Distribution and turnover of phosphorus and BHC in a grassland were analysed in Oita Prefecture and Kumamoto Prefecture from March to September in 1983. Large differences in bioconcentration between phosphorus and BHC in the organisms of a grassland ecosystem were observed. The content of TP (total phosphorus) in organisms increased with the elevation of the ecological position of the food chain, whereas the opposite phenomenon was observed in BHC residues whose concentration was high in soil (H-layer in Senomoto Table Land; a meadow, Kumamoto Pref.) and litter (in Bogazuru, Oita Pref.), and low in plants, insects and mammals. The content of BHC residues increased with plant growth and after dry grass in the grassland had been burned, the content of residues in soil increased.

View full abstract

Movements of 28-spotted lady-beetles were investigated in applying the mark-recapture method in an area (390×270m) within Nagoya Univ. campus where food plants were artificially dispensed in 16 small patches. Throughout two years (1978-1979), both the adult density and the rate of patch-to-patch movements were the highest in the first generation adults, moderate in the second generation adults before hibernation and the lowest in the overwintered second generation adults. Thus the adult movement pattern appeared to be, at least in part, density-dependent. This finding was also supported by the results of release experiments, where the proportion of females remaining within the patches where they had been released was lower in those patches where a large number of adults had been released. The rate of movement of females was significantly higher than that of males in the first generation. The number of eggs laid per female seemed to decrease when the adult density on host plants was high. Both the density-dependent adult movements and the densitydependent decrease in fecundity were considered to be major factors responsible for the relative stability in the abundance of this species.

View full abstract

The first incidence of the azuki bean weevil, Callosobruchus chinensis (L.), was observed in the middle of August in the three Aki-azuki bean fields located in the northern part of Okayama. Thereafter the number of weevils changed and several peaks were found in the number of immigrants to the field until early November. These adults were most abundant in early October, and they laid their eggs on the mature pods from mid-September to mid-October. The mature pods of the height of 15-20cm above the ground were the mostly preferred for the oviposition sites. At the same time, it was found that the number of adults that emerged from harvested beans was highest in the central ridges and decreased towards the peripheral ridges of the field. The number of eggs per pod reached 2.06 at harvest. The larval survival rate from the egg deposition to the newly hatched larva boring into the bean in the pod was estimated to be 0.41. The percentage of beans infested by the weevils reached 14.26, that by Matsumuraeses phaseoli M. 7.19 and that by stink bug and fungi 0.52, in the field without insecticidal control. The traditional exposure of the harvested beans to the sun for a period of 1-3 days did not affect the survival of the larvae in the beans though the inner temperature of the beans reached 33.6°C and the water content was reduced by 2.5% after the exposure.

View full abstract

Adults of Saprinus speciosus ERICHSON flied continually to the trap with chicken liver from May to October, and the number of adult caught by the trap became maximum in summer. The flying activity of adults was done at temperature above 19°C, and it was reduced by the rainfall. Most of adults were active in the daytime, the number of adults caught by the trap became maximum after four days since chicken liver was placed. At this time, maggots of fly, the prey of the histerid, have already grown up to the final instar. The larvae of the histerid have only two instars and this shortened developmental period, about 10 days, coincides well with the rapid development of prey maggots.

View full abstract

Oviposition and larval feeding habits of the pea blue, Lampides boeticus L. on the lablab bean, Dolichos lablab L. were studied in the field and laboratory. In the field, most of the eggs were laid on the young flower buds in an apical position in the order of inflorescence, but few on the undeveloped flower buds, open flowers, pods, leaves, and stems. The 1st- and 2nd-instar larvae were found mainly in young flower buds, whereas the 3rd- and 4th-instar larvae were found in flowers or pods. The 1st- and 2nd-instar larvae attacked exclusively the anthers of flower buds. This characteristic feeding habit was also demonstrated by a laboratory test, i.e. the newly-hatched larvae inoculated on young flower buds penetrated within 24hr into the distal part of the flower buds where the anthers were located, and consumed them selectively. Larvae inoculated on the pods were not successful in penetrating into them and they died or dispersed.

