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PRELIMINARY SURVEY OF THE
OF THE RIUKIU ISLANDS
ROBERT F. INGER
VOLUME 32, NUMBER 5
CHICAGO NATURAL HISTORY MUSEUM
DECEMBER 8, 1947
PRELIMINARY SURVEY OF THE
OF THE RIUKIU ISLANDS
ROBERT F. INGER
University of Chicago
VOLUME 32, NUMBER 5
CHICAGO NATURAL HISTORY MUSEUM
DECEMBER 8, 1947
THE LIBRARY OF THE
JAN 2 !940
UNIVERSITY OF ILLINOIS
PRINTED IN THE UNITED STATES OF AMERICA
BY CHICAGO NATURAL HISTORY MUSEUM PRESS
The purpose of this paper is to present a preliminary analysis
of the amphibian fauna of the Riukiu Islands, both as to its nature
and its origins. The Riukiu Archipelago, lying between Japan proper
and Formosa, forms one of the great series of island arcs that fringe
the eastern border of the Asiatic continent. Their animal life is
3 especially notable for its considerable differentiation of species that
" are found nowhere else. This fauna affords a unique opportunity
to examine the phenomena of the origin of species in a linear chain
of islands of moderate age.
Unfortunately, information concerning the Riukius is either
: scattered in travelers' accounts or written in Japanese. In the
I latter case it is almost inaccessible; in the former, it is difficult to
I locate and assemble. Therefore, in certain instances I have included
non-zoological data in greater detail than would be required by the
scope of this paper, with the hope that they will facilitate future
faunal studies. One case in point is the meteorological data; another
is the geologic history.
I wish to acknowledge my indebtedness to the authorities of the
California Academy of Sciences and the United States National
Museum for the loan of material, and to the authorities of Chicago
Natural History Museum for the use of collections and laboratory
space. I wish to thank Messrs. David Zaid and Charles A.
Wonderley of Philadelphia, Robert Burton of Evanston, Illinois, and
James A. Slater of the University of Illinois for specimens collected
by them and now in Chicago Natural History Museum. I am also
indebted to Mr. D. D wight Davis and Dr. Rainer Zangerl of Chicago
Natural History Museum and Mr. Ernest N. Poll of the University
of Chicago for assistance with photographs and to Mrs. Peggy Brown,
formerly of Chicago Natural History Museum, for the drawings
I contained herein. To Messrs. Karl P. Schmidt and Clifford H. Pope
of Chicago Natural History Museum, and to my wife, Mary Lee
Inger, I wish to extend my gratitude for much helpful advice and
The Riukiu Islands, ' situated south of Japan, have been the
subject of many investigations in fields ranging from ethnology to
298 FIELDIANA: ZOOLOGY, VOLUME 32
herpetology. The spelling of the name of the archipelago in the
papers that have been written about it has been as variable as
the points of view of the men who have written them. Most of the
early workers referred to the islands as Loo Choo, Liu Chiu, and
Liu Kiu. More recently, and especially by the Japanese, they have
been known as Ryu Kyu or Riu Kiu, written together more recently
as Ryukyu or Riukiu. I am using the last form because it is the
one that seems to be most frequently used at the present time.
Herpetological exploration of the Riukius began with the expedi-
tions of Commodore Perry and Captain Rogers to the north Pacific
in the 1850's. The type specimens of several of the species reported
on in this paper were collected by Rogers' expedition and were
described by Hallowell (1860). Between 1860 and the recent war
most of the collecting was done by biologists from Japan, which
had had possession of the islands during the period. The notable
exception was the large collection made for the California Academy
of Sciences by Victor Kuhn in 1910. During World War II medical
units of the United States Navy made an excellent collection.
Smaller series were collected by individual members of the armed
Stejneger's (1907) volume, The Herpetology of Japan, contained
the first complete account of the herpetofauna of the Riukius. Sub-
sequent to that, a good, though not comprehensive, survey was made
by Van Denburgh (1912b). In 1931 both Okada and Tago published
their monographs on the frogs and salamanders of the Japanese
Empire. It is with these two orders of amphibians that this paper
GEOGRAPHY OF THE ISLANDS
The Riukiu Islands extend in an arc convex southeastward from
south of Kyushu to a point northeast of Formosa (see Map 1).
The numerous islands and islets (about 95) which make up the chain
have been divided into groups by Tokunaga (1901) and subsequent
geographers. These groups, together with some of the principal
islands 1 of each, are as follows, with the groups (after Hanzawa,
1935) in geographic order from north to south:
Tokara (Linshoten) group: Takara, Kotakara.
Oshima group: Amami, Kikaiga, Tokuno, Okierabu.
1 Properly the names of the islands bear the suffix -shima or -jima. For the
sake of uniformity and simplicity these suffixes are not used in this report.
MAP 1. Bathymetric chart of northwest Pacific area.
300 FIELDIANA: ZOOLOGY, VOLUME 32
Okinawa group: Okinawa, le, Iheya, Kume, Ke, Tokashiki.
Miyako group: Miyako, Irabu.
Yaeyama group: Ishigaki, Iriomote, Hateruma, Yonaguni.
Map 2 shows these islands in greater detail. Hanzawa included
still another group, the Osumi, lying just south of Kyushu. For
reasons given below I do not consider that the islands of the Osumi
group are part of the Riukius.
The topography and geology of the region has been worked out
in some detail by Koto (1897) and Hanzawa. The account that
follows is based largely upon these two authors, supplemented by
the correlative work of Yabe and Aoki (1923). The islands may be
divided into two curves. The inner or western curve, comprising the
Tokara group, Kume, and several small islands lying to the north-
east of Formosa, is of volcanic origin. These islands rise out of the
trough at the eastern rim of the East China Sea. The outer curve
includes all of the other islands. These are made up of Proterozoic,
Paleozoic, and igneous rocks or Tertiary and younger rocks. In
either case the islands of the outer curve are remnants of the Riukiu
The different groups are separated from one another by sea basins
from 400 to 2,000 meters in depth. The deepest of these, the Tokara
Strait, lies between Amami and the Osumi group. The Osumi
group is but 40 km. south of Kyushu and lies on the same submarine
platform. The maximum depth of the channel between Kyushu
and the Osumi group, 200 meters, is considerably less than the
Tokara Strait. Thus, the Osumi group is more closely related to the
Japanese Islands than to the Riukius on the basis of topography.
This relationship is emphasized by the fauna, as will be shown later.
The Okinawa group is separated from the Oshima group by a basin
800 meters deep, and from the Miyako by one slightly under 1,000
meters deep. The Miyako group is divided from the Yaeyama by
a strait only 400 meters in depth. Formosa and the Yaeyama group
are separated by a basin reaching 800 meters. The trough out of
which the volcanic islands of the Tokara group rise is 800 meters
deep and is directed north-northeast and south-southwest between
the Tokaras and Amami. According to Koto, these straits, with the
exception of the last, are developed across the strike of the Paleozoic
rocks of the cordillera and are probably the result of faults.
The islands vary considerably in size, the largest, Okinawa,
being 110 km. and 20 km. in its greatest dimensions. The maximum
1 / KIKAIGA
5 m TOKUNO
IRABU " MIYAKO
MAP 2. Map showing islands of Riukiu Archipelago.
MAP 3. Probable lapd area of the Riukiu Islands at the climax of the land
submergence between the Oligocene and the Pliocene. Present areas of China,
Formosa, and Kyushu shown in black.
INGER: AMPHIBIA OF RIUKIU ISLANDS 303
length and width of Amami are 57 km. and 30 km., of Miyako 25 km.
and 15 km., of Ishigaki 35 km. and 20 km. The smallest islets are
less than one square kilometer. In relief the islands also show much
variation. Some, like Miyako, are relatively flat, with one or two
low ridges. Iriomote consists of many flat-topped ridges. Ishigaki
and Okinawa are mountainous in parts and relatively flat in others.
The greatest elevation is 690 meters, on Amami.
GEOLOGIC HISTORY OF THE ISLANDS
The Riukiu cordillera arose in the late Permian or early Mesozoic
Era. The history of the islands between the Permian and upper
Eocene is uncertain. Nevertheless, it is probable that during that
interval the cordillera was broken into a number of mountain masses
by erosion and faulting. Subsequent to the Eocene there have been
many fluctuations in sea level great enough to alter radically the
area available for habitation by land animals. In the first of these
fluctuations the islands were inundated from the upper Eocene
through the lower Oligocene (Yabe and Aoki, 1923; Hanzawa, 1935).
Only the Yaeyama group shows direct evidence of submergence
at that time. The land rose during the middle and upper Oligocene.
Next began the most extensive submergence in the northwest
Pacific since the end of the Paleozoic. Apparently only the highest
points of Amami, Tokuno, Okierabu, Okinawa, Ishigaki, and Irio-
mote were above sea level. Toward the end of this stage, in the
middle Pliocene, volcanic activity broke out. Hanzawa implied that
the Tokara group owes its origin to this volcanism. At the height
of the land emergence that followed, sea bottom that is now at a
depth of 700 meters was raised above sea level (Yabe, 1929a, b).
Thus during the late Pliocene the distance between the continent
and the center of the Riukiu curve could not have exceeded seventy
miles. This figure was determined by measuring the distance between
the 500-meter submarine contours on Map 1. At this time the Riu-
kius formed a more or less continuous peninsula projecting from the
Another period of inundation followed, during which only the
tops of Takara, Kotakara, Amami, Tokuno, Okierabu, Okinawa,
Iheya, Kume, Tokashiki, Ishigaki, and Iriomote remained above
sea level. When the land arose in the earliest Pleistocene, Takara
and Kotakara were united as a single island, as were all of the islands
in each of the other groups. Hanzawa stated that the Oshima and
Okinawa groups were connected, as were the Miyako and Yaeyama
304 FIELDIANA: ZOOLOGY, VOLUME 32
groups. However, that would imply an emergence at least as great
as that of the late Pliocene unless the channels separating the
groups were not as deep then as now. Hanzawa also stated that in
all probability the latest tectonic movements have given the channels
their present depth.
The islands were once more inundated (early-middle Pleistocene)
except for the tops of the islands listed in the preceding paragraph.
In the following land emergence the larger islands were connected
with their surrounding islets. Subsequent shifts in sea level have
not exceeded 20 meters and have resulted in the present conformation
of the islands.
, In summary then, since the Eocene there have been three
stages when the Riukius could have had direct land connections with
Asia through Formosa: during the Oligocene, the late Pliocene, and
the early Pleistocene. The entire Miyako group, Hateruma and
Yonaguni in the Yaeyama group, Kume and most of the lesser
islands in the Okinawa group, and Kikaiga in the Oshima group
seem to have been most subject to inundation during the stages of
land submergence. Maps 3 and 4 illustrate different stages in the
geologic history of the Riukiu cordillera.
CLIMATE OF THE ISLANDS
From the standpoint of the physical requirements of life, the
climate of the Riukiu Islands is almost ideal. The following tables
are adapted from Simon (1914):
MONTHLY AVERAGE TEMPERATURES AT FOUR STATIONS
Average temperatures in degrees Fahrenheit
Maxima and minima in degrees Centigrade
Kyushu Amami Okinawa Formosa
January 44.6 (7 C) 58.8 61.7 62.1
February 44.6 57.2 (14 C) 59.9 (15.5 C) 57.7 (14.3 C)
March 51.1 62.3 64.8 62.3
April 59.5 67.7 70.0 68.4
May 65.3 71.8 74.3 74.3
June 71.1 76.6 78.4 78.3
July 78.1 81.0 82.0(27.80) 81. 5 (27. 5 C)
August 79. 5(26. 4 C) 81.0(27.20) 81.9 81.1
September 75.2 78.4 79.7 78.4
October 66.2 72.9 75.0 73.4
November 56.7 66.9 69.4 67.6
December 47.8 61.0 63.7 62.6
Number of years
observed 25 10 % 10 9
Positions of sta-
tions 31 35' N. 28 23' N. 26 13' N. 25 9' N.
130 33' E. 120 30' E. 127 41' E. 121 45' E.
MAP 4. Probable maximum extension of land in late Pliocene,
of China, Formosa, and Kyushu shown in black.
306 FIELDIANA: ZOOLOGY, VOLUME 32
AVERAGE MONTHLY RAINFALL IN INCHES IN AMAMI AND OKINAWA
Positions of stations same as in table on page 30 %
January 9.0 5.9
February 6.1 4.4
March 9.2 6.0
April ;... 9.8 5.5
May 17.4 8.2
June 19.0 11.6
July 10.3 7.4
August 7.8 9.0
September 11.2 7.4
October 12.9 6.7
November 6.9 6.0
December.. 6.9 5.2
Total 126.5 (3213 mm.) 83.3 (2115 mm.)
Number of years observed 5 10
FLORA OF THE ISLANDS
Analyses of the flora of the Riukiu Islands have been made by
Warburg (1890), Wilson (1920), and Masamune (1934, 1935). The
best picture of the woody vegetation was given by Wilson: "In
general the ligneous vegetation of the Liu Kiu Archipelago consists
of a littoral fringe of plants wide-spread in warm temperate and
sub-tropical regions. On the mountains are found a comparatively
small number of Japanese and a considerable number of endemic
species. Evergreen ... is a marked feature of the vegetation. The
presence of mangrove-like trees and the endemic Cycas revoluta and
Pinus luchuensis are the three plants which give character to the
vegetation." The pine, the commonest tree from sea level to
mountain top, forms pure stands that usually have dense under-
growths of evergreen shrubs, small palms, and the cycad. The palms
accentuate the tropical relations of the flora. The coral fringes and
sea cliffs frequently bear heavy growths of the cycad. Generally
the mountains are wooded. The lower levels are under cultivation,
principally with rice, sweet potatoes, and sugar cane. The extensive
rice fields, of course, form a very important ecological niche for the
Of the 351 species of woody plants found by Wilson in the Riukius,
seventy-one are endemic. As might be expected, the flora of the
Oshima group shows more affinities to the flora of Japan than does
that of the southern islands. Interestingly enough, the Tokara
Strait seems to have the same significance for the woody vegetation
that it does for the fauna. As Wilson pointed out, most of the typical
INGER: AMPHIBIA OF RIUKIU ISLANDS 307
ligneous plants of Japan reach their southern limit in the Osumi
group lying on the north side of the strait.
