William Edward Duellman

“ Despite the similarity in color pattern, size, and structure, we are reluctant to place the two taxa in the same species until data on coloration in life, mating calls, and life history are available for Hyla misera and compared with those of Hyla microcephala. ”

“ The calling location of the males generally is on vegetation above, or at the edge of, the water. Hyla microcephala and H. phlebodes call almost exclusively from grasses and sedges; phlebodes usually calls from taller and more dense grasses than does microcephala. Except for some minor differences in calling location observed by the junior author (Fouquette, 1960b) in the Canal Zone, the differences in density and height of grasses utilized for calling-locations probably is dependent primarily on the nature of the available vegetation. ”

“ The frogs of the Hyla microcephala group breed in shallow grassy ponds. In some places they breed in permanent ponds, but usually congregate around temporary pools, such as depressions in forests, flooded fields, and roadside ditches. At the height of their breeding season, usually in the early part of the rainy season, the congregations are made up of large numbers of individuals. ”

“ Table 2.--Variation in Color Pattern in Hyla microcephala underwoodi
[A] Longitudinal stripes present in two specimens.
[Pg 531] When this frog is active at night its dorsum is pale yellow; faint flecks are present in some individuals. The white dorsolateral line usually is evident in the tympanic region, but in many individuals a dorsal pattern of lines and other marks is not evident. By day the dorsum changes to yellowish tan or pale brown with dark brown or reddish brown markings (Pl. 13) . The venter is white, and the vocal sac in breeding males is yellow. ”

“ Except for the central area of the Canal Zone the subspecies is unknown from the Caribbean drainage in Central America, but in Colombia the subspecies occurs only in the Caribbean drainage. In Central America this frog occurs mostly on the coastal lowlands; the highest recorded elevation is 560 meters at El Valle, Coclé, Panamá. Throughout most of its range Hyla microcephala microcephala occurs in disturbed habitats—cut-over forests, secondary growth, and pastureland. ”

“ Geographic variation in call.—Hyla m. microcephala has higher fundamental and dominant frequencies in Costa Rica than in Panamá. In Costa Rican H. m. underwoodi the fundamental and dominant frequencies are lower than in other parts of the range. Frogs of this subspecies recorded in Nicaragua and Honduras have slightly lower dominant frequencies and higher fundamental frequencies than those recorded in Guatemala or Oaxaca. The duration of both primary and secondary notes decreases to the south; samples from Nicaragua and Costa Rica have the shortest notes. ”

“ Of 103 males from the Canal Zone, all lack an interorbital dark bar, and all have a dark longitudinal line on the dorsal surface of the shank and a narrow lateral dark stripe, bordered above by a narrow white line, extending to the groin. The longitudinal dark lines on the dorsum are continuous to the groin in 95 specimens and fragmented in two specimens. ”

“ Except for calling males observed around a pool in a stream-bed 11.8 kilometers west-northwest of Tierra Colorada, Guerrero, all breeding congregations have been found at temporary ponds.
Smith (1951:186) named Hyla sartori as a subspecies of Hyla microcephala. This subspecific relationship seemed reasonable until analysis of the mating calls showed that the call of H. sartori is more nearly like that of H. phlebodes than that of H. microcephala. The broad hiatus separating the ranges of H. microcephala and H. sartori is additional evidence for considering H. sartori as a distinct species. ”

“ Data accumulated in 1961 through field studies by the senior author at the type locality, Bebedero, and other localities in Guanacaste and Puntarenas provinces in Costa Rica provide a reasonable explanation of the differences in color pattern. As noted in the preceding description of this subspecies, at night the dorsal markings [Pg 532] are not evident in many living individuals, whereas by day the dorsal markings are prominent. Most collectors prepare their specimens by day; consequently the majority of specimens have a pronounced dorsal pattern. ”