View full abstract

When reared on an artificial diet, silkworm larvae show a remarkable accumulation of urea in the cocoon layer, the pupal hemolymph and in the eggs laid by the adult. Urea biosynthesis from arginine was therefore compared between silkworms fed on mulberry leaves and those fed on an artificial diet. In both dietary groups, radioactivities were detected in urea and ornithine 24hr after injection of L-(U-¹⁴C)-arginine into 5th instar larvae, whereas radioactivities in pupae injected with ¹⁴C-arginine were distributed in proline, glycine and two unidentified compounds in addition to the above two amino acids. Radioactivities of urea in silkworms fed on an artificial diet were slightly lower than in those fed on mulberry leaves. These facts strongly suggest that the accumulation of urea in silkworms reared on an artificial diet is not caused by the activation of urea biosynthesis but is attributable rather to the absence of degradation of urea.

View full abstract

Studies on the unidentified agent causing damage to the tuberous roots of the Chinese yam, Dioscorea opposita THUNB, cultivated in Ishikawa Prefecture were carried out. It was found that African mole crickets caused the damage and a variety of symptoms affecting the size and shape of every part of the tuberous roots was observed. The damage which appeared in early September when the cracks under the ground around the yam began to be formed due to the rapid growth of the tuberous roots persisted until early October. It was considered that the cracks were used as tunnels through which mole crickets moved to the tuberous roots to attack them. Soil application of isoxathion micro-granules was effective in preventing the damage. Appropriate timing of the application of the chemical was early and late September which coincided with the active period of mole crickets. Soil treatment with isoxathion micro-granules or its dust mixed with rice bran before planting was not very effective.

View full abstract

The degree of wing wear and tear of the rice leaf roller, Cnaphalocrocis medinalis, collected in paddy fields was investigated on the basis of the loss of wing cilia. In early stages of the development of the rice plants the adult population consisted of mated moths with wings damaged in various grades. Virgin moths with complete wings and mated moths with severely damaged wings were observed in the transitional period when the proportion of mated moths in the paddy population decreased rapidly. After about 10 days after the flowering stage of the rice plants most moths were virgin and showed complete wings. These findings suggest that moths do not mate in paddy fields after the flowering stage of rice and emigrate shortly after their eclosion in this season.

View full abstract

To determine the sample size for the estimation of the mean density, the distribution pattern of the rice water weevil, Lissorhoptrus oryzophilus, in a paddy field was analyzed by the m-*m regression method proposed by IWAO (1968). Overwintered adults were nearly randomly distributed among rice hills with a slight tendency to aggregation. The distribution of larvae and pupae also was nearly random. Based on these results, the diagrams which determine the sample size required to estimate the mean density with a desired precision were drawn by using the method developed by IWAO and KUNO (1968)

View full abstract

The zymogram patterns obtained by electrophoresis and the sensitivity to the inhibitor (dichlorvos) of non-specific esterases which hydrolyze α- and β-naphthyl acetate (NA) were studied. The esterases which hydrolyze α- and β-NA showed very similar zymogram patterns by agar-gel electrophoresis. Esterase activity from the non-diapausing strain was slightly higher toward α-NA than β-NA, but that from the diapausing strain was not significantly different between the two substrates. These esterases showed similar values for the bimolecular rate constants (k_i) as well as similar inhibition patterns by dichlorvos.

View full abstract

To identify the cue eliciting the switchover in the searching behavior of Coccinella septempunctata, the duration of area-concentrated search (GUT: giving-up time) was determined by the method described by NAKAMUTA (1982) after each of the following five feeding stimuli was provided: (a) contact with an aphid (Myzus persicae), (b) biting an aphid (an aphid was immediately removed after the beetle bit the prey), (c) consumption of an aphid, (d) contact with an agar block (ca. 2×2×2mm), (e) consumption of an agar block with a droplet of aphid body fluid on it. Switchover in searching behavior was observed in every case. It is suggested that the contact with a prey rather than its consumption is the cue that elicits the switchover. On the other hand, the GUT varied with the feeding stimulus (a≈d<b<e<c). The GUT was positively correlated with the feeding time of an aphid which represented the size of the prey consumed. To determine whether the GUT was controlled by the amount or by the size of the prey consumed, the GUT was measured after the labybeetle had fed successively on a large and a small aphid (Sequence A) and after it had fed on a small followed by a large aphid (Sequence B). Although the beetle consumed the same amount of aphids both in Sequence A and B, the beetle showed a longer GUT in Sequence B than in Sequence A. Therefore, it can be concluded that the GUT is determined by the size of the prey most recently consumed, which is not consistent with the predictions based on the classical patch use model developed by CHARNOV (1976).

