticulated. The specimen from San Vicente, Oaxaca, has black dashes on the flanks (Smith and Williams, 1963:23), whereas a specimen from Cerro San Felipe, Oaxaca, has no pattern on the flanks. In general, specimens from western México have reticulate mottling on the flanks as compared with the marbling on the flanks in specimens from eastern México. On the basis of available data, the recognition of subspecies in Hyla bistincta is unwarranted.

The tadpoles of this species described by Duellman (1961:47) are like those of Hyla robertsorum in having ⅔ tooth-rows, peglike serrations on the beaks, and long, rounded tails. At Uruapan tadpoles were found in a rocky stream on April 24, 1956, and metamorphosing young were found there on August 2, 1956. A completely metamorphosed juvenile has a snout-vent length of 24.8 mm.

Hyla bistincta is found only along streams, where individuals can be seen clinging to vines and other vegetation closely over-hanging fast-moving parts of the stream.

Distribution.—Hyla bistincta occurs at elevations from 1400 to 2600 meters in the mountains of the Sierra Madre Occidental in western Jalisco southward through the Cordillera Volcánica in Michoacán, México, and Morelos, the Sierra de Coalcomán in Michoacán, and the Sierra Madre del Sur in Guerrero and Oaxaca, and thence northward in the Sierra Madre Oriental to central Veracruz (Fig. 2).

Specimens examined.—Guerrero: Omiltemi, UIMNH 38023-5. Jalisco: 25 km. SE Autlán, UMMZ 102076. Mexico: 19 km. W Villa Victoria, UIMNH 28162, USNM 114513. Morelos: Cuernavaca, USNM 121523; 3 km. N Cuernavaca, UIMNH 28168-70. Michoacan: Cerro San Andrés, UMMZ 102075; Dos Aguas, UMMZ 119193; 12.5 km. ENE Dos Aguas, UMMZ 119194; Los Conejos, UMMZ 94238-40; Uruapan, KU 68077-8, 69093 (skeleton), UIMNH 20457, 28167, UMMZ 85452-3, 112838, 112839 (16), 115231 (tadpoles), 115232, 115233 (12), 121515, S-1699 (skeleton), S-1826 (skeleton), USNM 114514-5, 114517-24. Oaxaca: Cerro San Felipe, UIMNH 28163; Pluma Hidalgo, AMNH 13447; San Lucas Camotlán, USNM 123689; San Vincente, UIMNH 51346 (Smith and Williams, 1963:23). Veracruz: no specific locality, USNM 32261; Cumbres de Acultzingo, CNHM 105482-3, UIMNH 28164-6, 49133-4, USNM 114525.