Aphidius ervi Hal. parasitised natural populations of Acyrthosiphon pisum (Harris), Sitobion avenae (F.) and Microlophium carnosum (Buckt.) in Britain but parasitised few examples of S. avenae placed on trap plants in winter wheat, nettle-grass edge areas or lucerne-wheat strip crops. In laboratory experiments, Aphidius ervi reared from Acyrthosiphon pisum did not parasitise M. carnosum, and significantly fewer mummies were formed on S. avenae than on A. pisum. After rearing Aphidius ervi for 4–5 generations on S. avenae, similar numbers of mummies were formed on both hosts. The switch of hosts from Acyrthosiphon pisum to S. avenae was associated with the loss of certain parasitoid esterase enzyme bands revealed following electrophoretic separation of parasitoid proteins. Slow adaptation to new aphid hosts by polyphagous parasitoids such as Aphidius ervi may reduce the usefulness of reservoirs as a source of beneficial species.

Screened and unscreened eucalyptus trap-logs infested by Phoracantha semipunctata (F.) were used to examine the excavating habits of the Syrian woodpecker (Picoides syriacus), its annual course of predation and its effect on the survival rate of Phoracantha semipunctata larvae in Israel. The bird excavated predation holes only in trap-logs with larvae within the bark. Predation holes density increased during the spring and summer. Towards the autumn, egg-masses were killed too. The average mortality due to predation was 29·21% of total larval mortality and 78·7% among larvae that survived intraspecific competition. The mortality caused by the woodpecker decreased with increasing density of larvae. The natural control of P. semipunctata in Israel and the borer-woodpecker ecosystem are discussed.

Descriptions are given of two new species of pentatomid bug, one known to transmit the disease ‘marchitez’ (caused by Phytomonas staheli) of oil palm in Ecuador and the other associated with hartrot (caused by the same flagellate) in coconut palm in French Guiana. Notes are included on a third species also associated with hartrot in French Guiana. The species are Lincus lethifer sp.n., L. apollo sp.n. and L. croupius Rolston.

A laboratory colony of Glossina morsitans submorsitans Newst. originating from Nigeria exhibits an excess of females over males. The sex ratio distortion of more than two females to one male was studied by the maintenance of individual flies. Five males sired more than ten daughters without producing any sons when mated to several females, whilst other males fathered approximately equal numbers of male and female offspring; there was no evidence for selective abortion of male embryos. The presence of these ‘distorter’ males, which produce only female offspring, was found to cause the sex ratio distortion. The results are discussed with reference to data from the field which indicate that this genetic aberration is not confined to the laboratory; possible implications for chemical control programmes are assessed.

Crosses of Sudanese strains of Anopheles arabiensis Patt. resistant and susceptible to malathion indicated that the resistance was incompletely dominant. The results of tests of male progeny of successive backcrosses agreed well with the hypothesis of control of the resistance by a single gene. However, the results from females suggested the additional involvement of a sex-limited modifier. Tests of mixtures initiated with a 1:1 ratio of resistant and susceptible first-instar larvae gave little evidence for selective mortality during the larval stage. However, the mortalities in tests on malathion recorded among adults emerging on successive days from these mixtures, and also from F2 and backcross progenies, indicated that the development of the resistant larvae was significantly faster than that of the susceptible ones. The fact that this occurred in the F2 and backcross progenies indicates that it may be due to a pleiotropic effect of the resistance gene, but it is pointed out that results from much more prolonged backcrossing would be necessary to rule out the possible effects of linked genes.

The vigour, i.e. survival and wood consumption, of groups of Coptotermes lacteus (Frogg.) and Nasutitermes exitiosus (Hill) was measured when termites were kept at different population densities by changing group size and/or volume of the holding container. A characteristic pattern emerged for subterranean termite species. At low population densities (<0·01 g termites/ml), performance improved with an increase in group size; at higher densities, it tended to decline. The impact of altering group size and container volume on termite vigour was most pronounced at low population densities; at higher population densities, performance tended to be more stable but declined markedly when termites became overcrowded. In most jar-type experiments on termites, especially those conducted in Europe and the USA, small groups of termites are housed in disproportionately large jars, resulting in very low, sub-optimal population densities. Suggestions are made for improvement in experimental design that would lead to an enhancement of the comparability of results from different laboratories.

Ivermectin injected subcutaneously into calves at the rate of 200 μ/kg body weight completely eliminated females of Psoroptes ovis (Her.) in 22 days. Injection of ivermectin also adversely affected the number and hatch of eggs and the proportion of adult males forming attachment pairs. The reduced number of eggs recovered in skin scrapings was apparently the result of a significantly lower fecundity among females that temporarily survived on treated calves. Females that were exposed to ivermectin for only three days did not recover their full reproductive potential even though they were transferred to calves not injected with ivermectin. The proportion of ovigerous females among survivors was not significantly affected five days after injection. Since the number of eggs recovered in skin scrapings was substantially reduced after only three days, the effect of ivermectin on female fecundity was not primarily gonadal. Reduction in the number of P. ovis eggs three days after treatment probably occurred because of a combination of mortality of adult females and reduced oviposition by ovigerous females surviving in the population.

