Understanding the relationship among the spotted stem borer (Chilo partellus) damage parameters and grain yield reduction on maize (Zea mays L.) will aid in elucidation of the most important damage parameters that reduce yield, and may consequently lead to development of functional criteria to quantify tolerance and resistance. Correlations, stepwise multiple regressions and path coefficient analyses were used to study the interrelationship among the three damage parameters (foliar lesions, dead heart and stem tunnelling) and their contribution to grain yield reduction using three separate groups of genotypes in trials conducted between 1990 and 1991. Foliar lesions and stem tunnelling were positively correlated. Reduction in the number of ears harvested due to larval infestation was the primary cause of grain yield loss. The combined effect of both number of ears and stem tunnelling accounted for 34%, 37% and 43% of yield reduction in the three groups of entries, while the additional contribution of any other trait was a maximum of 2%. Using path analysis, the direct effect of ear number and stem tunnelling on yield loss was consistently large and the direct effect of foliar lesion or dead heart was secondary when compared to that of stem tunnelling. When the effects of only the damage parameters were considered, foliar lesions, acting primarily via stem tunnelling, had the highest total indirect effects in all groups of entries. In effect, yield loss caused by the spotted stem borer is primarily due to stem tunnelling of the plants.

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We compared biotypes of the brown planthopper (BPH) populations collected in Japan and Indochina Peninsula in 1992 to investigate possible source areas of the planthoppers that invade Japan. We quantified the honeydew excreted by the insects on six standard rice varieties to determine their biotypes. Eight populations used were roughly classified into two groups according to ASD7 rice with a bph2 resistant gene. Low proportions (10-30%) of planthoppers in Japanese and Red River Delta populations were capable of feeding on ASD7, unlike most planthoppers (80-93%) from the tropical Indochina Peninsula. On IR26, which has a Bph1 resistant gene, Japanese and Red River Delta planthoppers excreted ca. 30-50% of the quantity of honeydew excreted by BPH feeding on TN1 (no resistant gene), indicating the moderate susceptibility of the former to these planthoppers. Tropical populations collected from Mekong Delta and Thailand had slightly higher virulence to IR26. Rath Heenati and Babawee with Bph3 and bph4 resistant genes, respectively, remained highly resistant to all populations except those of the Mekong Delta. As result, the biotype of Japanese populations bore a close resemblance to that of Red River Delta populations.

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White-spotted longicorn beetles, Anoplophora malasiaca (THOMSON), were reared in the laboratory under a varying temperature regime simulating both diel and seasonal fluctuations of natural temperatures, and at three constant temperatures of 20, 25 and 30°C. In the fluctuating-temperature regime, three groups which had different starting points of the seasonal fluctuation were examined to elucidate the effect of different oviposition times on the A. malasiaca life cycle. Small bolts of freshly cut citrus tree were used as food for the larvae. The photoperiod was constant darkness. With fluctuating temperatures, more than 70% of the larvae survived and required 1 or 2 years to complete their life cycle (from egg to adult eclosion). The proportion of individuals with a 2-year life cycle increased as the oviposition time was delayed. Most larvae spent a several-month period without feeding before pupation. Adults emerged simultaneously in June irrespective of their life cycle type. At 20°C, 57% of the individuals completed their development and emerged as adults during the period from 306 to 704 days after oviposition. At 25 and 30°C, all the individuals eventually died during the larval stage. Lower developmental threshold temperatures for eggs and young larvae were estimated to be 6.7 and 11.6°C, respectively.

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This paper investigated the relationship between the circadian system and photoperiodic time measurement in different geographic strains of Drosophila triauraria which enters reproductive diapause at short daylenggths. The critical daylength varied among the geographic strains, about 13 h in the ON (originated from Onuma, 42°N), 12 h in the OI (Oita, 33.2°°N) and 10 h in the YK (Yakushima, 30.3°N) strains at 15°C. All the strains exhibited a weak“circadian”oscillation pattern in diapause incidence on NANDA-HAMNER protocol. The dependence of photoperiodic time measurement on cycle lengths close to module τ was shown for the ON and OI strains by experiments using non-24 h light-dark cycles. Thus, no evidence was obtained for covariation between critical daylength and circadian oscillation pattern. The ON and OI strains showed similar patterns ofresponse in the night-interruption experiment, despite the one-hour difference in critical photoperiod.

