九州産カヤネズミ

Through the collection and rearing of the Japanese harvest mouse occurs in Kyushu, the author has noticed that neither the relation between head and body length (HB) and tail length (T) nor the coloration of pellage does accord with the hitherto theory of some previous investigators. Until the present, the harvest mouse occurs in Kyushu Micromys japonicus japonicus, has been said to have a tail shorter than head and body length, while the one in Honshu, M. j. hondonis, have a tail longer than head and body length, As one of other characteristics to distinguish these two subspecies, it has been said that M. j. japonicus has belly hairs suffused with slate at their bases, while M. j. hondonis has pure white belly hairs from their roots. This time the author has reexamined statistically six external characters of. M. j. japonicus, that is, body weight (BW), head and body length (HB), tail length (T), ear length (E), hind foot length (HF) and tail coefficient (TC). At the same time, comparison between M. j. japonicus and M. j. hondonis has been made statistically, too. The following is the summary of the present study. 1) The materials consist of adult harvest mice collected in the suburbs of Fukuoka and Kurume City, which involve both sexes of individuals. Not only collected mice in the field, but also reared ones under artificial conditions were made the object of the statistical examination.2) Aging was done by body weight, that is, males that have body weight over 6.5 grams and females over 6.0 grams were regarded as adults. The histological investigation of genital organs supported this aging by body weight (Tables. 1-3). 3) Actually, being only a few specimens obtained by the author himself, external measurements concerning individuals in Honshu have been gathered from the data of the previous investigators (Table. 4). 4) The statistical examination was carried out using t-test under the level of significance 1% (Tables. 10, 11). 5) The significant difference between males and females was found only in body weight of M. j. japonicus under artificial rearing. 6) The significant differences between the individuals under natural and artificial conditions, which occur in Kyushu, are recognized in tail length and tail ratio in males, while in head and body length, tail length and tail ratio in females. So far as the result shows, the harvest mice under artificial conditions can be said to have longer tails than wild ones. 7) Between the males in Kyushu and Honshu, differences are significant in tail and ear length. Even in mice in Kyushu, those which have tha tails as long as or longer than head and body length, occupy a greater parts of materials, that is, 95.6% in males and 94.0% in females. Whether tail is longer or shorter than head and body length can not be made one of subspecific characteristics between M. j. japonicus and M. j. hondonis, as it used to be done. Between the two subspecies of females, significant differences are recognized in four external characters, that is, head and body length, tail, ear and hind foot length. From the above fact, females in Honshu can be distinguished in their size from the ones occur in Kyushu. 8) As the result of comparison of M. j. japonicus under artificial conditions with M. j. hondonis, difference is found significantly only in ear length in both sexes. 9) The author has collected mice in the field which have white belly hairs from their roots even in Kyushu. Besides the above mention, reared mice have come to show bellies pure white from hair roots under artificial conditions. The difference in coloration of belly hairs can not be made one of subspecific characteristics, though the reason of change of coloration under rearing conditions is obscure. 10) Concerning the reexamination of one more subspecies in Japan, M. j. aokii, which occurs in Tsushima islands, the author expects the arrival of another opportunity when more available data come to his hand.