Ptychohyla ignicolor and several small and moderate sized hylids are sympatric. From P. ignicolor these hylids can be distinguished as follows: Hyla dendroscarta has a round snout and yellow dorsum; Hyla erythromma has a round snout, green dorsum, white flanks, and a red eye; Hyla hazelae has a tarsal fold, green dorsum, and a black line on the canthus; and Ptychohyla leonhardschultzei has a tarsal fold, brown dorsum, black and white flanks, and horny nuptial spines in breeding males.
Life History.—At Vista Hermosa, Oaxaca, males were calling on vegetation above small streams on March 30, 1959, and on June 28, 1962; males were found on vegetation overhanging a stream 6 kilometers south of Vista Hermosa on June 27 and July 3, 1962. The call consists of a series of short notes, three to thirteen notes per series, sounding like "raa-raa-raa." The duration of each note is about .08 of a second and has a rate of 123 to 129 pulses per second. The dominant frequency of notes in short series is about 2100 cycles per second, whereas the dominant frequency of notes in long series is about 3150 cycles per second ([Pl. 11E]).
On June 28, 1962, two tadpoles of this species were found in a quiet pool in a spring-fed rivulet at Vista Hermosa, Oaxaca. Females are unknown.
Remarks.—The absence of a tarsal fold and of nuptial spines in breeding males, the nature of the breeding call, and the form of tadpole are characters that place Ptychohyla ignicolor in the P. schmidtorum-group.
Distribution.—This species is known from only two localities at elevations of 1500 and 1850 meters in the cloud forest on the northern (Atlantic) slopes of the Sierra Madre Oriental in northern Oaxaca.
Specimens examined.—Mexico: Oaxaca: Vista Hermosa, KU 71334, 71716 (tadpoles), UMMZ 119602; 6 km. S of Vista Hermosa, KU 71335-42, 71343 (skeleton), UMMZ 119603, 123327 (2).
DISTRIBUTION AND ECOLOGY
Geographic Distribution of the Species