In the previous papers I have reported that the injury of the rice plant caused by the rice stem borer (Chiro suppressalis WALKER) was reduced when the slag was supplied in the soil. However, the slag used contained several available elements such as Ca, Fe, Mg, Al and Na in addition to Si.
In the present experiment, the silica gel prepared from Na₂SiO₃ by the treatment with HCl was used as a silica source to check the effects of the elements included in the slag on the rice plant. The results obtained were as follows, and almost agreed with the previous studies.
1. The silica content in the rice plant was increased by supplying the silica gel.
2. The mandibles of the larvae fed on the silicated rice plant remarkably diminished. It seems that the rice plant stem hardened by absorption of the silica.
3. The larvae prefered the rice plant stem cultured in the control plot to that in the soil supplied silica.
The remarkable preference was also observed for alcohol or ether extract of the rice plant stems cultured in control plot.

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In the present paper, the authors wish to discuss the effects of various temperatures on the development of the Asiatic common looper, Plusia nigrisigna WALKER. The eggs were obtained from laboratory breedings. They were reared in incubators regulated at 25°C and 30°C. Some of the materials were bred in rooms with various temperatures, i.e. about 14°C, 22°C and 28°C.
Observations were made on the developmental velocities of all the stages and on the longevities of adults. The larvae were bred under crowded (20 individuals per container) or solitary condition.
1. The developmental zero points in the crowded culture supplied with burdock leaves as diet, were 8.0°C for the eggs, 8.0∼9.6°C for the larvae and 12.4°C for the pupae, and the total effective temperatures were calculated as 66.7, 223.6 and 101.8 day degrees respectively. The effects of various temperatures upon the duration of developmental stages are given in Tables 1 and 2.
2. The males and females showed no significant difference in their developmental velocity under a moderate condition. Different from the case of Plusia gamma (LONG, 1953), no crowding effects were observed in this species (Tables 4 and 5).
3. The ordinary moulting numbers of the larvae were four, but five moultings frequently occurred. However, it seems that temperatures do not play a decisive rôle in the induction of the increase of moulting numbers (Tables 6 and 7).
4. The longevities of adults supplied with sugar solution as a diet were 17 days in an average at about 22°C and 9 days at about 28°C. Sexual difference was not observed (Table 8).
5. The development of this species belongs to multivoltine type, showing no sign of diapause at any stage. It is supposed from the law of total effective temperature that there can be five generations a year at Fuchû district in Tokyo (Table 9).

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It is well known that under epidemic condition the caterpillar of Leucania unipuncta known as a grass-feeder often feeds on a wide variety of plants owing to the shortage of its suitable food plant.
Experiments were done to analyse whether the larvae found in dense population are more tolerant to unpalatable food than the individuals in low density. The larvae which had been reared in isolation and in crowds on normal diet (i.e. maize or Bromus unioloides) were separated individually into containers at the end of their 5th instar, and were forced to feed on the leaves of unusual food plants such as Sasa albo-marginata (Gramineae), Brassica chinensis (Cruciferae), Achyranthes japonica (Amaranthaceae) or Quercus glauca (Fagaceae), except those reared on grasses. The similar experiments were repeated twice under temperatures of 20∼26°C.
All of the individuals reared on grass pupated within a week from the final moult, regardless of their previous condition of rearing density. The body weight at pupal stage was consistently heavier in low-density type (pale larvae) than in high-density type (dark larvae), but there was no significant difference in the ratios of the pupal weight to the final weight of 5th instar (P/V) between both types.
When the larvae were transferred to Sasa or Brassica, their pupation retarded for 1∼3 days and pupal weight decreased, as compared with those of grass-eating insects. In the latter case these harmful effects were more marked in pale larvae than in dark ones. Some of the larvae reared on Achyranthes failed to reach their maturity. Again, the mortality was much higher in low density type; 67 per cent of pale larvae and 27 per cent of dark ones died in one experiment, and 25 and 0 per cent respectively in another. Survived pale larvae also required longer period than the dark ones to complete the development, and the pupal weights of both types were not different from one another. The larvae fed on Quercus died out within few days and no differnce was found in the mortality curves between both types of larvae.
Mean number of faecal pellets per day decreased as increasing the unsuitability of food. The degree of such reduction was marked in high-density type while the lowering of growth ratio was small in it. This may suggest that dark larvae have better ability to utilize unpalatable food than pale ones.
Some of the numerical data in the 2nd experiment are summarized in the following table:
The results mentioned above apparently indicate that the larvae grown under crowded condition have wider range of food tolerance than the larvae in isolation. It is interesting to understand the ecological meaning of phases observed in this insect.

