The action of some systemic aphicides on the eggs of Anthocoris nemorum (L.) and A. confusus Reut

Comparisons were made of the systemic action of phorate, menazon and dimethoate on Aphis fabae Scop, and on the eggs of the aphidophagous Anthocoridae Anthocoris nemorum (L.) and A. confusus Reut., which are laid within plant tissue. Against 4th-instar apterous A. fabae the order of toxicity of the insecticides taken up by roots of the field bean Vicia faba L. was: menazon > dimethoate > phorate. Phorate concentrations needed to kill all A. fabae (10–15 ppm of wet weight of plant) killed most A. nemorum eggs but did not harm A. confusus eggs. Few A. nemorum eggs were killed by 15 ppm of menazon or 5 ppm of dimethoate. In the field a commercial in-row treatment of 1·5 lb/acre of phorate applied as granules in the seed drill of field beans sown in late April killed 86 % of eggs laid in June by overwintered A. nemorum and 30% of those laid in late July by second-generation females. Plants initially treated with 6 lb of in-row phorate per acre killed 74% of A. nemorum eggs in late July but did not harm A. confusus eggs. A. nemorum eggs laid in early June were unharmed by 1·5 lb/acre of in-row menazon. Of the A. nemorum eggs, 92–96% were inserted into the stipules and leaf margins of young bean plants, i.e. in the region (peripheral and distal part of the leaf) where most ³²P from labelled phorate accumulates after root uptake. The egg-laying sites of A. nemorum in potatoes and brussels sprouts (edges of the leaves) and in oats (the leaf tips) are also where most of the ³²P accumulates. In contrast, 98% of A. confusus eggs were laid in the stems, petioles and leaf midribs of field beans, where there was generally much less ³²P from labelled phorate.     

The action of some systemic aphicides on the nymphs of Anthocoris nemorum (L.) and A. confusus Reut

The aphicides phorate, dimethoate and menazon were compared to elucidate the different pathways by which they can affect Anthocoris nymphs and their aphid prey.
When nymphs were caged in contact with deposits on bean leaves phorate and dimethoate had contact LC 50s of 20 and 3 μg/cm² respectively to Anthocoris nemorum and 46 and 6 μg/cm² to A. confusus. When the nymphs were confined on treated leaves on the opposite surface to the deposits, neither phorate nor dimethoate killed them. Menazon did not kill anthocorids at any dosage. All three aphicides killed over 50% of Acyrthosiphon pisum (Kalt.) on bean leaves at 1.6 μg/cm² whether the aphids were on the treated or untreated surface.
Experiments with ³⁵S-labelled phorate showed that anthocorids confined on phorate-treated bean plants, with or without insect food, accumulated the insecticide or its labelled derivatives. In field experiments in which A. nemorum were caged on plants treated with phorate, many were killed on young newly treated plants but not on older plants. A. confusus was relatively unaffected.
Anthocorids were reared from 2nd-instar nymphs to adults on aphids killed systemically with phorate, dimethoate or menazon without ill effects, despite evidence that ³⁵S-labelled phorate was ingested from the aphids and excreted in the faeces.
In the field, fewer large A. nemorum nymphs were found in August in plots of tick beans treated with phorate granules at 6 lb/acre (6.7 kg/ha) when sown, than in plots treated at 1.5 lb/acre (1.7 kg/ha) with phorate or menazon or untreated plots.     

The effects on soil fauna of insecticides tested against wireworms (Agriotes spp.) in wheat

The organophosphorus insecticides Bayer 38156 (O-ethyl S-p-tolyl ethyl phosphonodithioate), trichloronate, Stauffer N 2790 (O-ethyl S-phenyl ethyl phosphonodithioate), thionazin and fenitrothion were compared with aldrin, dieldrin and γ-BHC for their effects on soil fauna, particularly wire-worms, and on crop yields in 1964 and 1965. At 1·5 lb active ingredient/acre, none of the organophosphates had as great an effect on wireworms as an aldrin spray at 2·25 lb a.i./acre or a dieldrin seed dressing at 2·25 lb a.i./acre. Some treatments significantly increased and some significantly decreased numbers of mites and Collembola. Except for Allolobophora chlorotica in plots treated with Bayer 38156, earthworm numbers were greater in plots sprayed with Bayer 38156 or aldrin, or sown with dieldrin-dressed seeds, than in untreated plots. In May 1964, one month after sowing, untreated plots had significantly fewer plants than plots sprayed with aldrin, trichloronate or Bayer 38156, or sown with γ-BHC or dieldrin-dressed seeds, but yields from untreated plots at harvest were high for such a large wireworm population and did not differ significantly from yields of treated plots in either year. The persistence of thionazin and Bayer 38156 in treated plots was measured by a bioassay using Collembola. Bayer 38156 was detected in plots 1 month after spraying but not after 6 months. Thionazin left detectable residues 1 month after spraying in the two acid plots but not in the two alkaline plots. More frequent samples taken from thionazin-treated plots in 1965 showed a similar pattern of persistence, and laboratory tests, using soil mixed with various amounts of powdered calcium carbonate, confirmed that thionazin persisted longer in more acid soils.     

