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Ground beetles have been used as bioindicators for monitoring environmental changes. However, to interpret monitoring results, we need further information on their life history traits. We selected Harpalus griseus, H. eous, H. tridens, Synuchus cycloderus and Carabus procerulus, species common in Honshu Island, Japan. We examined their hind wings, flight muscles, gut contents and ovarian eggs to understand their flight activity, feeding traits and reproductive strategies. The three Harpalus species showed wing length / body length ratios (W/B) of 0.88 - 0.99. In H. tridens, the proportion of individuals with flight muscles and caught in aerial traps was lower than in the other two. S. cycloderus was macropterous with a W/B ratio of 0.75, but no individuals were caught in aerial traps, and none possessed flight muscles. C. procerulus was brachypterous. The three Harpalus species fed mainly on seeds and partly on arthropods. S. cycloderus was a generalist predator. Gut contents of C. procerulus consisted of amorphous fluid, suggesting extra-oral digestion. Egg type was categorized by the number and size of ovarian eggs. S. cycloderus had many-small eggs, while the other four had few but large eggs.

Effective insect management strategies require a firm understanding of the factors determining host preference, particularly in highly mobile insect herbivores. Host preference studies commonly employ average or first position as a proxy for preference. Yet few studies have explored host preference in relation to transitory attraction and leaving rates, yet these are both components of host plant selection. We investigated the transitory dynamics of preference by the green rice leafhopper, Nephotettix cincticeps (Uhler) (Hemiptera: Cicadellidae) by conducting experiments on groups of females, males, or mixed-sex leafhoppers, and recording their position over time between low-N and normal-N rice plants. Utilizing a log-linear model and variants of a biostatistical model we used these positional data to extract attraction, leaving and tenure rates to better understand the process of host-plant selection. We found a general preference for normal-N over low-N plants at equilibrium. However, between sexes there was variation in the relative significance of attraction or leaving rates on that preference. Female leafhoppers were more attracted to host plants with higher nitrogen content. Male leafhoppers were less discriminate in their initial attraction to hosts but left low-N hosts at a faster rate. Whereas estimated tenure times on both normal- and low-N plants exceeded transmission times for the leafhopper-transmitted rice dwarf virus, longer tenure on normal-N plants likely increases the likelihood of virus acquisition from these plants. Our findings support previous recommendations that growers can mitigate the risks of leafhopper damage and pathogen transmission by optimizing their application of nitrogenous fertilizers.

Agricultural imports are the primary pathway for the introduction of exotic insect pests. The invasion records of exotic insect pests are also influenced by the lag time before detection and saturation caused by the limited species pool of potential invaders. We compiled an exhaustive list of exotic insect species in mainland Japan and tried to evaluate the connection between the commodity types of agricultural imports and insect types of agricultural pests, in addition to the effects of lag time and saturation. We found that lag time was prominent when all pest types were merged into one group, whilst saturation always existed when we divided the records into the four agricultural pest types. Saturation was especially prominent in stored product pests because this group contained many cosmopolitan insect pests that could have easily inhabited the newly built mills throughout Japan in the 1950s. We suspect that the saturation effect was masked by admixture amongst pests with different saturation patterns. Our findings indicate that all commodities, i.e. flowers, fruits, vegetables, cereal and timber, contributed to the invasion of pest insects as potential pathways. However, it was unclear if certain items had comparatively greater significance in this process.

Understanding the regulation of natural populations has been a long-standing problem in ecology. Here we analyze the population dynamics of 17 species of saproxylic beetles in Shizuoka Prefecture, Japan collected over 11–12 years using autoregressive integrated moving average (ARIMA) models. We first examined the dynamics for indications of the order of the ARIMA models and evaluated the time series to determine that it was not simply a random, white noise sequence. All species dynamics were not mere random noise, and ARIMA models up to lag 3 were considered. The best model was selected from the possible ones using several criteria: model convergence, weak residual autocorrelation, the small sample AIC must be among the smallest that were not significantly different, and the lag indicated by the cutoff values in the detrended partial autocorrelation function. We found significant and nearly significant direct density-dependence for 14 of the 17 species, varying from −0.709 and stronger. The characteristic return rates were strong and only one species had a weak return rate (>0.9), implying that these species were strongly regulated by density-dependent factors. We found that populations with higher order ARIMA models (lag 2 and 3) had weaker return rates than populations with ARIMA models with only one lag, suggesting that species with more complex dynamics were more weakly regulated. These results contrast with previous suggestions that 20+ years are needed to detect density dependence from population time series and that most populations are weakly regulated.

