The pattern of spatial distribution of the larvae of the rice stem borer, Chilo suppressalis WALKER was analysed statistically by using the data on the population censuses in the paddy-field of the Takawashi farm, the southern region in Osaka prefecture.
The fitness of the observed data to the theoretical distribution expected from the POISSON'S series was examined. The frequency distribution of number of larvae per hill of rice plant did not agree with the POLSSON'S series throughout the infant larval period, the young larval period and the full-grown larval period. The co-efficient of dispersion (s²/x……x: mean number of larvae on a hill of rice plant, s²: variance of it) changes in value remarkably with the growth of larvae. Namely, they changed 37.98, 10.89, 2.67 from the infant to the full-grown larval period.
By these facts, the following conclusion can bededuced that the distribution of this larva is not random in each growth period. Namely, each plant in the field shows differential attractiveness to the larvae. It is considered that the cause of such a difference among the plants is due to the complex, both the tendency of the insect itself and the heterogeneity of the environmental conditions.

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Studies were made in an attempt to find whether there are cytohistological changes in the leafhoppers when they are infected with the virus of the yellow dwarf disease of the rice plant. The results obtained may be summarized as follows:
The adipose cells of the affected insect assume a characteristic symptom that distinguishes them from those of healthy individuals. After about 10-15 days of infection the nuclei of the fatty cells become larger in size and somewhat irregular in form. After about 20 days the enlarged nuclei shrink and increase irregularity in form with the simultaneous occurrence of vacuoles of varying sizes in the cytoplasm. Finally after about 25 days whence the virulence of the virus begins to come into play for the plant, the shrinkage of the nuclei as well as of the cells attains the maximum, and the vacuoles increase so enormously in number that the whole cells appear completely reticulation.
Cytochemical changes also occur in the same tissue of the viruliferous animales. The FEULGEN reaction as well as the methyl green staining tends to become stronger in intensity at the beginning of the infection, showing presumably the increase of the content of DNA, and the cytoplasm stains heavily with pyronine, suggesting that the increase of RNA content takes place. Then both reaction and staining become less intense, and finally at the highest vacuolar stage of the cytoplasm, they show only the weakest intense.
The above mentioned results were obtained withthe exception of a few individuals. Ten adult insects were examined to one batch. The exceptional figure was observed in only 10-20 per cent of the insects.

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The larvae of the rice stem borer, Chilo suppressalis, hatched from an egg mass show clumped distribution in a paddy field. The degree of clumping is determined by the size of the larvai colony hatched from an egg mass. The authors studied the characteristics of the larval colony in a paddy field of the university farm at Takatuki (2nd generation) and the farm of our laboratory (1st generation) from 1960 to 1961.
2nd generation
For the duration of 10 days after hatching, most of the hatched larvae form a colony in the stalk on which an egg mass was set. As the mortality of the hatched larvae in the small larval colony was high and vice versa, there was a positive correlation between the size of larval colony and the percentage of the survival of larvae before larval dispersion.
The larvae began to disperse actively about 15 days after hatching. The rate of dispersion and mortality in the large larval colony was higher than that in the small one. Therefore, the correlation mentioned above disappered gradually with the days after larval dispersion.
1st generation
The rice plant at this period was not enough to support the larval growth. At the young larvalstages, in 3 and 8 days after hatching, the mortality of the hatched larvae was very high in any size of the larval colony. So, there seemed to be no correlation between the size of larval colony and the percentage of the survival of larvae.

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The tea red spider mite, Tetranychus kanzawai KISHIDA, is one of the serious pests of tea plant in Japan. So far as field observations are concerned there are susceptible and resistant varieties of tea plant to the infestation of the tea red spider mite. Some examinations were carried out to make clear this resistant nature, and the results obtained are summarized as follows.
The differences in the mite infestation among the 12 varieties tested are statistically significant. Such varieties as Asatuyu, Benihomare, Tamamidori, U-4 and Y-1 are susceptible to the mite infestation, while Y-3, Y-5 and Z-1 are resistant.
There are number of susceptible varieties in the seedlings selected from domestic variety, but selffertilized new varieties from registered good variety are not susceptible to the mite infestation.
It is not evident whether the varietal differences are due to host-selection of mite or antibiosis of host-plant.

