PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES Volume 50, No. 1 bution patterns of the species, the reasons for the large samples from Bohol and Negros and relatively small samples from other localities, the recent reduction of suitable habitat for some populations, and the difficulties which limit further sampling in areas other than Cuernos de Negros (Negros Island) and Mt. Maquiling and Mt. Banahao (Luzon Island). Factors Limiting Recording of Advertisement Calls The advertisement calls reported here are the result of the recent acquisition of suitable recording equipment and the availability of bases at the University of the Philippines, Los Bafios, Luzon Island and Silliman University, Negros Island. These bases made possible the numerous field trips necessary (1994-96) to secure suitable recordings of the voices of the species of Platymantis in those areas. We can continue this study in these localities when environmental conditions are suitable. The possibility of obtaining voice-recordings for the populations of P. guentheri and P. rabori on Bohol or northeastern Mindanao Islands are, however, subject to the same limitations as attempts to increase the size of the samples from those populations (see Introduction). Voice Records of Platymantis on Mt. Maquiling and Mt. Banahao Recent field work on Mt. Maquiling and Mt. Banahao has not only provided voice records reported here for P. luzonensis and P. banahao, but also records of the advertisement calls of other species of Platymantis. During some field trips, calls of three species (P. dorsalis, P. mimulus, and P. luzonensis) were heard and recorded on Mt. Maquiling and six species (P. dorsalis, P. mimulus, P. banahao, P. luzonensis, P. montanus, and P. undescribed dorsalis Group) on Mt. Banahao. Frequently all six species were calling at the same time. The advertisement calls reported here for P. luzonensis and P. banahao are very different (to the human ear), as were the calls for P. dorsalis and P. mimulus reported earlier (Brown et al. 1997). The analysis of their voice records contributed to more complete diagnoses of P. negrosensis, P. luzonensis, and P. banahao. We hope that similar voice records can be obtained for P. guentheri and P. rabori when conditions permit. The voice of P. luzonensis sounds like "kwenk-kwenk-kwenk. The notes are repeated three to five or six times in one or two seconds, or the notes may be more isolated and widely spaced. The voice of P. banahao sounds like "tuk-tuk-tuk-tuk" repeated six to 20 or more times at a rate of four to five times a second. It can be described as the sound of a machine gun. The voice of P. negrosensis is more like that of P. luzonensis but differs in dominant frequency and other characteristics (see Fig. 1A-C and Table 4). Advertisement calls such as those recorded for P. luzonensis and P. banahao are generally accepted as probably the primary means of species identification (see Blackwell and Passmore 1991). Voice Records of Other Species of Platymantis The only other voice record for a Philippine population of Platymantis is that of P. dorsalis from Cuernos de Negros, Negros Island (Kuramoto 1997). Our voice record for this population of P. dorsalis differs in the lower kilohertz, closer to 3,000 than 4,000, and time intervals separating calls (or notes). Our records have not yet been published. Records of voices for several non-philippine species were reported much earlier: that of P. papuensis from New Guinea (Zweifel 1969) and those of P. schmidti, P. solomonis, P. magnus, and P. neckeri from the Bismarcks and Solomons (Menzies 1982). These reports provide varying amounts of information in terms of monogram, their analyses, and interpretations. Certainly establishment of uniform terminology as well as reanalysis of these published monogram which would permit direct comparisons of both Philippine and non-philippine species are desirable projects, but are not the purpose of this study. Discussion The five species of the P. guentheri Group recognized at this time are based on large samples (over 100 specimens each for P. guentheri, P. rabori, and P. negrosensis) and smaller samples of 12-20 specimens for P. banahao and P. luzonensis. Differences in their advertisement calls were important clues to our diagnosing the latter two species. Other populations from isolated mountains such as Mt. Isarog on Luzon, or