イヘダニに關する研究 : (第2報)性比及び處女生殖に就て

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This is the second report of the biological studies on the tropical rat mite. In the former report the author described the life history of this mite experimented upon during June to July, 1935 in our laboratory. But in it exact data was shown neither on the sex ratio nor on the parthenogenesis. In the present work which was carried out in the same laboratory during the months from December, 1935 to May, 1936, an investigation was made mainly on the sex ratio of offspring of impregnated females and on the parthenogenesis of unimpregnated females. The results are generally summerized as follows: 1) Sex ratio of the offspring of impregnated females are, as shown in Table I, II and III, represented in the ratio of females of about 30% to males of about 70%. In precise examination, however, the percentage of females is somewhat smaller than that of males at the start, but soon the females increase to about 80%; nevertheless, then they decrease gradually to 0 because when two-thirds of the whole period of oviposition is passed, female eggs are no longer deposited. 2) Unimpregnated females, when engorged with blood, begin to lay eggs after a period of nearly the same as in the case of impregnated females (Table IV). 3) All eggs laid by unimpregnated females develop into adult males (Table IV). 4) Oviposition period, number of eggs laid and duration of unimpregnated females are tabulated in Table IV for the purpose of comparing with those of impregnated females. 5) Egg period and period of each succeeding developmental stages of the offspring of unimpregnated females are nearly the same as those of male offspring of impregnated females (Table V). 6) When the body length and width in each developmental stage of the offspring of unimpregnated females are compared with those of male offspring of unimpregnated females. we see that the data obtained are nearly same in every stage of both; but strictly speaking. we may say that the former are a little larger than latter as shown in Table VI. The same phenomenon is seen in the case of experiments made during last summer. (In Table VII are shown measurements of adults only.) This phenomenon, however, may be explained by the fact that, of the eggs laid by unimpregnated females, there are large eggs in considerable numbers and extremely small eggs are rare, as is shown in Fig I. 7) When the body length of adults of winter season are compared with that of summer season, the former is noticeably larger than the latter (Table VII). This is due to the fact that the eggs laid in winter are larger than those in summer as shown in Fig.I; the reason is, however, still unknown. 8) The virility of the adult males which are developed from the eggs laid by unimpregnated females is normal (Table III). 9) The length curve of male eggs laid by impregnated female resembles much to that of eggs by unimpregnated female (Fig.I). It seems to suggest that male eggs laid by impregnated female are not fertilized ones.
1936-10-15

イヘダニに關する研究 : (第2報)性比及び處女生殖に就て

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