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Many species of tarsonemid mites, family Tarsonemidae, are recognized as a pest of plants. We have found many species of the mite living on wild plants or crops. In the present paper, the author described three new species of tarsonemid mites which belong to the genus Tarsonemus.
1. Tarsonemus yoshidai n. sp.
Only males of this species are found. The species are easily distinguished from the other species of the genus Tarsonemus by the presence of a broad inner spur-like projection of femur IV.
Holotype: Specimen was collected on a leaf of Vitis vinifera LINNÉ, captured by Mr. Kazuo YOSHIDA at Higashi-Matsuyama City, Saitama Prefecture on 18th October 1961.
Paratype: One male, same data as holotype.
2. Tarsonemus sasai n. sp.
Only a male of this species is found. Male of thespecies is easily distinguished by the presence of inner flange-like expansion of femur IV, one long drsal seta of tibia IV, claw IV reducing to a knobstike.
Holotype: Specimen was collected on a leaf of Vitis vinifera LINNÉ, captured by Mr. Kazuo YOSHIDA, at Higashi-Matsuyama City, Saitama Prefecture on 18th October, 1961.
3. Tarsonemus misakai n. sp.
Only a male of this species is found. The species is distinguished by the following features: Tarsus I and II are elongated, each of the segment with a elongated dorsal annulated seta. Ventral setae of femur IV stout. Dorsal seta of tibia IV longer than the segment. A ventral seta of tarsus IV long.
Holotype: Specimen was collected on a leaf of Diospyros Kaki THUNBERG, captured by Mr. Kazuo YOSHIDA, at Fukaya City, Saitama Prefecture on 28th September, 1961.

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1. In the spermatogenesis of the rice stem borer, it can be most easily judged from the changes in the external form of cyst without staining whether the meiosis has finished in male sex-cells.
2. It is also confirmed in this paper that the gonads of the larva remain in a definite size till a certain time of the hibernating period and grow in size coinciding with the inner histological development even after, as already shown by the previous workers. That is, even the most developed sex-cells in the male larva in diapause remain in the stage just before the meiosis takes place during a considerable period. These facts are not, however, recognized in the male larva in non-diapause. On the other hand, on the female larva in diapause, it is impossible to distinguish between oocyte and nurse cell.
3. The change in size of the corpus cardiarum and corpus allatum complex in the hibernating male larva synchronizes approximately simultaneously with that in the female.
4. The gonads of the hibernating larvae begin to develop, as the corpus cardiacum and corpus allatum complex begins to decrease in size.
5. Judging from the results obtained in these experiments and the fact that the reduction of the activity in the corpus allatum; the decrease in size of the complex, connects closely with the diapause break, the diapause break may be determined easily by observing. the gonads; size of the testis or external form of cyst in the male larva and external form of the ovaries in the female. However, the termination of diapause can be decided most easily by judging from the changes in the external form of cyst whether the meiosis has finished, or not.
6. The total effective temperatures during the post-diapause period are 273 day degrees in the male larva and 286 day degrees in the female on the average, respectively.

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The causes of recent increase of the population of the southern green stink bug, Nezara viridula, were analyzed by the construction of life tables of three consecutive generations in 1961.
236 plants of potato, 1, 250 plants of early planting rice, and two plots of late planting rice, each contained 500 plants, the one as the untreated and the other as the spider-erradicated where spiders were erradicated by hands every other day, were used for investigations in the first, the second and the third generations, respectively. Census was made twice a week for the first (7th May to 17th July) and the second generations (5th July to 16th Aug.), and every other day for the third generation (5th Sept, to 29th Oct.).
Actual numbers were used for each stage of the first generation and for egg, the first instar and the second instar of other consecutive twogenerations. Corrected value of the population of each stage less the third instar was obtained by the following formula: A⋅P/I=N…(1), where A=total counts of incidence of each instar, P=the mean interval of surveys for the period of incidence of the instar concerned, and I=the mean developmental duration of the instar. Duration of each stage was assessed at 30°C on pods of the common haricot for the second generation and directly in the census paddy-field for the third generation. Total durations from egg to adult are 40.1, 34.7 and 42.5 days at 25°, 30°C and under natural conditions of the third generation, respectively. Period of egg laying was two to three weeks. Mean densities of egg masses per plant were 0.10, 0.10 and 0.07 and the mean number of eggs per mass 74.1, 82.5 and 97.9 for each successive generation.
Survivorship curves for the period egg to adult emergence exhibit moderately concave curves, somewhat between the curves of Type II and III in Deevey's sense. Mortality curves for the generations of the first and the second have a peak in the period of early stages, two peaks can be expected for the third generation which should have another peak of mortality in adult stage before egg laying caused by overwintering death. The 100qx of the first generation from egg to the second instar decreases, and increases as the stage advances, on the contrary, in the generations of the second and the third. These differences among generations are largely due to the high percentage of parasitism among eggs of the first generation.
Principal mortality factors in egg stage are egg-parasites, physiological death and climatic factors. Asolcus mitsukurii is the commonest species throughout seasons, but Telenomus nakagawai rarely appears in the third generation. Other species, namely T. gifuensis and a Eulophid species almost confined their activities to the second generation. Total percentage parasitism was 74, 26 and 22 per cent. for three consecutive generations. A clear relationship was observed for A. mitsukurii that eggs laid in the later period of egg laying are attacked more intensively than those in the early period. But this relationship does not hold for T. nakagawai.
For larvae of young stages predation by spiders or destruction by weather factors usually resulted in the disappearance of larval colony as a whole due to the gregarious habit of young larvae. Studies for 95 egg-masses of both the first and the third generations, and calculation of the disappearance rate for the second generation revealed that the larvae of the second instar are most vulnerable to the predation of spiders. The rôle of spiders in the third generation estimated as percentage reduction of larval loss which are attributable to erradication of spiders was at least 2.30% in terms of the number of larvae that hatched.
Weather as direct death factor seems to be immaterial to egg and mature larvae under usual conditions.

