Myosoma nyanzaensis sp. n. is described and illustrated, and is distinguished from the only other known Old World species, M. chinensis (Szépligeti) comb. n. (= Bracon chinensis Szépligeti). M. nyanzaensis is the first species of the genus to be described from the Afrotropical Region, where it has been reared as a gregarious ectoparasitoid of larvae of the pyralid moth Chilo partellus (Swinhoe) infesting maize and sorghum.

Termite damage is a major problem in tropical forestry especially where exotic tree species are used. Stressed tress are generally the most susceptible to attack. Dry-wood termites (Kalotermitidae) live and feed in dead wood but sometimes attack living parts of mature trees; generally, they are pests only in the humid tropics, causing local but sometimes serious damage. Coptotermes (Rhinotermitidae) causes more widespread and serious damage to mature trees, especially in Malaysia and Australia. The most serious losses (up to 100%), due predominantly to various Macrotermitinae (Termitidae) such as Macrotermes, Odontotermes and Microtermes, occur in young, exotictrees such as Eucalyptus in dry regions in Africa and India. Chemical control of dry-wood termites is not feasible; use of resistant trees is probably the only satisfactory strategy. Control of Coptotermes by various methods has been suggested; but only insecticide injection into nests within affected trunks (Australia) and destruction of nests with explosives prior to planting, followed by destruction of queens in subsequently located nests (Papua New Guinea), are effective and economically viable. Attack on seedings, especially by Macrotermitinae in Africa and India, can be prevented by the increasingly unacceptable persistent cyclodienes used as mound poisons or as a barrier around the roots preventing attack by subterranean species. Controlled-release formulations of otherwise non-persistent insecticides are being development but are expensive and not widely available. Many non-chemical measures have been suggested, but none has been rigorously evaluated; none will provide the almost complete protection afforded by cyclodienes. Biological control shows little promise. Use of resistant tree species and development of resistant varieties offers the only long-term solution, but until these are available there will be a need to continue using cyclodienes or rapidly to develop alternative control methods.

The biology and pest status of Rhopalosiphum padi (L.) in Europe are critically reviewed. New data are presented and the temporal occurrence of the aphid and its host-plants considered. In Britain, R. padi is a pest mainly because of its ability to transmit virus diseases, in particular barley yellow dwarf virus. In other European countries, especially in Scandinavia, R. padi is a pest in its own right. Predator and parasite complexes in Britain and Finland are compared and contrasted. The occurrence of R. padi as a pest of cereals in Europe is compared with that of Sitobion avenae (F.) and Metopolophium dirhodum (Walker). It is postulated that the great abundance of the primary host of R. padi, bird cherry (Prunus padus), and the spring planting of cereals in colder climates such as in Finland are major factors contributing to the differences in pest status of this aphid between Britain and in Scandinavia.

Feeding by adults of Neochetina eichhorniae Warner on water hyacinth, Eichhornia crassipes, significantly increased the hardness of the lamina of the youngest leaf and the petioles of the youngest three leaves, while the moisture content of the petioles and laminae was significantly reduced. However, variations in leaf hardness did not significantly affect feeding by the weevils, and leaf age was considered to have a greater effect. The results help explain field observations of the relative abundances of N. eichhorniae and the pyralid Sameodes albiguttalis (Warren), which also attacks water hyacinth.

High levels (>1000-fold) of resistance to DDT, permethrin and deltamethrin were detected in Culex quinquefasciatus Say from Saudi Arabia. Biochemical enzyme and metabolic studies indicated that there is evidence for a metabolic basis to both the organochlorine and pyrethroid resistances. Electrophysiological studies indicated that there is no kdr-type mechanism conferring resistance to the pyrethroid lambda-cyhalothrin neurophysiologically, although there is evidence of cross-resistance between DDT and the pyrethroids by bioassays. There was a change in the oxidase system in both the DDT- and permethrin-selected strains and an increase in glutathione transferase activity in the DDT-selected line. Metabolic studies indicated that both oxidases and glutathione transferases are involved with DDT resistance as DDA and DDE were the predominant metabolites after a 5-h in-vitro incubation period. Permethrin resistance is likely to involve an increase in oxidative degradation, but further metabolic studies are needed to confirm this.