The amphibian fauna of the Riukius is made up primarily of
two elements: endemic forms (derived presumably from Oriental
species) and Oriental species that reach the islands without changes
regarded as of specific grade. The following species are part of the
general Oriental fauna: Microhyla ornata, Rana limnocharis, Rhaco-
phorus schlegelii, Rhacophorus eiffingeri, Rhacophorus japonicus.
Microhyla ornata is found in China, Formosa, and southeastern Asia,
as well as the Riukius. Rana limnocharis, generally distributed in the
East Indies, southeastern Asia, and China, is one of the few Oriental
species reaching Japan. Outside of the Riukius Rhacophorus
japonicus has been reported from Formosa only. Though R. schle-
gelii and JR. eiffingeri either occur in Japan or are closely related
to Japanese forms, the distribution of the genus is southern, being
found in the East Indies, southeastern Asia, and Madagascar.
Rhacophorus reaches its northern limit (approximately 40 N. Lat.)
Approximately one-half of the amphibian species of the Riukius
are endemic. They are: Caudata: Triturus ensicaudus, Tylototriton
andersoni; Salientia: Hyla hallowelli, Rana holsti, R. subaspera,
R. ishikawae, R. narina, R. namiyei, R. okinavana. Of these, five
show affinities to contemporary Oriental species. Only four other
species of Tylototriton are known, and they are from isolated localities
in southern and western China. Hyla hallowelli is similar to chinen-
sis of Formosa (Van Denburgh, 1912b) and Rana namiyei to kuhlii
of Formosa and southern China. Stejneger (1907) cites the relation-
ships, which are open to question, of R. narina to everetti of the
Philippines and of R. okinavana to lateralis of southeastern Asia.
Triturus ensicaudus is closely related to T. pyrrhogaster of Japan.
The genus is Holarctic in distribution. The remaining three species,
Rana subaspera, R. holsti, and R. ishikawae, do not have clearly
defined geographic relations.
The extent of endemism in the fauna of the islands is reflected
in the inter-island differences of species endemic to the Riukiu chain,
and even in the more widespread, relatively undifferentiated forms.
308 FIELDIANA: ZOOLOGY, VOLUME 32
Illustrative of this is the local differentiation of Rhacophorus schlegelii.
In this species the populations on the various groups of islands differ
with respect to coloration, texture of skin, and body proportions.
Also, within an island group there may be intra-specific differences
such as exist between the Amami and Kikaiga populations of Hyla
hallowelli. These variations are discussed in some detail under each
species. However, it should be said that they may be qualitative,
as in changes of color pattern in Rhacophorus schlegelii, or quantita-
tive, as in the differences of body proportions in Hyla hallowelli. In
Rana limnocharis, as in Rhacophorus schlegelii, there are inter-island
differences in coloration and body proportions.
At this juncture it would be well to point out the suitability of
the Riukius as a "natural laboratory." The one-dimensional range
afforded by the elongate and narrow Riukiu chain has a decided
effect on its populations. In this type of range, differentiation in-
creases much more rapidly with increasing distance than in a two-
dimensional range. The change in rate of differentiation is brought
about by the reduction in the effective size of the population (Wright,
1940). The breaking up of the Riukiu cordillera would result in the
introduction of discontinuities in any existing clines. Once the
isolation produced by the division of the cordillera was established,
local selection could act more effectively and would add to the
increase in the rate of differentiation. Also, as the cordillera became
divided into smaller units, the resulting fragmented populations would
tend to show the Sewall Wright drift effect (Wright, 1940), with
non-adaptive added to the increasing adaptive differentiation.
Although I am at present unable to demonstrate the adaptive
nature of any inter-island variation that I have found, it is not
unreasonable to expect that further intensive investigation will
reveal inter-island adaptive differentiation. In Rana holsti and
R. subaspera the metacarpal spine, which is of obvious value to the
male during amplexus (see p. 328), presents a case in which differen-
tiation has been adaptive. As an example of non-adaptive differen-
tiation I offer the light mid-dorsal line found in R. limnocharis of
Ishigaki but not in limnocharis of Okinawa. Investigation of the
smaller islets that are not inhabited by man should reveal more
examples of both the intensification of local selection and the increase
of non-adaptive mutations due to the drift effect.
Bufo bufo gargarizans, with its distribution limited to Miyako,
is the only strictly Palearctic form in the Riukius. The presence
INGER: AMPHIBIA OF RIUKIU ISLANDS 309
of this toad on only one island and its similarity to gargarizans of
China indicate that it may be a recent introduction. The fact that
it is restricted to Miyako eliminates the possibility of its being the
remnant of a form widely distributed in the archipelago at one time;
for, as I have pointed out earlier, Miyako has been subject to com-
plete inundation and has been, therefore, an unsatisfactory habitat
over a long period of time.
In the Osumi group are found such Palearctic species as Hyla
arborea japonica, Rana japonica, R. nigromaculata, R. rugosa, and
R. temporaria. All of these frogs occur in Japan but none south of
the Tokara Strait. None of the species found in the Riukius (as
here restricted) has been recorded from the Osumi group, even
though two are found in Japan. The split in the frog fauna at the
Tokara Strait is parallel to the separation of Palearctic and Oriental
mammalian faunas. This faunal division, known as Watase's Line
(Okada, 1931), coincides with the geographic division mentioned
previously. Apparently the channel between the Osumis and the
Oshima group has proven a barrier to the southward migration of
The distribution of the non-endemic species and that of forms
allied to the endemic ones indicate a southern origin for the amphibian
fauna of the Riukius. As stated above, there were at least three
periods of land emergence when the islands might have been con-
nected with the continent. An examination of the bathymetric data
of Map 1 indicates that less change in sea level would be required
to link Formosa with the southern Riukius than would be needed to
link the islands with Japan. Thus Formosa is a more probable
"bridge" to the archipelago than is Japan.
An alternative mode of dispersal, by no means exclusive of the
possibility of emigration by land from Formosa, is accidental trans-
portation (waifing) on drifting masses of vegetation. If this method
of dispersal is utilized at all by amphibians, it is of greatest importance
where the water gap to be crossed is the least. On Map 4 is shown
the probable maximum extension of land during the Pliocene. At
this stage the easternmost points of the continent were not more
than seventy miles from parts of the Riukius. Under this circum-
stance waifing from the continent becomes likely. It is apparent
that waifing from Formosa, if there were no direct land connection,
would also be facilitated at this time.
310 FIELDIANA: ZOOLOGY, VOLUME 32
The importance of accidental transportation can be brought out
by a comparison of the frog faunas of Japan and the Riukius. Such
Oriental (and Riukiu) species as Rana limnocharis and Rhacophorus
schlegelii are found in Japan. The bulk of the Japanese fauna, how-
ever, is composed of Palearctic forms, for example, Rana nigro-
maculata, R. japonica, R. temporaria, Hyla arborea japonica, and
Bufo bufo japonicus. In the coastal provinces of China, Rana nigro-
maculata ranges as far south as Kwangtung, R. japonica as far as
Fukien, and Bufo bufo as far as Kwangtung and even into Formosa.
These ranges, which extend farther south than the Riukiu Archi-
pelago, indicate that these species can tolerate the climatic conditions
of the Riukius. Rana limnocharis, in China, is not found north of
Shantung, approximately the latitude of southern Honshu. Rhaco-
phorus schlegelii does not occur on the continent at all. The question
arises as to the manner in which these last two species reached
Japan. If they did not enter by way of Korea and their present
ranges place this avenue in doubt perhaps they used a land bridge
between the northern Riukius and the Osumi group; but this sugges-
tion can be discarded at once because it assumes that the Palearctic
species, which are not present in the archipelago, could not utilize
the same land bridge to expand their ranges southward. The only
explanation remaining is waifing: that Rana limnocharis and Rhaco-
phorus schlegelii managed to reach Japan by accidental transportation
on rafts of vegetation. Again, the Palearctic species of Japan must
be considered. The waifing explanation still assumes some selective
mechanism that the land bridge hypothesis could not supply. But
in this case natural selective mechanisms exist, for the ocean currents,
prevailing winds, and typhoon tracks along the coast of Asia are all
directed northward. All three physical factors are obviously related
to waifing and all are favorable to the idea- presented above. Here,
then, is a likely explanation for the significance of Watase's Line
to the distribution of amphibians and mammals.
The direction of water and wind currents lends further support
to the idea of a southern origin for the frog fauna of the Riukiu
Islands. The presence of the salamander Tylototriton in the archi-
pelago may also be the result of waifing from Formosa or southern
China. The only form whose distribution seems to defy such an
explanation is Triturus ensicaudus.
The differences in the distribution of the various forms is of signi-
ficance to the study of the order in which they reached the archi-
pelago. Generally, the endemic forms must be said to have entered
INGER: AMPHIBIA OF RIUKIU ISLANDS 311
the islands earlier than those found also on the continent. Forms
found on the periphery of continents are frequently primitive. The
Riukius present an almost ideally peripheral area with respect to
Asia. Island forms are also released from selection pressures to which
continental species are subject. Given primitive forms and reduced
selection pressure, it follows that the longer an island form is isolated
the less able it is to expand its range in the face of immigrations of
continental ones. It is also true that the longer a species exists in
an elongate and narrow range such as is provided by the Riukiu
chain the more likely are discontinuities to develop in the distribution.
In a chain of islands this will be a direct result of the fluctuations
in sea level over a long period of time (see p. 303 ff.). Therefore, from
the preceding observations, an endemic form, found only on certain
of the islands, probably has been in the archipelago longer than one
found throughout the length of the chain and on the continent as well.
To utilize this idea, I have divided the frog fauna as follows:
Limited dispersal Moderate dispersal Wide dispersal *
Hyla hallowelli Rhacophoriis eiffingeri Microhyla ornata
Rana holsti Rhacophorus japonicus Rana limnocharis
Rana ishikawae Rhacophorus schlegelii
By limited dispersal is meant distribution limited to one or two
island groups in the Riukiu chain. By moderate dispersal is meant
dispersal in more than two island groups, plus Formosa and/or
Japan. The final category, wide dispersal, indicates dispersal
throughout the archipelago plus southeastern Asia. If the hypoth-
esis that restricted range is an indication of early entry is true,
the "limited" species were in the early wave (or waves) of immigra-
tion, whereas the others entered later. I am not prepared to dis-
tinguish between the last two groups of species.
It is possible to see the effect of fluctuations in sea level on the
distribution. Rana okinavana, for example, has been recorded from
Ishigaki in the south and Okinawa in the north. For this discussion
I assume that the localities are correct and that exploration on
Miyako will fail to reveal okinavana there. The Miyako group (see
Map 2) lies between Okinawa and Ishigaki, and geologic investiga-
tion of the Miyako group has shown that these islands are completely
covered by early Pleistocene limestone formations. The islands
must have been entirely under water when those rocks were deposited,
312 FIELDIANA: ZOOLOGY, VOLUME 32
and their populations of frogs would thus have been destroyed. If
okinavana had a continuous distribution in the archipelago before
the early Pleistocene, the subsequent changes in sea level would
have interrupted that distribution by destroying at least the Miyako
population. The distribution of R. narina, found in the Yaeyama
and Okinawa groups, can be explained in the same fashion.
Hyla hallowelli presents a slightly different problem. This species
occurs only, on Amami and Kikaiga in the Oshima group. Its
similarity to H. chinensis of Formosa seems to eliminate the possi-
bility of a Japanese origin. One must assume either that the present
population is the remnant of a species formerly widely distributed
(in the Riukius) or that it originally entered the Oshima group as a
waif from eastern Asia or Formosa and has never extended its range.
Whichever of the above assumptions is true, the presence of hallo-
welli on Kikaiga cannot antedate the early Pleistocene because the
entire island is covered with a Pleistocene limestone, indicating
complete submergence. However, the date of entry into Amami
cannot be so easily determined. Much depends on which of the
assumptions is correct. It should be pointed out that the chances
for waifing directly from the continent have been reduced since the
Pliocene, when the water gap was narrowest.
The question of vagility cannot be ignored in these deductions.
Waifing depends on the size of the animal and the size of the popula-
tion from which it originates. Therefore, such forms as Rana
limnocharis, Microhyla ornata, and Rhacophorus japonicus mus
possess a great deal of vagility as compared to the large Ra
namiyei, which exists in relatively small numbers. It is probable
that the presence of -Rana limnocharis and Rhacophorus japoni
in so many islands is as much a result of waifing as of dispersal alon;
land routes. Yet one is immediately struck by the contrast mad
by the relatively restricted ranges of Rana okinavana and Hy\
hattowelli, which are of approximately the same size as Rana Urn
charis and Rhacophorus japonicus respectively. Another factor i
vagility is ecological opportunity. Obviously, to be strictly com
parable, two species must be similar ecologically; for example, one
should not be a tree frog and the other a grass frog. The pairs of
species limnocharis-okinavana and japonicus-hallowetti satisfy this
requirement. It might be argued that the differences in extent of
range are due merely to differences in vagility and not related to
length of occupancy in the islands. However, vagility is one of the
attributes of biological "success." As I said before, the longer a
INGER: AMPHIBIA OF RIUKIU ISLANDS 313
species remains in the islands the less successful it is likely to be.
