Larvae of Hyphantria cunea and Spodoptera litura (formerly Prodenia litura) fed with artificial diets containing ¹⁵³Eu₂O₃ grew and survived at the same rate as larvae fed with normal (control) diet. Dried specimens of larvae and adults were activated by thermal neutron irradiation and examined with a multichannel pulse height analyzer. The larvae reared on Eu-diet showed clear radioactivity peakes of ^152mEu, especially at the point of SmKα X-ray (40.1 keV). Even adults of S. litura, where the last instar larvae were reared on Eu-diet, were also detectable. Under the condition of neutron flux, minimum detectable limit of Eu was about 0.02 μg per medium-sized insect. No traces of Eu was found in larvae and adults reared on control diets. It was concluded that activated Europium-151 is useful activable tracer for insect population studies.

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The effects were examined of some insect hormones on the multiplication rates of cells in cultures obtained from Antheraea eucalypti pupal ovarioles. 20-hydroxyecdysone and ponasterone A showed stimulating effects on cell multiplication at the concentration of 0.1 μg per ml. Proteinic brain hormone, and farnesol had no stimulating effect on the cell growth. At the concentration of 10.0 μg per ml, 20-hydroxyecdysone, ponasterone A and farnesol impaired the cell growth markedly if no protein was present in the culture media, but this deleterious effect was moderated in each instance by the addition of bovine plasma albumin to the culture medium. Combinations of 20-hydroxyecdysone and farnesol at various ratios caused no stimulation of the cell multiplication.

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In order to make clear the possible role of the age-related effects of parents on the ecology of the green rice leafhopper, females were allowed to deposit eggs under a constant experimental condition (25°C, 70%RH, 16 hr day-length) and the ensuing larvae from the eggs laid by the mothers of different ages were reared individually with the young seedling of rice plant as their food. Differences in the physiological characteristics were compared with each other among the progeny produced from parents of different ages. The daily oviposition rate and the hatchability and size of eggs laid, on 1st to 2nd, 6th to 7th, 11th to 12th, 13th to 14th and later than 15th days elapsed after the beginning of oviposition, increased at first, attaining their maxima on 6-7th or 11-12th days and then decreased with increasing maternal age, forming parabolic trends. Daily changes in the number of eggs laid by each female, however, showed a cyclic fluctuation at intervals of 3-4 days over her oviposition period. In each cycle, most of the eggs were laid on the first day, and the later the day in the cycle the fewer were the eggs deposited. The same cyclic trends were also detected in the daily hatchability and size of eggs laid over the whole oviposition period. It was considered, therefore, that female physiological activity gradually decreases after passing the postemergence maturatoin period so that the trend will become parabolic and that the nuequal partitioning of maternal food reserves will cause a change for the worse in the viability of the progeny produced during the last half of individual ovipositional cycles. The incubation period of eggs and most characteristics in the larval period, the size of the hatchling, survival time of unfed hatchling, length of period from oviposition to adult emergence, survival at larval stage etc monotonously changed with the aging of mothers. This gap, between the parabolic trends observed at the egg stage and the monotonous changes at the later stage, may be accounted for by the possibility of many deaths of weak progeny that result from selective elimination which could be associated with the unequal partitioning of the egg substrate, and also from the posponed manifestation of age related qualitative difference of the progeny itself. The difference of parental age gave rise to the qualitative variability of the adult progeny. Young mothers brought forth their progeny with protracted preoviposition period, low fecundity and long life-span. On the other hand remarkably persevering adults which withstood starvation longer came into being from old mothers. It is suggested that both adult progenies will assume different functions in the life of this species.

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Aminopterin at a 50 μg dosage had no effect on the fertility of the male silkworm when injected in the fifth larval instar, but fertility decreased markedly when it was injected at the period from the start of spining to the begining of the pupal stage. However, when injected at the latter half of the pupal stage the fertility increased again. Spermatogenic cells in the testes treated at the most sensitive stage exhibited no visible abnormality following the treatment and developed normally. At emergence, spermatozoa safely penetrated into the vas efferens, but the number in the ampulla ductus deferentis of the treated male was considerably reduced and either no spermatozoa or very few, if any, were found in the reproductive organs of the untreated female mated with the sterilized male.

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The quantitative composition of the oribatid mite community of three different forests in Hokkaido was discussed. The average population density (individual number per 20 cm²) of the upper 15 cm of soil over the 15 sampling occasions was 13.8±6.9 in the natural Picea forest, 4.1±2.9 in the Abies plantation and 11.7±6.7 in the natural mixed forest. The most complicated faunal composition was observed in the natural mixed forest. In most cases the population density of the 0-5 cm layer of soil was significantly greater than those in the 5-10 and 10-15 cm strata. Hypochthonius rufulus and Perlohmannia coiffaiti, however, were abundant in the deper strate rather than in the top soil layer.

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The incidence of pupal diapause in the cabbage white butterfly, Pieris rapae crucivora, fed on artificial diet was investigated under various photoperiodic conditions. The Tokyo population showed a typical long-day response curve with 50% incidence daylength of 12 hr 10 min at 20°C, while a high temperature of 25°C prevented the diapause incidence even under short photoperiods. When the 5th instar larvae which had been exposed to the short photoperiod were transferred to the long photoperiod, their diapause was prevented. In this case, the adult development was delayed in proportion to the intercal between the 4th molt and the transference to long photoperiod. One hour light-break at different times in the scotophase of short-day cycle reduced the diapause incidence. Especially, when the light-break was timed from 13 hr to 14 hr after the onset of photophase, diapause was almost prevented. Another slight reduction of diapause incidence occurred at 11-13 hr after the onset of scotophase. Larvae responded to supplementary illumination of even 1 lux for diapause inhibition. The present results correlated well with the photoperiodic conditions of the diapause incidence observed in the field late in October.

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