The control of black fly larvae in the natural streams was carried out from Feb. 1956 to Nov. 1957 in Yase district near Kyoto-city. The breeding species and its rate in these streams were as follows: Simulium (Gnus) nacojapi 55.9%, S. (Odagmia) bidentatum 35.8%, S. (O.) aokii 2.8% S. (Simulium) venustum 3.1%, S. (S.) tuberosum 0.6%, S. (Eusimulium) uchidai 0.8%, S. (E.) sp. 1.0% respectively. According to the results of biting collections in this district, the dominant species of black flies which bite men and domestic animals was S. (G.) nacojapi (95.6%).
We strewed the 1ppm concentration of lindane emulsions for a period of 5 minutes on all breeding streams in this district once a month from Feb. to Nov.
Owing to the observation of 24 hours after the treatment. 95∼96% of Simulium larvae were driven away for a distance of 500∼800 meters. After these treatments for a year, the decrease rate of adults which bite men was 36.2% as compared with an untreated year.
The effects of 1ppm concentration of lindane emulsions were not noticeable upon the trout, Plecoglossus altivelis, that are of considerable economic important in this district.
On the other hand we observed that a great deal of fresh water arthropods, especially larvae of may flies, caddis-flies and stone flies, were destroyed when such insecticide was stewed in the streams. It seems that these treatments cause important effects on depleting the food chains of fish in these streams.

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Although they say the_recent outbreak of mite following by the use of new acaricides are generally attributed to the destruction of their natural enemies by those materials, little definite evidence has yet been presented to verify this supposition. Since the mite problem is quite serious in Hokkaido and since many unusual fluctuations in population of the pest had been observed, a field test was carried out in 1956 in the orchard of Hokkaido Agri ultural Experiment Station to ascertain the relationship between the reduction of their natural enemies and the increased number of European red mite.
For mite and predator experiment, five apple trees (of the same variety) were selected and each one of those sprayed with machine Oil, DDT, BHC and parathion respectively. Number of mite, egg, predator was counted under hand magnifier on 10 leaves per tree and population-data were based on the investigations which were made twice a week at intervals of three days.
The results of the test are shown in Figures 1, 2 and Table 1.
In the middle of July there was a heavy mite population in DDT plot and this continued until the middle of August. Then the leaves of the tree discoloured, because of severe mite injury and then there was a rapid fall in number of mite and egg. In September and October, an extremely small number of winter eggs were found on twigs of the tree.
Non-sprayed plot showed significantly lower population than DDT plot throughout summer, but it was observed that there were mites enough to cause foliage injury. In autumn a small number of winter egg was found in this plot.
On the contrary, in three plots where machine oil, BHC and parathion were used respectively, the population of mite and egg remained low from the beginning of July to the beginning of August and no visual discoloration of foliage was observed. But rapid increase in number of mites started in the middle of August in each and all of those three plots received heavy winter egg infestation.
Mite predators were very scarce in all plots until August, but in autumn Scymnus and others were counted in DDT and non-sprayed plots. It seems that this increase in number of predator came too late to have any appreciable effect on the summer mite population.
According to our observation, it is evident that the increase in number of mite in BHC, parathion and machine oil plots in autumn is mainly due to the fact that good condition of foliage was favorable for the mite, not from the decrease of their natural enemies caused by the application of those acaricides. The factors which are responsible for the great summer, increase of egg and mite in DDT plot are unknown.

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In the previous reports, the authors have studied the stabilization of organophosphorus insecticides and have reported that the surface acidity ofmineral carriers effects the stability of methyl parathion dust formulation with stabilizers, such as polyoxyethylene alkyl ether (PAE), polyoxyethylene dialkyl ether etc. The crop field tests and laboratory experiments were made in order to observe the effect of stabilizers on the insecticidal activity in methy parathion dust formulations. In the laboratory experiment, Callosobruchus chinensis LINNÉ and Allantus luctifer SMITH were used as test insects. In the crop field test, the first and second broods of the rice stem borer, Chilo suppressalis WALKER were used as test insects. Methyl parathion dust formulations with clay, clay plus talc (1:1), clay plus talc (3:1) and stabilizers were used as test insecticides (Tables 1, 2). Stabilizers used were PAE, alkyl naphthalene sulfonic acid salt (ANS), #0 fatty acid, and cuttlefish oil.
The results of biological assay were shown in Tables 2, 4, 7 and 8, and these values, when transfered into probit unite and plotted against the time on logarithmic scale, revealed linear regressions in the condition under which the experiment was carried out (Tables 3, 5, 6). In the case of methyl parathion dust formulations with stabilizer, the effect on the insecticidal activity depends upon the sort of mineral carriers and stabilizers. When clay only was used as a diluent, PAE 0.5% as a stabilizer increased rather than obstructed the insecticidal activity of methyl parathion dust formulations.
When clay plus talc (1:1) was used as a diluent, cuttle fish oil as a stabilizer obstructed the insecticidal activity and it was inferior to methyl parathion dust formulation without stabilizer. ANS had no connection with any sort of mineral carrier and rarely obstructed the insecticidal activity. Methyl parathion dust formulations with clay plus talc (3:1) were scarcely influenced by stabilizers and the result obtained by Bliss probit method is insignificant.
But perhaps, the influence of talc brings about the tendency that dust formulations with PAE are slightly inferior to that with #0 fatty acid on ANS in the insecticidal activity.
When talc is used as a diluent, stabilizing effect by compounds of PAE series is not remarkable, as the authors have explained in the previous reports. Though we could not ascertain the relationship between the quantity of stabilizer and insecticidal activity in this test, the result obtained by the crop field test shows, evidently that the insecticidal activity of dust formulations with 0.5% stabilizer is superior to that of dust formulations with 2.0% stabilizer and a proper quantity of stabilizer is approximately 0.5-0.7%.
Consequently, in the search of a stabilizer for methyl parathion dust formulation use, we should carry out the biological assay in company with the chemical test of stability, sufficiently to determine the proper quantity of stabilizer, stabilizing effect, and the degree of obstructive action.