Therefore, if ecologically similar animals are compared, differences
in vagility support the hypothesis that the "limited dispersal"
species were the first to enter the islands.
The problem of the order of entry into the Riukius may be
attacked from a slightly different angle. Let us suppose that Species
A is found only on Amami and Okinawa, with no closely related
form or forms either in other parts of the archipelago or on the
continent. Species B is found throughout the islands and on the con-
tinent. Assuming that the emigrations of both are relatively limited
by water, the last time the Amami and Okinawa populations of
both A and B were able to interbreed freely (i.e. Amami Ax Oki-
nawa A; Amami Bx Okinawa B) was at the time of the last connec-
tion of the two islands. Suppose that a comparison of the two
populations of each species reveals that Species B shows more inter-
island variation than A. We may then conclude that B has a more
rapid rate of evolution than A. The fact that A has speciated (i.e.
diverged farther from its continental allies) despite its slower rate
of evolution, whereas B has not, indicates that A has been in the
islands longer than B.
Again the question of vagility arises. Granting the relatively
great vagility of small forms occurring in large numbers, once such
a species has become established on any of the larger islands the
effect of accidental introductions on the population is slight. It is
inconceivable that the amount of waifing per year into any one of
the larger islands should exceed one thousandth of one per cent of the
population on that island in the case of a frog like Rana limnocharis.
The number of individuals of limnocharis on the larger islands must
be very large, judging by its abundance in other parts of its range.
Consequently, the effect of the introduced individuals would be
negligible. The fact that the effect is not enough to offset the
divergence of two separate populations is apparent from the differ-
ences observed between the Ishigaki and Okinawa series of limno-
charis that I have examined (see p. 336). In those species occurring
in such small numbers that introductions would have a definite effect,
the opportunities for waifing are reduced because of the small size
of the population. Therefore, as concerns this second method of
determining the order of entry of the fauna into the islands (i.e.
using the criteria of speciation and inter-island variations), differen-
tial probabilities for chance introduction are not important.
I have used body proportions extensively as a means of deter-
mining inter-island distinctions within species. Primarily, three
314 FIELDIANA: ZOOLOGY, VOLUME 32
ratios were used: body length/leg length; tibia length/leg length; and
head width/body length. In addition, the body lengths were used
directly for comparison. The body length dimension was measured
from the tip of the snout to the posterior tip of the body. Leg
length was determined by the distance from the vent to the tip of
the longest toe. The width of the head was measured at the level
of the tympanum. Tibia length is the length in the flesh. All
measurements were made to the nearest half millimeter. Where
the body lengths were used for comparison, they were converted
to logarithms to the base 10, to bring their distribution closer to
normality. Student's t test was applied in all cases to the differences
between means. Because only preserved material was available,
I have avoided color as a criterion of intraspecific variation. How-
ever, I have used the pattern of pigmentation, and, in one case, the
intensity of pigmentation. The following common abbreviations
have been applied to designate the collections of the various museums:
C.A.S., California Academy of Sciences; C.N.H.M., Chicago Natural
History Museum; U.S.N.M., United States National Museum.
KEY TO RIUKIU SALAMANDERS
A series of conspicuous knob-like tubercles along each side . . Tylototriton andersoni
Sides without knob-like tubercles; venter light yellow with dark markings.
Tylototriton andersoni Boulenger
Tylototriton andersoni Boulenger, Ann. Mag. Nat. Hist., (6), 10, p. 304,
1892 type locality Okinawa; Fritze, Zool. Jahrb. Syst., 7, p. 865, 1894;
Boettger, Offenbach. Ver. Naturk., Ber. 33-36, p. 107, 1895; Barbour,
Proc. New Eng. Zool. Club, 4, p. 54, 1909; Wolterstorff, Blatt. Aquar.
Terr. Stuttgart, 6, p. 95, 1929; Tago, Imori to Sansyouo (Salamanders of
Japan), p. 26, pi. i, 1931; Okada, Copeia, 1934, p. 17, 1934.
Distribution. This salamander has been recorded from Okinawa
and Amami (Tago, 1931).
Specimens examined. Okinawa, 41 (C.A.S.).
Diagnosis. The series of conspicuous knob-like lateral glands
characteristic of this genus serve to distinguish andersoni from the
only other Riukiu salamander. The present species is uniformly
dark brown with the exception of the lower margin of the tail and
the under sides of the feet, which are pale orange or yellow.
Secondary sexual characters. I have not observed any obvious
morphological distinctions between the sexes. The lengths of both
INGER: AMPHIBIA OF RIUKIU ISLANDS 315
body and tail are greater in the females, but these differences are
apparent only in large series. Although the absolute lengths differ,
the ratio of tail to body length does not. The data are presented in
the following table.
COMPARISON OF MALE AND FEMALE Tylototriton andersoni
Male Female Diff. t n P
Log body length. 1.84500. 0127 1.89760.0063 0.0526 4.200 38 0.001
Body length in
mm 69.99 79.00
Log tail length... 1.79880.0139 1.83750.0107 0.0387 2.113 35 0.05
Tail length in mm. 62 .92 68 . 80
length 0.899 0.013 0.886 0.016 0.013 0.548 35 0.60
There are no other discernible sexual differentiations in body pro-
Breeding habits. There is no mention of the breeding habits of
this form in the literature. The entire series I examined was collected
between May 5 and May 11. Three females, the smallest of which
had a body length of 83.8 mm., contained enlarged eggs. That
such a small proportion of specimens contained eggs seems to
indicate that the series was taken at the end of the breeding season,
as is also likely in view of the late date.
Remarks. In the series I have examined there is an interesting
variability in the number and development of the toes. The majority
of individuals have five well-developed toes, but there are many in
which the fifth toe appears only as a small tubercle; in others there
is no external sign of the fifth toe. Still another variation appears
in six specimens with fused toes. X-ray analysis reveals that not
only is the number of digits variable, but also that the number of
tarsal bones is not constant. Considering the number of feet rather
than individuals, seven are syndactylous, three have no fifth meta-
tarsal or corresponding phalanges, twenty-five have a fifth metatarsal
but no accompanying phalanges, and forty-five have a fifth meta-
tarsal with one phalange. Nineteen of the feet show no external
sign of the fifth toe. Thus, some of these apparently four-toed
specimens have a fifth metatarsal that has no effect on the adjacent
skin. Where syndactyly appears, the entire structure of the foot
shows disorganization the tarsals are reduced in number and/or
the metatarsals are reduced.
Whether the population is in process of shifting from the five-
toed to the four-toed condition or is in a state of equilibrium is un-
316 FIELDIANA: ZOOLOGY, VOLUME 32
known at present. As the entire series was collected in 1910, it is
possible that a new collection might provide the solution, even in
the relatively short interval of thirty-five generations. Syndactyly
may develop during regeneration of the limb. In one instance the
leg bearing a syndactylous foot is abnormally short. Regardless
of the circumstances surrounding syndactyly, whether it is associated
with regeneration only or with embryogenesis, the condition must
have a genetic basis. The occurrence of such an obviously detri-
mental character is typical of insular forms. The questions asked
concerning the number of digits may be asked regarding syndactyly.
In this case also, new collections may provide the answers.
Triturus ensicaudus Hallowell
Triton subcristatus Hallowell, Proc. Acad. Nat. Sci. Phila., p. 494, 1860 (in
part; not of Schlegel).
Triton ensicauda Hallowell, Proc. Acad. Nat. Sci. Phila., p. 494, 1860 type
Molge pyrrhogaster ensicauda Boulenger, Proc. Zool. Soc. Lond., p. 150, 1887;
Boettger, Offenbach. Ver. Naturk., Ber. 33-36, p. 106, 1895.
Molge pyrrhogastra ensicaudus Okada, Cat. Vert. Japan, p. 65, 1891; Fritze,
Zool. Jahrb. Syst., 7, p. 865, 1894.
Molge pyrrhogastra ensicauda Brown, Proc. Acad. Nat. Sci. Phila., p. 186, 1902.
Diemictylus ensicauda Stejneger, Bull. U. S. Nat. Mus., 58, p. 21, figs. 9-15,
1907; Tago, Imori to Sansyouo (Salamanders of Japan), p. 39, pi. i, 1931.
Triturus ensicaudus Okada, Copeia, 1934, p. 17, 1934; Gressitt, Proc. Biol.
Soc. Wash., 51, p. 159, 1938.
Distribution. This salamander occurs in the Oshima and Oki-
nawa groups. It has been specifically recorded from Amami and
Kakeroma in the Oshima group and from Okinawa; it is here recorded
from Tokashiki in the Okinawa group. T. ensicaudus is found in
rice fields, drainage ditches, and pools of standing water.
Specimens examined. Okinawa, 153 (25 C.A.S.; 118 U.S.N.M.;
10 C.N.H.M.); Amami, 51 (C.A.S.); Tokashiki, 6 (C.N.H.M.).
Diagnosis. The absence of large tubercles on the back and sides
and the light coloring on the ventral surface immediately distinguish
this species from Tylototriton. In many of the individuals of ensi-
caudus the sides bear light blotches or stripes.
Secondary sexual characters. As in many other salamanders, the
males may be distinguished from the females by the globular swelling
of the cloaca. In females there is no enlargement at that region,
the opening of the cloaca being at the free edge of a narrow dermal
extension. The females are larger than the males in both body and
INGER: AMPHIBIA OF RIUKIU ISLANDS 317
tail length. These differences are set forth in the following table,
and a difference in the body proportions is also revealed in the
SEXUAL DIFFERENTIATION IN LENGTH IN Triturus ensicaudus
Amami Male Female Diff. t n P
Log body length. 1.76770.0050 1.79960.0052 0.0319 4.290 48 0.001
Body length in
mm 58.56 63.04
Log tail length... 1 .70180.0070 1 .85570.0080 0.1539 13.99 48 0.001
Tail length in mm. 50 .32 71 . 73
Log body length. 1.7445^0.0027 1.77940.0039 0.0349 7.581141 0.001
Body length in
mm 55.52 60.16
Log tail length. . 1.67520. 0037 1 .82510.0052 0.149924.53 141 0.001
Tail length in mm. 47.33 66.85
The tail in females is considerably greater than the body length,
whereas in males the tail is less than the body length. Tago (1931)
states that in males the tail is 1.5 times the length of the trunk and
in females 1.3 times the trunk, with which my observations obviously
do not agree. Based on a rough estimate from the table, the ratio
of tail to body is 0.85 in males and 1.14 in females. Tago did not
define his measurements beyond "trunk" and "tail." Nevertheless
one obtains from his data the erroneous idea that the tail of the
male is relatively longer than that of the female.
Breeding habits. According to Tago, spawning takes place from
March to June, with the peak period in April. The eggs are laid
singly or in small groups and attached to submerged vegetation or
Inter-island variation. The ground color of the lateral and dorsal
surfaces is dark brown or black. As stated in the diagnosis, frequently
light markings of two types occur on these regions. The first type
is a dorso-lateral line that may vary in length between the eye and
the groin. The second type is a spotting most common between the
dorso-lateral lines. The spotting, too, may vary from a few scattered
spots to large confluent blotches occupying the entire mid-dorsal
region. Some individuals display both types. A comparison of the
Okinawa and Amami series indicates that the spotting is character-
istic of the former and the dorso-lateral stripes characteristic of the
latter. I have used a contingency table to test the significance of
the observed differences between two series. For the spotting:
318 FIELDIANA: ZOOLOGY, VOLUME 32
Amami Okinawa Total
Spots present 1 75 76
Spots absent 50 74 124
Total 51 149 200
Amami Okinawa Total
Spots present 19.38 56.62 76.00
Spots absent 31.62 92.38 . 124.00
Total.. . 51.00 149.00 200.00
Chi-square computed from the above equals 37.74. With one
degree of freedom, P is less than 0.001. Similarly, for the dorso-
Amami Okinawa Total
Lines present 24 30 54
Lines absent 27 119 146
Total 51 149 200
Amami Okinawa Total
Lines present 13.77 40.23 54.00
Lines absent .. .37. 23 108. 77 146.00
Total 51.00 149.00 200.00
Chi-square computed from these data is equal to 13.97. At this
value, with one degree of freedom, P is less than 0.001. Conse-
quently, the differences between the two series observed for both
types of markings are statistically significant. The dark spots on
the venter also show considerable variation; however, the nature
of these spots is such as to make any comparison between the series
Differences between the two series are also found in the body
proportions. Though in the table on page 317 the series appear to
be different in length, the observed differences are not statistically
significant. However, with regard to the two ratios shown in the
following table, the series are significantly different. The head
depth measurement was made immediately behind the orbit and
varies somewhat with the size of the paratoid gland.
INGER: AMPHIBIA OF RIUKIU ISLANDS 319
DIFFERENCES IN BODY PROPORTIONS OF Two SERIES OF Triturus ensicaudus
Amami Okinawa Diff. t n P
length 0.2040.008 0.1960.001 0.008 5.263 187 0.001
length 0.0940.001 0.0900.0004 0.004 5.000 187 0.001
The differences between the Amami and Okinawa populations are
such as to warrant their nomenclatural distinction as subspecies.
Triturus ensicaudus ensicaudus Hallowell
Type from Amami.
Diagnosis. As indicated in the foregoing, the typical form is
usually uniformly dark on the dorsal surfaces with the exception
of a dorso-lateral light line found in almost half of the individuals.
Triturus ensicaudus popei 1 subsp. nov.
Type from Kin, Okinawa. No. 45039 Chicago Natural History
Museum. Adult female. Collected by Messrs. J. A. Slater and
J. W. Faulk on October 3, 1945.
Diagnosis. This form differs from the typical in that almost
half of the individuals have light cream or yellow spots in the mid-
dorsal region. In some specimens these spots occupy most of the
Description of type. Body moderately slender; fingers and toes
touching when limbs adpressed; maximum width of head greater
than width of body at shoulders; paratoid glands distinct, extending
from upper posterior border of orbit to posterior of neck; nostrils
small, situated at tip of snout; a median ridge from base of tail,
bifurcating on occipital region but not reaching, paratoids; tail long,
compressed laterally; skin rugose except on anterior portion of head.
