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PRELIMINARY SURVEY OF THE 

AMPHIBIANS 
OF THE RIUKIU ISLANDS 



ROBERT F. INGER 



FIELDIANA: ZOOLOGY 
VOLUME 32, NUMBER 5 

Published by 

CHICAGO NATURAL HISTORY MUSEUM 
DECEMBER 8, 1947 



PRELIMINARY SURVEY OF THE 

AMPHIBIANS 
OF THE RIUKIU ISLANDS 



ROBERT F. INGER 

University of Chicago 



FIELDIANA: ZOOLOGY 
VOLUME 32, NUMBER 5 

Published by 

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 



INTRODUCTION 

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 
criticism. 

The Riukiu Islands, ' situated south of Japan, have been the 
subject of many investigations in fields ranging from ethnology to 

297 



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 
forces. 

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 
is concerned. 

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. 



299 



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 
cordillera. 

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 




EAST CHINA 
SEA 



* KUCHINO 

* 

4 SUWANOSE 



A 
O 

KOTAKARA -f, 

TAKARA -a 

-ft 



1 / KIKAIGA 
AMAMI 



-A 
\ 



5 m TOKUNO 

r 

CO 

^OKIERABU 



OKINAWA 



'KUME TOKASMIKI 



G 

IRABU " MIYAKO 



ISHIGAKI 
IRIOMOTE 




MAP 2. Map showing islands of Riukiu Archipelago. 



301 



EAST CHINA 
SEA 




Amami 

r* 

Tokuno 



+ OKierabu 



/^Okinawa 




Ishigaki 

y 

'iriomote 



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. 



302 



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 
Formosa area. 

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. 



Present areas 



305 



306 FIELDIANA: ZOOLOGY, VOLUME 32 

AVERAGE MONTHLY RAINFALL IN INCHES IN AMAMI AND OKINAWA 
Positions of stations same as in table on page 30 % 

Amami Okinawa 

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 
amphibia. 

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. 

FAUNAL ANALYSIS 
Oriental Species 

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.) 
in Japan. 

Endemic Species 

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. 

Palearctic Species 

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 
northern forms. 

FAUNAL ORIGINS 

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 

Rana narina 

Rana namiyei 

Rana okinavana 

Rana subaspera 

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. 

CAUDATA 

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. 

Triturus ensicaudus 

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 
Tail length/body 

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- 
portions. 

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 

locality Amami. 
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 
table. 

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 

Okinawa 

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 
rubbish. 

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 

OBSERVED FREQUENCY 

Amami Okinawa Total 

Spots present 1 75 76 

Spots absent 50 74 124 

Total 51 149 200 

CALCULATED FREQUENCY 

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- 
lateral lines: 

OBSERVED FREQUENCY 

Amami Okinawa Total 

Lines present 24 30 54 

Lines absent 27 119 146 

Total 51 149 200 

CALCULATED FREQUENCY 

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 
extremely complex. 

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 

Head width/body 

length 0.2040.008 0.1960.001 0.008 5.263 187 0.001 

Head depth/body 

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 
dorsal surfaces. 

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 
Museum. 



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. 

SALIENTIA 

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. 

Rana subaspera 
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. 

Rhacophorus japonicus 

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, 
Rhacophorus schlegelii. 



INGER: AMPHIBIA OF RIUKIU ISLANDS 321 

Bufo bufo gargarizans Cantor 

Bufo gargarizans Cantor, Ann. Mag. Nat. Hist., (1), 9, p. 483, 1842 type 

locality Chusan. 

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 
or March. 

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, 
21 (C.A.S.). 

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 
of May. 

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 
subspecies. 

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 
Head width/body 

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 
significant difference. 

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 
webbed. 

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 
is obvious. 



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 
two series: 

MALES FEMALES 

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 

n=12 n=15 

Log body length .... 2 . 03120 . 0057 2 . 06630 .0041 . 0351 5 . 089 . 001 
Body length in mm. . 107.46 116.50 
Body length/leg 

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 
difference. 

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 
warty. 

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 
season. 

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 
from damage. 

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 

Body length/leg 

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 

Head width/body 

length 0.408 -0.003 0.403 0.029 0.005 0.309 0.76 

Tympanum /body 

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 
Formosa. 

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 
narina. 



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 

Head width/body 

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 

Body length/leg 

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 
oviducts observed. 



334 FIELDIANA: ZOOLOGY, VOLUME 32 

Rana ishikawae Stejneger 

Buergeria ishikawae Stejneger, Proc. Biol. Soc. Wash., 14, p. 190, 1901 type 

locality Okinawa. 
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 
(C.N.H.M.). 

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 
proportions. f 

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 

Body length/leg 

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 
Head width/body 

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: 

Form Distribution 

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 
subspecies level. 