Lucerne labelled with 131I or 125I was used to mark field colonies of the harvester termite Hodotermes mossambicus (Hagen) in South Africa. The foraging area was delineated by plotting the distribution range of radioactive workers collected on the soil surface over a period of up to 57 days. Foraging areas of single colonies varied between 0.5 and 3.1 ha. These areas were not necessarily the exclusive territory of a single colony. Inter-worker aggression assays confirmed these conclusions.

A Robinson 125-W mercury-vapour light-trap was operated at an exposed site near Cranfield aerodrome, south-eastern England. The effects of moon-light, temperature and wind speed on light-trap catch were investigated. The dependent variable, In (catch +1), was compared with the independent variables moonlight illuminance, air temperature and wind speed, using multiple regression analysis. An algorithm was developed and used to estimate moonlight illuminance. Increases in mean illuminance and mean wind speed were associated with a decreased light-trap catch. Increases in mean temperature were associated with an increased catch. When the moth catch was broken down into individual families and species, other trends became apparent. Catches of noctuid moths were unaffected by variation in mean illuminance, although they were influenced by variation in mean temperature and mean wind speed. On the other hand, catches of crambine moths were very sensitive to fluctuations in mean illuminance and mean wind speed although unaffected by changes in mean temperature. The multiple regression equations were used to predict future light-trap catches. The correlations between observed and predicted In (catch +1) for (a) all moths, (b) noctuid moths and (c) crambine moths, were very good. It is suggested that the observed moonlight trend for crambine moths is a consequence of changing behaviour as moonlight illuminance changes rather than the alternative of changing light-trap effectiveness.

The performance of Cactoblastis cactorum (Berg) as a biological control agent of the cactus weeds Opuntia ficus-indica and O. aurantiaca was assessed by compiling life-tables for each host-plant, in both a summer and a winter generation, at a site in South Africa. Egg predation, mostly by ants, ranged from 54 to 74% and was significantly higher on O. aurantiaca than on O. ficus-indica. Larval mortality on O. aurantiaca was high during the summer generation (65%), possibly because of dehydration of cladodes. Survival on O. aurantiaca was 55 and 60% of that on O. ficus-indica in the summer and winter generations, respectively. Adult mortality, calculated from the life-tables, was 45 and 84% in the summer and winter generations, respectively. The most important components of mortality were natural enemies in the summer generation and weather-related factors in the winter generation. Host-plant-related mortality was not as great as was formerly supposed.

A strain of Anopheles culicifaciesGiles (species B) originally collected from Aurangabad, Maharashtra State, India, showed highly specific resistance to malathion. Homogenates of one-day-old adults metabolized 14C-labelled malathion at a level comparable with strains of A. stephensi Liston and A. arabiensis Patton known to possess the malathion carboxylesterase resistance mechanism and at a higher rate (6.4 and 7.8 times, respectively) than malathion-susceptible strains of these species. The major metabolite obtained was malathion dicarboxylic acid, a carboxylesterase product, which suggests that this may be the principal resistance mechanism in this strain. Levels of non-specific esterase activity in larvae and adults were similar to those shown by both the susceptible and resistant strains of A. stephensi, implying that no quantitative increase in esterases had occurred. Microtitre plate assays on individual mosquitoes provided no evidence for the presence of the insensitive acetylcholinesterase resistance mechanism.

