天敵

It is well known that Pseudaphycus malinus Gahan is one of the most beneficial agents among the parasites of Pseudococcus comstocki Kuwana. In this paper, the author dealt with mainly the reproductive capacity of this parasites and the difference of the number of eggs laid in one individual of the host scale in connection with the degree of its development. All experiments were made at the temperature of 25℃, 1963-1965. The parasites used in the experiments were younger than 24 hours old. In the first experiment, the reproductive capacity of the parasites which were emerged from the host scales of different developmental stages was examined. Thirty individuals emerged from host scales of different developmental stages were used. Each female parasite was confined to a test tube and provided with undiluted honey as food and 10 healthy host scales for oviposition every 3 days. After 72 hours exposure to the parasites the host scales were dissected to examine the number of eggs laid in one individual of the host scale. Although there was a slight difference in the number of parasites in one host scale with the degree of development of the host scale, the number of eggs laid by this parasite was about 100 and varied scarcely with the developmental stages of the host scales which their parents had attacked. The number of parasite eggs was seemed to be related to the longevity of the parasite rather than the body size of the parasite. In the second experiment, each 5 individuals of both 1st and 2nd instar nymphs were exposed to one parasite in a test tube. In this case, the number of eggs laid in one host scale was more abundant in the 2nd instar nymphs than in the 1st instar nymphs. Various combination of other instars of host scale showed that the larger the host scales the more the number of eggs laid in one individual of the host scale. In another word the maximum number of eggs of the parasite was found in the female adult scale. The third experiment was m ade for the purpose of examining the number of eggs laid in one individual of the host scale and the number of the adult parasites emerged from one host scale in connection with the degree of development of host scales by using a larger glass cylinder containing one pumpkin harboring 450 individuals of 2nd and 3rd nymphal and female adult host scales. The number of female parasite liberated into each cylinder was 150. In the case of the 1st instar host nymphs, 80 female parasites were liberated against 250 individuals of host scales. The result of this experiment was almost the same as that of the second experiment. For example, the average number of eggs laid in the 1st, 2nd, 3rd instar nymphs and the female adults was 1.3, 1.9, 12.5 and 16.7 respectively. Further, the experiment showed that most of eggs deposited by the parasites were not failed to develop to the adult wasps. The maximum number of parasites emerged from one host scale was 27 and the minimum was 1.