Influence of soil moisture on the performance of granular systemic insecticides applied to soil

Control of aphids by the four systemic insecticides, dimethoate, disulfoton, menazon and phorate, applied as granules below seed potatoes at planting, was investigated under different soil moisture conditions. Results confirmed previous conclusions that dimethoate and menazon are more effective in wet than in dry soils, whereas disulfoton and phorate are equally effective in both. However, even with dimethoate and menazon effects of moisture were small and were probably the result of several different interacting factors.     

Effects of oximecarbamate, organophosphate and benzimidazole nematicides on life cycle stages of root-knot nematodes, Meloidogyne spp.

A study was made of the effects of concentrations of 2 to 32 ppm of oximecarbamate, organophosphate and benzimidazole nematicides on the hatch, larval viability and migration of Meloidogyne javanica, M. incognita and M. hapla and on development of M. javanica in roots. Aldicarb at less than 8 ppm had little effect on hatch and methomyl markedly affected only the hatch of M. hapla. As little as 2 ppm of fenamiphos or thionazin markedly reduced hatch of all three species but less than 8 ppm ethoprophos significantly reduced only the hatch of M. incognita and phorate had little effect on hatch. Benomyl and thiabendazole had no significant effects on hatch. When egg masses of M. incognita were transferred from nematicides which suppressed hatch to water, hatching occurred, but aldicarb, fenamiphos, ethoprophos and thionazin significantly reduced total hatch. None of the nematicides killed larvae of the three species immersed in 16 and 32 ppm solutions of them for 3 days. Aldicarb at 2 ppm reduced migrations of all three species; the effects of methomyl, fenamiphos or thionazin on migration varied according to species, while phorate, ethoprophos, benomyl or thiabendazole had little or no effect on migration. Aldicarb or thionazin at 2 ppm stopped development of M. javanica in roots of tomato seedlings while methomyl, ethoprophos or fenamiphos at 4 ppm reduced development by 60% and at 8 ppm of ethoprophos or fenamiphos or 16 ppm of methomyl, development was stopped. Phorate had little effect on development and benomyl or thiabendazole had no effect. Nematicide concentrations which reduced development prevented the normal orientation of larvae in the roots and reduced or prevented giant cell formation.     

The control of Aphis fabae Scop, on spring-sown field beans (Vicia faba L.)

Disulfoton or phorate granules or demeton-S-methyl, menazon and vamidothion sprays, applied once in early June as preventive treatments before heavy aphid colonies developed, gave good control of Aphis fabae Scop, on field beans. Phosalone gave relatively poor results and DDT was ineffective. Applications in June to crops sown in February and early March were made with minimal wheel damage to the crop and are known to be less harmful to bees than sprays at flowering time. Eradicant treatments with demeton-S-methyl and dimethoate sprays or with disulfoton or phorate granules on heavily infested plants during flowering were also effective, but menazon was less satisfactory. These eradicant sprays are likely to be harmful to bees, and wheel damage in late June reduced yield by 1–2 cwt/acre (125–250 kg/ha). Peak populations of 3000 aphids/plant in early July reduced yield by 6 cwt/acre (750 kg/ha) in one trial.     

Effects of fungicides and insecticides applied to spring barley sown on different dates in 1976-79

Factorial experiments in 1976–1979 investigated the effects of sowing date, fungicides (ethirimol seed treatments and tridemorph sprays) and insecticides (phorate applied to the soil, and menazon or dimethoate sprays) on powdery mildew, aphids, barley yellow dwarf virus (BYDV) and grain yield of spring barley (cv. Julia in 1976 and 1977; cv. Wing in 1978 and 1979). Late sowing usually increased the severity of powdery mildew, numbers of aphids and incidence of BYDV and generally decreased yield. Responses to pesticides were commonly greater on the late-sown than on the early-sown barley. Response to fungicides are principally attributed to the control of powdery mildew (Erysiphe graminis f. sp. hordei; the target species) but responses to insecticides cannot be attributed to virus control and seem unlikely to be due solely to control of aphids, whose numbers were relatively small. There were some effects of fungicides on aphids and insecticides on mildew, but they were inconsistent and too small to affect crop protection strategies.     