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In the present paper, the data on the frequency distribution of infested stems per rice hill caused by the rice stem borer, Chilo suppressalis, were used. These data were collected from 41 different rice fields in Western Japan over several years. From these data the relation between the mean number of infested stems per rice hill and the proportion of infested units is obtained as shown in Fig. 1, abscissa showing density of infested stems (λ) and ordinate percentages of infested units (P). This relation opens the way to estimate λ by P.
If the frequency distribution of infested stems per unit is fully random, the proportion of infested units (P) is to be expected as follow,
P=1-e^-λ,
where λ is the mean number of infested stems per unit. In practice, P is usually shown somewhat underestimated, because of the departure from random distribution. The “negative binomial” often gives a good fit to the actual distribution of infested stems per unit. Thus, the above equation will be changed as follow,
P=1-e^-aλb,
where a and b are constant. Putting m=aλ^b, P can be transformed in to m, by using Table 1. Fitness of this equation can be examined by a lineality between logλ and logm. The empirical data well agree with this equation. (Fig. 2) By estimating the paramaters, a and b, the following formula was obtained.
P=1-e^{-0.487λ0.937}
Table 1 gives calculated values of λ to different percentages of P.
This method is intended to save work, because it is far easier to count the number of infested hills than to count infested stems per hill. Some factors affecting this method are discussed.

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1. It has been known that the soy-bean pod borer lives on Glycine ussuriensis (Leguminosae) in Manchuria and Sophora flavescens (Leguminosae) in Honshu as the wild host-plants, and there has been no record of a wild host-plant in Hokkaido.
2. In 1956 the authors discovered that this insect lives on the arrowroot (Pueraria lobata) in Hokkaido.
3. Arrowroot attacked by this insect grows in the mountainous land isolated from the crop-field.
4. By the field and insectary experiments, it was confirmed that the insects from the arrowroot can attack soy-bean.
5. Judging from these facts, it can be said that the arrowroot is a wild host-plant of this insect and there is a possibility of other wild host-plants belonging Leguminosae in which the pod formation periods coincide with the period of adult emergence.

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The spiders of the citrus orchard has received little attention by any entomologist, though they are important for the Arthropod community of the orchard because of their predatory activities. This paper presents a list of 53 species collected in a citrus orchard near Fukuoka from 1955 to 1956. Among them 35 are webbing species, 18 beingnon-webbing ones. This orchard has not been subjected to pest control since 1945, but has been well managed.
All the specimens recorded in this list are preserved in the Entomological Laboratory, Faculty of Agriculture, Kyushu University.