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Embryonic development was studied to elucidate the diapause stage of four spider mite species belonging to the genus Panonychus. Liquid paraffin proved to be useful for continuous observation of living embryos. Embryonic development was divided into 18 stages, which were illustrated and described. The initial phase of embryonic development was characterized by two total and equal divisions. This was followed a superficial cleavage. Embryonic development of diapause eggs was suppressed at the late blastula stage shortly before the appendage formation.

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In the dichloromethane extract of field-collected millipedes Epanerchodus japonicus CARL, three components were detected as possible defense substances by gas-liquid chromatography (GC). the chemicals were identified as benzaldehyde, phenol and mandelonitrile, by comparison of their retention times of GC and of their GC-mass (GC/MS) spectra with those of authentic compounds using a fused silica capillary column. Quantitative determination of each component by GC and high performance liquid chromatography (HPLC) revealed that individual millipedes contained 82-210μg of mandelonitrile, 1.7-3.6μg of benzaldehyde and 2.4-6.9μg of phenol. The content of mandelonitrile was determined for the first time, and it corresponded to 0.12-0.40% of the fresh body weight.

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Biotypes of brown planthopper populations collected in and around the Muda area in Peninsular Malaysia in 1989 and 1990 were examined by comparing the amount of honeydew excreted by the female adults on 5 standard rice varieties: Mudgo (which has the Bph 1 gene for resistance to the brown planthopper), ASD7 (bph 2), Rathu Heenati (Bph 3), Babawee (Bph 4) and TN1 (no resistance genes). Most populations from the Muda area showed similar biotypical properties regardless of the collection sites or crop seasons. Among the 4 resistant varieties used, high mortality was recorded on Rathu Heenati and Babawee. A relatively larger amount of honeydew was discharged on ASD7; this was followed by Mudgo. Little honeydew excretion was recorded on Rathu Heenati and Babawee. A similar trend was also observed in most populations collected from other sites on the west and east coasts of Peninsular Malaysia. Two explanations are considered for this phenomenon, i.e., these biotypes had developed in Malaysia or immigrated from Sumatra, Indonesia.

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Antifeedant activity of extracts from Andrographis paniculata against the 1st and the 4th-instar larvae of the diamondback moth (DBM), Plutella xylostella, was tested by using leaf disc of cabbage. Furthermore, the antioviposition effect was also observed on the caged cabbage plant treated with the fractions. The active fractions from the acetone extract suppressed feeding by the 1st and 4th-instar larvae at the concentrations of 60 ppm and 500 ppm, respectively. The antioviposition activity against DBM females was also found at the concentration of 125 ppm.

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The toxic effects of 14 organophosphates (OP's), 7 carbamates, 4 synthetic pyrethroids, cartap and imidacloprid on the entomopathogenic nematode Steinernema carpocapsae WEISER were tested by checking the mortality of infective juveniles (IJs) in insecticide solutions. Cartap and two OP's (profenofos and pyraclofos) were the most toxic to the IJs: 83.4% mortality for cartap and 57.1 and 47.8% for profenofos and pyraclofos, respectively, in solutions of 100μg/ml after 48 h exposure. Seven OP's (diazinon, dichlorvos, fenthion, malathion, trichlorfon, propetamphos and prothiofos) showed weak toxicity at 100μg/ml. Other chemicals tested showed no toxicity to the IJs at 100μg/ml. The IJs were incubated in insecticide solutions (100μg/ml) for 24 h and then used to treat newly-molted last instar Spodoptera litura larvae. OP's (except acephate, malathion and temephos), 1 carbamate (methomyl), 2 pyrethroids (permethrin and ethofenprox) and cartap apparently inhibited infectivities of IJs to these larvae. However, when insecticides were washed off the body surface of IJs, only cartap (⪈ 10μg/ml) and profenofos (100μg/ml) left a detrimental effect on the IJ infectivity.

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The regulatory function of photoperiod and temperature on the life-cycle of Coccinella septempunctata brucki MULSANT in Hokkaido populations was investigate. Dissection of adults from Sapporo (43°N) in mid-October showed diapausing adults (partly hidden in grass tussocks) possessing enlarged fat body, ovaria without vitellinized oocytes and at a beginning of regression of testicular follicle tissue. Some of the females had sperm in their spermathecae. Experimental rearings under contrasting photoperiods (12L-12D, 16L-8D) and three temperatures (20, 25 and 30°C) of insects sampled in early September, and of their offspring, showed that the Sapporo population gas a long-day photoperiodic response adequate for the induction of winter diapause. This is in contrast to short-day response inducing summer diapause in the Nagoya (35°C) plains, but similar to C. septempunctata septempunctata in France and central and northern Europe, i.e. regions with climate similar to Hokkaido.

