Virgin females of Anicetus ceroplastis Ishii oviposit as readily as copulated ones, but their progeny are males (arrhenotokous parthenogenesis). In a large number of individuals reared from copulated females the numbers of both sexes were equal. This parasite seems unable to detect already parasitized scales. Therefore, superparasitism occurs with this species. If host scales, Ceroplastes rubens Maskell, are insufficient in number, such as in a small glass vial, superparasitism may occur quite commonly. In any case only one parasite larva survives. Average number of eggs deposited per female per day was about 5. Comparative records of the daily egg production of five female parasites are presented in Tables 1 and 2. So far as has been considered in the present study, one female parasite may deposit, at least, 400 eggs under favourable field conditions. According fo Kuwana (1923), Mizusawa and Fujita (1936) and Kono (1951), the average number of eggs deposited by one female Ceroplastes rubens was 500 or 700. But not a single investigation on the natural mortality of this scale has ever been performed in Japan. Studies made in 1951 indicated the following facts. About 20 per cent of crawlers of this scale failed to become established. About 50 per cent of scales died during the settled stage of the first instar and during the early part of the second instar from causes other than parasites and predators, even though conditions were apparently favourable for development. Further about 30 per cent of the remaining scales died during autumn and winter, probably also during spring, and failed to produce eggs. Thus it is estimated that out of 500 or 700 eggs deposited by a single scale individual only 140 or 196 scales may reach maturity in spite of such natural mortality as environmental resistance, host resistance and factors other than parasites and predators. The time factor in controlling Ceroplastes rubens by Anicetus ce roplastis was calculated by applying the equation developed by Thompson (1951). The power of reproduction of this parasite has close relation to the power of survival. Normal activity of this parasite was found below 25℃. Under favourable temperature conditions the adult parasite, irrespective of its sex, can be kept alive for several months even in a small glass vial with honey as food. Temperature higher than 25℃ may act as fatal to the parasite. The power of survival of this parasite is partly responsible to its ability to find food. In this connection this parasite is very easy to find food, because food of the parasite is honey dew secreted by its host-scales and Aphides. As indicated by Flanders (1947) the power of survival of the parasite is further dependent upon its ability to avoid detrimental environmental conditions such as excessive moisture and dryness or natural enemies. In case a heavy rainstorm comes or insecticides are sprayed in the commercial orchard, this parasite comes to rest on the underside of leaves or other places where it will be protected easily. Fortunately enough this parasite has not a single species of secondary parasite. The female of this parasite has the power of oosorption. In liberations of the first brood of this parasite it is, therefore, unnecessary to induce the earlier emergence of adult parasites by exposing their pupae to higher temperature or much more delayed emergence by placing pupae at a cooler condition.