Chapter I: Part 1

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University of Kansas Publications

Museum of Natural History

Volume 17, No. 12, pp. 517-557, pls. 13-16, 9 figs. March 20, 1968

Middle American Frogs of the Hyla microcephala Group

BY

WILLIAM E. DUELLMAN AND M. J. FOUQUETTE, JR.

University of Kansas Lawrence 1968

University of Kansas Publications, Museum of Natural History

Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Frank B. Cross

Volume 17, No. 12, pp. 517-557, 4 pls. 9 figs. Published March 20, 1968

University of Kansas Lawrence, Kansas

PRINTED BY ROBERT R. (BOB) SANDERS, STATE PRINTER TOPEKA, KANSAS 1968

31-9419

Middle American Frogs of the Hyla microcephala Group

BY WILLIAM E. DUELLMAN AND M. J. FOUQUETTE, JR.

CONTENTS

PAGE

Introduction 519
Acknowledgments 520
Materials and Methods 520

Hyla microcephala Group 521
Key to Species and Subspecies 522

Accounts of Species and Subspecies 523

Cranial Osteology 540

Analysis of Mating Calls 544

Life History 550

Phylogenetic Relationships 552

Literature Cited 556

INTRODUCTION

The small yellow tree frogs, _Hyla microcephala_ and its relatives, are among the most frequently heard and commonly collected frogs in the lowlands of southern Mexico and Central America. The similarities in size, proportions, and coloration of the different species have resulted not so much in a multiplicity of specific names, but in differences of opinion on the application of existing names to the various taxa. For example, the populations on the Atlantic lowlands have been known by three names, two of which have been applied to other taxa. Much of the confusion has been the result of previous workers' unfamiliarity with the animals in life and unawareness of the intraspecific geographic variation in the most widespread species.

Independently we undertook studies of these frogs in the field. The second author worked on the interspecific relationships and isolating mechanisms in Panama (Fouquette, 1960b) and later studied the species in southern Mexico. As part of his survey of the hylids of Middle America, the first author accumulated field and laboratory data on the frogs throughout their ranges in Mexico and Central America. The purpose of this report is to present our findings on the four species of Middle American frogs that we place in the _Hyla microcephala_ group. In addition to conventional taxonomic characters, we have utilized the features of the cranial osteology and have relied heavily on the data obtained from an analysis of the mating calls. Furthermore, we have included ecological and distributional data in our synthesis of interspecific relationships.

ACKNOWLEDGMENTS

Examination of specimens was made possible by the provision of working space at various institutions or through the loan of specimens. For their generosity in this manner we are grateful to Richard J. Baldauf, Charles M. Bogert, James E. Boehlke, Doris M. Cochran, Robert F. Inger, John M. Legler, Alan E. Leviton, Gerald Raun, Jay M. Savage, Hobart M. Smith, Robert C. Stebbins, Wilmer W. Tanner, Charles F. Walker, Ernest E. Williams, and Richard G. Zweifel.

Duellman is especially grateful to Charles W. Myers, Linda Trueb, Jerome B. Tulecke, and John Wellman for their assistance in the field and to Linda Trueb for her work on the cranial osteology that is incorporated in this report. Fouquette is indebted to H. Morgan Smith and A. C. Collins for assistance in the field, to A. J. Delahoussaye for assistance in the laboratory, and to W. Frank Blair for use of the facilities of the sound laboratory at the University of Texas and for much help in the early stages of this study.

The research reported herein was accomplished mainly through support by the National Science Foundation (grants NSF G-9827 and GB-1441 to Duellman and GB-599 to Fouquette). The latter's field work in Mexico was assisted in part by NSF Grant G-4956 to W. Frank Blair. Some of the field studies carried out in Panama by Duellman were supported by a grant from the National Institutes of Health (NIH GM-12020).

We are grateful to many persons, too numerous to mention, who in various ways aided our field work in Middle America. We are especially indebted to Dr. Rodolfo Hernandez Corzo and the late Ing. Luis Macias Arellano of the Direccion General de la Fauna Silvestre of the Mexican government for providing permits to collect in Mexico.

Materials and Methods

For this report, data has been obtained from 2829 preserved frogs, 42 skeletal preparations, 8 lots of tadpoles and young, and 4 lots of eggs. Much of the material was collected in our independent field work, which has extended over a period of 11 years.

Measurements were taken in the manner described by Duellman (1956). 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 slight differences in results were found to be less than the error in measurement, so the data from all sources were combined without correction. The techniques and terminology of the calls are those defined by Fouquette (1960a, 1960b).

In the accounts of the species we have attempted to give a complete synonymy. 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 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:

AMNH --American Museum of Natural History
ANSP --Academy of Natural Sciences of Philadelphia
BMNH --British Museum (Natural History)
BYU --Brigham Young University
CAS --California Academy of Sciences
FMNH --Field Museum of Natural History
KU --University of Kansas Museum of Natural History
MCZ --Museum of Comparative Zoology
MVZ --Museum of Vertebrate Zoology
SU --Stanford University
UIMNH--University of Illinois Museum of Natural History
UMMZ --University of Michigan Museum of Zoology
USC --University of Southern California
USNM --United States National Museum
UU --University of Utah
TCWC --Texas Cooperative Wildlife Collection
TNHM --Texas Natural History Museum

HYLA MICROCEPHALA GROUP

_Definition._--Small hylids attaining a maximum snout-vent length of 27 mm. in males and 32 mm. in females; dorsum yellowish tan with brown markings; thighs uniformly yellow, vocal sac in breeding males yellow; snout truncate in lateral profile; tympanum distinct, usually slightly smaller than one-half diameter of eye; vocal sac single, median, subgular; fingers about one-third webbed; toes webbed nearly to bases of discs, except only to middle of antepenultimate or base of penultimate phalanx of fourth toe; tarsal fold weak; inner metatarsal tubercle low, flat, elliptical; axillary membrane present; pupil horizontally elliptical; palpebral membrane unmarked; cranial elements reduced in ossification; sphenethmoid small, short; frontoparietal fontanelle large; tegmen tympani not extensive; quadratojugal greatly reduced; anterior arm of squamosal extending only about one-fourth distance to maxillary; posterior arm of squamosal not having bony connection with prootic; nasals lacking maxillary processes; medial ramus of pterygoid not having bony attachment to prootic; maxillary, premaxilary, and prevomerine teeth present; palatine and parasphenoid teeth absent; Mentomeckelians ossified; tadpoles having xiphicercal tails with deep caudal fins and terminal mouth lacking teeth; mating call consisting of one primary note followed by a series of shorter secondary notes; haploid number of chromosomes, 15 (known only in _H. microcephala_ and _H. phlebodes_.)

_Content._--As recognized here the _Hyla microcephala_ group contains four species, one having two subspecies. An alphabetical list of the specific and subspecific names that we consider to be applicable to the _Hyla microcephala_ group are listed below.