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 
reproductively isolated. 

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 
sexual differentiation. 

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 



LENGTH 

(in mm.) 1 

19.5-20.45 
20.5-21.45 
21.5-22.45 
22.5-23.45 
23.5-24.45 
24.5-25.45 
25.5-26.45 
26.5-27.45 
27.5-28.45 
28.5-29.45 
29.5-30.45 
30.5-31.45 
31.5-32.45 
32.5-33.45 
33.5-34.45 
34.5-35.45 
35.5-36.45 
36.5-37.45 
37.5-38.45 
38.5-39.45 
39.5-40.45 
40.5-41.45 
41.5^42.45 
42.5-43.45 
43.5-44.45 
44.5-45.45 
45.5-46.45 
46.5^17.45 
47.5-48.45 
48.5-49.45 
49.5-50.45 
50.5-51.45 
51.5-52.45 
52.5-53.45 
53.5-54.45 
54.5-55.45 
55.5-56.45 
56.5-57.45 
57.5-58.45 
58.5-59.45 
59.5-60.45 
60.5-61.45 
61.5-62.45 
62.5-63.45 






FIG. 55. Size frequency distribution of Rhacophorus schlegelii owstoni. 



339 



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 
birth. 

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 



341 



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 
Length 



Subspecies 
owstoni 


Sex 


in mm. 
26.70 


1 


Mean 
.42670 


.0100 


] 


Diff. 




t 


n 


P 


owstoni. . . 


. . . 9 


26.58 


1 


.42460 


.0115 





.0021 





.001 


51 


0.99 


viridis .... 


. . . d" 


25.74 


1 


.41070 


.0221 














viridis .... 


9 


25.30 


1 


.40310 


.0162 





.0076 





.021 


8 


0.97 


owstoni 


d" 


26.70 


1 


.42670 


,0100 














viridis .... 


. . . d" 


25.74 


1 


.41070, 


,0221 





.0160 





.688 


33 


0.50 


owstoni 


9 


26.58 


1 


,42460 


,0115 














viridis 


9 


25.30 


1 


.40310, 


,0162 





,0215 





.623 


26 


0.54 


owstoni. . . 
viridis . . 


. . rf 1 9 
. d< 9 


26.61 
25.64 


1 

1 


,42520 
.40900 


.0075 
.0154 





.0162 





.861 


61 


0.39 



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 
slightly rugose. 

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 



342 



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 
Formosa. 

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 



343 



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 







Body length 


amamiensis 


No. 
. . 14 


Leg length 
0.6660.008 


Difference . . . 
t 




0.001 
0.175 


Prob 




0.86 


viridis 


.. 35 


0.6670.004 


Difference . . . 
t 




0.012 
2.294 


Prob. 




0.03 


owstoni. . 


. 45 


0.6790.003 



Tibia 
Leg length 
0.2960.001 
0.006 
2.940 
0.007 

0.3020.001 
0.008 
5.574 
0.001 
0.2940.001 



Head width 
Body length 

0.34^0.003 

0.003 

0.672 

0.51 

0.3510.003 

0.026 

7.239 

0.001 

0.3770.002 



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 
islands. 

SUBSPECIES OF Rhacophorus schlegelii 
Analysis of size of specimens one or more years old 



Length 


Subspecies 


Sex 


in mm. 


Mean 


Diff. 


t 


n 


P 


amamiensis . . 
viridis. . . 


<? 
cf 


46. 
44, 


.03 

,20 


1, 

1 


,66320 
,64540 


.0084 
.0112 


0. 


,0178 


1.298 


14 


.0.22 


owstoni 


rf 1 


45 


,07 


1 


.65400 


.0055 





.0086 


0.740 


25 


0.47 


amamiensis . . 
viridis 


9 
9 


70. 
56 


70 

.87 


1, 
1, 


,84940 
,75500 


.0115 
0128 


0. 


0944 


3.043 


31 


0.007 


owstoni 


9 


53. 


92 


1, 


,73180 


,0071 


0. 


0232 


1.563 


53 


0.13 


amamiensis . . 
amamiensis . . 


tf 

9 


46, 
70. 


,03 
70 


1, 
1, 


.66320 
,84940 


.0084 
.0115 


0. 


,1862 


13.181 


12 


0.001 


viridis 


cf 
9 


44. 
56 


,20 

.87 


1, 
1, 


.64540 
.75500 


.0112 
.0128 


0. 


,1096 


4.144 


33 


0.001 


viridis 


owstoni. . . . 


(f 

9 


45 
53 


.07 
,92 


1 

1 


,65400 
.7318+0 


.0055 
.0071 


0, 


,0778 


8.101 


45 


0.001 


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; 
heels touching. 

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 
8.0 mm. 

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 
Okinawa group. 

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, 
1895. 