Females of Anopheles darlingi Root were the commonest (98·6%) of 5464 anophelines taken in 866 man-hours of human bait catches at night, in or near houses in the rain forest in Suriname during 1979–81, but their abundance could not be related to the prevalence of human malaria. In most endemic areas, few females were taken. At Aseli Kamp (4°17'N, 53°24'W) on the Lawa River, biting females were most abundant from April to June, during the long rainy season and rare or absent from September to March, during the long dry, short rainy and short dry seasons. At Apoma Tapoe, however, only 40 km downstream, they were most abundant in october and November, during the long dry season. Females entered houses to feed, with peak biting activity between 22·00 and 23·00 h, and were observed to rest near the collector for a mean of 7·7 min before and 17·1 min after feeding. No females were found resting by day, in buildings or out of doors. The mean parous rate of 827 females from biting catches was 43·6%. The expected biting rate of females was reduced by 20·3% in a house for six nights after it had been sprayed with DDT wettable powder (2 g/m2 active ingredient), and by a mean of 82·6% during seven nights in a camp where the edge of the surrounding forest was sprayed with an ultra-low-volume mist of 95% fenitrothion (1·3 ml active ingredient per metre of perimeter) on the first, third and sixth days. A. darlingi larvae were found at Aseli Kamp in all seasons along the river's edge between water hyacinth plants (Eichhornia) and floating debris, and during the long rains in flooded forest.

Field studies were carried out between 1974 and 1978 on the hispine Uroplata lantanae Buzzi & Winder which feeds on Lantana tiliaefolia plants under shade in temperate climate areas of Paraná State, southern Brazil. The life-cycle from egg to adult took 48–54 days between October and January with only one generation a year. Adults fed by rasping leaves and larvae mined leaves, occasionally destroying up to 24% on individual plants. Adults colonised tall plants preferentially and chose to oviposit on the higher branches, which suffered significantly less leaf abscission. Greater numbers of all stages of the hispine were found on lantana plants around which a plant-free zone was created compared with those growing amongst other understorey plants. Larvae were parasitised by a complex of braconid, eulophid, chalcid and torymid parasitoids, with greater parasitisation occurring at lower branch heights. Multiple-choice host-specificity tests and field observations showed that U. lantanae fed only on L. tiliaefolia and L. camara. The effectiveness of U. lantanae as a biological control agent of lantana in Australia is discussed.

In the Zambezi Valley of Zimbabwe, the numbers of Glossina morsitans morsitans Westw. and G. pallidipes Aust. electrocuted as they arrived near a visual target were increased five times by the release of a mixture of carbon dioxide and acetone vapour at the target. Catches declined to near the no-odour level as the odours were moved to release points 32–40 m upwind or downwind of the baits. This pattern of catches at the target changed when flies were trapped at the odour release points 4–40 m from the target, and changed when the odour was released at each of several points along the axis of the wind instead of at a single point. These changes suggest that the flies responded to a single-point release of the odours at distances of 30–60 m from the release point, that, when the flies arrived at the upwind end of a plume and discovered no visual bait, they flew upwind for a few metres and returned downwind for about 8 m and that the flies navigated effectively up a composite plume made by 2–33 separate release points, 1–8 m apart, along a line up to 30° from the mean direction of the wind. Data for Muscidae are also presented.

To elucidate how thrips feed, the mouthparts of Limothrips cerealium (Hal.) were examined in dead specimens by scanning electron microscopy and plasma-ashing, and in living specimens by cinematography as individuals fed through a transparent membrane on clear liquid containing small polystyrene latex particles that made its flow visible. Close contact with the food substrate was maintained by the labral pad. The single mandible was used to pierce the membrane and was then withdrawn rapidly and replaced by the maxillary stylets, which formed a tube with either a terminal or sub-terminal opening into which food was drawn by cibarial pumping at 2–6 pulsations/s. Oscillations in the surrounding fluid caused by such pumping were detectable up to 58 μm from the maxillary opening. Feeding persisted from a few seconds to up to half an hour, and when complete the stylets were withdrawn either rapidly and together, or more gradually by sliding one against the other. Whole chloroplasts up to 6 μm in diameter were ingested even though the diameter of the maxillary tube was about 1 μm. The thrips consumed the contents of ruptured plant cells at about 8·5 × 1O-5 μl/min, equivalent to almost 12·5% of their body weight per hour. Probing and feeding removed the surface wax from leaves, and the cuticle was so exposed that it often wrinkled. Leaf cells beneath a pierced epidermal cell were usually emptied completely, and little seepage from the wounded tissue occurred after stylet withdrawal. After intensive feeding, many mesophyll cells were totally destroyed and others showed extreme plasmolysis; grana sacks were contorted and large starch grains formed due to desiccation. Above such internal damage the epidermal cells collapsed, and the outer cuticle wrinkled and appeared silvery before turning yellow and brown.