Ground color of dorsal surfaces very dark brown; scattered yellow
blotches on mid-dorsal region from occiput to anterior two-thirds
of tail; sides with irregular pale yellow green spots from orbit to
post-femoral region; chin and throat yellow with six very small dark
dots; rest of venter and under surfaces of limbs yellow with scattered
dark spots of varying size; lower edge of tail yellow.
Measurements of type. Snout to vent 57.5 mm., tail 53.0 mm.,
head width behind orbit 11.3 mm., head depth behind orbit 4.6 mm.,
snout to posterior of paratoids 15.5 mm.
1 Named for Clifford H. Pope, Curator of Reptiles, Chicago Natural History
320 FIELDIANA: ZOOLOGY, VOLUME 32
Paratypes C.N.H.M. 45037-38, 45040-46 (Kin, Okinawa);
C.A.S. 22309-33 (Nago, Okinawa); U.S.N.M. 7451 (2), 36555,
122118-33, 123032-130 (Okinawa).
Provisionally, I am including in this subspecies the six specimens,
C.N.H.M. 43696-701, from Tokashiki, in the Okinawa group. These
differ from the others examined in having an extremely granular
skin. An adequate series from Tokashiki might show this character
to be typical of that population.
KEY TO RIUKIU FROGS
1. Epicoracoids overlapping at mid-line 1 2
Epicoracoids not overlapping at mid-line 3
2. Back warty; paratoid glands present Bufo bufo gargarizans
Back smooth; no paratoids; green in life Hyla hallowelli
3. Center of back occupied by dark pvv mark Microhyla ornata
No such mark on back 4
4. Large disks on digits 11
Tips of fingers and toes pointed or slightly swollen 5
5. A "thumb" or "fifth digit" on hand 6
No "thumb" 7
6. Large dorsal tubercles surmounted with small white granules; Oshima group.
No white granules on larger tubercles; Okinawa group Rana holsti
7. Front of lower jaw with two large projections Rana namiyei
Lower jaw without a pair of tooth-like processes.' 8
8. White or light line below eye parallel to mouth 9
No white line above mouth 10
9. Tympanum surrounded by bead-like white tubercles; usually three complete
crossbars on tibia Rana narina
Tympanum not surrounded by tubercles; usually one complete crossbar on
tibia Rana okinavana
10. Large dorsal tubercles with radiating striations Rana ishikawae
Dorsal tubercles without radiating striations Rana limnocharis
11. Dorsum with dark markings 12
Dorsum uniform green (blue or gray when preserved) . . Rhacophorus schlegelii
12. Leg short; tibio-tarsal articulation does not reach tip of snout when limb is
carried forward Rhacophorus eiffingeri
Leg long; tibio-tarsal articulation reaches beyond tip of snout.
1 For identification of live material it is unnecessary to examine the epicora-
coids if it is remembered that Bufo b. gargarizans has a dry warty skin and con-
spicuous paratoid glands, and that Hyla hallowelli is one of the two green species.
The diagnoses will assist in distinguishing hallowelli from the other green frog,
INGER: AMPHIBIA OF RIUKIU ISLANDS 321
Bufo bufo gargarizans Cantor
Bufo gargarizans Cantor, Ann. Mag. Nat. Hist., (1), 9, p. 483, 1842 type
Bufo bufo japonicus Stejneger, Bull. U. S. Nat. Mus., 58, p. 69, 1907.
Bufo bufo miyakonis Okada, Tailless Batr. Jap. Emp., p. 47, pi. iii, figs. 1-2,
pi. xviii, fig. 3, pi. xxii, fig. 5, text figs. 19-20, 1931; Gressitt, Proc. Biol
Soc. Wash., 51, p. 161, 1938.
Bufo bufo gargarizans Boring, Pek. Nat. Hist. Bull., 13, pt. 2, p. 91, 1939.
Distribution. The common large toad of central China is found
only on Miyako in the Riukius. The presence of the toad on this
particular island and the absence of the genus in the other islands
indicate that this toad may have been introduced (see p. 309).
Taxonomic notes. Okada (1931) described the Miyako popula-
tion of this toad as a new subspecies, B. b. miyakonis. It is difficult
to determine just how he differentiated it from gargarizans. He
gave no diagnostic characters and his description of the type fits
Chinese specimens of gargarizans perfectly. The obvious similarity
to the latter plus the peculiar distribution seem to place Okada's
name in the synonymy of gargarizans. No Miyako specimens have
been available for examination, and this is obviously essential for
decision regarding their relations to the mainland populations.
Breeding habits. Okada reported seeing tadpoles with hind limbs
in late March on Miyako. Probably breeding takes place in February
Hyla hallowelli Van Denburgh
Hyla hallowelli Van Denburgh, Adv. Diag. Kept. Amph., p. 4, 1912 type
locality Kikaiga; Van Denburgh, Proc. Calif. Acad. Sci., (4), 3, p. 190,
1912; Okada, Tailless Batr. Jap. Emp., p. 67, pi. vi, fig. 1, pi. xxiii, fig. 5,
text fig. 32, 1931.
Distribution. This species is known with certainty only from
Amami and Kikaiga. Okada (1926) reported it from Yoron; how-
ever, he later (1931) stated that it did not occur on any island of
the Oshima group save Amami and Kikaiga.
Specimens examined. Kikaiga, type locality, 24 (C.A.S.) ; Amami,
Diagnosis. The toe pads and green color (gray or slate blue in
alcohol) distinguish Hylajiallowelli from all other Riukiu Salientia
except immature individuals of Rhacophorus schlegelii. Both species
are green in life, have digital pads, and approximately the same
amount of webbing. There is a difference in the position of the
322 FIELDIANA: ZOOLOGY, VOLUME 32
nostrils, however. In Hyla hallowelli they are situated at the tip
of the snout, whereas in Rhacophorus schlegelii they are set back
about one-third the distance from the end of the snout to the eye.
Furthermore, the snout of the present species is truncate. Adults
of Hyla hallowelli are small, averaging around 30.5 mm., which is
tonly slightly larger than Microhyla ornata but much smaller than
Rhacophorus schlegelii (see p. 343).
Secondary sexual characters. The males have a median external
vocal sac and a nuptial pad on the mesial surface of the first digit.
As all of the males examined possess these structures, they are pre-
sumably mature. The mean length will be given below. Only one
female, C.A.S. 23819, was in the series examined. Consequently no
comparison of the sexes was possible. Suffice it to say that the female
lay well within the ranges of size and body proportions of the males.
Breeding habits.- The specimens were collected between April 26
and May 1. As only one female is included in the series of forty-
five individuals, one might assume that the dates of collection fall
just prior to the general emergence of that sex. The female con-
tained eggs that were ready to be shed. The inference, then, is that
breeding takes place from the end of April through the first part
Inter-island variation. The two groups of specimens display
differences in coloration, size, and body proportions. On the basis
of these minor distinctions, this species is here broken into two
Hyla hallowelli hallowelli Van Denburgh
Diagnosis. In all of the specimens of the typical form examined,
the dark dots on the posterior of the thigh are discrete. The dorsal
surface of the body is consistently light gray.
Hyla hallowelli schmidti 1 subsp. nov.
Type from Naze, Amami. No. 23852 California Academy of
Sciences. Adult male. Collected by Mr. Victor Kuhne, April 26
to May 1, 1910.
Diagnosis. Most specimens of this form are darker than those
of the typical subspecies. In many individuals of schmidti the
brown dots on the thigh unite to form reticulations. The comparison
1 The new form is named for Karl P. Schmidt, Chief Curator, Department
of Zoology, Chicago Natural History Museum.
INGER: AMPHIBIA OF RIUKIU ISLANDS 323
given in the following table demonstrates further differences between
schmidti and hallowelli.
BODY PROPORTIONS OF Two FORMS OF Hyla hallowelli
hallowelli schmidti Diff. t n P
Logbody length. 1.48260. 0034 1.50310.0041 0.0205 3.727 42 0.001
Body length in
mm 30.39 31.86
Body length /leg
length 0.611 0.004 0.619 0.003 0.008 1.638 43 0.12
Tibia/leg length. 0.313 0.002 0.301 0.002 0.012 5.591 42 0.001
length 0.336 0.003 0.315 0.002 0.021 4.905 43 0.001
Only in the body length/leg length ratio is there no statistically
Description of type. Body moderately slender, tapering to in-
guinal region; head same width as anterior portion of trunk; snout
blunt; nostrils at tip of snout; canthus rostralis distinct; lores deeply
concave; interorbital distance greater than width of upper eyelid;
diameter of orbit equal to its distance from snout tip; tympanum
distinct, one-fourth diameter of orbit; legs long, heels overlapping,
tibio-tarsal joint reaching between eye and nostril; disks of digits
well developed, those of fingers larger; disk of third finger larger
than tympanum; fingers one-fourth webbed; toes almost completely
Skin finely shagreened; venter coarsely granulated; color of
dorsal surfaces dark slate; ventral surfaces except for chin immacu-
late deep cream, chin faintly mottled with brown; posterior aspect
of thighs with brown dots, many of which fuse to form reticulations.
Measurements of type. Snout to vent 30.5 mm., leg length
49.5 mm/, tibia length 14.5 mm., head width 10 mm.
Affinities. In the absence of large black spots on the thighs
and the presence of the dorsal color on the digits, hallowelli resembles
H. arbor ea japonica. As pointed out by Van Denburgh (1912b), the
homogeneous dorsal coloration and the position of the vomerine
teeth ally hallowelli to H. chinensis. H. hallowelli shows more
similarity in size to chinensis than to japonica. Japanese specimens
of japonica are frequently over 40 mm. in body length (Okada, 1931) ;
of 35 male chinensis measured by Pope (1931), the largest was
32.5 mm.; the largest of the 45 individuals of hallowelli examined
by me was 34 mm. When the general body form and the shape of
the head are considered, the relationship of hallowelli to chinensis
324 FIELDIANA: ZOOLOGY, VOLUME 32
Microhyla ornata Dumeril and Bibron
Engystoma ornatum Dumeril and Bibron, Erp. Gen., 8, p. 175, 1841 type
locality Malabar coast.
Microhyla ornata Boulenger, Cat. Batr. Sal. Brit. Mus., ed. 2, p. 165, 1882;
Gressitt, Proc. Biol. Soc. Wash., 51, p. 164, 1938.
Microhyla fissipes Boulenger, Ann. Mag. Nat. Hist., (5), 13, p. 397, 1884;
Boulenger, Proc. Zool. Soc. Lond., p. 150, 1887; Okada, Cat. Vert. Jap.,
p. 66, 1891; Fritze, Zool. Jahrb. Syst., 7, p. 865, 1894; Boettger, Offenbach.
Ver. Naturk., Ber. 33-36, p. 106, 1895; Okada, Tailless Batr. Jap. Emp.,
p. 71, pi. vii, fig. 3, pi. xviii, fig. 7, pi. xxiii, fig. 6, text figs. 33-34.
Microhyla okinavensis Stejneger, Proc. Biol. Soc. Wash., 14, p. 189, 1901;
Stejneger, Bull. U. S. Nat. Mus., 58, p. 89, figs. 71-75, 1907; Barbour,
Proc. New Eng. Zool. Club, 4, p. 58, 1909; Parker, Ann. Mag. Nat. Hist.,
(10), 2, p. 492, 1928; Parker, Mono. Microhylidae, p. 138, 1934.
Microhyla undulata Brown, Proc. Acad. Nat. Sci. Phila., p. 186, 1902.
Distribution. This species has been found in all groups of the
Riukius south of the Tokara Strait with the exception of the Tokaras.
In addition, its range includes southern China, Formosa, Hainan,
and all of southeastern Asia.
Specimens examined. Okinawa, 13 metamorphosed individuals,
9 larvae (C.N.H.M.); Ishigaki, 17 adults (U.S.N.M.).
Taxonomic notes. Parker (1928, 1934) recognized okinavensis
as the form generally distributed through the archipelago. His
diagnostic characters were the lateral fringes and a trace of a dorsal
cleft on the toes, though the appearance of the cleft was erratic.
The first character does not serve to distinguish Riukiu specimens
from ornata of the continent. I have observed lateral fringes on the
toes of several specimens from Szechwan, China (C.N.H.M. 18875-6).
Parker also indicated that the tibio-tarsal articulation reached
slightly farther anterior in okinavensis. Though there 'was some
difference in this point between the Riukiu and the Chinese speci-
mens I have examined, the range of this character in each series
overlaps that in the other to a large extent. The tadpoles from
Okinawa are indistinguishable from some from Szechwan which
Dr. C. C. Liu was kind enough to make available. It is possible
that further investigation will reveal differences of a subspecific
nature; however, at the present time there is no basis for maintaining
ornata and okinavensis as distinct species.
Diagnosis. This species is the smallest frog in the Riukius,
adults rarely exceeding 31 mm. It can be distinguished from all
other frogs in the islands by the brown mark on the back (see key,
p. 320). This mark, extending from the tip of the snout to the in-
INGER: AMPHIBIA OF RIUKIU ISLANDS 325
sertion of the legs, varies in form somewhat. M. ornata also differs
from the rest of the frogs, with the exception of Bufo b. gargarizans,
by the absence of teeth in the upper jaw. The smooth skin of ornata
as well as the peculiar mark on the back separates it from the toad.
In the field, ornata may be identified by the extremely long leaps
it makes (approximately six feet).