Adults of Musca vetustissima Walker that were caught when attracted to humans in the field responded positively in a later test when a hand was inserted in a cage, both in terms of proportion responding and time spent on the hand. Flies with a similar adult diet, whether of culture origin or the first-generation offspring of field-caught flies, responded similarly to the hand in the cage provided they were of similar size. A larger proportion of small flies than of large ones came to the hand, and stayed for longer periods. Large protein-deprived and dung-fed (suboptimal protein) flies had a nuisance value between 28 and 35 times as great as large blood-fed flies, while small blood-fed flies had a nuisance value 18 times as great. The nuisance value of small protein-deprived and dung-fed flies was between 61 and 67 times as great. Residence period on the hand increased with time in large protein-deprived flies but not in flies in the other categories tested. Few flies responded to the hand during the first 15 day-degrees C post eclosion, or when gravid or nearly gravid; the most responsive flies were in ovarian stages 0B, 1, 2 and 3. The implications of these results are discussed in terms of the fly nuisance levels experienced in south-eastern Australia.

Copidosoma graminis sp. n., a polyembryonic encyrtid parasitoid of armyworm pests of gramineous crops and pasture in Australia, is described and compared with related species. The parasitoid plays an important role in the natural control of these pests in Australia.

A key for the identification of males of all Afrotropical species of the subgenus Atherigona of Atherigona described to date is presented. Four new species, A. alaotrana sp. n. from Madagascar, A. bowdeni sp. n. from Uganda, A. dentifolia sp. n. from Kenya and A. palpalis sp. n. from Nigeria, are described.

Four groundnut genotypes were grown in a randomized block design across a drought-stress gradient to determine the influence of this factor on insect distribution in the 1985–86 post-rainly season near Hyderabad, in peninsular India. The leaf-miner Aproaerema modicella (Deventer) was most abundant on the most stressed plants. The cicadellid Empoasca kerri Pruthi had the reverse distribution. The thrips Frankliniella schultzei (Trybom) and Scirtothrips dorsalis Hood were at first densest where drought stress was least. Their distribution subsequently became reversed and, as the condition of their hosts worsened, they again became most abundant at the wetter end of the gradient. Bud necrosis disease caused most mortality where drought stress was highest. A subsidiary experiment indicated that the intensity of overhead irrigation did not influence the density of A. modicella. There were marked genotype effects: JL 24 carried the highest density of insects and was most susceptible to bud necrosis disease: NC Ac 343 had the lowest leaf-miner and cicadellid populations. M 13 and ICGS 11 had intermediate characteristics.

Metopolophium dirhodum (Walker) is occasionally a pest of cereals in the UK. A simulation model was developed to study its population dynamics and damage potential. The model was initiated by the aphid immigration as measured by 12·2-m suction trap samples and with temperature as the major driving variable. It was validated with field observations from three contrasting years, 1979, 1985 and 1986. The model accurately predicted aphid populations and yield loss in a major outbreak year (1979) but was less accurate when densities were lower (1985 & 1986). Possible reasons for these discrepancies are discussed.

Bruchus dentipes Baudi was found to have four larval instars, and the sex ratio was very close to 1:1. Both sexes fed on pollen and nectar of faba beans (Vicia faba) for seven days before and throughout the oviposition period of the females, which was about 33 (range 26–40) days. The beginning and peak of oviposition were influenced by the phenology of the crop, particularly flowering and pod-setting dates, but also temperature. Females laid an average of 123 (range 28–310) eggs, and the end of the adult life in the field came in May when the pods had matured. In different years, peak oviposition occurred on different dates in April when the pods were still all green. During the quiescence period in the winter, females obtained from wetted seeds were fed with different diets in the laboratory, but only those supplied with faba bean flowers laid eggs. No major adult mortality occurred in seeds harvested in May and stored until the end of March of the following year, after which mortality rose steeply till all adults had died by early June. Therefore, storing seeds and delaying their planting till the following year will ensure 100% adult mortality. As the seeds remain viable, such storage is one method for reducing infestation in the field. Mortality of larvae in the stored seeds was from cannibalism when two larvae met at the same tunnel (10%), from the mite Pyemotes tritici (Lagrèze-Fossat & Montagné) (11%), from the braconid larval parasite Triaspis thoracicus (Curtis) (2%) and from unknown reasons (5%).