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During the course of the feeding tests of the vegetable weevil, Listroderes costirostris obliquus KLUG, on various plants, in relation to the host selection studies, it was indicated that the adults could hardly eat leaves of sweet clover, Melilotus alba and M. officinalis. Some investigations were made to elucidate the factors participating in this uneatability of sweet clover for the adults. The results obtained are as follows:
1. Adults were olf actorily attracted by the odor of sweet clover leaf and its juice, and furthermore they could perform the antennal tapping, mouth-touching, and biting which are the preceding steps of the continuous feeding. However, they could hardly perform the continuous feeding on them. Especially in the case of juice, the biting action was impeded promptly.
2. On the juice of Santohakusai leaves added with the juice of sweet clover leaves, the continuous feeding did not proceed so successfully as on the juice of Santohakusai leaves in control.
3. It was suggested from these results that sweet clover leaf contains not only some attracting odorous substances, but also some feeding inhibitory substances.
4. Coumarin, an principal odorous constituent of sweet clover was tested and it was foundto be effective as an attractant. But, adults could not proceed into the later attacking steps, the antennal tapping, mouth-touching, biting, and continuous feeding.
5. A diet containing coumarin and Santohakusai leaf juice was tested. Adults were attracted by it, and could proceed at least to the biting step and somewhat to the continuous feeding step. But the biting and the continuous feeding were impeded in the presence of coumarin (0.10∼0.017%) likewise in the attacking case to sweet clover leaf or its juice.
6. It is not difficult, from these facts, to accept the conclusion that coumarin is a chemical factor pertaining in the uneatability of sweet clover for adults of this insect.
7. The dual effect of coumarin, attraction and feeding inhibition makes a contrast with the effects of leaf alcohol, mustard oils, and umbelliferous essential oils which elicit the biting action together with the attraction.
8. It would seem that the first receptors of inhibition by some substances including coumarin are there on the maxillary palpi.

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The effect of formulation on the toxicity of DDT to the adzuki-bean weevil, Callosobruchus chinensis, L. and the flesh fly, Sarcophaga peregrina ROBINEAU-DESVOIDY wasstudied. Three proprietary wettable powder formulations, three proprietary emulsifiable concentrates and a laboratory prepared DDT-acetone emulsifiable concentrate were included in this study. Suspensions or emulsions of these formulations in water were applied by means of a settling-mist tower either directly on the adult flies and weevils, to measure contact toxicity, or on lacquered paper discs which when placed in a cage with the adult insects measured the residual toxicity. The median-lethal concentrations of the formulations based on their p, p'-DDT content were calculated. The use of the emulsifiable concentrates resulted in greater contact toxicity than did the wettable powders. However, residues of the wettable powders were more toxic than all of the emulsifiable concentrates except a paste formulation which was equally toxic to the adzuki-bean weevil.
A study was also conducted on the effect of various solvents on the contact and residual toxicity of p, p'-DDT to the adzuki-bean weevil. When applied directly to the weevil without DDT, kerosene, α-methylnaphthalene, and cyclohexanone caused 100 per cent mortality Xylene solutions of DDT were as effective contact poisons as the water emulsions, but an acetone solution was less effective than the DDT-acetone-water emulsion. None of the solutions produced appreciably toxic residues.

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