Secondary sexual characters. The males have a median internal
subgular vocal sac, the openings of which lie in the anterior floor
of the mouth. There are no nuptial pads. The gular region of the
males is densely mottled with very dark brown or black. In the
females this region is less densely mottled, with the same drab or
light brown found on the dorsum.
The females are slightly larger than the males. In the Ishigaki
series the three males average 25.33 mm., the fourteen females 28.32.
The value of P for this difference is 0.005 (=3.458), a significant
figure even though very few males were used in the computations.
The mean length of nine Okinawa males was 23.39 mm. Two mature
females from Okinawa measured 22.0 and 22.5 mm. The smaller
of these contained eggs. Okada (1931) reported that the male was
larger than the female. Yet he presented data in which the males
averaged 24.5 and the females 28.4 mm.
In the Okinawa series there appeared to be a difference between
males and females with respect to the body length/leg length ratio.
However, the same did not hold for the Ishigaki sample. The
following is a comparison of the ratio in males and females of the
Mean No. Mean No. Diff. t P
Okinawa 0.5550.012 9 0.4890.000 2 0.066 2.427 0.04
Ishigaki 0.5830.011 3 0.5890.005 14 0.066 0.583 0.56
Inasmuch as there were only two females from Okinawa and the
value of the ratio for those was so much smaller than in the Ishigaki
females, I believe that the difference observed in the former series
is due to chance despite the apparent significance of P.
Breeding habits. There has been no specific mention in the
literature of the breeding season of the Riukiu population. The
Okinawa tadpoles, some of which had hind-limb buds, were collected
on May 5, giving an indication of the breeding period. Pope (1931)
stated that ornata tadpoles in Fukien could be found in any small
rain pool. Doubtless the Riukiu population breeds in similar
326 FIELDIANA: ZOOLOGY, VOLUME 32
temporary water sites as well as in rice paddies. The larval period
is very short, lasting approximately from 20 to 30 days (Pope, 1931).
Inter-island variation. As indicated in the section dealing with
sexual differences, the males of ttie Okinawa series are apparently
smaller than those of the Ishigaki. P of the observed difference
(1.94 mm.) is 0.03 (t= 2.808, w=10). The Okinawa female (22 mm.),
which contains eggs and is therefore adult, is smaller than the smallest
Ishigaki female (25 mm.).
There are small but statistically significant differences in the body
proportions of the two Riukiu series as follows:
Okinawa Ishigaki Diff. t P(n=26)
Body length/leg length. . 0.5430. 013 0.5880.004 0.045 3.750 0.001
Tibia/leg length 0.3020.003 0.2880.002 0.014 4.117 0.001
In preparation of the above table, males and females were combined.
Elimination of the two Okinawa females does not alter appreciably
the value of P.
Rana holsti Boulenger
Rana holsti Boulenger, Ann. Mag. Nat. Hist., (6), 10, p. 302, 1892 type
locality Okinawa; Fritze, Zool. Jahrb. Syst., 7, p. 865, 1894; Stejneger,
Bull. U. S. Nat. Mus., 58, p. 105, fig. 84, 1907.
Babina holsti Van Denburgh, Adv. Diag. New Kept. Amph., p. 1, 1912;
Van Denburgh, Proc. Calif. Acad. Sci., (4), 3, p. 197, 1912; Okada, Tailless
Batr. Jap. Emp., p. 173, pi. xiii, fig. 1, pi. xxi, figs. 2-3, pi. xxviii, fig. 1,
text figs. 78-80, 1931.
Distribution. This species is apparently restricted to the moun-
tainous region of Okinawa.
Specimens examined. Okinawa, 12 males (C.A.S.).
Taxonomic notes. This species and the allied R. subaspera are
remarkable in that the first metacarpal is elongated into a curved
spine approximately 15 mm. long in mature individuals. The
spine is encased in a fleshy sheath ventral and medial to the first
finger. On the basis of this character, Van Denburgh (1912a)
established the genus Babina. He believed the spine to be a defensive
mechanism. Inasmuch as the structure is obviously a sexual
character (Boulenger, 1918), and considering the diversity of sexual
adaptations in the genus Rana, it is much more reasonable to assign
these two species to Rana, which they resemble in all other respects.
Diagnosis. The metacarpal spur or "fifth digit" serves to dis-
tinguish this frog from all others in the islands save subaspera. From
INGER: AMPHIBIA OF RIUKIU ISLANDS 327
the latter it may be separated by the absence of large tubercles on
the anterior portion of the back, There are numerous small white
granules on the dorsum, but they are not concentrated on the large
tubercles as in subaspera. The average body length of the series
examined was 107.45 mm. (minimum 99.5, maximum 118.5). Judg-
ing by the presence of nuptial pads and vocal sacs, all were mature.
Secondary sexual characters. The males have a median internal
subgular vocal sac. Spiny nuptial asperities are present on the spur
sheath and first finger of the males. Because of the great similarity
between holsti and subaspera, it is a safe assumption that the sexual
differences of the latter (see p. 328) apply also to holsti.
Inter-island variation. The relationship of holsti and subaspera
is sufficiently close to be discussed in this section. In addition to
the distinctions already mentioned in the diagnoses there are other
differences, not so obvious, between these species. The body propor-
tions are compared in the following table. To eliminate any dis-
crepancies of a sexual nature only the males are considered.
COMPARISON OF MALES OF Rana holsti AND R. subaspera
Mean holsti subaspera Diff. t P
Log body length .... 2 . 03120 . 0057 2 . 06630 .0041 . 0351 5 . 089 . 001
Body length in mm. . 107.46 116.50
length 0.602 0.004 0.601 0.004 0.001 0.013 0.97
Tibia/leg length 0.303 0.002 0.297 0.001 0.006 2.935 0.008
Head width /body
length 0.397 0.003 0.408 0.003 0.011 2.697 0.012
Only the body length /leg length ratio fails to show a significant
Okada (1931) indicated that the two species could be separated
by a reduced web between the first and second fingers of holsti;
I have found no web in the hand of either form.
Rana subaspera Barbour
Rana subaspera Barbour, Proc. Biol. Soc. Wash., 21, p. 189, 1908 type
locality Amami; Barbour, Proc. New Eng. Zool. Club, p. 58, 1909.
Babina subaspera Van Denburgh, Adv. Diag. New Kept. Amph., p. 1, 1912;
Van Denburgh, Proc. Calif. Acad. Sci., (4), 3, p. 199, 1912; Okada, Tail-
less Batr. Jap. Emp., p. 171, pi. xiv, fig. 1, pi. xv, fig. 1, pi. xix, fig. 7,
text figs. 76-77, 1931.
Distribution. Barbour (1908) and Van Denburgh (1912b) re-
corded this species from Amami only. Okada (1926, 1931) added
Tokuno to the known range.
328 FIELDIANA: ZOOLOGY, VOLUME 32
Specimens examined. Amami, 16 males, 5 females (C.A.S.).
Diagnosis. This is the only frog in the Oshima group having a
spur such as is found in R. holsti. R. subaspera is distinguished from
holsti by clusters of white granules on the large tubercles of the
back. The anterior portion of the back of the present species is
Secondary sexual characters. Adult males are readily identified
by the light-colored spinules appearing on the dorsal surfaces of the
fingers. These asperities are concentrated into nuptial pads on the
spur sheath and first digit. Another diagnostic feature of the male
is the granular nature of the venter; in the female this surface is
smooth. In holsti the ventral granules of the male are restricted to
the pectoral region. The males of the present species, like holsti,
have median internal subgular vocal sacs.
Van Denburgh (1912b, 1920) maintained on the basis of the field
notes of his collector that the spine had a defensive function: a
specimen of holsti stabbed the thumb of the collector with the spurs;
also several specimens of R. namiyei were badly slashed after being
carried in a bag containing holsti. Boulenger (1918) explained the
behavior of holsti by pointing out the well-known fact that male
frogs will clasp other species and even inanimate objects during the
breeding season. All of Van Denburgh's specimens of holsti were
collected between May 5 and May 11, near if not within the breeding
Both Van Denburgh (1920) and Noble (1920) rejected the sexual
interpretation because the spine appeared in both sexes. This is
hardly a valid point. Both men and women have mammae; yet
that does not alter the sexual nature of the glands.
In all of the adult males I have examined of both species (total
27), the sheath was punctured, whereas, in the five adult females
of subaspera, there was no such perforation. The one available
juvenile male of subaspera lacked the perforation also. These data
indicate that the spine has a sexual function in males. Since the
punctures vary in position and shape from male to male, and are
not even constant from one hand to the other in a single individual,
it is. my opinion that the spine is forced through the sheath during
amplexus. The extremely thick and tough skin protects the female
With the exception of the body length/leg length ratio, the body
proportions show no sexual differentiation. A comparison of the
sexes is given in the following table. The measurements of twenty
INGER: AMPHIBIA OF RIUKIU ISLANDS 329
adults were used. Maturity in the males was determined by the
presence of nuptial pads and vocal sacs; maturity in the females was
based on the presence of ovulated eggs.
SIZE AND BODY PROPORTIONS IN Rana subaspera
Male Female Diff. t P(n=18)
Log body length.... 2.06630.0041 2.06840.0067 0.0021 0.254 0.80
Body length in mm. . 116.50 117.04
length 0.601 0.004 0.636 0.008 0.035 3.944 0.001
Tibia/leg length 0.297 0.001 0.299 0.003 0.002 0.960 0.35
length 0.408 -0.003 0.403 0.029 0.005 0.309 0.76
length 0.00690.0002 0.00650.0002 0.0004 1.225 0.24
According to Okada the male has a blunter snout and a larger
tympanum. As for the first point, I found no such distinction, and
the table shows that there was no difference observed in the tympana.
Breeding habits. The specimens examined were collected between
April 26 and May 1. As all five females contained eggs ready to be
shed, one concludes that breeding takes place during the last part
of April and early May.
Rana namiyei Stejneger
Rana namiyei Stejneger, Proc. Biol. Soc. Wash., 14, p. 190, 1901 type
locality Okinawa; Stejneger, Bull. U. S. Nat. Mus., 58, figs. 122-126,
p. 136, 1907; Van Denburgh, Proc. Calif. Acad. Sci., (4), 3, p. 194, 1912;
Okada, Tailless Batr. Jap. Emp., pi. xii, fig. 1, pi. xxi, fig. 1, pi. xxvii,
fig. 5, text figs. 69-71, p. 156, 1931.
Rana kuhlii Boulenger, Rec. Ind. Mus., 20, p. 62, 1920.
Distribution. Adults have been recorded from Okinawa only.
This frog inhabits the pools and quiet water of the mountainous
region. In this respect it is similar. to R. kuhlii (Pope, 1931). Okada
reported seeing tadpoles of namiyei on Amami.
Specimens examined. Okinawa, 7 males, 10 females (C.A.S.).
Taxonomic notes. Rana namiyei has been considered a synonym
of kuhlii. The close relationship of the two forms is obvious. The
question of the validity of the former is dependent upon two factors,
isolation and differentiation. R. namiyei has not been found south
of Okinawa. The nearest population of kuhlii is on Formosa. As
exploration of the amphibian fauna of intervening Ishigaki has been
extensive we can safely assume that the two are effectively isolated.
330 FIELDIANA: ZOOLOGY, VOLUME 32
There has been some differentiation. Of ninety-nine individuals
of kuhlii from Fukien, the largest measured by Pope (1931) was
67 mm. long. The largest of forty- three specimens examined by
Boulenger (1920) was 87 mm. The latter's specimens came from
various points in the range of kuhlii. In the Okinawa series the
mean length of six mature males was 83.44 mm., with a. maximum
of 102.5. The mean length of eight females containing eggs was
75.10 mm., with a maximum of 88.5. Okada (1931) listed six males
of which the mean length was 96.0 mm., with a maximum of 113.
He also recorded a female that measured 102 mm. It is apparent
that namiyei is larger than kuhlii. There are other minor differences.
The band between the eyes is much wider in namiyei. As pointed
out by Van Denburgh (1912b), in the present form the web and
dermal margin of the fifth toe are more extensive. These differences,
of course, reflect differences in the genetic make-up of the two forms.
Inasmuch as the two most important criteria of species are
satisfied, namely, effective reproductive isolation (by virtue of the
wide separation in distance and in geologic time) and genetic dis-
tinction, namiyei should be maintained as a distinct species.
Diagnosis. Rana namiyei is distinguished from other frogs in
the islands by the two projections in the anterior part of the lower
jaw. These processes fit into depressions of the upper jaw. R.
limnocharis is the only other frog with a similar structure; however,
in limnocharis there is only a single median projection. The present
species is one of the largest in the islands. Data on length are given
elsewhere. The general aspect of the body is broad and flat.
Secondary sexual characters. As stated above, the mean length
of the mature males examined for this study was 83.44 mm., of the
females 75.10 mm. The difference between these figures is not signi-
ficant (P=0.24, t= 1.235). Nevertheless, a large series probably
would show a significant difference between the sexes. In kuhlii
Pope has demonstrated the presence of such a difference, due pri-
marily to the large size of the head in males. The same condition
holds true in namiyei. The head width /body length ratio of males
in the present series was 0.455, that of females 0.435. P of the
difference was 0.05 (t= 2.125). However, of more importance is the
fact that in the males there was a correlation of +0.79 (P=0.04)
of the head width ratio to the logarithm of body length. In the
females the correlation had a value of +0.02 (P=0.97).
For the comparison of the lengths only sexually mature individ-
uals were used. In the males, maturity was determined by the
INGER: AMPHIBIA OF RIUKIU ISLANDS 331
presence of the secondary sex structures, paired internal subgular
vocal sacs, and granular nuptial pads on the first digit. Maturity
in the females was determined by the presence of ovulated eggs.
Breeding habits. All of the specimens were collected in the
period from May 5 to May 11. The imminence of breeding at the
time of capture is indicated by the presence of ovulated eggs in all
of the large females.