Oviposition sites of Phlyctinus callosus (Schoenherr) in an apple and a nectarine orchard in the South Western Cape, South Africa, were investigated. No eggs were found on the fruit trees, only in different fractions of the orchard floor, viz. in orchard weeds, leaf litter and soil. Significantly more oviposition took place in plant material on the orchard floor than in the top 20 mm of the soil. Microscopic dissection of samples of such plant material revealed that females prefer to oviposit in confined or hollow spaces in moist, live or decaying plant tissue on the soil surface or in weeds comprising the cover-crop. P. callosus females favoured certain weeds above others for oviposition. The dispersion pattern of eggs in the cover-crop was contagious. The implications of the observed ovipostion behaviour in terms of control strategy, and for exploitation in a monitoring system for this species, are discussed.

Adults of Stomoxys calcitrans (L.) that fed on stroma-contaminated haemoglobin plus bovine serum albumin had normal survival, fecundity and egg hatch. Feeding on haemoglobin from which the erythrocyte membrane strome had been removed, together with bovine serum albumin, reduced fecundity to zero. The addition of membrane ghost preparation to a lipid-free haemoglobin and bovine serum albumin diet restored the essential nutrients for normal fly fecundity. For normal reproduction therefore, S. calcitrans adults require erythrocyte stroma.

Pelidnoptera nigripennis (F.) is a parasitoid of the millipedes Ommatoiulus spp. in Portugal. It is univoltine. The adults lay eggs on their hosts during the spring in southern Portugal, and the first-instar larva penetrates through the soft tissue of the millipede. The parasitoid spends the summer as a firstinstar larva, kills the host during the autumn when in the third instar and overwinters in the pupal stage. P. nigripennis occurs in habitats of low bushes, but not in open grasslands. The female searches for prey by day. The maximum rate of parasitism recorded in this study was 20%. In laboratory specificity studies, 15 species of millipedes from five families were exposed to P. nigripennis, but only julid millipedes were successfully parasitized. Synchronization of the life-cycle in the laboratory with the seasons of the southern hemisphere was achieved by inducing pupation five months prematurely after cooling to 10°C.

The impact of Phenacoccus manihoti Matile-Ferrero on growth and tuber yield of cassava, and the results of its biological control by the exotic parasitoid Epidinocarsis lopezi (De Santis) were investigated in a survey of 60 farmers' fields in Ghana and Ivory Coast over an area of 180 000 km2 of the savana and forest ecosystems. Twenty-nine variables associated with plant growth, agronomic and environmental factors, and insect populations were recorded. Densities of P. manihoti were closely correlated with stunting of the cassava shoot tips and, less so, with the rate of stunting early in the growing season. With increasing mealybug infestations, average harvest indices declined and populations of E. lopezi and of indigenous coccinellids increased, but parasitoids were found at lower host levels than were predators. The length of time E. lopezi had been present in an area was the most important factor influencing mealybug densities. Thus, P. manihoti populations were significantly lower where E. lopezi had been present for more than half the planting season than in areas where E. lopezi was lacking or had been only recently introduced. A significant proportion of the farmers in the savanna zone, where P. manihoti populations were much higher than in the forest zone, had observed this decline due to E. lopezi. Tuber yield losses due to P. manihoti in the absence of E. lopezi were tentatively estimated at 463 g/plant in the savanna zone. No significant effect was found in the forest region. When E. lopezi was present, average P. manihoti damage scores were reduced significantly, both in the savanna and forest regions. The increase in yields was 228g/plant or about 2.48 t/ha in the savanna region.

Field screening experiments for resistance of faba bean (Vicia faba) to Bruchus dentipes Baudi in Syria between 1982 and 1985 involved about 1000 accessions and indicated that only phenological resistance was present. Two accessions were chosen, on the basis of seed infestation with larvae, for further study. The two accessions (BPL33 and ILB1814) were tested against natural infestations as well as under four levels of bruchid infestation and at two different times of release of adults. BPL 33 maintained its resistance (about 50%) in relation to ILB1814 under these different conditions, except when adults were released at a time when both accessions carried pods simultaneously. This confirms that the resistance of BPL33 was phenological, related to late flowering and late pod setting. An intergrated control approach is there fore suggested.