Produced by Chris Curnow, Tom Cosmas, Joseph Cooper and the Online Distributed Proofreading Team at https://www.pgdp.net 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 México 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.