For ectotherms such as insects, their low- and/or high-temperature tolerance is one of the most important traits not only for their physiological as well as ecological and evolutional processes. Here, we review the temperature tolerance of insects in relation to their development and suggest a novel method of specifying low and high threshold temperatures. To date, the upper and lower critical thermal threshold for development as Tmin and Tmax, respectively, which are derived from nonlinear empirical models, has been extensively used. These indicators, which originated from the artificial empirical models, however, may not be reliable. Consequently, the Sharpe-Schoolfield-Ikemoto (SSI) model which is a nonlinear theoretical model based on thermodynamics, was implemented as an alternative tool to express tolerance temperatures. In the model equation constructed with subunits, when the reversed denominator (P2 function) is maximum (nearly 100% in general), it denotes the probability of an enzyme being in the almost fully-active state of the intrinsic optimum temperature (TΦ). The profile of the P2 function shows a peak at the TΦ temperature and the two temperatures of TL50 and TH50 which indicate the 50% active and 50% inactive state (P2 = 50%), respectively, are given as parameters in the P2 function of the SSI model. Even so, it is possible to select any values within the range of 0

Among the various animal taxa that are have established outside their native ranges, invasions by insect species are the most numerous worldwide. In order to better understand the characteristics of insect species that make them more invasion prone, the characteristics of habitats that make them more susceptible to invasions and to understand the pathways that facilitate invasions, we compared the compositions of the native and non-native insect communities among five Pacific regions: North America, the Hawaiian Islands, mainland Japan, Ogasawara and Okinawa Islands. These regions comprise both island and mainland habitats and have historically been subjected to varying activities affecting insect movement. Among the five regions, the oceanic islands, Hawaii and Ogasawara, appear to be the most prone to invasions. Specific insect orders such as the Blattodea, Siphonaptera, Thysanoptera and Hemiptera are disproportionally represented in the non-native insect fauna compared to the native fauna in all regions. A large fraction of the non-native insect species in North America (9.4 %) and Hawaii (13.2 %) were introduced intentionally, as part of biological control programs, which were historically pursued more vigorously in those regions than in Japan. Dominance by individual insect orders within invaded communities can be explained by the historical importance of invasion pathways, some of which were likely similar among regions (e.g., movement on live plants), while other pathways appear more region specific. Translocation of insect species among world regions appears to be affected by climatic similarity, host plant similarity and propagule pressure, though these effects are often confounded.

Birds are believed to be one of the principal predators of butterflies. The beak marks (BMs) left on the butterfly wings are useful indices of bird predation. We performed 84 collections in grasslands and woodlands during 2002–2006 in Ito, Shizuoka prefecture, and collected 893 specimens belonging to 48 species. In general, the larger was the body size the higher was the BM rate. There were two peaks in the BM rate and the peaks were higher by 13–14 % in autumn than in spring in both grasslands and woodlands. During 2007 and 2008, capture-mark-recapture surveys were conducted 82 times in a flight path of black swallowtail butterflies (BSBs). A total of 443 BSB were individually marked and released at a site 400 m away from the flight path after examining for BM, degree of wing damage, body size, sex and species. The BM% of BSB ranged from 40 to 46 %, which was the highest among the observed butterflies. The recapture rate was negatively correlated with the BM rate suggesting that the avian predation was strong enough to affect the survival rate of BSB adults. In addition, the BM rate showed a delayed positive response to BSB density in the previous month. Variation in the BM rate was analyzed with a multivariate model; it indicated that month and wing length were significant explanatory variables. In addition, the highest BM rate was observed at an intermediate wing size. These results strongly suggested that variation in the BM rate was caused by variation in avian life history and predator size. All the evidence suggested that an appreciable predation pressure by birds operated on BSB adult populations.