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Attempts were made to determine the method of forecasting the first appearance of larvae from the overwintering eggs of the Comstock mealy-bug, based on observations and investigations carried out in the laboratory as well as the field during the period 1949∼1958.
1. The laboratory tests revealed the fact that a temperature of about 9°C was the lower limit for the development of the overwintering eggs and that an accumulated effective temperature of 220 day-degrees C was required to complete the development of eggs laid in autumn.
2. The results obtained in the laboratory were checked on the field, taking into consideration the normal date of hatch, and the accumulated temperature above 9°C. It was found that there was a high correlation between the date of hatch, and the accumulated temperature during the period from March 1st to May 20th of the said ten years.
3. Furthermore, the relationship of egg hatch to the commencement and peak of bloom in the American Summer Pearmain, Jonathan and Ralls Janet were traced numerically.
Since these factors showed a high degree of correlation, there was the possibility of forecasting the first day of hatch by applying the following formulae.
a. American Summer Pearmain:
Y=5.662+1.171X
(Y: Initial date of hatch, X: Peak date of bloom)
b. Jonathan:
Y₁=7.532+1.344X₁
(Y₁: Initial date of hatch, X₁: Initial date of bloom)
Y₂=8.119+0.801X₂
(Y₂: Do, X₂: Peak date of bloom)
c. Ralls Janet:
Y₁=4.673+1.132X₁
(Y₁: Initial date of hatch, X₁: Initial date of bloom)
Y₂=5.570+0.729X₂
(Y₂: Do, X₂: Peak date of bloom)
4. The dates of hatch (Y) showed a correlation of r=-0.647 with the average maximum temperatures of late April (X). Thus an equation is given as follows:
Y=51.951-2.001X
5. The foregoing formulae for forecasting thedate of hatch, could also be utilized in the timing of insecticidal application. Insecticides, if applied, 10∼14 days after the initial date of hatch, would be effective and economical. It is also advisable to paint the branches of the trees with “tanglefoot” 2∼3 days before the date of hatch.

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Statistical analysis was made on the annual fluctuation of population density of the rice stem borer, Chilo suppressalis, from generation to generation using the records of number of moth captured by light trap at several different points in Japan. In Fig. 1, two examples of it obtained at Okayama and Siga are shown. Figs. 3 and 4 show the relation between the population density in a certain generation (n₁) and the increase (or decrease) of the density from this generation to that of the next generation (n₁-n₂). If the fluctuation of population density is governed perfectly by chance, the points in the figure representing the relation between (n₁) and (n₁-n₂) in each generation should be expected to fall on or near the diagonal line passing through abscissa at the point of mean density. As seen in these four examples on the rice stem borer, almost all of the points fall on or near the diagonal line excepting the some points representing the outbreak generation. The same is observed in the population fluctuation of a pine forest pest in Germany, Bupalus piniarius, and that of the wheat blossom midge, Sitodiplosis mosellana, in England. From this departure of the point, we can conceive that the population density at the retro-gradation stage of outbreak may increase without any restriction working in the normal year. It is further noteworthy that the point of post-outbreak generation falls on the line and thus it can be assumed that the outbreak comes to an end by the same mechanism regulating the population density in the normal year. In the normal year, the population fluctuates with certain width of departure of random source having a definite mean density of the equilibrium, being regulated by many compensating factors.

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In view of the previous experiment showing that the embryoless seeds in soybean varieties are increased with the number of the borer eggs deposited artificially (NISHIJIMA, 1954), an investigation is undertaken to ascertain whether the soybean sterility occurs or not by the feeding of the soybean pod borer, Grapholitha glycinivorella MATSUMURA, under the field conditions. The results are summarized as follows.
In the funicular part of a seed, a small feeding trace of the borer, like a pinhole, is often observed when the first instar larva entered into the pod and died before feeding the seed. In such a case, it is found that the seed becomes an “embryoless seed” which is considered here.
It is shown that the embryoless seed occurs independently of the variation in the numbers of pod, seed-room and the entrance hole of the borer found along the sutural part of the pod. The percentage of the embryoless seeds to the total number of injured seeds differs significantly with the varieties tested, showing higher percentage in a strain of “Nagaha-Daizu” than others.
The embryoless seed is mostly found in the second seed-room, while that having no symptom in the funicle is in the first one. This indicates that in the majority of cases the embryoless seeds are caused by the pinhole injury of the borer. An experiment giving an artificial pinhole in the funicle shows that the seed stops its growth if the treatment is given in young stage of the seed. Some possible factors causing the embryoless seed are discussed. It is suggested that the embryoless seed is the result of mechanical injury in the funicle.