Pesticides and the soil fauna: effects of aldrin and DDT in an arable field

Aldrin dust (3 cwt. of 1¼% per acre) or DDT dust (2 cwt. of 5 % per acre) was applied to small plots replicated four times and four plots were untreated. All plots were kept fallow for one year. Soil samples were taken at 2 to 3-monthly intervals and the fauna extracted by a notation method. The insecticides did not affect Lumbricidae, Enchytraeidae or Nematoda. Nearly 100 species of arthropods were found, and the greatest effects were those of DDT on mesostigmatid mites and of aldrin on entomobryid or isotomid Collembola and on Pauropoda. Most species of Collembola increased in DDT-treated plots, apparently because mesostigmatid mites were reduced. In terms of biomass Coleoptera and Diptera were most affected. Both insecticides killed more pests than predators or beneficial animals. The effects of the insecticides were greatest during late summer or autumn.     

八大公山自然保护区森林土壤动物群落多样性的初步研究

对八大公山自然保护区森林土壤动物群落的多样性进行了初步研究,共获得２７类土壤动物,隶属５门１２纲,其中螨类、弹尾类、线虫类和线蚓类为优势类群,占全捕量的８８．６７％,是该区土壤动物的主体。土壤动物密度与土壤类型和土壤性质有一定的关系,主要土壤类型层中动物密度为：黑色石灰土中１２５．６万个／,棕色石灰土中１０４．３万个／ｍ＾３,山地生草黄棕壤中９１．３万个／ｍ＾３,山地黄棕壤中７４．２万个／ｍ＾３。     

Experiments on integration of chemical and biological control of aphids on brussels sprouts

Two field experiments were made to test whether natural enemies would take over control of brussels sprouts aphids at the time when protection from a selectively acting, soil-applied systemic insecticide, menazon, began to fail. The natural enemies, notably Syrphidae, proved ineffective against Brevicoryne brassicae L. despite advantages given by the insecticide and by close planting, which greatly increased the ratio of numbers of syrphid eggs and larvae to aphids. Thus, development of the aphid population was little altered when infested plants were kept free of most natural enemies by hand removal. I lb/acre (1–12 kg/ha) of menazon applied as spot treatments to the soil at planting-out time decreased the number of overwintering parasite mummies by 70 % but such ‘mortality’ was compensated for by decreased mortality from hyperparasites and other causes, so the numbers of adults of the primary parasite Diaretiella rapae (McIntosh) which emerged in the spring were similar to those from untreated plots. Soil cultivation in winter drastically decreased the numbers of emerging adult primary parasites, hyperparasites and syrphids. The menazon treatment designed for integrated control (1 lb/acre) seemed too unpredictable in action, e.g. less effective in dry than in damp conditions, to provide the hoped-for chemical control needed until natural enemies became abundant. Menazon at 4 lb/acre (4·48 kg/ha) protected the crop throughout the growing season and bioassays showed that menazon or its toxic derivatives continued to occur in leaves during cool periods in winter and also in the following April-May nearly 1 year after application. The same amount of menazon per unit area of crop was less effective on 1 ft 6 in (45·6 cm) spaced than on 3 ft (91·2 cm) spaced brussels sprouts plants.     

浦东滩涂中型土壤动物群落结构及土质酸碱度生物评价分析

1999年,对上海浦东滩涂4类不同酸碱度土壤中的中型土壤动物进行了调查。应用物种丰富度,个体数多度,多样性指数和均匀度4个群落参数,并结合种类研究,讨论了土壤动物群落结构与不同酸碱度土壤的关系。结果表明,土壤中弹尾目和蜱螨目对不同酸碱度土壤反应敏感。弹尾目的3个群落参数和蜱螨目的4个参数均很好地反映与土壤反应敏感。弹尾目的3个群落参数和蜱螨目的4个参数均很好地反映与土壤pH的关系,相关系数分别在0．9以上和0．85左右,在pH相差较大的情况下,可以区分不同酸碱度的土壤。弹尾目的符Tao(Paranura sp.)可用于评价酸碱度较接近的土壤,球角Tao(Hypogastrura sp.）可用于评价酸碱度相差较大,高pH或环境条件较恶劣的土壤。     