Climate change affects the pattern of population dynamics of insects in different ways. Global warming not only leads to greater over-winter survival, earlier appearance in spring, an increase in the number of generations in a year, lengthening of the reproductive season, etc., but also affects their biotic associations as a result of changes in interspecific interactions. Changes in the density of insects in response to unusually hot summers provide us with useful indications of the potential effects of global warming. Different insect guilds respond differently to hot summers, which sometimes result in an increase in density and sometimes a decrease. These effects may occur immediately or be delayed by 1 or 2 years. As long as the regime remains unchanged, the affected population can recover sooner or later. Even a single-year change in climate, however, if it allows predators to outbreak, may be strong enough to cause a regime shift. Most insects are susceptible to heat stress between 28 and 32 °C, global warming could have a more profound impact on the population dynamics and biodiversity of arthropods than has previously been predicted.

Climate change and biological invasion are two of the most important ecological issues. Nezara viridula (SGS) is a good example of an alien species that increased in response to recent land use changes and global warming. The range limit of SGS coincided with the 5 °C isotherm of the mean monthly temperature for January. Since 2000, it has been warm enough for SGS to overwinter successfully outside its original range. Most invaded areas are now either occupied by SGS only or by mixed species of Nezara indicating that SGS is replacing its congeneric species, Nezara antennata , through interspecific mating. SGS population dynamics studies performed during 1961–1965 demonstrated that SGS abundance was density dependent and the independent processes worked alternately during the breeding season and winter. Although global warming would improve the winter survival of SGS adults, population density would be regulated at a new equilibrium specific to the area. Life tables demonstrated that all traits related to reproduction were poorly realized in the 2nd generation that occurs during summer. Heat stress syndrome due to global warming may be becoming apparent in SGS in spite of its subtropical origin. N. antennata may be able to avoid heat stress by aestivation. Whether SGS could continue to have a higher reproductive potential at the cost of heat stress over N. antennata is a significant ecological issue.

Carabid beetles can escape from pitfall traps. To determine whether or not a female-biased sex ratio for catches of Carabus lewisianus Breuning from pitfall traps could be explained by sexual differences in the rates of capture by and escape from traps, we performed two laboratory experiments to estimate these rates using mathematical models. The results indicated that the two sexes dropped into the pitfall traps at almost equal rates (0.0456/min for females and 0.0366/min for males) and that males escaped from the traps at rates of 0.0591 and 0.0889/min, but no females managed to escape. The bias of escape rates in the field is shown by the higher captures of female C. lewisianus by pitfall traps. Calibration of capture and escape rates suggested similar activity densities of the two sexes in the field. Development of more accurate measures of the number of the relevant sex on the soil surface, and of the methodology for estimating the values of parameters in the field is discussed.

Field surveys and light trap catches of Nezara viridula and N. antennata (Hemiptera: Pentatomidae) in Shikoku and Chugoku Districts, Japan showed that N. viridula is now distributed along the northern coastline of Shikoku District, and in Yamaguchi Prefecture, and along the northern coastline of Shimane Prefecture, south of Izumo, Chugoku District. The present data together with previous reports suggest that the northward range expansion of N. viridula is possibly due to global warming because the monthly mean temperature for January in newly invaded areas has exceeded 5°C in recent years, for example, since 1986 in Fukuoka, below which the winter mortality of N. viridula adults becomes higher. Around the northern limit of N. viridula in Shimane Prefecture, it was not found in April‐August 2008 because the monthly mean temperature for January 2008 fell below 5°C, below which the winter mortality of N. viridula becomes higher. Thus, the northern limit retreated depending on winter temperature. We confirmed the absence of N. viridula from 1979 until August 2008 in Izumo, Shimane Prefecture, and in 2007‐2008 in Tottori Prefecture. Most areas along the southern seacoast in Shikoku District were occupied only by N. viridula, suggesting that it has replaced N. antennata by interspecific mating. In the Chugoku District, no area was occupied only by N. viridula, but it was more abundant than N. antennata in southern Yamaguchi Prefecture, indicating that N. viridula is now replacing N. antennata in that area.