Names Proposed Valid Names

_Hyla cherrei_ Cope, 1894 ? = _H. m. microcephala_ _Hyla microcephala_ Cope, 1886 = _H. m. microcephala_ _Hyla microcephala_ Boulenger, 1898 (_nec_ Cope, 1886) = _H. microcephala underwoodi_ _Hyla microcephala martini_ Smith, 1951 = _H. microcephala underwoodi_ _Hyla microcephala sartori_ Smith, 1951 = _H. sartori_ _Hyla phlebodes_ Stejneger, 1906 = _H. phlebodes_ _Hyla robertmertensi_ Taylor, 1937 = _H. robertmertensi_ _Hyla underwoodi_ Boulenger, 1899 = _H. microcephala underwoodi_

_Discussion._--The color pattern is the most useful character in distinguishing the species of the _Hyla microcephala_ group from one another. Except in _Hyla microcephala_, little geographic variation in color pattern is noticeable. The features of color pattern that are helpful in identifying the species are: 1) presence or absence of lateral dark brown stripe; 2) longitudinal extent and width of lateral stripe, if present; 3) presence or absence of a narrow white line just dorsal to the lateral dark stripe; 4) presence or absence of an interorbital dark mark; 5) the arrangement of dark markings on the back, either as longitudinal lines or series of dashes, or in the form of various kinds of transverse markings; 6) presence of dark flecks, longitudinal line, or transverse marks on shanks.

Few consistent differences in measurements and proportions exist among the species (Table 1). The most obvious morphological difference is that the head is noticeably narrower in _H. robertmertensi_ than in the other species. _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_.

_Distribution._--The composite range of the Middle American frogs of the _Hyla microcephala_ group includes the lowlands of southern Mexico and Central America, in some places to elevations of 1200 meters, southeastward from southern Jalisco and southern Veracruz, excluding arid regions (northern Yucatan Peninsula, Balsas-Tepalcatepec Basin, Plains of Tehuantepec, Grijalva Valley, Salama Basin, and upper Motagua Valley) to the Pacific lowlands and the Cauca and Magdalena valleys in Colombia.

Key to Species and Subspecies

1. Lateral dark stripe, bordered above by narrow white line,
extending from snout at least to sacral region 2

Lateral dark stripe, if present, not extending posteriorly to
sacral region and not bordered above by narrow white line 4

2. Lateral dark stripe continuous to groin; dark flecks or
longitudinal line on shanks; interorbital dark bar absent;
dorsal pattern usually consisting of pair of longitudinal dark
lines or series of dashes 3

Lateral dark stripe usually extending only to sacral region;
dark transverse bars on shanks; interorbital bar usually
present; dorsal pattern usually consisting of interconnecting
dark lines, sometimes forming transverse marks
_H. microcephala underwoodi_

3. Lateral dark stripe narrow, covering only upper edge of
tympanum; dorsal longitudinal stripes continuous, extending to
vent _H. microcephala microcephala_

Lateral dark stripe wide, encompassing entire tympanum; dorsal
markings consisting of longitudinal series of flecks or dashes,
or of two lines, usually not extending to vent _H. robertmertensi_

4. Lateral dark stripe indistinct, present only above tympanum and
insertion of arm; dorsal markings consisting of narrow lines
and dashes, sometimes interconnected; transverse bars on shanks
narrow relative to interspaces _H. phlebodes_

Lateral dark stripe absent; dorsal markings consisting of two broad
chevron-shaped marks; transverse bars on shanks wide relative to
interspaces _H. sartori_

ACCOUNTS OF SPECIES AND SUBSPECIES

_Hyla microcephala_ Cope

_Diagnosis._--Lateral dark stripe narrow, covering only upper edge of tympanum, bordered above by narrow white stripe; dorsal pattern consisting of pair of longitudinal brown lines and no interorbital bar (eastern populations), or of irregular dark markings forming an X- or )(-shaped mark in scapular region and an interorbital bar (western populations).

_Content._--The populations inhabiting the Pacific lowlands of southeastern Costa Rica eastward to Colombia are recognized herein as _Hyla microcephala microcephala_ Cope; the populations in western Costa Rica northward to Mexico are assigned to _Hyla microcephala underwoodi_ Boulenger.

_Distribution._--Southern Veracruz and northern Oaxaca southeastward through the Atlantic lowlands of Central America to north-central Nicaragua, thence southeastward on the Pacific lowlands to eastern Panama, and thence into the Cauca and Magdalena valleys (Caribbean drainage) of Colombia (Fig. 1).

Table 1.--Variation in Certain Measurements and Properties in the
Hyla microcephala Group. (All Data Based on Adult Males;
Mean and Standard Error of Mean Below Observed Range.)

========================================================================
Locality | N | Snout-vent | Tibia length |Foot length|
| | length | ------------ | --------- |
| | (S-V L) | S-V L | S-V L |
------------------------------------------------------------------------
| _H. m. microcephala_
|
Panama: Canal Zone | 25 | 21.5-24.1 | 50.2-56.0 | 40.9-46.6 |
| | 22.8+-0.20 | 52.9+-0.37 | 43.5+-0.28 |
| | | | |
Costa Rica: Golfito | 25 | 18.5-24.5 | 49.1-54.4 | 41.8-48.0 |
| | 22.4+-0.27 | 51.6+-0.26 | 45.1+-0.32 |
|
| _H. m. underwoodi_
| |
Nicaragua: La Cumplida | 25 | 23.0-25.6 | 51.0-55.7 | 41.3-46.5 |
| | 24.1+-0.19 | 52.9+-0.25 | 43.7+-0.25 |
| | | | |
Guatemala: Finca Chama | 25 | 21.8-25.0 | 51.0-57.2 | 41.2-47.8 |
| | 23.5+-0.16 | 54.3+-0.39 | 44.4+-0.30 |
| | | | |
Tabasco: Teapa | 25 | 22.7-25.8 | 48.0-54.5 | 40.7-46.8 |
| | 24.3+-0.14 | 51.5+-0.29 | 43.3+-0.25 |
| | | | |
Oaxaca: Donaji-Sarabia | 25 | 22.1-25.9 | 49.8-55.6 | 40.5-46.6 |
| | 23.8+-0.19 | 52.8+-0.33 | 43.4+-0.27 |
| | | | |
Veracruz: Alvarado | 25 | 21.9-25.4 | 49.6-54.4 | 40.7-47.5 |
| | 24.1+-0.17 | 51.1+-0.28 | 42.6+-0.34 |
|
| _H. robertmertensi_
|
Guatemala: La Trinidad | 21 | 21.8-24.6 | 47.1-52.8 | 40.9-51.3 |
| | 23.4+-0.15 | 49.9+-0.34 | 43.5+-0.17 |
| | | | |
Chiapas: Acacoyagua | 25 | 21.4-25.7 | 47.8-52.4 | 41.7-46.3 |
| | 24.1+-0.20 | 50.4+-0.45 | 43.9+-0.23 |
| | | | |
Oaxaca: Tapanatepec | 25 | 22.4-26.4 | 44.1-48.3 | 39.1-44.5 |
| | 24.7+-0.18 | 46.4+-0.23 | 41.7+-0.23 |
|
| _H. phlebodes_
|
Panama: Canal Zone | 25 | 19.6-23.2 | 49.1-56.9 | 41.9-47.1 |
| | 22.2+-0.16 | 52.8+-0.35 | 45.4+-0.26 |
| | | | |
Costa Rica: Turrialba | 25 | 19.7-23.6 | 47.4-55.7 | 38.1-46.4 |
| | 22.0+-0.18 | 51.1+-0.35 | 42.8+-0.38 |
|
| _H. sartori_
|
Guerrero: Tierra Colorada| 25 | 23.7-26.0 | 47.2-51.4 | 42.4-47.8 |
| | 24.8+-0.13 | 49.6+-0.23 | 45.2+-0.27 |
------------------------------------------------------------------------
Table 1. (continued)
===============================================================
Locality | Head length | Head width | Tympanum
| ----------- | ---------- | --------
| S-V L | S-V L | Eye
---------------------------------------------------------------
| _H. m. microcephala_
|
Panama: Canal Zone | 28.5-32.8 | 28.1-30.9 | 44.0-54.1
| 31.0+-0.22 | 29.4+-0.11 | 49.0+-0.55
|
Costa Rica: Golfito | 30.2-35.5 | 29.0-32.7 | 40.0-57.8
| 33.1+-0.25 | 30.8+-0.16 | 48.4+-1.10
|
| _H. m. underwoodi_
|
Nicaragua: La Cumplida | 29.7-33.5 | 28.9-31.8 | 42.3-60.0
| 31.6+-0.19 | 30.4+-0.17 | 49.3+-0.97
|
Guatemala: Finca Chama | 30.8-35.3 | 29.6-33.6 | 37.5-56.4
| 33.0+-0.16 | 31.3+-0.36 | 45.2+-0.89
|
Tabasco: Teapa | 29.5-33.0 | 28.7-31.8 | 40.7-53.8
| 31.7+-0.17 | 30.3+-0.16 | 45.5+-0.38
|
Oaxaca: Donaji-Sarabia | 30.4-34.8 | 28.9-32.6 | 37.0-54.1
| 32.8+-0.19 | 30.8+-0.17 | 45.1+-0.76
|
Veracruz: Alvarado | 29.9-33.8 | 29.1-32.9 | 40.7-53.8
| 31.4+-0.18 | 30.5+-0.17 | 46.6+-0.65
|
| _H. robertmertensi_
|
Guatemala: La Trinidad | 30.0-33.3 | 27.3-29.8 | 44.4-50.0
| 31.3+-0.20 | 28.5+-0.23 | 47.4+-0.46
| | |
Chiapas: Acacoyagua | 29.1-32.7 | 26.0-30.3 | 42.8-53.8
| 31.2+-0.29 | 28.1+-0.20 | 46.5+-0.50
| | |
Oaxaca: Tapanatepec | 26.1-30.4 | 25.4-28.1 | 45.8-58.3
| 28.4+-0.16 | 26.8+-0.14 | 52.9+-0.77
|
| _H. phlebodes_
|
Panama: Canal Zone | 33.6-37.4 | 32.3-36.0 | 37.9-46.4
| 34.8+-0.18 | 33.8+-0.18 | 41.6+-0.49
| | |
Costa Rica: Turrialba | 32.6-35.9 | 30.5-35.0 | 35.7-48.2
| 34.1+-0.16 | 32.9+-0.17 | 40.1+-0.53
|
| _H. sartori_
|
Guerrero: Tierra Colorada| 29.4-31.8 | 28.9-31.0 | 42.3-52.0
| 30.6+-0.13 | 30.0+-0.12 | 47.4+-0.59
---------------------------------------------------------------

