_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.