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Considerable interest has developed in recent years as to the effects of nutritional changes in host plants agains insect infestation. Some workers reported that fertilizers influence the development of insects which are feeding on plants. In the rice stem borer, Chilo suppressalis WALKER, it has been observed that the greatest damage in the rice plant caused by the borer larva is frequently due to the increase of nitrogenous fertilizers applied to the crop. The more general use of nitrogenous fertilizers in the recent years may be an important factor in the serious damage of the rice plant caused by the larva. But there is seldom any experimental evidence to support such conclusions. Furthermore there is no information on the mode of the effect of the fertilizers on the insect fecundity.
The present experiments were undertaken, with nutritional physiology in our minds, in order to investigate exactly the growth of the larva which fed on the rice plants deficient in nitrogen, as compared with the growth on a diet of plants cultured in soil supplied with sufficient nitrogen. Two experiments were carried out, one of them is on the growth of the larvae fed on growing rice plants cultured in a greenhouse, and the other is on the growth of the larvae reared with sterilized rice stems in flasks under aseptic conditions.
The larvae fed on both rice stems were weighed individually after a rearing period. Some chemical compositions of the rice plant stems used for the rearing experiments were analysed to endorse the growth of the larvae.
The effects of the nitrogenous fertilizer have been found to be basically similar in both experiments. All the diets composed of the rice plant stems grown on low nitrogen soil had a marked effect on the growth of the rice stem borer larvae, significantly reducing larval weights as compared with the high nitrogen series. There is a close correlation between weights of larvae and nitrogen content of the rice stems. The superiority of the growth of the larva is largely due to the significantly high nitrogen content of the rice plants stems grown on high nitrogen soil.In the previous paper (ISHII and HIRANO, 1957), it has been reported that the growth of the larva reared with a synthetic food is faster on a protein rich medium than on a carbohydrate rich one. The results obtained from the present experiments agree with those of the previous experiments and show a rather high requirement of nitrogenous compounds for the larva.

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Experiments have been carried out in order to determine whether Chlorella, green-algae is a suitable material for studying and testing phyto-toxicity and other physiological effects caused by agricultural chemicals. Chlorella was affected by many kinds of solvents, and it was found that Chlorella has sensibility to these solvents parallel to that of soy-beans or green-peas.
The experiments with Chlorella revealed quantitatively that the solvents having higher boiling-point show stronger phyto-toxic activity, which has so far been known with other test organisms. Furthermore the experiments showed some interesting points to be solved. It was also observed that the growth of Chlorella was accelerated by γ-BHC, which has hitherto been observed with wheat, vegetables or other young trees.
In addition, Chlorella is cultivated more easily and experimented more conveniently than other higher plants. Therefore Chlorella seems to be a good material for studying and testing phyto-toxicity and other physiological effects caused by agricultural chemicals in comparison with higher plants.

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Recently the chemical control of injurious insects became remarkably effective but resistant varieties must be used as the basal practice in agriculture for the purpose of increase in yields of crops.
Although the breeders have exerted themselves to originate resistant varieties but excellent results are not obtained so easily, because the factors relating to resistance have to be take out from various compound factors. Most of the main factors related to insect resistance must be hereditery, therefore it is considered that these factors are contained within the seeds of plants. If so, the insect resistance of varieties may be compared with each other by the method which makes insect injure seedlings in the stage before the weaning period. Namely, in this stage the seedlings are depending upon the nutrition of albumen only, but not on fertilizers in soil.
In this standing the authors have studied the varietal difference of injury caused by the feeding of rice stem maggot which is known to have remarkable varietal difference. The adults used in this investigation were collected from the field in the beginning of October and then were reared on Agrostis matsumurae HACK. (A. perennans matsum. non TUCK. pro parte.), cereal weed till oviposition. The eggs laid on the surface of said weeds were floated on the water in an experimental dish, with the leaves. After about a week the larvae hatched out and fell into the water. On the other hand, the seedlings of rice plants in the stage before the weaning period were cultured under constant temperature.
Thus the artificial parasitisms of the larvae on seedlings were conducted and the seedlings were moved into an incubator of 25°C constant. The survivals and the body length of the larvae were surveyed about 10 days after artificial parasitisms because it was known, from the preliminary test, that the larvae reared on seedlings grew to the 3rd instar after 10 days from artificial parasitism.
The results obtained are summarized as follows:
1. There were considerable differences in the survivals of each instar but it was clear that the coincidental tendency in the total survival percent and the percentage of individuals that grew to 2nd and 3rd instar larvae, and the correlation coefficient between these two percentages is 0.9401.
2. There were correlations between the total survival per cent (x) of larvae bred on seedlings and the number of injured panicles per 20 hills (y) of each variety observed in the field, and the correlation coefficients and the regression equations of each varietal group which was grouped by their heading date were r=0.8565 and y=45, 76+1.17x in early maturing varieties, r=0.9975 and y=1.25 x-7.96 in medium maturing varieties, and r=0.7088 and y=4.12+0.62x in late maturing varieties, respectively.
3. The correlation coefficient between the total survival per cent (x) and the mean body length (y) of larvae bred on seedlings was 0.8273 and the regression equation was y=1.250+0.025x, and this equation agreed with 99% probability in any groups of varieties.
4. The close correlation between the mean body length (x) of larvae bred on seedlings and the number of injured panicles per 20 hills (y) of each variety observed in the field was recognized, and the correlation coefficients and the regression equations of each varietal group were r=0.8540 and y=41.89x-7.71 in early maturing varieties, r=0.5284 and y=39.90x-40.58 in medium maturing varieties and r=0.8193 and y=22.16x-19.74 in late maturing varieties, respectively.
5. From the observation on injured features of seedlings, the clear border of eating marks were recognized in the varieties on which larvae showed good growth