Rana narina Stejneger
Rana narina Stejneger, Proc. Biol. Soc. Wash., 14, p. 189, 1901 type locality
Okinawa; Stejneger, Bull. U. S. Nat. Mus., 58, p. 134, figs. 117-121,
1907; Okada, Tailless Batr. Jap. Emp., p. 1^3, pi. x, fig. 3, pi. xxvii, fig. 2,
text fig. 68, 1931.
Buergeria ijimae Stejneger, Proc. Biol. Soc. Wash., 14, p. 190, 1901.
Rana ijimae Stejneger, Bull. U. S. Nat. Mus., 58, p. 121, figs. 99-103, 1907;
Van Denburgh, Proc. Calif. Acad. Sci., (4), 3, p.'193, 1912; Okada, Tailless
Batr. Jap. Emp., p. 151, pi. xxvi, fig. 5, text fig. 67, 1931.
Distribution. This species has been recorded from Okinawa,
Amami, and Ishigaki. In addition, Okada has reported it from
Specimens examined. Ishigaki, 13 (C.A.S.).
Taxonomic notes. The descriptions of narina and ijimae in
Stejneger (1907) and Okada (1931) indicate that these are very
similar. The position of the vomerine teeth, the characteristic
tubercles surrounding the tympanum, the swollen tips of the digits,
the blunt snout, and the general form and size agree in both. From
Okada's figures of the skull and pectoral girdle, there is no basis
for distinction. Furthermore, his colored plate of narina fits his
description of ijimae. The only differences mentioned by Okada
are the relatively narrower head and shorter limbs in narina. How-
ever, those cannot be differences of the species level. When one
considers further that there is no way of knowing just how Okada
distinguished between the two, the differences he mentioned can
very well be interpreted as variations within a population.
Apparently Stejneger's designation of two specimens of this form
as the types of two distinct species was the result of poor preserva-
tion. In his Herpetology of Japan are figured the hand and foot of
the type of narina. The figures are obviously those of a dried speci-
men. When writing of ijimae in the same volume, Stejneger states
that the type specimen was too soft to determine the nature of the
dorso-lateral region. R. ijimae is here reduced to the synonymy of
332 FIELDIANA: ZOOLOGY, VOLUME 32
Diagnosis. Characteristic of this species are the light line above
the mouth and the white tubercles surrounding the tympanum.
The tips of the digits are swollen but, as in okinavana, are not as
large as the disks of Hyla or Rhacophorus. The snout is blunt.
There are usually three complete crossbars on the tibia.
Secondary sex characters. The average body length of eight
apparently mature females was 86.2 mm. (minimum 78.5, maximum
99.0). Of the three males available, the largest was 67.0 mm. This
specimen, C.A.S. 22827, was mature, having a well-developed nuptial
pad and paired lateral internal vocal sacs. The other males, the
smaller being 62.5 mm., lacked these structures and were presumably
immature. The larger of two males measured by Okada (1931) was
79 mm. long. Although it seems probable that the females were
larger than the males, the magnitude of the difference is impossible
to determine with the few specimens at hand.
A comparison of the body proportions of the two sexes is given
in the following table. Only in the head width/ body length ratio
is there a significant difference.
COMPARISON OP MALE AND FEMALE Rana narina
(3 males, 8 females)
Male (mean) Female (mean) Diff. t P (n=9)
Body length/leg length.. 0.5900. 004 0.5960.007 0.006 0.364 0.73
Tibia/leg length . 3070 .001 . 3090 .002 . 002 . 576 . 62
length 0.3280.004 0.3500.004 0.022 3.089 0.014
Okada (1931) stated that the hind limb and tibia of the males wer
shorter than those of the females. Such differences should be
reflected in the body length /leg length and tibia/leg length ratios.
The table, though admittedly weak because of the few specimens
involved, does not reveal either of these differences.
Breeding habits. All of the specimens examined were collect
between May 25 and June 2. As none of the females containec
ovulated eggs, it is evident that the breeding season occurs earlier.
There is nothing in the literature concerning breeding behavior.
Rana okinavana Boettger
Rana okinavana Boettger, Zool. Anz., 18, p. 266, 1895 type locality Okinawa;
Stejneger, Bull. U. S. Nat. Mus., 58, p. 102, 1907; Van Denburgh, Proc.
Calif. Acad. Sci., (4), 3, p. 192, 1912.
Rana macropus Okada, Tailless Batr. Jap. Emp., p. 95, pi. x, fig. 5, pi.
fig. 4, pi. xxiv, fig. 6, text figs. 42-43, 1931.
INGER: AMPHIBIA OF RIUKIU ISLANDS 333
Distribution. Only the type specimen has been recorded from
Okinawa. It has also been reported from Ishigaki (Van Denburgh,
1912b) and Amami (Okada, 1931).
Specimens examined. Ishigaki, 11 males, 12 females (C.A.S.).
Diagnosis. The absence of tubercles from the area surrounding
the tympanum and the single crossbar on the tibia distinguish this
species from R. narina. R. okinavana is also considerably smaller
than narina^ The mean of the series examined was 39.7 mm., with a
maximum of 43.0. Okada (1931) described a female that was 47 mm.
long. The smallest narina I examined measured 62.5 mm. The
white line above the lip and the swollen tips of the digits separate
okinavana from other members of the genus (with the exception of
narina). Though the tips of the digits are enlarged, they do not
approach the size of the disks of Rhacophorus and Hyla. The skin
of the back is smooth except near the vent.
Secondary sexual characters. The sexes are indistinguishable by
gross inspection. Examination of eleven males failed to reveal
nuptial pads or vocal sacs. However, that may be due to immaturity.
Analysis of the body proportions indicates very little difference
between the sexes. The following table summarizes the data on
body length and proportions.
COMPARISON OF MALE AND FEMALE Rana okinavana
(11 males, 12 females)
Male (mean) Female (mean) Diff. t P (n=21)
Log body length... 1.59340. 0043 1.60250.0061 0.0091 1.206 0.25
Body length in mm. 39 . 21 40 . 04
length 0.569 0.005 0.553 0.006 0.016 2.026 0.06
Tibia/leg length. .. 0.294 0.002 0.293 0.001 0.001 0.105 0.90
Head width /body
length 0.355 0.006 0.346 0.003 0.009 1.467 0.16
The only distinction between the sexes in the series lies in the body
length/ leg length ratio. Even that difference is just at the border-
line of significance (P=0.06).
Breeding habits. Practically nothing is known about the breed-
ing behavior of this frog. None of the females available to me con-
tained eggs. As all were collected in the period May 25 to June 2,
it is probable that the breeding season had already ended. That
the larger females were mature was evident from the relatively large
334 FIELDIANA: ZOOLOGY, VOLUME 32
Rana ishikawae Stejneger
Buergeria ishikawae Stejneger, Proc. Biol. Soc. Wash., 14, p. 190, 1901 type
Rana ishikawae Stejneger, Bull. U. S. Nat. Mus., 58, p. 132, figs. 111-116,
1907; Okada, Tailless Batr. Jap. Emp., p. 166, pi. xi, fig. 1, pi. xxvii,
fig. 1, text fig. 74, 1931.
The few specimens collected have come from the mountainous
region of Okinawa. I have not seen any individuals of this species.
According to Stejneger (1907) and Okada (1931) the large tubercles
of the back have radiating striae which immediately set this frog
apart from any other in the islands. The smaller tubercles lack these
ridges. The ends of the fingers and toes are slightly expanded. This
species approaches the size of R. holsti, one individual being recorded
as 115 mm. long (Okada, 1931). There is no reference to secondary
sexual characters or the breeding habits of ishikawae.
Rana limnocharis Wiegmann
Rana limnocharis Boie in Wiegmann, Nova Acta Acad. Leop. Carol., 17, pt. 1,
p. 255, 1835 type locality Java; Boulenger, Fauna Brit. India, Kept.,
p. 450, 1890; Fritze, Zool. Jahrb. Syst., 7, p. 865, 1894; Boettger, Offen-
bach. Ver. Naturk., Ber. 33-36, p. 103, 1894; Stejneger, Journ. Sci. Coll.
Tokyo, 12, pt. 3, p. 217, 1898; Stejneger, Bull. U. S. Nat. Mus., 58, p. 127,
figs. 107-110, 1907; Okada, Tailless Batr. Jap. Emp., p. 138, pi. vii, fig. 1,
pi. xix, fig. 5, pi. xxvi, fig. 4, text figs. 62-63, 1931; Gressitt, Proc. Biol.
Soc. Wash., 51, p. 162, 1938.
Rana gracilis Wiegmann, Nova Acta Acad. Leop. Carol., 17, pt. 1, p. 257,
1835; Hallowell, Proc. Acad. Nat. Sci. Phila., p. 505, 1860; Gunther,
Kept. Brit. India, p. 409, 1864; Martens, Preuss. Exped. Ost-Asien, Zool.,
1, p. 383, 1876; Boulenger, Cat. Batr. Sal. Brit. Mus., p. 28, 1882;
Boulenger, Proc. Zool. Soc. Lond., p. 149, 1887; Boettger, Offenbach.
Ver. Naturk., Ber. 24-25, p. 159, 1885; Okada, Cat. Vert. Jap., p. 67,
1891; Brown, Proc. Acad. Nat. Sci. Phila., p. 185, 1902.
Rana vittigera Gunther, Cat. Batr. Sal. Brit. Mus., p. 9, 1858; Martens,
Preuss. Exped. Ost-Asien, Zool., 1, p. 163, 1876.
Distribution. This frog is found in Kyushu, Shikoku, southern
Honshu, Korea, China, and other parts of southeastern Asia. In the
Riukius it has been recorded from all groups except the Tokaras.
Specimens examined. Riukiu Islands, 67 (Okinawa, 47, C.N.
H.M.; Ishigaki, 20, U.S.N.M.); Formosa, 9 (C.N.H.M.); Indo-
China, 29 (C.N.H.M.); Fukien, 12 (C.N.H.M.); Szechwan, 43
Diagnosis. The present species is one of the smaller representa-
tives of the genus, the largest individual from Okinawa examined
INGER: AMPHIBIA OF RIUKIU ISLANDS 335
being 49.0 mm., the largest from Ishigaki 53.5. The ground color
may be gray or brown, with several short black bands crossing the
center of the back. There are many scattered longitudinal ridges
on the back, especially posteriorly. The characters in the key are
sufficient to separate limnocharis from all other frogs in the islands,
the only possible confusion being with namiyei. The latter has two
large processes at the front of the lower jaw, whereas limnocharis
has a single median enlarged projection.
Secondary sexual characters. The males have a median external
subgular vocal sac. Coincident with the development of this
structure, the ventral fold anterior to the pectoral girdle is much
more pronounced than in the females. The nuptial pad of the male
is granular and located on the dorso-medial surface of the first
digit. Another male characteristic is the presence of black on the
throat, but the density of the pigment and its extent vary consider-
ably. When the amount of pigment is greatest, it extends in an
anteriorly directed arching band from the posterior corner of the
mouth across the throat. The maximum width of the band is
approximately 4.5 mm. The reductions in density and extent of
pigment begin in the same area, the center of the throat, though
not in all cases simultaneously. At the minimum the pigment is
present in a short pale band along the posterior margin of the jaw.
The females are slightly larger than the males. The Okinawa
series included fifteen mature males and fifteen mature females.
The mean lengths of these were 35.56 and 39.07 mm. In the Ishigaki
series the mean of the fourteen mature males was 48.68; of six females
51.16 mm. The probabilities that these sexual differences are due
to chance are P=0.03 ($=2.356) and P=0.05 (=2.119), respectively.
The significance of these figures is emphasized by comparison with
the samples from Indo-China and Szechwan. In the former the
mean for the males is 36.44; for females, 44.41 mm. The value of
P for this difference is 0.001 (=4.988). In the latter sample the
means are 37.64 and 41.02, P of the difference being equal to 0.02
(=2.482). I have found no distinction between the sexes in body
Okada (1931) made several statements concerning sexual differ-
ences for which I find no support. He reported that the males were
distinguished by the presence of "two distinct palmar tubercles on
the inner lateral margin of the first finger." In my series the females
are identical to the males in this respect. Okada also stated that in
the males the tibio-tarsal articulations did not overlap when the
336 FIELDIANA: ZOOLOGY, VOLUME 32
legs were folded at right angles to the body. In my series the articu-
lations overlapped in almost one-half of the individuals of both sexes.
Breeding habits. A detailed account of the breeding was given
by Pope (1931) in his observations on Chinese amphibians. Accord-
ing to Pope, laying takes place in quiet water. Depending on
temperature and availability of water, breeding may begin any time
from March to July. Generally the season lasts but six weeks.
Eight of eleven females collected on Okinawa between April 19 and
April 25 contained eggs. Two of the Ishigaki females also contained
eggs. These specimens were collected "April, 1899."
Inter-island variation. Stejneger (1907) reported that individuals
of limnocharis from Ishigaki were distinguished by a light mid-dorsal
line. Nineteen of the twenty examined for this study displayed
this character. The width of the stripe varied from 0.5 to 3.0 mm.
None of the Okinawa frogs had so much as a trace of the line. There
were also significant differences between the two samples in size and
body proportions, as illustrated in the following table.
COMPARISON OF Rana limnocharis FROM OKINAWA AND ISHIGAKI
Mean Sex Okinawa Ishigaki Diff. t n P
Log body length.... <? 1.55090.0087 1.68740.0064 0.1365 11.55 27 0.001
Body length in mm. d" 35.56 48.68
Log body length.... 9 1.59190.0133 1.70890.0034 0.1170 5.005 19 0.001
Body length in mm. 9 39.07 51.56
length 0.657 0.008 0.635 0.005 0.022 1.956490.056
Tibia/leg length. .. 0.284 0.001 0.297 0.002 0.013 5.200490.001
length 0.335 0.003 0.331 0.002 0.004 1.023490.32
Although the body length /leg length difference is on the border
line of significance, only in the head width ratio is there clearly no
distinction between the two groups.