_Hyla microcephala microcephala_ Cope

_Hyla microcephala_ Cope, Proc. Amer. Philos. Soc., 23:281, February
11, 1886 [Syntypes.--USNM 13473 (2 specimens, now lost) from
Chiriqui, Panama; Mr. MacNeil collector]; Bull. U.S. Natl. Mus.,
32:14, 1887. Guenther, Biologia-Centrali Americana, Reptilia and
Batrachia, p. 265, June, 1901. Dunn, Occas. Papers Boston Soc.
Nat. Hist., 5:413, October 10, 1931; Occas. Papers Boston Soc.
Nat. Hist., 8:72, June 7, 1933. Stebbins and Hendrickson, Univ.
California Publ. Zool., 56:524, February 17, 1959. Fouquette,
Evolution, 14:484, December 16, 1960. Busack, Copeia, 2:371,
June 21, 1966.

? _Hyla cherrei_ Cope, Proc. Acad. Nat. Sci. Philadelphia, 1894,
p. 195, 1894 [Holotype.--location unknown, apparently lost;
type-locality: "Alajuela, Costa Rica;" R. Alfaro collector].
Guenther, Biologia Centrali-Americana: Reptilia and Batrachia,
p. 264, June, 1901. Taylor, Univ. Kansas Sci. Bull., 35:846,
July 1, 1952.

_Hyla underwoodi_, Ruthven, Misc. Publ. Mus. Zool., Univ. Michigan,
8:55, September 15, 1922. Barbour, Proc. New England Zool. Club,
10:31, March 2, 1928.

_Hyla microcephala microcephala_, Smith, Herpetologica, 7:185,
December 31, 1951. Taylor, Univ. Kansas Sci. Bull., 39:23,
November 18, 1958.

_Diagnosis._--Brown lateral stripe narrow, extending from nostril along canthus, along upper edge of tympanum to groin, bordered above by narrow white line; pair of dark brown longitudinal lines on dorsum extending to vent; shanks having dark longitudinal line or flecks, no transverse bars; interorbital dark mark lacking.

_Description and Variation._--The color pattern is nearly constant. 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. In two others the lines converge and fuse in the scapular region, and in four specimens auxiliary, fragmented lines are present dorsolaterally.

In all specimens from southeastern Costa Rica (Golfito, Palmar Sur, and Villa Neilly) the pattern is constant, except that in about 10 per cent of the specimens the longitudinal line on the dorsal surface of the shank is replaced by a row of brown flecks.

Of the limited number of Colombian specimens examined, all are patterned normally, except three from Sautata, Choco, three from Curumani, and three from Arcataca, Magdalena, which have flecks on the dorsal surfaces of the shanks, and one from Espinal, Tolima, which has no markings on the shanks.

When active at night most individuals are pale yellowish tan dorsally; the white dorsolateral line is noticeable, but the brown lateral stripe, dorsal brown lines, and lines on shanks are so pale that often they are barely discernible. By day the dorsum changes to tan or pale reddish brown; the stripes are dark brown, and the dorsolateral stripe that is white at night becomes creamy yellow (Pl. 13). Small brown flecks are present on the dorsum of most individuals. The venter always is white, and the iris is pale bronze with a brown tint immediately anterior and posterior to the pupil. In breeding males the vocal sac is pale yellow.

_Tadpoles._--Tadpoles of this species have been found in weed-choked ponds in eastern Panama Province. The following description is based on KU 104097, a specimen in developmental stage 34 (Gosner, 1960).

Total length, 20.5 mm.; body length, 8.2 mm.; body slightly wider than deep; snout pointed; nostrils large, situated dorsally, much closer to snout than eyes, directed anteriorly; eyes moderately small, situated dorsolaterally and directed laterally; spiracle sinistral, located just posteroventral to eye; anal tube dextral. Tail xiphicercal; caudal musculature moderately deep, becoming slender posteriorly, extending beyond caudal fin; fins deepest at about one-third distance from body to tip of tail; dorsal fin extending onto body, deeper than deepest part of caudal musculature; ventral fin slightly shallower than musculature. Mouth small, terminal, lacking teeth and fringing papillae, but having finely serrate beaks. In preservative, top of head pale brown; dark stripe from tip of snout through eye to posterior edge of body, narrowing to thin line on proximal one-fourth of tail; venter white; tail creamy tan with fine black flecks most numerous posteriorly; posterior two-thirds of fins edged with black. 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 Rio 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. microcephala_ (Palmar Sur) to the southeasternmost locality for _H. m. underwoodi_ (Barranca). Although in most aspects of coloration the frogs are more nearly like _H. m. underwoodi_ than _H. m. microcephala_, some specimens have longitudinal lines on their shanks, such as are characteristic of _H. m. microcephala_. The dorsal pattern varies from nearly complete longitudinal lines to broken lines, fused into an X-shaped scapular mark or not.