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In the fall of 1955 the wheat stem fly, Chlorops sp., was discovered as a cereal pest in the coastal region of Akita Prefecture. Observations have been made on its morphology, bionomics and symptoms of attack on wheat.
Results of investigations in 1956 and 1957 are summarized as follows.
Short morphological descriptions in all stages of this pest were conducted. Besides this pest, the occurrences in the cereal fields and wild grasses of two other cereal pests, the rice stem maggot, Chlorops oryzae MATSUMURA, and the barley stem maggot, Meromyza saltatrix L., were observed. The wheat stem fly is morphologically very similar to the rice stem maggot in the egg and adult stages and to the barley stem maggot in the pupal and larval stages. Under the microscope it is easy to distinguish each species in some stages, but rather difficult to do so in other stages.
The wheat stem fly has two generations a year, overwintering as the full-grown larva which later pupates in the spring inside the stem of winter wheat. During the early part of May the first generation fly deposits its eggs singly on the upper surface of the winter wheat leaf in which young immature ear within the leaf sheath is enclosed. After hatching, the infant first instar larva makes its way in to the ear-bearing internode gnawing a food groove on one side as it moves downwards.
Pupation occurs in this food groove in the middle of June, and the second generation fly emerges during the early part of July when the wheat ears are almost ripe. After emergence, the flies appear to disperse throughout the fields, later laying their eggs on newly germinated wheat seedlings during the latter part of September and until the middle of October. A period of aestivation (summer dormancy) was confirmed by rearing the flies under laboratory conditions when the following facts emerged: The life of some flies in the second generation is from two to three months; the flies in the first generation lay their eggs within a few days of emergence whereas in the second generation the pre-oviposition period is much longer, and this delay in oviposition is caused by immature reproductive organs.
As noted, the eggs are laid singly on the upper surface of wheat leaves, and the hatched larva crawls into the stem. Characteristic injured leaves on all main stems attacked are produced, the injury appearing first as pin-holes later becomes largerpunctures as feeding continues. The injured leaves become broad and thick and all infested stems turn yellow, whither and die in the following spring when pupation occurs.
During the aestivation period of the second generation flies no intermediate generation was observed in the field, although in the experiment a possible existence of the intermediate generation could be found in the following fact: All the hatched larvae inoculated before the middle of August onto out-of-season wheat seedlings pupated until the middle of September. While it was not demonstrated whether these pupae hibernated as such or a third generation fly would have emerged, due to death of pupae.
Laboratory experiments verified that the maximum temperature for hatching is 30°C and the minimum humidity is about 80 per cent. In the field, hatching is observed in the early morning, and the hatched larvae crawl a distance of about 1 cm on the leaf towards the apex, turn around and then crawl in zigzag fashion downwards to the leaf base, penetrating into the stem in this area. 40 to 120 minutes are required to enter the stem from the time of hatching, and it is observed that the larvae reached the centre of the stem near the growth point some 6 hours after penetrating has started. 24 hours after initial penetrating the larva begins to feed and the gut turns green.
In the field, the total developmental period from egg to adult requires on the average 93 days in the first generation, and 270 days in the second or overwintering one.

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When the active prothoracic glands from Barathra prepupae were implanted into diapausing larvae, prothetely occurred in considerable percentage instead of normal pupation. But in the cases where the corpora allata were removed from diapausing larvae and active prothoracic glands were then implanted, the majority of the larvae pupated normally without a prothetelic moult.
From the experimental results hitherto obtained, it may be concluded that the larval diapause is characterized in the temporary failure in the activities of brain-prothoracic glands system accompanied with the high activity of the corpora allata.
The activity of the corpora allata, however, seems to decrease gradually with the lapse of time during post diapause period.

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The effects of light and darkness on the future development of wing were examined experimentally in the larvae of apple grain aphid, Rhopalosiphum prunifoliae, at a constant temperature of 25°C with the following results.
1. The different in the rate of wing development does not occur in the range of intensities of light between about 4, 000∼5, 000 and 580 luxes.
2. Far greater number of alate form are produced from larvae which were subjected to darkness in the early stage of development and thereafter exposed to light than from those treated by just the reverse way. The highest percentage value is obtained when the young are dealt with darkness for 20.5 hours since the birth.
3. Even when the total light exposures during the precritical period of determination of future wing development are the same, the alternation of light and darkness of every20 hours is far more effective in comparison with that of every hour in which the rate of alate form effected is not different from that of the young treated with either light or darkness throughout the development.4. The light action in the wing development does not depend upon the changes in the nutritional properties of the fbod plant, if they actually occur through the action of light.

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