A root-boring insect, Cheilosia yesonica MATSUMURA, has recently caused serious damage to the Japanese butter-bur, Petasites japonicus MIQ. Observations on the bionomics of Cheilosia yesonica in butter-bur planted fields were carried out in 1969 to 1971. The newly hatched larvae bored into the lower portions of the butter-bur stalk in autumn and burrowed their way into the root. They passed the winter as young larvae without any hibernation although development was slower during the winter. They fed sufficiently on root material from spring to early summer and reached maturity in the tunnels in summer. Pupation took place in the larval tunnels. The time of maximum abundance of adults in naturally infested field was from late-August to September. The adults laid their eggs near the base of the stalks. The larvae hatched after about two weeks. The development of Cheilosia yesonica was completed in one year. In forced field cultures of the butter-bur plant for the winter to early spring production, the adults emerged in spring. This phenomenon may be attributed to influences of soil-temperature conditions subsequent to the use of polyetylene film facilities for forced culture.

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The mating behavior of Lithocolletis ringoniella MATSUMURA was observed in the laboratory in 1969 and 1970. Under natural light conditions the 1st generation (June 14) mated from 4:18 a.m. (after the sunrise) until 6:02 a.m., and the 3rd generation (August 24) mated from 4:41 a.m. (before the sunrise) until 5:47 a.m. Male moths were positively attracted to virgin females which took the calling position suggesting the secretion of a sex pheromone by females. Under artificial light conditions adult moths which were kept in the dark 8 hours or more mated normally when exposed to light intensity of 1lux or more. However, moths exposed to dark periods of 4 hours could not be mated. It was also suggested that the gradual increase of light intensity may be an important factor for the mating of this species. Such a combination of dark and light conditions was more important for the mating of females than males.

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The damage to crucifers inflicted by the diamond-back moth, Plutella xylostella (L.) varies both in season and locality in Japan. In Kanagawa Prefecture, a conspicuous tendency was recognized i.e., the damage in summer is moderate whereas it becomes serious to a large extent in winter. This work was conducted as a part of studies which were carried out to clarify the reason why the above mentioned phenomenon is caused, and the following facts were determined: (1) As a result of a succesive four year observation the monthly number of adult moth, caught in light traps, reached its peak in May and June and fell in August. Furthermore, there was a marked tendency for the forewings of adult moths to be minimal in length for both sexes, in August but the length appeared increased before and after this month. (2) Pupae were collected seasonally from grown cabbage leaves and the adult moths that emerged were kept as 25°C under 12- and 16-hr. photoperiods, respectively, to investigate longevity and fecundity. The summer female moths (emerged from pupae collected in August) were short-lived and laid less eggs, whereas the winter moths (emerged from pupae collected in December and January) were long-lived and laid more eggs. Both spring moths and autumn moths had an intermediate character. It was concluded that the fecundity of adult moths was not merely associated with longevity, but was determined by pupal sige and this was affected by the temperature during immature stages. It was also observed that the difference in daylength in the adult stage had no influence on the above mentioned characteristics of the adult.

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This study was carried out to clarify the primary hosts of Marietta carnesi and its host relationship. In Fukuoka and Miyazaki, Aonidiella taxus was parasitized by Comperiella bifasciata, Aspidiotiphagus citrinus, Aphytis sp. A and two species of Prospaltella, whereas, Chrysomphalus bifasciculatus by C. bifasciata and Aphytis sp. B. All of these primary parasites were attacked by the hyperparasite, M. carnesi. This hyperparasite was determined to be a “direct secondary parasite” as defined by FLANDERS (1963). However, it deposits its eggs in a different manner between generations. From spring to autumn, the eggs are laid on or near pupae of primary parasites, whereas the overwintering eggs are deposited on the living adult scales containing young larvae of primary parasites, and never on scales which had not been parasitized by any primary parasite. This seems to be an evolutionary adaptation for hibernation of this hyperparasite. Two types cf intraspecific competition, i.e. phenomena of superparasitism and autoparasitism, were observed. Auto-parasitism seems to play an important role for density regulation and maintenance of its population, when abundance of the hyperparasite overwhelmed the primary parasite.

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The smaller tea tortrix larvae, Adoxophyes fasciata, are susceptible to a granulosis virus which is pathogenic to the fat body. Electron micrographs revealed the sequence of virogenesis and encapsulation in fat cells of infected larvae. The size of the virus rod was approximately 305nm in length and 70nm in width, while the ellipsoidal capsule had a size of 500-540nm in length and 250-280nm in width. Abnormally shaped capsules were occasionally found among normal capsules and infected cells containing only abnormal capsules were also found. Few infected cells, packed with a great number of immature virus rods and no capsules were detected in a late stage of infection, suggesting that defects in synthesis of virus and capsule proteins had occurred in the host cells.

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Aspidiotiphagus citrinus CRAW is a dominant parasite of Unaspis yanonensis (KUWANA) in Japan. In this paper the author reports on the studies related to the effect of age in days, after the emergence of the parasite, upon the number of mature ovarian eggs and the number of eggs laid. All experiments were carried out at the temperature of 25°C. A. citrinus is a pro-ovigenic species. The mature ovarian eggs per female numbered approximately 32 at the day of emergence. The newly emerged parasites were reared with the supply of honey and were dissected every day to count the number of mature ovarian eggs. The egg number exhibited a peak on the second day after emergence. Thereafter the eggs were absorbed. Daily rate of oviposition was examined by counting the number of eggs laid in about 20 host scales, second stage larvae of Aonidiella taxus LEONARDI, exposed to a single parasite every day. The newly emerged parasite laid 68 eggs until the parasite died. But the number of eggs laid by [the parasite from 4 and 8 days] old after emergence was 14 and 3, respectively. Thus the oviposition of the parasite is greatly influenced by its age.

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Preliminary life tables of the tobacco cutworm, Spodoptera litura, were developed in taro fields in 1970 and 1971 in Ino, Kochi. Three kinds of plots were prepared to evaluate the role of natural enemies: (1) caging of host plants by nylon gauze to exclude all natural enemies; (2) enclosure by a plastic plate (30cm in height) which was coated by tangle-foot to prevent the invasion of the plot by natural enemies of ground fauna, and (3) the untreated plot. All the natural enemies in plot 1 and that of the ground fauna alone in plot 2 were eliminated one month before the experiment with insecticides (BHC and Mesomil) as well as by hand-picking. Six species of parasites and 13 species of predators were recorded, and they were responsible for 68-89 per cent loss of the caterpillars. Ground-living invertebrate predators attacked middle-stage caterpillars, whereas natural enemies of air-borne type did so at the early or late stages of the host. The survivorship curve was concave in early summer when the micryphantid was abundant. This spider greately affected the survival of hatchlings by disturbing the larval aggregation of the 1st instar. In midsummer when the density of micryphantids was low, the survivorship curve became diagonal. Nevertheless, predation of mature larvae by Polistes wasps became important and the survivorship curves in the plots from which natural enemies were excluded were convex throughout the seasons. The survival rate of the 1st instar larvae decreased linearly with increasing density of micryphantids. That of the 2nd instar larvae was lower in the rainy season than in the summer season and vice versa for the 4th and 5th instar larvae. These phenomena can be caused by seasonal variations in the activity of major natural enemies, i.e. ground-living invertebrate predators in the 2nd instar and the Polistes wasps in 4th and 5th instars.

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