A ground beetle, Carabus lewisianus Breuning, inhabiting woodlands in Izu peninsula, was studied to determine its reproductive phenology. Adults were collected by pitfall traps and dissected to determine their reproductive status. The lower development threshold (T0) and the thermal constant (K) were estimated for egg development. Overwintered adults appeared in late April. No gravid females were found after mid-September. Three peaks were observed in May, June and August during the beetle catches, and each seemed to correspond with the first, second and third oviposition activities of overwintered females, respectively. The expected per capita fecundity was estimated to be less than 50 eggs. The values of T0 and K for eggs were 6.36°C and 133.3 dd using the conventional method, and 7.86°C and 120 dd using Ikemoto and Takai's method. K values from egg to adult were estimated assuming isomorphy, so that the egg period accounted for 18% of the total developmental period. Based on the common temperature of development, i.e. 15–16°C, this species may have originated in a temperate area. Although the total available effective temperature from May to August was sufficient to allow two complete generations, this species reproduced by only one generation a year due to reproductive diapause.

Intensive and successive field surveys on the relative abundance of Nezara viridula (Hemiptera: Pentatomidae) and N. antennata at various localities in northern Kyushu, Japan, together with scattered collection records of N. viridula in Kyushu and Honshu, clearly showed that N. viridula has been expanding its range northward since the 1960s. The present range of N. viridula in Kyushu coincided well with the areas where the mean temperature of the coldest month exceeds 5°C that has been suggested to be the lowest thermal limit for N. viridula to overwinter successfully. The future range of N. viridula is predicted to cover a large area of Kyushu if the temperature rises by 1.4 to 5.8°C by 2100. In some places, N. antennata seemed to have been replaced by N. viridula as a result of their interspecific mating that prevented N. antennata from intraspecific mating. This is because N. antennata was overwhelmed, in abundance, by N. viridula, which has a higher reproductive potential than N. antennata under warm conditions with a sufficient amount of food resources. Conversely, N. antennata populations recovered in a few places where N. viridula had replaced N. antennata in the 1950s, probably due to the shortage of rice plants on which N. viridula preferably reproduces.

The mean surface temperature rose by 1.0°C over the last 40 years in Japan. Changes in the pest status, distribution range, winter mortality, and the synchronization in phenology were examined. The increase in the number of annual generations of each taxon was predicted based on the lower developmental threshold and the thermal constant. Increasing damage due to rice- and fruit-infesting bugs, their simultaneous outbreaks and the poleward geographic spread observed for six species may be triggered by global warming. The winter mortality of adults of Nezara viridula and Halyomorpha halys is predicted to be reduced by 15% by each rise of 1°C. More than 50 species of butterflies showed northward range expansions and ten species of previously migrant butterflies established on Nansei Islands during 1966–1987. Global warming may be responsible for the recent decline in abundance of Plutella xylostella and the increase in Helicoverpa armigera and Trichoplusia ni. In general, global warming may work in favour of natural enemies (except for spiders) by increasing the number of generations more than in their host species. Biological control utilizing native natural enemies is expected to become a more important control tactic in the future. Greenhouse culture may provide a model of a temperate agroecosystem after global warming. The increasing occurrence of alien species of tropical origin in association with the increase in pesticide applications might be expected. Interception of alien pests by plant quarantine followed by integrated pest management is needed.

In order to project the influence of global climatic changes on insects, we examined the effects of a rise in temperature of 2–3°C on the phenology and occurrence of arthropod crop pests using data obtained from Kagoshima Prefecture, southwestern Japan, in 1998. The average temperature of this year was 2°C higher than that between 1960–1998. Several arthropod species emerged earlier than previous years because of the unusually high average temperature. These species were Homona magnanima, Adoxophyes honmai, Scirtothrips dorsalis, Pseudaulacaspis pentagona, aphids (mainly Myzus persicae and Lipaphis erysimi), and Tetranychus kanzawai. All species showed developmental zeros of less than 10°C. In contrast, Spodoptera litura and Helicoverpa armigera, whose developmental zeros were above the mean winter temperature, emerged as usual in the spring. A possible increase in the number of generations per year was not clearly shown by the trap capture records, but all species are likely to have 1–2 more generations. The total number of male S. litura captured by pheromone traps in 1998 was the largest during the past 14 years. There was a positive correlation between the abundance of males and the mean annual temperatures. In contrast, H. magnanima, A. honmai and aphids were less abundant in 1998, and this occurs once per 4–10 years. No detectable difference in abundance was observed in H. armigera. We concluded that an elevation in mean temperature of 2°C would impact the phenology of insects, but the pattern of response would greatly vary among species.

