抄録
In order to ascertain some influences of the density of parasite progeny upon the parasite itself when the host, Pieris rapae crucivora, was attacked repeatedly by Apanteles glomeratus, the present experiment was carried out and the result was as follows : 1. The development of parasites in the host bodies seemed not to be disturbed at all in spite of the increase of the times of attacks, when the real state of emergence of the parasites from hosts and their developmental period was observed. But this was due to the fact that the calculation excepted the number of parasites whose development was disturbed and remained in the host bodies. If the calculation could be made to include the number of these unemerged parasites, we could not affirm the above explanation and we must say that the remarkable influences upon the development of parasites were brought. 2. The rate of emergence of the parasites from host bodies, the rate of cocooning, and that of emergence of adult wasps decreased remarkably with the increase of the times of attacks. Perhaps it was due to the mutual disturbance of development of the parasites in the host body when the parasite density was raised and this would be due to the high mortality of the parasites after their emergence from hosts. 3. The size of adult wasps became remarkably small and their longevity was also remarkably shortened with the increase of the times of attacks . 4. The sex ratio of the emerged wasps changed abnormally when the times of attacks were increased and the number of male wasps was larger although matured females were used for attacks in the present experiment.