瑞昌石灰岩红壤区退耕还林土壤动物群落特征

以江西瑞昌石灰岩红壤区采取多树种混交、竹阔混交和林苗一体化3种模式退耕还林6年后的林地为研究对象,分析退耕还林对土壤动物群落及其数量变化的影响.退耕还林地土壤动物隶属于6门17纲34目,优势类群为线虫纲,占总类群数的86.7％;常见类群为蜱螨目、线蚓科以及弹尾目.对照农耕地土壤动物隶属于5门10纲21目,优势类群为线虫纲,占总密度的86.7％;常见类群为蜱螨目和线蚓科.退耕还林地土壤稀有类群数(30类)明显大于农耕地(18类).除冬季外退耕还林地土壤动物类群数和平均密度显著高于农耕地.土壤动物的垂直分布具有明显的表聚性,表层(0～5 cm)土壤动物数量与5～10、10～15 cm土层存在极显著差异,且退耕还林地表聚性较农耕地更明显.退耕还林地土壤动物类群数均为夏季＞秋季＞春季＞冬季,且夏、秋季与春、冬季差异显著;平均密度为秋季＞夏季＞春季＞冬季,季节间差异显著.退耕还林地土壤动物生物多样性指数显著高于农耕地,3种退耕还林模式中,多树种混交模式的生物多样性最高,林苗一体化模式最低.     

Links between the detritivore and the herbivore system: effects of earthworms and Collembola on plant growth and aphid development

Effects of Collembola (Heteromurus nitidus and Onychiurus scotarius) and earthworms (Aporrectodea caliginosa and Octolasion tyrtaeum) on the growth of two plant species from different functional groups (Poa annua and Trifolium repens), and on the development of aphids (Myzus persicae) were investigated in a laboratory experiment lasting 20 weeks. Using soil from a fallow site which had been set aside for about 15 years, we expected that nitrogen would be of limited supply to plants and hypothesized that the soil animals studied, particularly earthworms, would increase nutrient availability to plants and thereby also modify aphid reproduction and development. Plant growth was modified strongly by the presence of soil animals. Earthworms caused a more than twofold increase in shoot and root mass of P. annua but increased that of T. repens by only 18% and 6%, respectively. However, earthworms neither affected plant shoot/root ratio nor the nitrogen concentration in plant tissue. In contrast, the presence of Collembola caused a reduction in plant biomass particularly that of P. annua roots, but plant tissue nitrogen concentration was increased, although only slightly. Aphid reproduction on T. repens was lowered in the presence of Collembola on average by 45% but on P. annua increased by a factor of about 3. It is concluded that Collembola decrease aphid reproduction on more palatable host plants like T. repens but increase that on less palatable ones like P. annua. Earthworm presence also affected aphid reproduction but the effect was less consistent than that of Collembola. In the presence of earthworms, aphid reproduction was in one experimental period increased by some 70%. Earthworms also modified the numbers of Collembola and their vertical distribution in experimental chambers. Exploitation of deeper soil layers by H. nitidus was increased but, generally, O. scotarius numbers were reduced whereas those of H. nitidus increased in earthworm treatments. The presence of Collembola also influenced earthworm body mass during the experiment. In general it declined, but in the presence of Collembola loss of body mass of A. caliginosa was more pronounced. We conclude that inhibiting effects between Collembola and earthworms resulted from the use of a common resource, litter material rich in nitrogen. This is supported by the higher C/N ratio of the litter material in the presence of earthworms and Collembola by the end of the experiment. Effects of soil invertebrates like Collembola and earthworms on plant performance and aphid development are assumed to be modified by complex direct and indirect interactions among soil animal groups. Received: 6 July 1998 / Accepted: 1 March 1999     

Laboratory and field tests in 1966-67 on chemical control of wireworms (Agriotes spp.)