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In order to investigate the reproductive traits of Monochamus saltuarius, 25 pairs of adults were reared under constant conditions of 25°C, 90-100% R. H. and a photoperiod of 12L-12D. The mean oviposition ratio (number of eggs/number of oviposition marks) was 0.51. The mean lengths of preoviposition and oviposition periods were 11.2 and 41.7 days, respectively. The mean lifetime fecundity was 69.7 eggs ranging from 0 to 172 eggs. Lifetime fecundity is divided into two components, i.e. oviposition period and rate. Actually, it was highly correlated with each of these components. Oviposition period is correlated significantly with longevity while oviposition rate is with adult female size. However, there were no correlations between oviposition period and rate nor between longevity and body size. Dissection showed that the number of ovarioles in a female averaged 21.5 and did not vary in proportion to material body size.

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Experiments for the introduction of Entomophthora muscae to populations of the house fly adults were carried out. Rearing of 50 healthy flies in a 27-l cage with 1, 4, or 10 fresh cadavers attached to the inside top of the cage as conidial sources initiated death of flies from approximately 6 days after introduction. Including secondary infections, the fly populations finally collapsed within 11 days with the application of more than 4 cadavers. When 2, 4, or 10 living flies injected with E. muscae protoplasts were released into the population of 50 healthy flies in a 27-l cage, the 1st mortality peak of non-injected flies occurred 4 to 6 days after the death of the injected flies, and the 2nd peak of mortality detected several more days after this. The non-injected flies were totally killed within 17 days by releasing more than 4 living infected flies. The epizootics also occurred when more than 2 conidia-discharging cadavers were attached within a 0.8-m³ cage, and the population of 50 healthy flies were killed within 14 days. Both the application of fresh fly cadavers and release of living-infected flies were thought to be effective means of introduction of E. muscae into house fly populations.

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The rate of development of the andromeda lace bug, Stephanitis takeyai, reared on two of its main host plants, Pieris japonica and Lyonia elliptica, was measured at various temperatures. The overall pattern of the effects of temperature were similar on the two hosts and in both sexes. The developmental period was slightly shorter on P. japonica than on L. elliptica in both eggs and nymphs. However, adult longevity was much longer on L. elliptica. It was suggested that L. elliptica is therefore likely to be a better host than P. japonica. Except for a generally shorter development time at low temperatures, the developmental pattern was similar to that found in the azalea lace bug, S. pyrioides, as previously reported by NEAL and DOUGRASS (Environ. Entomol. 17 : 827-831, 1988).

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The local distributions of the two common large orb-web spiders Nephila clavata and Argiope bruennichii are somewhat different; the former lives in woodlands and their surroundings, while the latter inhabits grasslands and their periphery. To explore factors limiting local distributions of these spiders, three plots (in the forest edge, and in the grassland) with the same physical support were established, into which spiders were released. The decreasing patterns of numbers at the three plots were quite different between the two species; Nephila showed the highest decreasing rate in the grassland and lowest in the forest, while Argiope showed the opposite tendency. The body size of Nephila tended to be larger in the grassland. Matured females of Argiope appeared to be larger in the grassland, though the sample size was too small to test. Potential prey, estimated by using a trap for capturing flying insects, was most abundant in the grassland and least in the forest. Thus, the availability of web support could not explain the difference in local distribution between the species. Food supply was not a critical factor for the distribution of Nephila either. Possible factors concerning the differences in the decreasing patterns among habitats and between species were discussed.

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Developmental zero from egg to the adult emergence in the stink bug, Piezodorus hybueri, was 14.2°C in both sexes and effective heat units for females and males were 283.0 and 277.8 day-degrees, respectively. Developmental zero for preoviposition period was 18.4°C and effective heat unit was 70.0 day-degrees. Critical photoperiod for the diapause induction in Kumamoto Prefecture was considered to fall between 12L-12D and 13L-11D. Most females emerged on and after 15 September had immature ovaries and entered reproductive diapause. Survivorship curves of overwintering females and males declined steadily, and 35.0% of females and 28.6% of males remained alive until 6 April next spring. Oviposition of these overwintered females occurred between middle April and early May. The number of generations per year was estimated with the developmental zero and the effective heat unit of P. hybneri. The stink bug possibly has four generations per year in Kyushu, southwest Japan. The peak of the start of oviposition in the first generation was estimated in late June. Therefore, it is concluded that mated females with mature eggs which invaded summer soybean fields from early July are newly emerged adults of the first generation.

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