As noted by Rivero (1961:135), _Hyla microcephala_ seems to be closely related to _Hyla misera_ Werner, a species having a wide distribution east of the Andes in South America. 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 status of Cope's _Hyla cherrei_ is questionable. Since the type, the only specimen ever referred to the species, apparently is lost, the only extant information regarding the taxon is contained in the original description (Cope, 1894). There the species was characterized as having a narrow dorsolateral white stripe and lacking pigment on the upper arms and thighs. These characteristics of the color pattern combined with the statements "vomerine teeth few, opposite the middle of the very large choanae" and "tympanic drum distinct, one half the area of eye" serve to distinguish _H. cherrei_ from all other Costa Rican hylids, except _H. m. microcephala_ and _H. m. underwoodi_. No statements in the type description will definitely associate _cherrei_ with one or the other of these subspecies. Since it seems obvious that _H. cherrei_ can be associated with _H. microcephala_, we prefer to place the name in the synonymy of the nominate subspecies, thereby preserving the commonly used name _H. underwoodi_ (Boulenger, 1899) as a subspecies of _H. microcephala_.

_Distribution._--_Hyla microcephala microcephala_ inhabits coastal lowlands from the area of Golfo Dulce (apparently absent from the Osa Peninsula) in southeastern Costa Rica eastward in Panama, including the Azuero Peninsula to northern Colombia and thence southward in the valleys of the Rio Cauca and Rio Magdalena in Colombia (Fig. 1). 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, Cocle, Panama. Throughout most of its range _Hyla microcephala microcephala_ occurs in disturbed habitats--cut-over forests, secondary growth, and pastureland. It does not seem to be an inhabitant of either primary forest or of _Curatella_-savanna.

_Specimens examined._--522, as follows: +Costa Rica+: Puntarenas: Golfito, KU 32172-207; 3 km. E Golfito, KU 86399, USC 2757-8; Palmar Sur, KU 64591-608, USC 2650 (14), UU 3907-32; *1.5-2.5 km. ESE Palmar Sur, KU 68293-7 (skeletons), 93957-62; Parrita, USC 8254 (2), 8255, 8256 (4), 8258 (2) [intergrades with _H. m. underwoodi_]; 3 km. NW Piedras Blancas, KU 103689; 6.1 km. NE mouth of Rio Tarcoles, USC 818 (2), 6081-2 [intergrades with _H. m. underwoodi_]; Villa Neilly, USC 2651; *1-5 km. WNW Villa Neilly, USC 6182-4, 8003 (4), 8031 (3), 8032; *10.5 km. WNW Villa Neilly, KU 64609-27, 68398 (eggs).

+Panama+: Canal Zone: Albrook Air Base, TNHC 23389, 23497; Balboa, ANSP 19555-6; *Fort Clayton, UIMNH 42008-12; *2.8 km. SW Fort Kobbe, KU 96015-25; *Frijoles, MCZ 19208; *Bamboa, MCZ 21507; *8.3 km. N Gatun Locks, TNHC 23441; *Juan Diaz, MCZ 13747; *Juan Mina, AMNH 55436-7, ANSP 21811-2, UMMZ 126734, 126735 (6), UU 3900-6; *8-14 km. N Miraflores Locks, TNHC 23374-88, 23390-409, 23411-38, 23440, 23442-60, 23462-76; 23478-83, 23492, 23555-60, 23562-76; *Rio Chagres, AMNH 55430, 55439; *Rio Cocoli, 3.5 km. N Miraflores Locks, TNHC 23410; *Summit, ANSP 23365-71, FMNH 22966-9, KU 97783-87. Chiriqui: 5.5 km. E Concepcion, AMNH 69772; *14.4 km. E Concepcion, AMNH 69773-8; 2 km. S David, AMNH 69779; *Progreso, UMMZ 58252, 58253 (2), 58254, 58436; Rio Gariche, 8.3 km. ESE Paso Canoas, KU 103065-8. Cocle: 1 km. SE El Cano, KU 103042-51; El Valle de Anton, AMNH 59614-18 (10), 69785, ANSP 23502-5, KU 77201-14, MVZ 66578-83, UIMNH 46532. Colon: Cement Plant, Transisthmian Highway, FMNH 60394-5. Darien: El Real, KU 80454-5, 103052-64, UMMZ 125036 (10), USNM 140567-8; Rio Canclon at Rio Chucunaque, UMMZ 125035; *Rio Chucunaque, near Yavisa, AMNH 59523. Los Santos: Tonosi, KU 101606-9. Panama: 5 km. S Bejuco, AMNH 69782; 3 km. W Chepo, KU 77172-4, 104097-8 (tadpoles); *6 km. WSW Chepo, KU 77175; *Chico, Rio La Jagua, USNM 129070; *La Joya, Cacora, ANSP 25129-33; Madden Dam, FMNH 67819; Nueva Gorgona, AMNH 69780-1; *1.6 km. W Nueva Gorgona, AMNH 69783-4; 1.5 km. W Pacora, 77176-200; *Rio La Laja, near Chame, ANSP 21845; *Rio Tapia, MCZ 10048; *Tapia, AMNH 18930, 18950, 18952-3; *18 km. E Tocumen, MVZ 78662.

+Colombia+: Choco: Sautata, Atrato, FMNH 74918 (2), 74919. Magdalena: Aracataca, ANSP 19755-7; Curumani, MCZ 21465-74, UIMNH 28855; UMMZ 90168, USNM 118247; El Banco, Rio Magdalena, ANSP 25061; Fundacion, UMMZ 48281-2. Tolima: Espinal, MCZ 15068; Mariquita, FMNH 81822-3. Valle: Sevilla, MCZ 13751-3.

_Hyla microcephala underwoodi_ Boulenger

_Hyla microcephala_ Boulenger, Proc. Zool. Soc. London, p. 481,
October 1, 1898 [Syntypes.--BMNH 94. 11. 1532-33 from Bebedero,
Guanacaste Province, Costa Rica; C. F. Underwood collector] (not
_Hyla microcephala_ Cope, Proc. Amer. Philos. Soc., 23:281,
February 11, 1886, from Chiriqui, Panama).

_Hyla underwoodi_ Boulenger, Ann. Mag. Nat. Hist., ser. 7, 3:277,
April, 1899 (substitute name for _Hyla microcephala_ Boulenger,
preoccupied). Guenther, Biologia-Centrali Americana, Reptilia and
Batrachia, p. 278, September, 1901. Dunn and Emlen, Proc. Acad.
Nat. Sci. Philadelphia, 84:25, March 22, 1932. Stuart, Misc. Publ.
Mus. Zool., Univ. Michigan, 29:39, October 1, 1935. Taylor, Proc.
Biol. Soc. Washington, 50:44, April 21, 1937. Stuart, Occas.
Papers Mus. Zool., Univ. Michigan, 471:15, May 17, 1943. Taylor
and Smith, Proc. U. S. Natl. Mus., 95:586, June 30, 1945. Stuart,
Misc. Publ. Mus. Zool., Univ. Michigan, 69:35, June 12, 1948.
Smith and Taylor, Bull. U. S. Natl. Mus., 194:85, June 17, 1948;
Univ. Kansas Sci. Bull., 33:316, March 20, 1950. Stuart, Contr.
Lab. Vert. Biol., Univ. Michigan, 45:48, May, 1950. Taylor, Univ.
Kansas Sci. Bull., 35:891, July 1, 1952; Univ. Kansas Sci. Bull.,
39:25, November 18, 1958.