Of sixteen compounds applied to soil in laboratory tests, azinphos-ethyl, P2188 (O,O-diethyl S-chloromethyl phosphorothiolothionate), ‘Dursban’ (O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate), P1973 (S-(N-methoxycarbonyl-N-methylcarbamoylmethyl) dimethyl phosphorothiolothionate), B77488 (O,O-diethylphosphorothioate O-esterwith phenylglyoxylonitrile oxime) and R42211 (O,O-diethyl O-(2-diethylamino-6-methyl-pyrimidin-4-yl) phosphorothioate) killed wireworms when first tested, but in second tests with the same soils only ‘Dursban’, P2188 and B77488 did so. Treating seeds with ‘Dyfonate’ (O-ethyl S-phenyl ethyl phosphonodithioate) or with ethion/γ-BHC mixtures killed few wireworms. Three field trials compared the organophosphorus insecticides ‘Dursban’, ‘Dyfonate’ and phorate with organochlorine standards. In trials with barley and potatoes the standard was 3 lb a.i./acre (3·36 kg/ha) of aldrin. The organophosphorus compounds increased plant stands of barley almost as much as aldrin, although they killed fewer wireworms; and they protected fewer potato tubers from wireworm damage. The third trial compared the organophosphorus compounds with 0·5 lb a.i./acre (0·56 kg/ha) γ-BHC sprayed on a site drilled with sugar beet seed dressed with dieldrin. The γ-BHC increased plant stands almost as much as did 3 lb a.i./acre of the organophosphorus insecticides, and killed as many wireworms.     

Valuation of efficacy and nonrepellency of indoxacarb and fipronil-treated soil at various concentrations and thicknesses against two subterranean termites (Isoptera: Rhinotermitidae)

The efficacy and nonrepellency of indoxacarb (150 SC, 150 g [AI]/liter) and fipronil (Termidor SC, 9.1% [Al]) against field-collected eastern subterranean termite, Reticulitermes flavipes (Kollar), and the Formosan subterranean termite, Coptotermes formosanus Shiraki, were evaluated for mortality and penetration into treated soil in laboratory glass tube bioassays. Both insecticides were tested at five concentrations (0, 1, 10, 50, and 100 ppm) and two thicknesses (20 and 50 mm) of treated soil. Indoxacarb caused significantly greater mortality than controls at all treatment thicknesses of > or = 10 ppm, but not at 1 ppm. Concentration and treatment thickness of indoxacarb significantly affected termite mortality. Eastern subterranean termites were significantly more susceptible to indoxacarb than Formosan subterranean termites, but there were no intercolony differences in either species. Termites completely penetrated through all treatment thickness of indoxacarb-treated soil at all concentrations, except one of the six Formosan subterranean termite replicates of 50 mm at 50 ppm, when all termites were killed before tunneling through the treated soil. Fipronil resulted in significantly faster and greater termite mortality than indoxacarb at corresponding concentrations. Concentration and treatment thickness of fipronil also significantly affected termite mortality. There was no intercolony difference in susceptibility to either insecticide in either termite. Both termite species completely penetrated 20-mm treatments of all tested fipronil concentrations, as well as 50-mm soil treated with fipronil at < or = 10 ppm. At 50 and 100 ppm fipronil, termites tunneled only a mean of 87 +/- 0.21 and 47 +/- 0.18% deep into 50-mm treated soil, respectively, before death. Both insecticides demonstrated a delayed mode of activity and nonrepellency against the two termite species.     

Monitoring of chemical fertilizers on toxicity of two carbamate insecticides to the cyanobacterium Anabaena PCC 7120

The effects of individual chemical fertilizers (urea, superphosphate and potash) on the toxicity of two carbamate insecticides (carbaryl and carbofuran) to the nitrogen-fixing cyanobacterium Anabaena PCC 7120, were studied in vitro at partial lethal levels of each insecticide. Urea at 10 and 50 ppm levels reduced the toxicity due to carbaryl at 50 ppm partial lethal dose and due to carbofuran at 100 and 250 ppm partial lethal doses. Urea at 100 ppm enchanced the toxicity of both insecticides. Superphosphate at 10 ppm reduced the toxicity of carbaryl at 50 ppm and carbofuran at 100 and 250 ppm, but it enhanced the toxicity due to both insecticides at 50 ppm superphosphate. The toxicity due to carbaryl at 40 and 60 ppm were reduced by 100 and 200 ppm potash, but higher potash levels caused enhancement of toxicity. Carbofuran toxicity at 100 ppm was reduced but at 250 ppm the toxicity was enhanced with 100 ppm potash. Urea, superphosphate and potash caused no significant change in number of vegetative cells between the successive heterocysts at 10 and 50 ppm of urea and superphosphate, respectively, and 100 ppm of potash.     