The insect fauna in paddy fields is composed of resident, migratory and aquatic species each corresponding to the continuous cropping of rice in the same field, harvesting rice as an annual crop, and originating from still water habitats in wetlands. Although IPM is becoming popular in the control of rice pests, those ‘minor’ insects and aquatic insects that have no direct economic impact on rice production have received little attention. Consequently, some of them are in danger of extinction requiring conservation. A new concept, ‘Integrated biodiversity management (IBM)’, is proposed under which IPM and conservation are reconciled and made compatible with each other. As an operational concept in agroecology, premises for implementing IBM are suggested.

Population trends of Chilo suppressalis during the past 20–35 years in Japan, Korea and Taiwan were compared in terms of light trap records and the area infested by Chilo. In all three countries, Chilo showed a declining population trend, first observed in the late 1950s in Japan, followed by the same pattern in Taiwan and Korea, successively. Among the contributing factors, the early planting of rice was suggested as one common factor. This early planting of rice is also followed by, or associated with, various agronomic practices, e.g. the use of varieties with a larger number of tillers, more intensive pesticide control, early harvesting, the mechanization of agricultural practices, etc. An integrated technology system based on early planting was considered the primary factor responsible for the recent decrease in Chilo. The increased utilization of machinery in rice production will encourage a further decline in Chilo in this region. Local and small scale outbreaks of Chilo were observed in all three countries, due to the widespread use of straw for the culture of special crops. However, so long as the current production system remains the same, there is no scope for Chilo’s revival.

The butterfliesPapilio helenus andP. protenor were shown to feed mainly on the nectar of the glory bower,Clerodendron trichotomum, which was the most abundant nectar plant in summer in the study area. Both the species were found to have a proboscis longer than 24 mm corresponding to the length of the corolla tube ofC. trichotomum. Visits to the flowers by these butterflies were observed more frequently than visits by sphingid moths which had previously been believed to be the major pollinators ofC. trichotomum. The male butterflies visited trees ofC. trichotomum frequently, while visits by the females were less frequent. However, once females had visited the tree ofC. trichotomum, they remained there longer than the males. Since the flower ofC. trichotomum has long protruding sexual organs, its pollen grains were found to adhere efficiently to the bodies of butterflies, mainly the thorax, during nectar feeding. Most of the butterflies became loaded withC. trichotomum pollen, and the mean number of pollen grains per butterfly was 1,776 forP. helenus and 2,817 forP. protenor. The flowers opened at any time of day but more frequently in the morning. The nectar was secreted throughout the day. In the maturation of the protandrous flower ofC. trichotomum, the duration of the pistillate phase was about twice as long as the staminate phase. The long flowering period and the short duration of the staminate phase resulted in asynchrony of the flowering stages even within a single cyme on a tree. Such asynchrony and the abundance of attractive flowers on a tree facilitates efficient pollination by the butterflies.

application/pdf, In order to assess the fecundity and the fertility (oviposition rate) of the black swallowtail butterflies (BSB), Papilio helenus and P. protenor, the number of eggs in the ovaries of field-collected females was examined by dissection. Eggs were classified into three categories according to the degree of their maturation. Estimated fecundities (number of eggs in ovaries for the youngest age class) were 530 in P. helenus and 410 in P. protenor. Oviposition of the BSB took place from afternoon to evening. Young females were found to deposit 80 and 35 eggs a day and old females 60 and 25 eggs in P. helenus and P. protenor, respectively. Thus, P. helenus likely has a greater fecundity than P. protenor.