_Hyla phlebodes_, Cole and Barbour, Bull. Mus. Comp. Zool., 50:154,
November, 1906. Kellogg, Bull. U. S. Natl. Mus., 160:172,
March 31, 1932.

_Hyla microcephala martini_ Smith, Herpetologica, 7:187, December
31, 1951 [Holotype.--UIMNH 20965 from Encarnacion, Campeche,
Mexico; H. M. Smith collector]. Stuart, Contr. Lab. Vert. Biol.,
Univ. Michigan, 68:46, November, 1954. Fugler and Webb,
Herpetologica, 13:105, July 10, 1957. Stuart, Contr. Lab. Vert.
Biol., Univ. Michigan, 75:17, June, 1958. Neill and Allen, Publ.
Research Div., Ross Allen's Reptile Inst., 2:26, November 10,
1959. Duellman, Univ. Kansas Publ., Mus. Nat. Hist., 13:62,
August 16, 1960. Stuart, Herpetologica, 17:74, July 11, 1961.
Hensley and Smith, Herpetologica, 18:70, April 9, 1962. Stuart,
Misc. Publ. Mus. Zool., Univ. Michigan, 122:36, April 2, 1963.
Holman and Birkenholz, Herpetologica, 19:144, July 3, 1963.
Duellman, Univ. Kansas Publ., Mus. Nat. Hist., 15:225, October 4,
1963; Univ. Kansas Publ., Mus. Nat. Hist., 15:588, June 22, 1965.

_Hyla microcephala underwoodi_, Smith, Herpetologica, 7:188,
December 31, 1951.

_Diagnosis._--Brown lateral stripe narrow, extending to groin or only to sacral region, bordered above by narrow white line; dorsal pattern bold, consisting of X- or )(-shaped mark in scapular region or pair of interconnected dark lines on back; interorbital dark mark usually present; shanks usually having dark transverse bars.

_Description and Variation._--The dorsal color pattern is highly variable. The various permutations of the X-shaped scapular mark and dark sacral marks differ proportionately in different samples. The variation in color pattern in 12 samples is summarized in Table 2. 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 Mexico 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. The X- or )(-shaped scapular markings and /\- or / \-shaped sacral markings are most prevalent in northern samples, whereas to the south the dorsal markings are more commonly arranged in a pattern of paired lines, which usually are discontinuous and usually extend posteriorly only to the sacral region. Thus, the color pattern in _H. m. underwoodi_ in the southern part of its range shows trends towards the pattern characteristic of _H. m. microcephala_. Intergrades between these two subspecies have been discussed in the account of the nominate subspecies.

Table 2.--Variation in Color Pattern in Hyla microcephala underwoodi
==========================================================================
Population | N | Shanks || Interorbital || Dorsolateral |
| | || bar || stripe |
| |-------------||----------------||--------------|
| | Bars |Flecks|| Present| Absent|| Groin| Sacrum|
--------------------------------------------------------------------------
Oaxaca: | 27 | 22 | 5 || 27 | 0 || 0 | 27 |
Donaji-Sarabia | | | || | || | |
| | | || | || | |
Tabasco: | 55 | 46 | 9 || 55 | 0 || 0 | 55 |
Teapa-Villahermosa| | | || | || | |
| | | || | || | |
Guatemala: | 51 | 51 | 0 || 51 | 0 || 17 | 34 |
La Libertad | | | || | || | |
| | | || | || | |
Guatemala: | 32 | 32 | 0 || 32 | 0 || 0 | 32 |
Finca Chama | | | || | || | |
| | | || | || | |
Guatemala: | 31 | 31 | 0 || 31 | 0 || 14 | 17 |
Puerto Barrios | | | || | || | |
| | | || | || | |
Honduras: | 13 | 13 | 0 || 13 | 0 || 9 | 4 |
Lago Yojoa | | | || | || | |
| | | || | || | |
Nicaragua: | 56 | 44 | 12 || 54 | 2 || 13 | 43 |
La Cumplida | | | || | || | |
| | | || | || | |
Nicaragua: | 10 | 10 | 0 || 10 | 0 || 8 | 2 |
Tipitapa | | | || | || | |
| | | || | || | |
Nicaragua: | 10 | 10 | 0 || 10 | 0 || 8 | 2 |
Santo Thomas | | | || | || | |
| | | || | || | |
Costa Rica: | 12 | 0 | 12 || 6 | 6 || 7 | 5 |
Tenorio-Tilaran | | | || | || | |
| | | || | || | |
Costa Rica: | 38 | 21[A]| 15 || 34 | 4 || 25 | 13 |
Las Canas-Liberia | | | || | || | |
| | | || | || | |
Costa Rica: | 32 | 26 | 6 || 29 | 3 || 30 | 2 |
Esparta | | | || | || | |
--------------------------------------------------------------------------

==========================================================================
Population | Scapular markings || Sacral |
| || markings |
|----------------------------||----------------------|
| X | )( | ][ | Other || /\ | / \ | Other |
--------------------------------------------------------------------------
Oaxaca: | 23 | 4 | 0 | 0 || 7 | 6 | 14 |
Donaji-Sarabia | | | | || | | |
| | | | || | | |
Tabasco: | 53 | 2 | 0 | 0 || 19 | 11 | 23 |
Teapa-Villahermosa| | | | || | | |
| | | | || | | |
Guatemala: | 45 | 6 | 0 | 0 || 16 | 14 | 21 |
La Libertad | | | | || | | |
| | | | || | | |
Guatemala: | 32 | 0 | 0 | 0 || 26 | 2 | 4 |
Finca Chama | | | | || | | |
| | | | || | | |
Guatemala: | 23 | 0 | 4 | 4 || 6 | 4 | 21 |
Puerto Barrios | | | | || | | |
| | | | || | | |
Honduras: | 3 | 2 | 3 | 5 || 2 | 1 | 10 |
Lago Yojoa | | | | || | | |
| | | | || | | |
Nicaragua: | 11 | 35 | 8 | 2 || 0 | 19 | 37 |
La Cumplida | | | | || | | |
| | | | || | | |
Nicaragua: | 0 | 5 | 3 | 2 || 0 | 3 | 7 |
Tipitapa | | | | || | | |
| | | | || | | |
Nicaragua: | 3 | 0 | 7 | 0 || 0 | 5 | 5 |
Santo Thomas | | | | || | | |
| | | | || | | |
Costa Rica: | 0 | 0 | 12 | 0 || 0 | 0 | 12 |
Tenorio-Tilaran | | | | || | | |
| | | | || | | |
Costa Rica: | 0 | 11 | 19 | 8 || 0 | 0 | 38 |
Las Canas-Liberia | | | | || | | |
| | | | || | | |
Costa Rica: | 0 | 0 | 14 | 18 || 0 | 0 | 32 |
Esparta | | | | || | | |
--------------------------------------------------------------------------

[Footnote A: Longitudinal stripes present in two specimens.]

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. The iris is pale bronze with a brown tint anterior and posterior to the pupil.