When compared with specimens from the continent, the Ishigaki
series is similar to the populations in Formosa, Fukien, and Indo-
China. The resemblance lies in the frequency of the median line
(present in seven of nine specimens from Formosa, five of twelve
from Fukien, and twenty of twenty-nine from Indo-China), size,
and proportions. Strangely enough, the Okinawa series shows
remarkable similarity to the sample from Szechwan in these char-
acters. Not one of forty-three individuals from this Chinese province
has a median line. In other respects the various samples are all
very much alike. It seems likely that there are at least two sub-
species, one in western China and the other in southeastern Asia
INGER: AMPHIBIA OF RIUKIU ISLANDS 337
including Formosa and, possibly, the southern Riukius. The relation
of the Okinawa population to the rest of the species is not determin-
able at present, the final analysis requiring comparison with material
from the Oshima group and Japan.
Rhkcophorus schlegelii Gunther
Distribution. This species is found in the southern half of
Honshu, in Shikoku, Kyushu, all of the groups of the Riukius except
the Tokaras, and in Formosa. It is the only frog known to have
this range. All of the others that occur both in Japan and the Riu-
kius are also found in China.
Specimens examined. Total, 174: Japan, 8 (schlegelii); Amami,
14 (amamiensis); Okinawa, 47 (viridis); Ishigaki, 100 (owstoni);
Formosa, 5 (moltrechti). Most of these were from the collections
of the California Academy of Sciences; some specimens were from
the United States National Museum.
Taxonomic notes. The schlegelii group as here interpreted con-
tains the following forms:
schlegelii schlegelii Gunther Japan
schlegelii arborea Okada and Kawano Japan
schlegelii amamiensis subsp. nov Oshima group
schlegelii viridis Hallowell Okinawa group
schlegelii owstoni Stejneger Yaeyama group
schlegelii moltrechti Boulenger Formosa
These have been variously considered as species and as subspecies.
Stejneger (1907), though recognizing the close relationship, believed
they were separate species. Okada and Kawano (1924) considered
arborea to be a subspecies of schlegelii. They also described another
subspecies, intermedia, which is probably the intergrading popula-
tion of arborea and schlegelii as it is intermediate between them in
range and breeding habits. There are apparently no morphological
differences among these three. Okada (1926, 1931) treated viridis,
owstoni, and moltrechti as separate species. But his interpretation
of the relationships of these forms was in error, for he reported both
viridis and owstoni from Formosa and Okinawa. Van Denburgh
.(1912b) reduced the forms, with the exception of moltrechti, to the
Wolf (1936) added moltrechti and many currently recognized
species to the list of subspecies of schlegelii. His forms can be
divided into three geographically isolated groups: (1) an East Indies
338 FIELDIANA: ZOOLOGY, VOLUME 32
unit consisting of javanus, poecilonotus, acutirostris, and monticola;
(2) a Chinese unit of davidi; and (3) the present East China Sea
group of schlegelii, viridis, owstoni, and moltrechti. From the ranges
and the fact that the members of the first two divisions are spotted
dorsally, one concludes that Wolf was dealing with three separate
species complexes. It is apparent that his conception of a species
differs from mine. I believe that these forms are related subspecies
of the same species. The occurrence of schlegelii on every island
group and the similarity between successive populations lead me to
the conclusion that the populations have been separated for a
relatively short period of time, probably not long enough to become
Diagnosis. This is the only Rhacophorus with a uniformly green
back. In preserved material the color may be blue or slate. Because
of the disks of the digits, schlegelii will not be confused with any of
the species of Rana or the only Bufo found in the islands. How-
ever, juvenile schlegelii amamiensis (the only form found in the
range of hallowelli) are superficially very similar to Hyla hallowelli.
Older specimens are larger than hallowelli (more than 40 mm. as
compared to 35 or less) and have dark blotches on the sides and
thighs. Juvenile schlegelii may be differentiated from the Hyla by
the position of the nostrils (see p. 322).
Secondary sexual characters. These are of the type so common
among frogs. The males when mature have granular nuptial pads
on the first two fingers and a median internal subgular vocal sac.
The first metacarpal of the female, in contrast to the rounded one
of the males, is blade-like. The relative breadth of the metacarpal
increases considerably with age. In addition, the females are much
larger than the males, as is shown in figure 55 and in the table on
page 343. With regard to body proportions, there was no significant
Breeding habits. Okada (1928, 1931) stated that breeding of
the typical form occurs from mid-April to June. Among the speci-
mens examined, all of which were collected between April 26 and
June 2, only one female contained eggs. Apparently the active
period of egg-laying had passed. Okada (1928) reported seeing on
March 25 an egg mass at the edge of a rice paddy on Amami. As
none of the five large females of amamiensis, collected from April 26
to May 1, contained mature ova, it is likely that, on Amami at least,
the breeding season begins in March and ends in April. Presumably
the more southerly forms breed slightly earlier.
NUMBER OF SPECIMENS
(in mm.) 1
FIG. 55. Size frequency distribution of Rhacophorus schlegelii owstoni.
340 FIELDIANA: ZOOLOGY, VOLUME 32
The eggs of the typical subspecies are laid in a hole on the sloping
banks of ponds and rice paddies (Ikeda, 1897; Okada, 1928). That
the Riukiu forms have the same habit seems likely, in view of Okada's
observation of the egg mass on Amami. On the basis of field observa-
tions Ikeda and Okada attributed the nest preparation to the female.
The latter reported that prior to mating several males were frequently
found in the same hole with a single female. During deposition both
male and female beat up the gelatinous material covering the eggs
into a white frothy mass. According to Ikeda the jelly becomes
liquefied at about the time the eggs hatch. When the liquid reaches
the proper consistency, it flows out of the opening through which
the adults left the nest. The eggs will not develop in water.
Life cycle and growth. Figure 55 is a graph of length frequencies
of the Ishigaki (owstoni} series that was collected between May 25
and June 2. The frequencies are plotted at the center of one milli-
meter class intervals. There is a pronounced break in the distribu-
tion of both males and females. In the former the gap runs from
35.0 mm. (the actual measurement) to 41.0 mm.; in the females
from 37.0 to 46.0 mm. This gap is probably the separation of two
age groups which we shall temporarily call "younger" and "older."
In the Okinawa (viridis) series there were five individuals that
were incompletely metamorphosed. The range of body length of
these, which still retained the tail, was from 17.5 to 19.0 mm. The
viridis series was collected from May 5 to May 11. As the distribu-
tion of the "younger" owstoni group falls immediately beyond the
range of the tailed specimens, I conclude that the young of the two
species were born at approximately the same time. The age assigned
to the "younger" group depends on whether metamorphosis occurs
shortly after birth or whether the tadpole stage lasts a full year.
In the relatively cool climate of our Great Lakes region, Hyla versi-
color metamorphoses when approximately 17 mm. long and within
sixty-five days after hatching. It is difficult to believe that, in the
much warmer climate (rarely below 50 F.) of the Riukius, it takes
R. schlegelii a year to reach the same size. ' Consequently I assume
that metamorphosis in schlegelii takes place about forty days after
That assumption leads to the conclusion that the "younger
group consists of young of the year. In the table on page 341 it is
shown that there is no significant difference between the sexes ir
this age group. However, the graph (fig. 55) shows a sexual dif
ferentiation in the "older" group, the significance of the differen
INGER: AMPHIBIA OF RIUKIU ISLANDS
being shown in the table (bottom, p. 343). The explanation of the
difference is that the growth rate of the females is greater than that
of the males during the first year. Whether or not the females or
both sexes grow appreciably after the second year cannot be deter-
mined from the data available; neither can the "older" group be
broken into its component age groups.
In the Okinawa (viridis) series only ten specimens measured less
than 40 mm. Of the ten, none was larger than 33.0 mm. Of those
over 40 mm., the smallest male measured 40.5 and the smallest
female 42.0 mm. None of the specimens from Amami (amamiensis)
was under 42.0 mm. Thus we can split the entire series into two age
groups in the vicinity of 40 mm.
(SUBSPECIES OF Rhacophorus schlegelii
Analysis of size of young of the year
owstoni. . .
. . . 9
. . . d"
. . . d"
owstoni. . .
viridis . .
. . rf 1 9
. d< 9
Inter-island variation. Generally the differences between sub-
species of schlegelii can be arranged in linear geographic series as
suggested by Van Denburgh (1912b). This phenomenon is illustrated
by the nature of the skin of the back. In a series ranging from north
to south, the amount of granulation on the dorsum decreases until
the skin is perfectly smooth in owstoni and moltrechti. Concurrently
there is reduction in the amount of granulation of the throat and
chin from schlegelii, which has a rough throat, to owstoni, which has
a very smooth throat. The gular region of moltrechti, however, is
Likewise, the dark markings change character. In the Japanese
specimens they are in the form of fine reticulations; in amamiensis
the markings become large, confluent blotche*s covering almost the
entire posterior surface of the thigh; in viridis they are constricted
into numerous discrete dots; in owstoni they are dots slightly reduced
in number and with some tendency to unite; in moltrechti the markings
are in the form of spots that are larger in size and fewer in number
FIELDIANA: ZOOLOGY, VOLUME 32
than in owstoni. With the omission of amamiensis, these changes
were pointed out by Van Denburgh (1912b). The gradation is illus-
trated in figure 56.
FIG. 56. Geographic variation in the color pattern in subspecies of Rhaco-
phorus schlegelii. The subspecies are arranged in geographic order from north
to south. The typical form is found in Japan, amamiensis in the Oshima group,
viridis in the Okinawa group, owstoni in the Yaeyama group, and moltrechti in
Further differences between these island populations are shown
by the changes in body proportions. These ratios were not com-
puted for schlegelii or moltrechti as too few specimens were available.
Of the other forms only those individuals that were over 40.0 mm
INGER: AMPHIBIA OF RIUKIU ISLANDS
in length were used in the comparison below. It will be recalled
that 40.0 mm. is approximately the lower limit of the individuals
one or more years old.
SUBSPECIES OF Rhacophorus schlegelii
Comparison of body proportions
. . 14
Difference . . .
Difference . . .
Only the means are cited. In all ratios used there is a significant
difference between viridis and owstoni. However, amamiensis differs
from viridis only in the tibia/leg length ratio. Undoubtedly the
greater distinction between viridis and owstoni reflects a longer period
of isolation, a conclusion supported by the geologic history of the
SUBSPECIES OF Rhacophorus schlegelii
Analysis of size of specimens one or more years old
amamiensis . .
viridis. . .
amamiensis . .
amamiensis . .
amamiensis . .
owstoni. . . .
The table indicates a statistically significant difference in size
between females of amamiensis and viridis. There were only five
specimens of the former available, all of which measured between
65 and 76 mm. Four females of viridis fell in the same range.
Although there may very well be a size difference between these
two subspecies I believe that it will not approach the magnitude
shown in the table and that the difference shown is the result of the
accidents of collecting.
344 FIELDIANA: ZOOLOGY, VOLUME 32
Rhacophorus schlegelii amamiensis subsp. nov.
Polypedates schlegelii viridis Van Denburgh, Proc. Calif. Acad. Sci., (4), 3,
p. 202, 1912.
Rhacophorus viridis Okada, Ann. Zool. Jap., 11, p. 102, 1926; Okada, Tailless
Batr. Jap. Emp., pi. xvi, fig. 3, pi. xxi, fig. 5, pi. xxix, fig. 1, text figs. 87-
89, p. 188, 1931.
Type from Naze, Amami. No. 23823 California Academy of
Sciences. Adult female. Collected April 26 to May 1, 1910, by
Mr. Victor Kuhn.
Diagnosis. This subspecies can be distinguished from the others
by the large confluent dark blotches on the posterior aspect of the
thighs and on the sides, as illustrated in figure 56. The dorsum
and throat are granulated, more so than in viridis but less so than
in the typical form. The gular region is faintly mottled with brown.
Data on size and body proportions are given in the tables on page
343. This subspecies is known only from Amami.
Description of type. Body tapering to inguinal region; head large,
interorbital distance greater than width of upper eyelid; nostril
one-third distance from tip of snout to orbit; canthus rostralis
distinct, lores obliquely concave; skin of back and throat finely
granulated; skin of venter more coarsely granulated; a dermal fold
from posterior border of orbit over tympanum to insertion of arm;
tympanum distinct, one-half diameter of orbit.
Fingers one-third webbed, first shorter than second; toes almost
fully webbed; disks of digits well developed, those of fingers largest;
Color of dorsal surfaces slate; throat faintly mottled with brown;
venter and under surfaces of limbs immaculate cream; posterior
aspect of thigh and lower portion of sides with confluent dark blotches.
Measurements of type. Snout to vent 76.0 mm., leg length 109.5
mm., tibia length 32.5 mm., head width 26.5 mm., interorbital width
Paratypes.C.A.S. 23824-6, 23830, 23839, 23842-43, 23848,
23856-58, 23860-61 (all from Naze, Amami).
Rhacophorus schlegelii viridis Hallowell
Polypedates viridis IJallowell, Proc. Acad. Nat. Sci. Phila., p. 55, 1860 type
locality Okinawa; Stejneger, Bull. U. S. Nat. Mus., 58, p. 147, 1907.
Rhacophorus viridis Boulenger, Proc. Zool. Soc. Lond., p. 149, 1887; Fritze,
Zool. Jahrb. Syst., 7, p. 865, 1894; Boettger, Offenbach. Ver. Naturk.,
Ber. 33-36, p. 106, 1895; Brown, Proc. Acad. Nat. Sci. Phila., p. 185,
INGER: AMPHIBIA OF RIUKIU ISLANDS 345
1902; Okada, Ann. Zool. Jap., 11, no. 2, p. 102, 1926; Okada, Tailless
Batr. Jap. Emp., pi. xvi, fig. 3, pi. xxi, fig. 5, pi. xxix, fig. 1, text figs. 87-
89, p. 188, 1931.