A simulation model of the green rice leafhopper-spiders system was presented. The validity of this model for simulation purpose was tested by comparing the calculated values with observed ones (Fig. 4). The effectiveness of various control measures against leafhoppers was evaluated by computer simulations. The computer simulation demonstrated that the wrong use of selective insecticide, contrary to expectation, brought an increase in the pest density, i. e., that the egg densities of leafhoppers in the 2nd and 3rd generations are increased by the insecticidal application in February, while they are decreased by the July application (Table 2). To obtain satisfactory control by sterile-male release, 320,000 sterile-male per square kilometer should be released even in the combined use with insecticides (Fig. 5). The escape of leafhoppers from predation by spiders was demonstrated by the simulation. It is suggested that spiders are able to suppress the leafhopper populations at a low density when there is a very favorable balance between spiders and leafhoppers, and this condition may be realized by sophisticated use of selective insecticides (Fig. 6). Factors and/or processes which have to be involved in a more improved systems model are discussed.

Control of rice insect pests has been the central problem among the farmers in Asia who depend primarily on rice as a subsistence crop. In Japan, for example, the endemic damage caused by the rice borers Tryporyza incertulas and Chilo suppressalis and the sudden occurrence of epidemics of the brown planthopper, Nilaparvata lugens, were the major causes of loss in rice yield during the pre-war period. Dropping whale oil onto the surface of irrigation water to fight N. lugens was practiced 250 years before the advent of synthetic insecticides. Control of rice borers by cultural practices (e.g. shifting transplanting dates, flooding fallow fields, hand removal of egg masses, and digging out or burning stubbles, in association with the use of light traps and conservation of egg parasites) was commonly used 100 years ago in Japan (94). Since then, massive reports on rice-pest control as well as on biology of the pests have been accumulated, particularly in Japan. More or less comprehensive reviews on the general subject are already available (e.g. 19, 25, 27, 3 1 , 79, 84, 94, 1 1 5, 165). Also, with regard to specific tactics in relation to rice-pest management, some detailed accounts have already been published on biological control (1 14, 143, 209), varietal resistance ( 152, 162, 163, 167), insecticides, (19, 38, 73, 8 1 , 89, 201), and cultural practices (64, 75, 144). Therefore, with this article I neither review all papers on the subject nor review all current research. Instead, I intend to bridge gaps such as the one between theory and practice in rice-pest management, as well as the one between temperate and tropical areas in terms of accumulated data con­ cerning a few selected groups of rice pests.

A predator-prey system involvingLycosa pseudoannulata as predators and both the green rice leafhopper,Nephotettix cincticeps and the brown planthopper,Nilaparvata lugens as prey was studied in an experimental paddy field. Daily predation rates on the prey and weekly disappearance rates ofLycosa females were related to densities of both predators and prey by multiple regression. During the off-season of reproduction for predators and prey, it proved possible to simulate the interaction betweenLycosa and its prey.

An epidemiological system model was developed to evaluate the role of factors which were responsible for the prevalence of rice dwarf virus (RDV) transmitted by the green rice leafhopper,Nephotettix cincticeps. Simulation tests were conducted by varying values of the following three parameters: the vector density, the coefficient of the efficiency of feeding acquisition of RDV of the vector, and that of efficiency of RDV transmission by the vector. The effect of each parameter was assessed in terms of changes in percentages of infected insects and of infected rice hills. Both the percentages of infected insects and of infected rice hills increased rapidly with increasing vector density within a range of low vector density. The former increased linearly when the acquisitive coefficient was increased. But the percentage of infected rice hills was affected to a lesser extent. The percentage of infected insects and that of infected rice hills increased exponentially with increasing values of the transmission coefficient. The results obtained from the simulation tests were discussed in relation to the ecological factors which caused the recent prevalence of RDV.

5,10,15,20,25°Cでキクヅキコモリグモ,コサラグモ,アオバアリガタハネカクシ,コナガゴミムシのツマグロヨコバイ老熟幼虫に対する日当たり攻撃頭数と捕食臨界温度を推定した。10°C以上ではコモリグモが捕食能力において他の3種より格段に優れていた。前2種では5∼10°Cでも捕食活動が認められた。冬期地表面の日平均気温は地上1.2mのそれより平均7°C高く,コモリグモの捕食臨界温度(5.2°C)をほとんど下廻ることがないので,冬期中も捕食活動が行なわれていると考えられる。他方,冬期休閑田に方形枠を設け,1週間毎の調査からコモリグモ,コサラグモ類,ハネカクシ,ゴミムシ類のそれぞれの延べ存在頭数とヨコバイ消失数間の重回帰分析を行なった結果,コモリグモがヨコバイ幼虫の死亡に最も重要な役割を果たしていると推察された。1月下旬から3月下旬の間のヨコバイ消失数は,コモリグモの存在しなかった枠のY=3.7に対し,存在した枠でY=19.5と格段に大きかった。コモリグモ延べ存在頭数とヨコバイ消失数の関係から,コモリグモ密度とヨコバイ消失数の関係式を得,模擬計算から,冬初期のヨコバイ密度が200頭/m2前後では,コモリグモ初期密度5頭/m2のとき越冬後ヨコバイ密度はほぼ半減するという結果を得た。