_Remarks._--_Hyla microcephala underwoodi_ has had a confused nomenclatural history. The taxon was first named _Hyla microcephala_ by Boulenger (1898); this name was preoccupied by _Hyla microcephala_ Cope (1886). Cole and Barbour (1906) and Kellogg (1932) used the name _Hyla phlebodes_ Stejneger (1906) for specimens of this frog from Mexico. Dunn (1931, 1933, 1934) applied the name _Hyla underwoodi_ to Panamanian specimens that we identify as _Hyla phlebodes_. Smith (1951) named _Hyla microcephala martini_ from southern Mexico and Guatemala and considered the northern populations to represent a subspecies distinct from the Costa Rican _Hyla microcephala underwoodi_, despite the fact the Stuart (1935:39) stated that comparisons of specimens from El Peten, Guatemala, with the holotype of _Hyla underwoodi_ showed only trivial differences.

Much of the confusion regarding the name _Hyla underwoodi_ stems from the illustration given by Boulenger (1898:pl. 39, fig. 3) and reproduced by Taylor (1952:892), which shows a frog having a unicolor dorsum, dorsolateral white lines, and dark flanks. This pattern is in marked contrast to the pattern seen in most preserved specimens, which have the dorsum variously marked by dark brown lines or irregular marks. Smith (1951:185), in his description of _Hyla microcephala martini_ from southern Mexico, considered _H. underwoodi_ to be a subspecies of _H. microcephala_ that lacked dorsal dark markings.

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 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. Of the frogs collected in Costa Rica in 1961, some specimens were preserved at night; others from the same series were preserved by day. The differences are striking. In those preserved at night, dorsal markings are faint, if present at all. Some specimens closely match the figure given by Boulenger (1898).

It is extremely doubtful if the frog described and illustrated by Boulenger could be associated with either _Hyla phlebodes_ or _H. microcephala microcephala_. Individuals of the former species lack a dorsolateral white line and always have some dorsal markings evident at night; furthermore, _H. phlebodes_ is not known to occur on the Pacific lowlands. _Hyla microcephala microcephala_ occurs farther southeast. Since there is no reason to doubt the type locality of _H. underwoodi_, since specimens from the area around the type locality that have been preserved at night are like the holotype in pattern, and since the characteristics of the populations of the frogs in Guanacaste are the same as, or gradually blend into those of, populations in northern Central America and southern Mexico, the frogs from throughout the entire range can be referred to one taxon, the earliest name for which is _Hyla underwoodi_ Boulenger, which herein is considered to be a subspecies of _H. microcephala_ Cope.

_Distribution._--_Hyla microcephala underwoodi_ inhabits the Atlantic slopes and lowlands from southern Veracruz and extreme northern Oaxaca eastward across the base of the Yucatan Peninsula (possibly the species is extant in the northern part of the peninsula) to British Honduras and thence southeastward through the Caribbean lowlands and interior valleys in Honduras to central Nicaragua, where it apparently avoids the forested Caribbean lowlands and the dry Pacific lowlands of northwestern Nicaragua, but in the vicinity of Managua invades the Pacific lowlands and continues southward into northwestern Costa Rica as far as the Puntarenas Peninsula (Fig. 1). In Mexico and Guatemala the species has not been taken at elevations of more than 350 meters, whereas farther south it occurs at higher elevations--780 meters at Silencio, Costa Rica, 830 meters on Montana de Guaimaca, Honduras, 960 meters at Finca Tepeyac, Nicaragua, and 1200 meters at Finca Venecia, Nicaragua.

_Specimens examined._--1270, as follows: +Mexico+: Campeche: Balchacaj, FMNH 100406, UIMNH 20944-6; Encarnacion, FMNH 27069-70, 75784, MCZ 28360, 29637, UIMNH 20948-58, 20965, USNM 134264-5; Escarcega, UMMZ 122999; *7.5 km. W Escarcega, KU 71229-43; Laguna Alvarado, 65 km. S Xpujil, KU 75084-9; Pacaitun, Rio Candelaria, FMNH 83118-20; *Tres Brazos, FMNH 113101-22, UIMNH 20947; 10 km. W Xpujil, KU 75082-3. Chiapas: Palenque, UIMNH 47984, 49139-50, USNM 114973-8. Oaxaca: *5 km. N Chiltepec, KU 87015-23; 3 km. N Donaji UMMZ 115249 (9); *3.7 km. N Donaji, UMMZ 115250 (5); *43 km. N Matias Romero, UIMNH 42550-68; *3.5 km. N Palomares, TNHC 25185, 25321-31, 25341-68; 4.6 km. N Sarabia, UMMZ 115247 (2); *6.1 km. N Sarabia, UMMZ 115248 (11), *3 km. N Tolocita, KU 39655; Tuxtepec, KU 87024-40. Tabasco: 24 km. N Frontera, MCZ 35665-70; 0.8 km. E Rio Tonola, TNHC 25189; Teapa, UMMZ 119218 (4); *2.7 km. N Teapa, UMMZ 119216 (4); *10 km. N Teapa, UMMZ 119217 (6); *11.5 km. N Teapa, UMMZ 119219; *15.2 km. N Teapa, UMMZ 119220 (4); *17.6 km. N Teapa, UMMZ 119221 (12), 3.3 km. S Villahermosa, UMMZ 119215 (12), *17.6 km. S Villahermosa, UMMZ 119214 (12). Veracruz: 2.1 km. N Acayucan, UIMNH 42547-9; *6.4 km. NW Acayucan, UMMZ 115254 (14); 1.6 km. ESE Alvarado, UMMZ 115258 (39); *2.4 km. ESE Alvarado, UMMZ 115251 (2); *4.5 km. S Aquilera, UMMZ 115252 (21); *8 km. SW Coatzacoalcos, UMMZ 119213 (10); 2.2 km. E Cosoleacaque, UMMZ 119222 (26); 10 km. SE Hueyapan, UMMZ 115255; 0.8 km. S Lerdo de Tejada, UMMZ 122778; *3.6 km. NE Minatitlan, TNHC 25150-2; 1.9 km. S Naranja, UMMZ 115253 (3); 4.5 km. NE Novillero, UMMZ 115256; San Andres Tuxtla, FMNH 113124-8, UIMNH 20942-3. Yucatan: Chichen-Itza, FMNH 36570, MCZ 2463 (2).

+British Honduras+: Cayo: 6.2 km. S El Cayo, MCZ 37885-92. Stann Creek: Stann Creek, FMNH 49068.

+Guatemala+: Alta Verapaz: 28.3 km. N Campur, KU 64578-90; Chinaja, KU 57425; Cubilquitz, UMMZ 90887, 90888 (4); Finca Chama, UMMZ 90879 (13), 90880 (4), 90881, 90882 (28), 90883 (12), 90884 (46), 90885 (39), 90886 (20); *Finca Tinaja, BYU 16032; Panzos, UMMZ 90889 (2). Chiquimula: Chiquimula, UMMZ 98113; 2 km. N Esquipulas, UMMZ 106844. El peten: La Libertad, KU 57447-97, 59907-11 (skeletons), MCZ 21461, UMMZ 75332 (13), 75333 (11), 75334 (14), 75335 (10); Piedras Negras, FMNH 113123, UIMNH 20966; *5 km. S Piedras Negras, USNM 114951-72; Tikal, UMMZ 117981 (2); Toocog, 15 km. SE La Libertad, KU 57426-46. El Quiche: Finca Tesoro, UMMZ 89165 (5). Huehuetenango: Finca San Rafael, 16 km. SE Barillas, FMNH 40917-9. Izabal: Puerto Barrios, FMNH 20004-7; 8 km. S Puerto Barrios, KU 57507-37, 59991 (eggs), 59992 (tadpoles); Quirigua, CAS 69657-701; 2.5 km. NE Rio Blanco, KU 57539; San Felipe, FMNH 35065. Zacapa: 14 km. ENE Mayuelas, KU 57502-6; 8 km. ENE Rio Hondo, KU 57498-501.