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 
female (C.N.H.M.). 

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 
in eiffingeri. 

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. 



REFERENCES 

BARBOUR, THOMAS 

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. 

HALLOWELL, EDWARD 

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. 

HANZAWA, SHOSHIRO 

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. 

IKEDA, S. 

1897. Notes on the breeding habits and development of Rhacophonis schlegelii 
Guenther.% Annot. Zool. Jap., 1, pp. 113-122. 

KOTO, B. 

1897. Geologic structure of Riu Kiu curve. Jour. Geol. Soc. Tokyo, 5, p. 1. 

MASAMUNE, GENKEI 

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. 

OKADA, YAICHIRO 

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. 

349 



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+ 
182 pp. 

STEJNEGER, LEONHARD 

1907. Herpetology of Japan. Bull. U. S. Nat. Mus., 58, pp. 1-577, pis. 1-35. 

TAGO, K. 

1931. Imori to Sansyouo (Salamanders of Japan). Pp. 1-210, pis. 1-28. 
[Original not seen.] 

TOKUNAGA, S. 

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, 

pp. 187-258. 
1920. Mr. Boulenger on the genus Babina. Copeia, No. 79, pp. 14-16. 

WARBURG, OTTO 

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, 
pp. 171-186. 

WOLF, SIEGFRIED 

1936. Revision der Untergattung Rhacophorus. Bull. Raffles Mus. Singapore, 
No. 12, pp. 137-217. 

WRIGHT, SEWALL 

1940. Breeding structure of populations in relation to speciation. Amer. Nat., 
74, pp. 232-248. 

YABE, H. 

1929a. The latest land connection of the Japanese islands to the Asiatic 

continent. Proc. Imp. Acad. Tokyo, 5, pp. 167-169. 
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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. 



INDEX 



amamiensis, Rhacophorus schlegelii, 338, 

344 
andersoni, Tylototriton, 314 

Babina, 326 

holsti, 326 

subaspera, 327 
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 
non-adaptive, 308 
rate of, 308; see also Evolution, rate 

of 
Dispersal, accidental transportation, 

309, 310 

land bridges, 310 
limited, 311 
moderate, 311 
waifing, 309 

Rana limnocharis, 310 

Rhacophorus schlegelii, 310 

water, currents of, 310 

winds, prevailing, 310 

typhoons, 310 

see also Vagility 

eiffingeri, Polypedates, 345 

Rhacophorus, 345 
Endemism, 307 
ensicauda, Diemictylus, 316 
ensicaudus, Triturus, 316 
Evolution, rate of, 313; see also Dif- 
ferentiation, rate of 

Fauna, Riukiu, 307 
analysis, 307 

endemic species, 307 

Oriental species, 307 

Palearctic species, 308 
order of entry, 310, 313 

dispersal, 311 

relation to vagility, 313 
origins, 309 

Formosa, 309 



Japan, 309, 310 
southern, 309 
fissipes, Microhyla, 324 

gargarizans, Bufo bufo, 308, 321 

hallowelli, Hyla, 312, 321 
holsti, Babina, 326 

Rana, 308, 326 
Hyla hallowelli, 321 

vagility, 312 
Hyla hallowelli schmidti, 322 

ijimae, Rana, 331 
ishikawae, Rana, 334 

Japan and origin of Riukiu fauna, 309, 

310 

japonicus, Polypedates, 346 
Rhacophorus, 312, 346 

limnocharis, Rana, 310, 312, 313, 334 

Microhyla fissipes, 324 

okinavensis, 324 

ornata, 324 

vagility, 312 
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 

fauna, 309 
owstoni, Polypedates schlegelii, 345 

Rhacophorus schlegelii, 345 

Polypedates eiffingeri, 345 

japonicus, 346 

schlegelii viridis, 344 

schlegelii owstoni, 345 
popei, Triturus ensicaudus, 319 

Rana holsti, 308, 326 
ijimae, 331 
ishikawae, 334 
limnocharis, 334 
vagility, 312, 313 
waifing, 310 



351 



352 



FIELDIANA: ZOOLOGY, VOLUME 32 



Rana namiyei, 329 

vagility, 312 
narina, 331 
okinavana, 332 

fluctuations in sea level, 311 

vagility, 312 
subaspera, 308, 327 
Range, fluctuations in sea level, 311 
one-dimensional, 308 
fragmented, 308 
form of, 311 

Rhacophorus eiffingeri, 345 
japonicus, 346 

vagility, 312 
schlegelii, 337 

amamiensis, 338, 344 

owstoni, 345 

viridis, 344 

waifing, 310 

Riukiu Islands, climate, 304 
flora, 306 
geography, 298 

maps, 299, 301 
geologic history, 303 

maps, 302, 305 



geology, 300 
topography, 300 

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