Polypedates schlegelii viridis Van Denburgh, Proc. Calif. Acad. Sci., (4), 3,
p. 202, 1912.
Rhacophorus schlegelii viridis Wolf, Bull. Raffles Mus., no. 12, p. 192, 1936.
Diagnosis. The markings of the sides and legs distinguish viridis
from the other subspecies (see fig. 56). The skin of the dorsal surface
is smooth, with only the faintest indication of shagreening. There
is no granulation of the throat. Occasionally the lower jaw has a
few faint dark spots, but these never extend across the throat.
Length and body proportions have already been discussed. The
range of viridis as here understood is limited to Okinawa. There
have been no specimens reported from the other islands of the
Rhacophorus schlegelii owstoni Stejneger
Polypedates owstoni Stejneger, Bull. U. S. Nat. Mus., 58, p. 149, 1907 type
locality Ishigaki; Gressitt, Proc. Biol. Soc. Wash., 51, p. 163, 1938.
Polypedates schlegelii owstoni Van Denburgh, Proc. Calif. Acad. Sci., (4), 3,
p. 202, 1912.
Rhacophorus owstoni Okada, Tailless Batr. Jap. Emp., pi. xvi, fig. 1, pi. xxix,
fig. 2, text fig. 91, p. 194.
Rhacophorus schlegelii owstoni Wolf, Bull. Raffles Mus., no. 12, p. 193, 1936.
Diagnosis. The markings of the legs and sides are in the form
of small dots differing from those of viridis in displaying a tendency
to unite and in being fewer in number (see fig. 56). The lower jaw
and throat are immaculate. There are no granulations of the dorsal
surface and throat. R. s. owstoni has been reported from Miyako,
Ishigaki, and Iriomote, all in the southern half of the Riukius.
Rhacophorus eiffingeri Boettger
Polypedates burgerii Hallowell, Proc. Acad. Nat. Sci. Phila., p. 501, 1860
not of Schlegel.
Rana eiffingeri Boettger, Zool. Anz., 18, p. 267, 1895 type locality Okinawa
or Amami; Boettger, Offenbach. Ver. Naturk., Ber. 33-36, p. 104, 1895.
Polypedates eiffingeri Stejneger, Bull. U. S. Nat. Mus., 58, p. 153, fig. 147,
1907; Stejneger, Proc. U. S. Nat. Mus., 38, p. 97, 1910; Van Denburgh,
Proc. Calif. Acad. Sci., (4), 3, p. 203, 1912; Okada, Tailless Batr. Jap.
Emp., p. 210, 1931.
Rhacophorus eiffingeri Boulenger, Ann. Mag. Nat. Hist., (8), 4, p. 495, 1909.
Distribution. This species has been recorded from Amami,
Okinawa, Ishigaki, and Formosa.
346 FIELDIANA: ZOOLOGY, VOLUME 32
Specimens examined. Formosa, 9 (U.S.N.M.).
Diagnosis. This species has the tips of the fingers and toes
developed into the disks common to Rhacophorus and Hyla. The
longitudinal dark lines on the back and the crossbars on the legs
distinguish it from Hyla hallowelli and Rhacophorus schlegelii. The
tibio-tarsal articulation of R. eiffingeri does not reach the snout as
it does in R. japonicus.
Secondary sexual characters. The nuptial pad of mature males
is in the form of a large swelling on the medial surface of the first
finger. The males also have a median internal subgular vocal sac
with openings near the corner of the mouth. The largest male of
the Formosa series measured 35.0 mm. The largest of three females
containing eggs measured 41.0 mm.
Rhacophorus japonicus Hallowell
Ixalus japonicus Hallowell, Proc. Acad. Nat. Sci. Phila., p. 501, 1860 type
locality Amami; Okada, Cat. Vert. Jap., p. 66, 1891; Fritze, Zool. Jahrb.
Syst., 7, p. 865, 1894.
Rana macropus Boulenger, Proc. Zool. Soc. Lond., p. 414, 1886; Boulenger,
Ann. Mag. Nat. Hist., (6), 10, p. 302, 1892; Fritze, Zool. Jahrb. Syst.,
7, p. 865, 1894; Boettger, Offenbach. Ver. Naturk., Ber. 33-36, p. 103,
Polypedates japonicus Stejneger, Bull. U. S. Nat. Mus., 58, p. 155, figs. 148-
153, 1907; Stejneger, Proc. U. S. Nat. Mus., 38, p. 97, 1910; Van Den-
burgh, Proc. Calif. Acad. Sci., (4), 3, p. 205, 1912; Okada, Tailless Batr.
Jap. Emp., p. 207, pi. xvii, fig. 2, pi. xix, fig. 5, text fig. 97, 1931.
Distribution. This tree frog is found in every group of the Riu-
kius from the Tokara Strait southward. Van Denburgh and Okada
have recorded it from Formosa.
Specimens examined. Okinawa group, Tokashiki, 1 male, 1
Diagnosis. The disks of the digits in combination with the dark
shaped markings of the back distinguish this species from all
other Riukiu frogs except R. eiffingeri. In japonicus the tibio-tarsal
joint reaches beyond the tip of the snout, considerably farther than
Secondary sexual characters. The male has a median internal
subgular vocal sac and a granular nuptial pad on the first digit.
According to Okada (1931) the female is larger than the male. The
INGER: AMPHIBIA OF RIUKIU ISLANDS 347
mean of five males measured by him was 29.00 mm., that of sixteen
females 31.07. The difference is not statistically significant, P being
equal to 0.15 (2=1.5). Unfortunately not enough specimens were
available to test the supposed sex dimorphism further. Okada also
reported that in the male the head is as long as broad. Although
he considered that condition diagnostic of males, he did not describe
the condition in the female. In the literature there is no mention
of the breeding behavior of this species.
1908. Some new Amphibia Salientia. Proc. Biol. Soc. Wash., 21, pp. 189-190.
BOULENGER, G. A.
1918. Sur la conformation des phalangettes chez certaines grenouilles d'Afrique.
C. R. Acad. Sci. Paris, 165, pp. 987-990.
1920. A monograph of the South Asian, Papuan, Melanesian and Australian
frogs of the genus Rana. Rec. Ind. Mus., 20, pp. 1-226.
1860. Report upon the Reptilia of the North Pacific Exploring Expedition,
under command of Capt. John Rogers, U.S.N. Proc. Acad. Nat. Sci. Phila.,
1860, pp. 480-510.
1935. Topography and geology of the Riukiu Islands. Tohoku Imp. Univ.
Sci. Rept., (2), Geology, 18, pp. 1-61, pis. 1-15, maps 1-5.
1897. Notes on the breeding habits and development of Rhacophonis schlegelii
Guenther.% Annot. Zool. Jap., 1, pp. 113-122.
1897. Geologic structure of Riu Kiu curve. Jour. Geol. Soc. Tokyo, 5, p. 1.
1934. On the phytogeography of the Ryukyu Archipelago. Bull. Biogeog. Soc.
Japan, 5, pp. 29-86.
1935. Review of the flora of the Ryukyu Archipelago. Trans. Nat. Hist. Soc.
Formosa, 25, pp. 253-254.
NOBLE, G. K.
1920. A note on Babina, the dagger-frog. Copeia, No. 79, pp. 16-18.
1926. A study on the distribution of tailless batrachians of Japan. Annot.
Zool. Jap., 11, pp. 97-103, pi. 1.
1928. Notes on the breeding habits of Rhacophorus in Japan. Annot. Zool.
Jap., 11, pp. 279-285, pi. 1.
1931. Tailless batrachians of the Japanese Empire. Tokyo, Nishigahara,
1931, ii+215pp., 29 pis.
OKADA, YAICHIRO and KAWANO, USABURO
1924. On the ecological distribution of two new varieties of Rhacophorus in
Japan. Jap. Zool. Mag., 36, pp. 140-153, pi. 3.
PARKER, H. W.
1928. The brevicipitid frogs of the genus Microhyla. Ann. Mag. Nat. Hist.,
(10), 2, pp. 473-499.
1934. A monograph of the frogs of the family Microhylidae. London, Jarrold
& Sons Ltd. viii+208 pp.
350 FIELDIANA: ZOOLOGY, VOLUME 32
POPE, C. H.
1931. Notes on amphibians from Fukien, Hainan, and other parts of China.
Bull. Amer. Mus. Nat. Hist., 61, pp. 397-611.
SIMON, E. M. H.
1914. Beitrage zur Kenntnis der Riukiu-Inseln. Leipzig, Voigtlander, xiv+
1907. Herpetology of Japan. Bull. U. S. Nat. Mus., 58, pp. 1-577, pis. 1-35.
1931. Imori to Sansyouo (Salamanders of Japan). Pp. 1-210, pis. 1-28.
[Original not seen.]
1901. Notes on the raised coral reefs of the Riu kiu curve. Jour. Coll. Sci.
Imp. Univ. Tokyo, 16, pt. 1. [Not seen.]
VAN DENBURGH, JOHN
1912a. Advance diagnoses of new reptiles and amphibians from the Loo Choo
Islands and Formosa. San Francisco, 8 pp. Privately printed.
1912b. Concerning certain species of reptiles and amphibians from China,
Japan, the Loo Choo Islands, and Formosa. Proc. Calif. Acad. Sci., (4), 3,
1920. Mr. Boulenger on the genus Babina. Copeia, No. 79, pp. 14-16.
1890. Die Liukiu Inseln. Mitt. Geogr. Ges. Hamburg, pp. 121-145.
WILSON, E. H.
1920. The Liukiu Islands and their ligneous vegetation. Jour. Arnold Arb., 1,
1936. Revision der Untergattung Rhacophorus. Bull. Raffles Mus. Singapore,
No. 12, pp. 137-217.
1940. Breeding structure of populations in relation to speciation. Amer. Nat.,
74, pp. 232-248.
1929a. The latest land connection of the Japanese islands to the Asiatic
continent. Proc. Imp. Acad. Tokyo, 5, pp. 167-169.
1929b. Geologic age of the latest continental stage of the Japanese islands.
Proc. Imp. Acad. Tokyo, 5, pp. 430-433.
YABE, H. and AOKI, R.
1923. A summary of the stratigraphical and paleontological studies of the
Cainozoic of Japan. Proc. Pan-Pacific Sci. Congr. (Australia), 1, pp. 954-969.
amamiensis, Rhacophorus schlegelii, 338,
andersoni, Tylototriton, 314
Bufo bufo gargarizans, 308, 321
Caudata, key to, 314
Diemictylus ensicauda, 316
Differentiation, adaptive, 308
inter-island, 307, 313
Hyla hallowelli, 322
Microhyla ornata, 326
Rana holsti, 327
Rana limnocharis, 336
Rhacophorus schlegelii, 341
Triturus ensicaudus, 317
rate of, 308; see also Evolution, rate
Dispersal, accidental transportation,
land bridges, 310
Rana limnocharis, 310
Rhacophorus schlegelii, 310
water, currents of, 310
winds, prevailing, 310
see also Vagility
eiffingeri, Polypedates, 345
ensicauda, Diemictylus, 316
ensicaudus, Triturus, 316
Evolution, rate of, 313; see also Dif-
ferentiation, rate of
Fauna, Riukiu, 307
endemic species, 307
Oriental species, 307
Palearctic species, 308
order of entry, 310, 313
relation to vagility, 313
Japan, 309, 310
fissipes, Microhyla, 324
gargarizans, Bufo bufo, 308, 321
hallowelli, Hyla, 312, 321
holsti, Babina, 326
Rana, 308, 326
Hyla hallowelli, 321
Hyla hallowelli schmidti, 322
ijimae, Rana, 331
ishikawae, Rana, 334
Japan and origin of Riukiu fauna, 309,
japonicus, Polypedates, 346
Rhacophorus, 312, 346
limnocharis, Rana, 310, 312, 313, 334
Microhyla fissipes, 324
Miyako group, 300, 304
namiyei, Rana, 312, 329
narina, Rana, 331
okinavana, Rana, 311, 312, 332
okinavensis, Microhyla, 324
Okinawa group, 300, 304
ornata, Microhyla, 312, 324
Oshima group, 298, 300, 303, 304
Osumi group, 300
owstoni, Polypedates schlegelii, 345
Rhacophorus schlegelii, 345
Polypedates eiffingeri, 345
schlegelii viridis, 344
schlegelii owstoni, 345
popei, Triturus ensicaudus, 319
Rana holsti, 308, 326
vagility, 312, 313
FIELDIANA: ZOOLOGY, VOLUME 32
Rana namiyei, 329
fluctuations in sea level, 311
subaspera, 308, 327
Range, fluctuations in sea level, 311
form of, 311
Rhacophorus eiffingeri, 345
amamiensis, 338, 344
Riukiu Islands, climate, 304
maps, 299, 301
geologic history, 303
maps, 302, 305
Salientia, key to, 320
schlegelii, Rhacophorus, 310, 337
schmidti, Hyla hallowelli, 322
subaspera, Babina, 327
Rana, 308, 327
Tokara group, 298, 303
Tokara Strait, 300, 306
Triturus ensicaudus, 316
ensicaudus popei, 319
Tylototriton andersoni, 314
Vagility, ecological opportunity, 312
order of entry of fauna, 313
size of animal, 312
size of population, 312, 313
viridis, Polypedates schlegelii, 345
Rhacophorus schlegelii, 344
Waifing, see Dispersal, waifing
Yaeyama group, 300, 303, 304
UNIVERSITY OF ILLINOIS-URBANA