+Honduras+: Atlantidad: La Ceiba, UMMZ 91948 (2), USNM 117593-600; Lancetilla, MCZ 17981. Cortes: Lago Yojoa, AMNH 54917-9, 54957, 55134, KU 64563-77. El Paraiso: Valle de Jamastran, AMNH 54807-12. Francisco-Moranza: El Zamorano, AMNH 54873-81, KU 103223, UMMZ 123101; Montana de Guaimaca, AMNH 54900-4 (8); Ranch San Diego, 19 km. SW Guaimaca, AMNH 53939. Itibuca: Vieja Itibuca, AMNH 54912-3.

+Nicaragua+: Chontales: 3 km. SW Santo Tomas, KU 64770-9, 68308 (skeleton). Esteli: Finca Venecia, 7 km. N, 16 km. E Condega, KU 85296; 2.4 km. N Esteli, MCZ 28933-7. MANAGUA: 12-13 km. E Managua, KU 85297-301; *10 km. SW Tipitapa, UMMZ 119977 (10). Matagalpa: *Finca Tepeyac, 10.5 km. N, 9 km. E Matagalpa, KU 85302-3; Hacienda La Cumplida, KU 64780-96, 68309-11 (skeletons), UMMZ 116482 (8), 116483 (23), 116484 (3), 116485 (5), 119984 (3). Rivas: *Finca Amayo, 13 km. S, 14 km. E Rivas, KU 85304-7; 16 km. S Rivas, MCZ 29011-7; *20.5 km. SE Rivas, KU 85308-10; 5 km. SE San Pablo, KU 43111-4.

+Costa Rica+: Guanacaste: Arenal, USC 6254 (2); *3 km. W Bagaces, USC 7019 (10); *3 km. NE Boca del Barranca, USC 8017 (21), *Finca San Bosco, USC 6272 (6), 6276 (3); *Guayabo de Bagaces, USC 7022 (4), 7023 (3), 7025; 12 km. S La Cruz, USC 8091 (2); *Laguna Arenal, USC 6262; *27 km. N Las Canas, USC 8171 (6); *16 km. E Las Canas, KU 102252-8; 16 km. SSE Las Canas, KU 65090-5; *20 km. SE Las Canas, KU 102251; Liberia, KU 30827-39; *7.3 km. N Liberia, USC 8096 (4); *10 km. N Liberia, USC 8085 (9); *7.5 km. SE Liberia, KU 65102-8, 68621-2 (skeletons); *14.7 km. S Liberia, USC 8238 (3); *4 km. W Liberia, KU 36847-57; 2 km. S Nicoya, USC 8230; *3-10 km. ESE Playa del Coco, USC 8012 (16), 8137 (14); *21.6 km. ESE Playa del Coco, USC 8138 (13); *Penas Blancas, KU 102247-50; *Rio Bebedero, 5 km. S Bebedero, KU 65089; *Rio Higueron, USC 7168 (2); Santa Cruz, USC 8232 (2); *Silencio, USC 6248; *Tenorio, KU 32313; Tilaran, KU 36858-60; *2 km. E Tilaran, KU 86403, *5 km. NE Tilaran, KU 36840-6 USC 6269. Puntarenas: Barranca, KU 32305-12, *5 km. WNW Barranca, UMMZ 119976 (2); *10 km. E Esparta, KU 86400-2; 1 km. WNW Esparta, KU 65101; *4 km. WNW Esparta, KU 65088; *10 km. WNW Esparta, KU 65063-87, 68616-20 (skeletons); *12 km. WNW Esparta, KU 65096-100, USC 8251; 21.8 km. W San Ramon, USC 8242 (15).

+Hyla robertmertensi+ Taylor

_Hyla robertmertensi_ Taylor, Proc. Biol. Soc. Washington, 50:43,
April 21, 1937 [Holotype.--CNHM 100096 (formerly EHT-HMS 2270)
from Tapachula, Chiapas, Mexico; H. M. Smith and E. H. Taylor
collectors]. Smith and Taylor, Bull. U. S. Natl. Mus., 194:84,
June 17, 1948; Univ. Kansas Sci. Bull., 33:326, March 20, 1950.
Mertens. Senckenbergiana, 33:170, June 15, 1952;
Senckenbergischen Naturf. Gesell., 487:30, December 1, 1952.
Stuart, Contr. Lab. Vert. Biol., Univ. Michigan, 68:47,
November, 1954. Duellman, Univ. Kansas Publ., Mus. Nat. Hist.,
13:63, August 16, 1960. Duellman and Hoyt, Copeia, 1961 (2): 417,
December 19, 1961. Porter, Herpetologica, 18:168, October 17,
1962. Stuart, Misc. Publ. Mus. Zool., Univ. Michigan, 122:36,
April 2, 1963. Duellman and Trueb, Univ. Kansas Publ., Mus. Nat.
Hist., 17:348, July 14, 1966.

_Diagnosis._--Brown lateral stripe wide, including loreal region and entire tympanum, extending to groin, bordered above by narrow white line; dorsum unicolor or with pair of dark lines (or rows of dashes) usually extending only to the sacral region; shanks having dark flecks, no transverse bars; interorbital bar lacking.

_Description and Variation._--Males attain a maximum snout-vent length of 26.4 mm. in Oaxaca, whereas in a sample from Acacoyagua, Chiapas, the largest male has a snout-vent length of 25.7 mm., and from La Trinidad, Guatemala, 24-6 mm. Specimens from the western part of the range (eastern Oaxaca) have slightly smaller heads and proportionately larger tympani than the more eastern populations (Table 1).

The color pattern shows little variation, except in the nature of the dorsal markings. In a few specimens from throughout the range, but especially in the eastern part of the range, the dorsum lacks markings between the dorsolateral white lines. In most specimens the dorsal pattern consists of flecks or dashes arranged in two parallel longitudinal rows, and in some specimens the marks are fused into parallel lines. Small brown flecks are present on the dorsal surfaces of the shanks; in some specimens these flecks tend to form a longitudinal stripe on the shank. An interorbital dark mark is invariably absent.

When active at night _Hyla robertmertensi_ is pale yellow above with a white dorsolateral line and pale brown lateral stripe; the dorsal markings are faint. By day the dorsum is yellowish tan with brown markings. The dorsolateral stripe is creamy white, and the lateral stripe is dark brown (Pl. 14). The venter is white, and the iris is dull bronze. In breeding males the vocal sac is yellow.

_Remarks._--Although this species superficially resembles _Hyla microcephala microcephala_, the latter is easily distinguished by the narrow brown lateral stripe, as compared with the much wider stripe in _H. robertmertensi_. No other hylids in northern Central America and southern Mexico can be confused with this species.