巨桉人工林中小型土壤动物类群分布规律

研究了四川省洪雅县巨桉人工林中小型土壤动物类群及数量分布规律.结果表明,巨桉人工林四季共获中小型土壤动物13 550头,分属6门13纲26目,以蜱螨目、线虫纲、弹尾目为优势类群,以线蚓科为常见类群.各样地中小型土壤动物类群数、个体数均有明显季节变化,以秋季或冬季最高,春季最低,夏季次之.中小型土壤动物密度剖面分布表聚性明显,但在5～10 cm和10～15 cm土层间有时会出现逆向分布现象.中小型湿生土壤动物密度为3.333×10³～2.533×10⁵个·m^-2,中小型干生土壤动物密度为1.670×10²～2.393×10⁵个·m^-2,中小型湿生土壤动物密度自上而下减少的速率小于中小型干生土壤动物.巨桉人工林中小型土壤动物密度-类群(DG)指数以春季最低,秋季或夏季最高（可达6.637）.巨桉人工林与青冈次生林中小型土壤动物密度及DG指数均无显著差异.     

Principles of insecticide action on mushroom cropping: incorporation into compost

A series of cropping experiments has demonstrated that mushroom yields show an approximate logistic response to a range of insecticide concentrations incorporated in the compost. This principle applies only to the cumulative yield at any flush, and the response of an individual flush is, therefore, related to the difference between two logistic curves. Increases in crop can thus occur in later flushes, partially compensating for earlier losses. With diazinon treatments, but not thionazin, some of this compensation was due to increases in the size of mushrooms. It is concluded that commercial applications of 50 ppm diazinon could cause up to 2–5 % reduction in crop and that 10 ppm thionazin may cause a 6% loss which must be weighed against the advantages of treatment. Suggestions are made for the design and interpretation of future trials.     

The toxicity of some soil-applied systemic insecticides to Aphis gossypii (Horn. Aphididae) and Phytoseiulus persimilis (Acarina: Phytoseiidae) on cucumbers

Tests with potted cucumber plants confirmed that granular or soil drench treatments applied against Aphis gossypii Glover may limit the performance of a predaceous species introduced to control another pest. Soil applications of thionazin, methomyl, demeton-S-methyl and aldicarb in equal amounts caused deaths, in descending order of toxicity, of the predatory mite Phytoseiulus persimilis Athias-Henriot. This effect was not demonstrated for pirimicarb, menazon or isolan on whole plants at rates up to 10 mg a.i. nor in laboratory tests on detached plant portions. Methomyl and thionazin, but not aldicarb, were relatively more toxic to P. persimilis than to its prey, Tetranychus urticae Koch. Some survival of P. persimilis occurred on plants treated with demeton-S-methyl, but this material was inferior to pirimicarb in both selectivity and persistence. Pirimicarb offers practical control of A. gossypii on cropping cucumbers, without phytoxicity or residues, when applied at 125 mg a.i./plant. It is therefore preferable to other aphicides for use on cucumbers during propagation or cropping, especially where the favoured means of control of T. urticae is by introductions of P. persimilis. Qualitative evidence of in vitro tests suggested that those systemic materials which affect P. persimilis do so by ‘food-chain’ toxicity, but that vaporization from the leaf may also be a factor.     

Seasonal fluctuation of different edaphic microarthropod population densities in relation to soil moisture and temperature in a pine,Pinus kesiya Royle plantation ecosystem

Seasonal fluctuations of soil and litter microarthropod populations in a pine,Pinus kesiya Royle plantation of North Eastern India were investigated between November 1976 and November 1977. Three major groups were recognized: (a) Collembola, (b) Acarina and (c) miscellaneous. Collembola was the most abundant group and was dominated byIsotoma trispinata (MacGillivray). The total microarthropod density ranged from 26,800 per m² to 145,200 per m². Collembola densities ranged from 10,000 to 121,200 per m², Acarina densities ranged from 8,800 to 41,600 per m², and the miscellaneous group ranged from 1,200 to 6,400 per m². Soil moisture was positively correlated with total arthropod, Collembola and Acarina densities. Soil temperature was positively correlated only with Acarina. Densities of Collembola and Acarina were negatively correlated.The work described in this paper was carried out while the author was at the Department of Zoology, North Eastern Hill University, Shillong, Mehgalaya (India).It was presented at the Ninth International Biometeorological Congress, 23rd Sptember–1st October, 1981, Osnabrück and Stuttgart-Hohenheim, FRG.