“ Although large breeding congregations are most common in the early parts of the rainy season, males probably call throughout the year. At Puerto Viejo in Costa Rica the senior author has heard Hyla phlebodes in February, April, June, July, and August. Charles W. Myers noted calling males of this species in the area around Almirante, Bocas del Toro Province, Panamá, in September, October, and February. ”

“ Calling males of robertmertensi have been found two meters above the ground in small trees.
Daytime retreats in the breeding season sometimes are no more than shaded clumps of vegetation adjacent to a pond or in clumps of grass in a pond. Individuals of H. m. underwoodi were found by day under the outer sheaths of banana plants next to a water-filled ditch. Dry season refuges are unknown.
Amplexus is axillary in all four species. Egg deposition has been observed in H. m. microcephala, m. underwoodi, and phlebodes. ”

“ Hyla phlebodes is the smallest species; adult males attain snout-vent lengths of only 23.6 mm. The body is slender in H. microcephala and robertmertensi, slightly wider in phlebodes, and noticeably broader in sartori. ”

“ In life, dorsum of body reddish tan mottled with darker brown; lateral stripe dark brown; belly white, mottled with brown and black; caudal musculature heavily pigmented [Pg 537] with grayish tan; posterior tip of tail marked with dark gray; caudal fins heavily blotched with grayish tan; iris orange-tan peripherally, red centrally (Pl. 15) .
Remarks.—This species has been confused with Hyla microcephala underwoodi by many workers. Dunn (1931, 1933, 1934) and Breder (1946) referred Panamanian specimens of H. phlebodes to H. underwoodi ”

“ In life, top of head yellowish tan; lateral stripe brown; belly white; anterior half of tail lacking pigment; posterior half deep orange; iris pale bronze (Pl. 15) .
Remarks.—Evidence for intergradation of Hyla microcephala with H. underwoodi is provided by four specimens [USC 818 (2) , 6081-2] from 6.1 kilometers northeast of the mouth of the Río Tarcoles, and nine specimens [USC 8254 (2) , 8255, 8256 (4) , 8258 (2) ] from Parrita, both in Puntarenas Province, Costa Rica. These localities lie about two-thirds the distance from the northwesternmost locality for H. m. ”

“ In samples from the southern part of the range (southern Nicaragua and Guanacaste Province, Costa Rica) more (40-93%) individuals have the lateral stripes extending to the groin than in northern samples (0-42%) from southern México and Guatemala. Likewise, the percentage of specimens lacking bars on the shanks and a dark interorbital bar is higher in the Costa Rican samples than elsewhere in the range. ”

“ Osteological data were obtained from specimens that were cleared in potassium hydroxide, stained with alizarin red, and stored in glycerine. Recordings were made by means of Magnemite portable tape recorders (Amplifier Corp. America) . The calls recorded by Fouquette were analyzed on a Sonagraph (Kay Electric Co.) at the University of Texas; those recorded by Duellman were analyzed mainly on a Vibralyzer (Kay Electric Co.) at the University of Kansas and in part on a Sonagraph at the University of Southwestern Louisiana. Sample calls were analyzed on all three instruments ”

“ The trivial differences among the other three species certainly are suggestive of close relationship, but on the basis of present knowledge of the evolutionary trends in hylid cranial osteology, the differences offer little evidence for determining phylogenetic lineage. ”

“ Although bushes and broad-leafed herbs are usually present at the breeding sites, males of these species seldom utilize them for calling locations. Both H. robertmertensi and H. sartori have been observed calling from grasses, herbs, bushes, and low trees. ”

“ At the end of each species account the localities from which specimens were examined are listed alphabetically within each state, province, or department, which in turn are listed alphabetically within each country. The countries are arranged from north to south. Localities preceded by an [Pg 521] asterisk (*) are not plotted on the accompanying maps due to the crowding of symbols that would have resulted. Abbreviations for museum specimens are listed below:
HYLA MICROCEPHALA GROUP
Definition.—Small hylids attaining a maximum snout-vent length of 27 mm. ”