_Distribution._--_Hyla robertmertensi_ inhabits the Pacific slopes (to elevations of 700 meters) and lowlands from eastern Oaxaca (east of the Plains of Tehuantepec) southeastward to central El Salvador. The species also occurs in the Cintalapa Valley (Atlantic drainage) in southwestern Chiapas (Fig. 2.) The distribution seems to be limited on the northwest and southeast by arid environments. The region in which _Hyla robertmertensi_ lives is characterized by higher rainfall and more luxuriant vegetation than occur on the Plains of Tehuantepec or on the Pacific lowlands of eastern El Salvador and southern Honduras. In addition to the localities listed below, Mertens (1952:30) recorded the species from Hacienda Cuyan-Cuya, Depto. Sonsonate, El Salvador.

_Specimens examined._--490, as follows: +Mexico+: Chiapas: Acacoyagua, USNM 114754-61; *2 km. W Acacoyagua, UMMZ 87843 (28), 87844 (50), 87845 (50), 87846 (45), 87847 (27), 87848 (3); 32 km. N Arriaga, KU 57619-24, 59917-8 (skeletons); Asuncion, FMNH 100413, 100501-4, UIMNH 26989-90, USNM 134267; *La Esperanza, USNM 114737-48, 114750-3, 17 km. S Las Cruces, KU 57625-49, 59997 (eggs); 8.5 km. N Puerto Madero, UMMZ 119981 (2); *11.7 km. N Puerto Madero, UMMZ 119982; Tapachula, FMNH 100096, UIMNH 26987; *11 km. S Tapachula, KU 57605-18, 59916 (skeleton); Tonola, FMNH 27073, 100505-10, UIMNH 26988. Oaxaca: Tapanatepec, UMMZ 115245 (2), *1.6 km. E Tapanatepec, UMMZ 115244 (14); *4.3 km. E Tapanatepec, UIMNH 38368-9; *7.5 km. W Tapanatepec, UMMZ 115246 (39); 12.8 km. W Tapanatepec, KU 65007-14; 7.2 km. WNW Zanatepec, UMMZ 115243 (77); *13.6 km. WNW Zanatepec, TNHC 25213-22; 22.7 km. WNW Zanatepec, TNHC 25203-9.

+Guatemala+: Jutiapa: Jutiapa, UMMZ 106848; La Trinidad, UMMZ 107733 (23). Retalhueleu: Casa Blanca, UMMZ 107732.

+El Salvador+: La Libertad: 16 km. NW Santa Tecla, KU 44112. San Salvador: 21.9 km. N San Salvador, UMMZ 119983 (6).

+Hyla phlebodes+ Stejneger

_Hyla phlebodes_ Stejneger, Proc. U. S. Natl. Mus., 30:817, June 4,
1906 [Holotype.--USNM 2997 from "San Carlos," Costa Rica;
Burgdorf and Schild collectors]. Taylor, Proc. Biol. Soc.
Washington, 50:44, April 21, 1937; Univ. Kansas Sci. Bull.,
35:888, July 1, 1952; Univ. Kansas Sci. Bull., 39:25, November
18, 1958. Fouquette, Evolution, 14:484, December 16, 1960.
Duellman and Trueb, Univ. Kansas Publ., Mus. Nat. Hist., 17:348,
July 14, 1966.

_Hyla underwoodi_, Dunn, Occas. Papers Boston Soc. Nat. Hist., 5:413,
October 10, 1931; Occas. Papers Boston Soc. Nat. Hist. 8:72,
June 7, 1933; Amer. Mus. Novitiates, 747.2, September 17, 1934,
Gaige, Hartweg, and Stuart, Occas. Papers Mus. Zool., Univ.
Michigan, 357:5, October 26, 1937. Breder, 1946, Bull. Amer. Mus.
Nat. Hist., 86:416, August 22, 1946.

_Diagnosis._--Dark brown lateral stripe, if present, usually extending only to insertion of forearm, never posteriorly to sacral region; white line above brown stripe absent or faint; dorsal pattern weak, usually consisting of irregular dashes or interconnected lines; interorbital dark mark present; shanks having weakly defined transverse bars.

_Description and variation._--In the majority of specimens (70%) the lateral dark stripe extends from the nostril to the eye and thence above the tympanum to a point above the insertion of the arm; in 17 per cent the stripe extends to the mid-flank, whereas in 13 per cent the stripe is absent. A narrow and faint white line is present on the canthus in some specimens, but no distinct white stripe is present above the lateral dark line posterior to the eye. An interorbital bar and transverse marks on the shanks are invariably present. The dorsal markings are variable, but in most specimens (92%) consist of either an X- or )(-shaped mark in the scapular region; in the other specimens the markings are irregular short lines or absent. Approximately equal numbers of specimens have a transverse bar, chevron, or broken lines in the sacral region, whereas about eight per cent of the specimens lack markings in the sacral region.

When active at night, individuals are pale yellowish tan with faint brown dorsal markings. By day they are tan with more distinct brown markings (Pl. 14). The thighs are pale yellow; the belly is white. The iris is pale creamy tan with brown flecks. In breeding males the vocal sac is yellow.

_Tadpoles._--Tadpoles of this species have been found in an extensive grassy pond at Puerto Viejo, Costa Rica. The following description is based on KU 104099, a specimen in development stage 36 (Gosner, 1960).

Total length, 21.0 mm.; body length, 6.7 mm.; body slightly wider than deep, snout pointed; nostrils large, directed anteriorly, situated near end of snout; eyes small, situated dorsolaterally, directed laterally; spiracle sinistral, located just posteroventral to eye; anal tube dextral. Tail xiphicercal; caudal musculature moderately deep, extending far beyond posterior edge of fins; fins deepest at about midlength; dorsal fin extending onto body, slightly deeper than caudal musculature; ventral fin slightly shallower than musculature. Mouth small, terminal, lacking teeth and fringing papillae, but having finely serrate beaks. In preservative top of head olive-tan with brown flecks; dark stripe from snout through eye to posterior edge of body; belly white, flecked with brown anteriorly; tail creamy tan with grayish brown blotches. 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 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_; likewise, Gaige, Hartweg, and Stuart (1937) made the same error. Cole and Barbour (1906) and Kellog (1932) used the name _H. phlebodes_ for Mexican specimens of _H. microcephala underwoodi_. The similarity in color pattern of _H. microcephala underwoodi_ and _H. phlebodes_ easily accounts for the misapplication of names. Although both species have nearly identical dorsal color patterns, that of _H. microcephala underwoodi_ usually is bolder. Furthermore, in that species a narrow white line usually is present above the well-defined lateral dark stripe, whereas the lateral dark stripe is short and posterior to the eye is not bordered above by a white line in _H. phlebodes_.

The type locality "San Carlos, Costa Rica" given by Stejneger (1906:817) apparently refers to a region, the Llanuras de San Carlos, in the northern part of Alajuela Province, Costa Rica.

_Distribution._--_Hyla phlebodes_ inhabits humid tropical forests from southeastern Nicaragua southeastward on the Caribbean slopes and lowlands to the Canal Zone in Panama, thence eastward in the Chucunaque Basin of eastern Panama and onto the Pacific lowlands of Colombia (Fig. 3). The species also reaches the Pacific slopes in the Arenal Depression in northwestern Costa Rica and in the Panamanian isthmus, where it occurs in humid forests on the Pacific slope of El Valle and Cerro La Campana. Mostly the species is found at low elevations, but it occurs at 600 meters at Turrialba and at 700 meters at Finca San Bosco in Costa Rica.

_Specimens examined._--410, as follows: +Nicaragua+: Zelaya: Isla Grande del Maiz, MCZ 14848; Rio Mico, El Recrero, UMMZ 79720 (6).