Abstract
In connection with various interesting sexual phenomena in Lymantria dispar L. reported by Goldschmidt in an extensive series of breeding experiments which were carried out with the so-called strong and weak races, the researches by means of gonadectomy and gonadal transplantation with these sex-races may be of importance, since many sex problems have been remained unsolved. With this view in mind, the present author has attempted some experiments in relation to the sexual phenomena with two remarkable sex-races occurring in Lymantria dispar. The results of study so far obtained are summarized as below:
1) The removal of hairs and bristles in the larval body brings about no harmful effect upon further development and metamorphosis of the insect.
2) In the experiment of gonadectomy, 31 out of 115 larvae operated emerged into moths (26.9%). Generally speaking, the gonadectomized larvae are inactive in behaviour and dirty in body color. Pupae from operated larvae show a hollow area in the dorsal part of the 5th abdominal segment. The wings of male moths of the strong race are darker in color in the operated animals than in the control ones.
3) The gonadal transplantation involves two different schemes of experiment (i and ii).
i. Testicular and ovarian transplantations were made in the larvae, either in the same race or between the strong and weak races, in every case of which the gonads of the hosts were not removed. The operation was made in 76 larvae and 75% of them became moths (Table II).
ii. The gonads were transplanted in the bodies of gonadectomized larvae between two races. The operation was successful in 26% (Table III).
As compared with the gonadectomized larvae, those belonging to this series of experiment are generally active in behaviour and remarkable in colouration.
4) Irrespective of the schemes of transplantation, the ovarian grafts attain as a whole a considerable development in the body of the host, forming the egg-tubes in which grown eggs are observable. The eggs produced by the ovary which developed in the male body are yellowish in color, while these from the ovary inserted into the female host are of light fleshcolor. Some of the ovarian eggs found in the female host, which previously received testicular grafts, are orange, a colouration similar to that of the epithelial covering of the testis.
5) In every case of experiments, a tendency of structural degeneration is common in the testicular grafts; they are poor in development and show a considerable structural deformation in most cases. But, an active spermatogenesis has taken place in the testes, even if the latter received ovarian grafts.
6) Generally speaking, both gonadectomy and gonadal transplantation bring about no modification of the sex characters.