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1. Here, the bacterial flora in the body of wireworms was studied.
2. Body surface of the worm, sterilized with alcohol and corrosive sublimate solution, was washed with sterile water for several times. The body, crushed and emulsified in a test tube containing 10cc of sterile water, was diluted to concentrations of 10^-2, 10^-3 and 10^-4, 1cc of which was taken and was cultured with beef extract agar and potato agar at 25°C. Colonies on the plate culture were examined 24∼48hr after the treatment.
3. Eight organisms (four genera) belonging to Eubacteriineae were isolated. The organisms S1, S4 and S6, were always isolated from wireworm, regardless of the collecting dates and places. S4 was isolated more in number than S6 and S1 at any time. The other organisms were found very few in the worm's body at any time, but they increased to some extent at their active (feeding) period. Therefore it seems probable that those organisms were taken into the body together with worm's food.
4. When the wireworm was bred in the sterilized breeding bottle in laboratory, S1, S4 and S6 were found while the others isolated disappeared about 10 days after breeding. S4 increased in number rapidly at the 30th day after breeding, while S1 and S6 did not increase.
5. S4 and S6, though not isolated from body fluid of wireworm, were much isolated from fat body. S4 was always more in number than S6.
6. In S4, the minimum temperature for growth was between 10°C and 15°C; this almost coincides with the average soil temperature (11∼13.5°C) at 5cm under soil surface during the period fromm the last ten days of March to the first ten days of April, when the wireworm begins to migrate near to the soil surface. It seems that the optimum temperature for growth lies between 30°C and 40°C.
7. Using the modified STAR'S medium, the response of S4 to cotton seed oil was examined.BTB turned to yellow. This shows that S4 resolved the cotton seed oil into fatty acid and glycerin. It may therefore be assumed that S4 resolves the body fat of worm.
8. S4 found in the worm killed with insecticides was greater in number than that of the normal individual.

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Previously the author reported with others on the relation of the sexual behaviour and the role of ganglia in Antheraea moths (YAMASAKI et al., 1953, 1954, 1955, 1956, 1957; NISHIMURA et al., 1958, 1959).
The present study reports upon the muscular system in appendages of the genital organ and upon the distribution of nerve fibres from the 9th ganglion in the male moth, which will contribute to the fundamental knowledge on the above-mentioned studies.
1. The muscular system consists of the muscles of tubercle, supra-anal plate, chitinous tubercle, uncate chitin, the 10th tergum, and penis at which three kinds of muscles (exo-, meso- and endo-muscle) distribute.
2. The nerve fibres from the 9th ganglion are composed of 9 pairs.
3. The distributions of the above-mentioned fibres are shown in Table 1.
4. It is observed by removing the ganglion of the pupa that the nerve (6) and (7) are originated in the 11th ganglion, the nerve (4), (5) and (9) (sympathetic nerve) in the 12th one, the nerve (1), (2), (3) and (8) (sympathetic nerve) in the 13th one.
Table 1

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Some rearing experiments were carried out to determine the stages sensitive to photoperiod inducing or completing the diapause in the green rice leafhopper, Nephotettix cincticeps UHLER. Rearings were carried out in a room of constant temperature of 20°C. 16hr illumination was given in the long day photoperiod and 8hr in the short day.
1. For the induction of diapause in all larvae subjected the short day treatment is required since the 1st larval stage. Even the long day during the 1st stage causes 60 to 70 per cent of the larvae to become non-diapause type.
2. The larvae of all stages which are reared under the short day photoperiod retain the sensitivity to the long day photoperiod, the sensitivity being shown in the acceleration of development thereafter.
3. The 4th and the 5th stage larvae which present the most clear elongation of development under the short day photoperiod react to the long day treatment in the similar way for each other, namely, the development is not accelerated in such a degree that the non-diapausing level is attained in that stage the treatment is commenced, but attains to the level provided the treatment is commenced in the preceding stage. It is difficult to determine which is the true diapausing stage the 4th or the 5th stage from the reaction to photoperiod.
The 3rd stage also reacts in the similar way but in a lesser degree.
4. The adults obtained from the various treatments mentioned above were measured in the length of the tegmen, the tibia and femur of the hind leg, and the head width. The typical summer form is obtained under the long day photoperiod throughout the development and the typical spring form under the short day. In the other treatments intermediate forms in the size and pigmentation are obtained, the longer the developmental period the more approaching to the spring form are the ensuing adults. A hyperbolic relation is found between the two variables, the length of tegmen or other body parts and the developmental period.
A ratio, length of tegmen/length of femur of the hind leg, was taken to study the relative growth of body parts. The ratio presents a similar trend with that of the length of tegmen itself with elongation of the developmental period. This fact means that the length of tegmen is most sensitive to the effect of photoperiod.
5. Elongation of the larval period due to low temperature shows no such a relation to the size of ensuing adult as in the former case due to the diapause.
6. Corpora allata are assumed as a common proximate centre of action inducing the diapause and the reduction of adult size.

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