View full abstract

Efficiency of various techniques used in the precipitation reaction was evaluated to identify the predator species of the diamondback moth, Plutella xylostella (L). Using 3rd to 4th instar larvae of P. xylostella as an antigen, the antiserum was prepared by immunizing a rabbit with it. The larvae were reared on seedlings of radish (Raphanus sativus L.) in the laboratory. The antiserum against P. xylostella constituents reacted with the homologous constituent, and also crossreacted with R. sativus. Thus the antiserum specific for P. xylostella was prepared by absorbing the antibody with the saline extracts of R. sativus. The Micro-Ouchterlony method (MO method) was sensitive enough to enable the detection of whole-body extracts of 3rd-4th instar larvae, pupae and adults of P. xylostella. The anti-P. xylostella serum did not induce cross-reactions with the constituents of other arthropods inhabiting the cabbage fields. It was concluded that the MO method was most useful for the identification of predators of P. xylostella, as compared with electrosyneresis or the precipitin ring test.

View full abstract

In order to forecast the dispersal period of the adults of the rice water weevil from overwintering sites to paddy fields, the temperature dependence of the flight muscle (epipleural muscle) development and flight activity was investigated. The threshold temperature for development of the flight muscle was 13.8°C. When the adults which were collected in woodlands in early spring were reared without food, the flight muscle showed only a little development. Fully developed flight muscles degenerated remarkably from 12 to 18 days after starvation. The overwintered adults started to fly from 6 to 8 days, and 50% of the adults from 9 to 12 days after rearing respectively. The relationship between the cumulative percentage of flying adults and effective cumulative temperature was represented by an equation. When the adults with developed flight muscles were kept in each plastic cup at different temperatures, the rates of adults flying out from the cups were very high at 25°C and 27.5°C, and the rates of flying adults decreased at 30°C and 22.5°C. But at 20°C the rate of flying adults was very low, and at 18.5°C no flying adults were observed. The period when adults which had overwintered migrated from bamboo grasses in the woodlands coincided precisely with the simulated period of flight initiation in the adults.

View full abstract

To define the injury caused by the rice leaf roller, larvae on the rice plant were collected and the relationship between yield loss and period and extent of damage was analysed. Yield loss was not observed when the damage occurred in the grain filling period, although 67% of the leaves were injured. Yield was reduced by the decrease in the percentage of ripened grains and 1, 000-kernel-weight when the damage occurred at heading time, even if the ratio of leaf injury was below 67%. Yield was reduced in proportion to the ratio of the damaged area of the two upper most leaves. The ratio of yield reduction (Y) increased in proportion to the square of the ratio of injured leaf (X) as represented by the regression equation Y=1.55+0.0067X² (r=0.9925).

View full abstract

Fifteen to thirty three percent of the adults of Dolycoris baccarum LINNAEUS were parasitized by Cylindromyia brassicaria (FABR.), which were collected at Morioka, Iwate Pref. from June to August, 1983. Only one parasitoid larva emerged from one host insect and the parasitism was found in both sexes of the host. Adults of C. brassicaria emerged from the end of July to August both in the laboratory and in the field. On the other hand, no parasitoid larvae emerged from D. baccarum adults collected in September before the winter.

View full abstract

A podborer, which has been confused with the soybean podborer, Leguminivora glycinivorella MATSUMURA, was identified with Fulcrifera orientis KUZNETZOV, and thus Sophora should be excluded from the host plant list of the soybean podborer. The adult morphology and life history of F. orientis were briefly described.

View full abstract

The handy mill (Freezer-Mill) is useful for a DNA extraction from tissues and organs. In the present experiment, we prepared a high molecular weight DNA (100 to 140kb) from the posterior silk gland of Bombyx mori by use of the mill.

View full abstract