On the basis of an artificial defoliation experiment, a new growth model of soybean was formulated through a modification of Rudd's (1980) model with regard to his equations for dry matter allocation. Compensatory growth for leaf damage was modelled by a single process in which the dry matter allocation changes dynamically according to the severity of leaf damage. The sums of squared differences between simulations and experimental soybean yields were much smaller in our modified model than in Rudd's original model. The modified model gave a better simulation of yield loss due to defoliation that varied in time and intensity. The relationship between various times and intensities of defoliation and yield loss was shown, which is essential for establishing the dynamic economic injury level in IPM.

イネミズゾウムシ個体群密度の制御機構と平衡密度について検討した。1) 越冬後成虫の産卵は1ポット当り2頭をこえると密度効果が認められ,1ポット当り8頭以上では産卵数の減少が著しかった。2) 経時的密度調査の結果より生存曲線を作成した。卵から成虫までの生存率は主として卵から若齢幼虫までの期間の生存率に支配されていること,またこの時期の死亡率は卵密度に正の依存性を示した。老齢幼虫から土繭形成までの期間の死亡率も密度依存的に変化することがみられた。3) 沿海部平坦地,内陸部平坦地,山間地の3地帯における年次別密度調査の結果では,発生後ほぼ4年目で平衡密度に達した。これらの地域別増殖曲線にロジスティク式をあてはめ平衡密度を計算したところ,沿海部平坦地では低く,山間地で高かった。

(1)幼虫を0, 10, 50, 100, 500, 1,000, 5,000,および10,000ppmの8段階濃度のメソミル溶液に浸漬処理したところ,10および100ppm区でそれぞれ1.3倍および1.5倍と無処理区よりも有意に産卵数が増加した。(2) 蛹を0, 10, 50, 100および500ppmの5通りのメソミル溶液に虫体浸漬した。供試蛹はすべて5.5∼6.5mgのものに限った。その結果,無処理と比較して産卵数および受精率の増加,さらに,成虫生存期間の短縮などが認められた。1日当り1雌当りの産卵数および受精卵数は増加した。こうしたことから内的自然増加率(r)や1か月後の期間増殖率(λ)の値は大きくなり,たとえば10ppmでは無処理と比較して,それぞれ1.13倍および2.03倍となった。

A sight-count method for evaluation of predation by spiders on the green rice leafhopper,Nephotettix cincticeps was proposed and its applicability was tested under natural conditions.

水稲害虫の総合防除の第1段階として,クモ類などの天敵類に影響の少ない,殺虫剤を用い散布回数と散布濃度の両面から,散布量を減少させる試みを行なった。1) 1969年にはニカメイガ防除剤としてBHC剤から有機燐剤(MEP,ダイアジノン剤)への移行の試みを行なった。その結果,有機燐剤の方がニカメイガに対する防除効果が高く,収量も慣行防除田よりは,増収が期待できることが実証された。2) 1970年にはクモ類に影響の少ない殺虫剤を用い,慣行より1∼2回少ない散布回数による防除を試みた。その結果,クモ類に影響の少ない薬剤の方がウンカ・ヨコバイ類に対する防除効果は高く,慣行より1∼2回防除回数を減らしても収量は慣行よりも高いことが実証された。3) 1971年にはクモ類に影響の少ない薬剤を,慣行より1∼2回散布回数を減少させたうえ,散布濃度を2分の1に減少させて防除を試みた。その結果,ニカメイガは発生が少なく防除効果を判定できなかったが,ウンカ・ヨコバイ類の防除は可能であり,収量も慣行防除田と同等であった。