The seasonal changes in density of a Lycosa T-insignita population in an area of Tokyo showed two peaks, one appeared in spring and the other in autumn. The spring peak consisted mainly of the overwintered last instar nymphs and the adults which had emerged from these nymphs. The autumn peak also consisted of the nymphs larger than 1.0 mm in carapace width and the last instar nymphs which should overwinter. It was considered that this spider generally repeatd two genrations annually, since the adult emergence showed two peaks which appeared in spring and summer. According to the incubtion experiment started in a different period from Novermber of 1967 to March of 1968, it could be said that the overwintering last instar nymphs were inhibited in therir development into the adult stage during late autumn and winter, suggesting that they were in a state of diapause. The degree of this inhibition of their development appeared most strongly in the period from November to December. The development during this period seemed to be partly advanced when food was provided during the incubation period. The disappearance of the inhibition of development began to occur in January and thereafter accelerated as the season progressed. The intensity of resistance against hunger among overwintering individuals changed parallel to the change in the degree of inhibition of the development into adult.

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The eggs of the adzuki-bean weevil, Callosobruchus chinensis L., were irradiated with different dosages ranging from 100 to 102, 400 rad with ⁶⁰Co. The eggs used were from 2 hr to 6 days old. The data revealed that the radiosensitivity was not necessarily in direct proportion to the age of the eggs. The 8 hr-old eggs were the most radiosensitive and the 5 day-old eggs were the most resistant to the radiation. In all the test series of younger eggs less than 2 days old, no egg was hatched when it was irradiated with dosages of more than 1, 600 rad. In those series of tests with older eggs more than 3 days old, radiosensitivity decreased, and 5 and 6 day-old eggs showed fairly good percentages of hatchability even when they were irradiated with a dosage of 25, 600 rad. The emergence of adults from these irradiated eggs was found to be checked when they were irradiated with a dosage of 3, 200 rad. Some adults emerging from 3 to 6 day-old eggs which were irradiated with a dosage of 1, 600 rad, were found to be sterile.

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Two new species of the genus Eotetranychus from Japan were described and illustrated : E. boreus from apricot, Japanese apricot and plum in Hokkaido and apricot in the Tohoku district; and E. geniculatus from grape and strawberry in the Tohoku district. Notes on some taxonomic characters of E. asiaticus EHARA were also given.

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In search of the attractant in rice grains for rice weevils, an olfactometer was devised. That was a modified CHAMBERLAIN'S cage type olfactometer and suitable for bioassay for the attractancy of rice grains and the extract of fractions from the rice grains. The bioassay was conducted at 25-30°C under darkness and 14-16% relative humidity, with 50 rice weevils that had been starved and cut water supply for 2 days prior to the test. This method gave good results for detecting the presence of attractive material in the sample.

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The separation of the attractive component for rice weevils from rice grains was attempted by various procedures. The ether extract of the polished rice grains gave attractancy. Results of fractionation and of reaction with chemical reagents indicated that main attracrtive compoent was an acidic substance, which is probably of carboxylic nature, with considerable partition to water.

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The adult eclosion of Hyphantria cunea of the summer generation under the field condition was concentrated for about 1 hr after dusk. Experiments analysing the timing mechanism of this event revealed that the eclosion was inhibited by the light and promoted by the change from light to dark. By experiments artificially shifting the dusk, the pupae kept under a field light condition were found to be ready to emerge by 14 : 00. Further experiments indicated that the time of eclosion was not determined by the absolute length of the light period prior to the dusk, but was dependent on the light and dark cycles repeated during the pupal stage. The latter entrains the endogenous circadian periodicity, which was clearly demonstrated under the continuous darkness, and when eclosion was fully prepared, the light-off stimulus acted as the direct inducer. Difference of the time of eclosion in the field between the overwintered and the summer generations was discussed in relation to the temperature drop in the afternoon.

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