Records of daily catches of males of Spodoptera littoralis (Boisd.) at pheromone traps in or near the Nile Delta, Egypt, during 1979 and 1980 were used to investigate both the seasonal variation in catch and the possibility that migration, associated with particular weather systems, may significantly affect moth numbers in a particular area. Although more moths were caught in 1979 than in 1980, in both years there was a similar seasonal variation in catch, with low numbers in January and February followed by an increase to a maximum in June or August. There was no systematic seasonal change in the area of highest catch that would suggest seasonal migrations. On some nights, large increases in catch were associated with weather disturbances, notably windshift lines, suggesting that flying moths are sometimes redistributed by wind systems. Catches at two traps far from the main source area suggest that moths may have flown at least 50 km downwind from sources in the Nile Delta. The pattern of nightly catches at most traps indicated that build-up of local populations is the most important factor affecting the population dynamics of the pest but that some, mainly local, redistribution by wind systems takes place.

The susceptibilities of 14 plastics formulations (four polyethylenes, one polypropylene, one polyester, two polyamides, one polyurethane and five poly(vinyl chlorides)) to attack by Coptotermes acinaciformis (Frogg.) and C. formosanus Shir. in the laboratory were broadly related to hardness and surface finish. Overall, C. acinaciformis inflicted more damage than C. formosanus, despite lower survival, but some formulations appeared more susceptible to C. formosanus than to C. acinaciformis.

Three French strains of Culex pipiens L. were compared at the fourth larval instar for tolerance to organophosphate and carbamate insecticides, with and without the addition of synergists (the oxidase inhibitors piperonyl butoxide and CGA 84708) (a propynyl compound) and the carboxylesterase inhibitors triphenyl phosphate (TPP) and S,S,S-tributyl phosphorotrithioate (TBPT). The S54 strain was resistant to all the organophosphates tested (chlorpyrifos, malathion, monocrotophos and profenofos) compared to the susceptible LA VIS strain but only slightly tolerant to the two carbamates (carbaryl and naphthyl phenylcarbamate). The MAURIN strain was resistant to all the insecticides, including the carbamates, at a higher level. The action of chlorpyrifos and malathion on S54 was very strongly synergised by TBPT, less strongly by TPP and not at all by piperonyl butoxide. In fact, resistance was enhanced by piperonyl butoxide, as was resistance to monocrotophos and profenofos by CGA 84708. No synergist had much effect on the MAURIN strain, although TPP slightly increased the toxicity of malathion, and piperonyl butoxide and CGA 84708 slightly increased the toxicity of carbaryl. The toxic effect of carbaryl was also increased by the addition of extra acetone. Electrophoretic studies showed that the carboxylesterase enzyme coded by gene Est-20.64 (which is in linkage disequilibrium withEst-3A and acts as a marker for it) was absent from LA VIS but present in the resistant strains; but, whereas S54 was monomorphic for the gene, MAURIN was polymorphic (frequency 0·5). It is concluded that organophosphate resistance in S54 was due to detoxification by carboxylesterase wherease organophosphate and carbamate resistance in MAURIN had a strong non-metabolic component, possibly an insensitive acetylcholinesterase.

Laboratory studies were carried out on different populations of Aphidius ervi Hal., A. picipes (Nees) and A. rhopalosiphi De Stef. collected in England from Acyrthosiphon pisum (Harris), Sitobion spp., Microlophium carnosum (Buckt.) and Metopolophium dirhodum (Wlk.). When mated females from each population were confined separately with 4–5 other species of these and other genera, each population varied in their host preferences, even though individual populations of each species were electrophoretically and morphometrically homogeneous. These host preferences differed in terms of fecundity. Different populations of Aphidius ervi exhibited markedly different host ranges. This behaviour is probably conditioned rather than inherited, and its significance to biological control is discussed. The results suggest a need to assess quantitatively the effect of temperature, host size and host species on the parasitoids' ability to control pest aphids.

The movement patterns of Glossina palpalis palpalis (R.-D.) around villages in Ivory Coast were investigated by means of mark-release-recapture studies at two different sites. At one site, Congo Aboisso I, there appears to have been a single fly population based on the village, with an asymmetric ebb and flow of flies between the village and the surrounding bush; flies tended to remain in or around the village once they had arrived there. At the other site, Degbézéré, on the other hand, there were two populations, one centred on the village and the other on a nearby lake, with considerable exchange between the two. It is suggested that flies go to Degbézéré Village and remain there to feed, primarily on domestic pigs, and females return to the lake briefly to larviposit; males stay longer at the lake, perhaps to increase their chances of mating with emerging females. Long-distance movement of flies between villages, and also an analysis of the spatial pattern of fly movement between Congo Aboisso I and the surrounding bush, shows that human activity may affect the pattern of tsetse movement. Flight activity, and the consequent fly movement, was related to the nutritional status of the flies; males with greater fat content undertook more flight activity and thus tended to move further away from the village. The implications of these results for attempts at local trypanosomiasis control are discussed.

In attempts at the biological control of Salvinia molesta in Australia, the curculionid Cyrtobagous sp. was released at eight sites and became established at seven of them. At these seven sites, air temperatures ranged from less than 0°C to more than 45°C and the mean concentration of nitrogen in S. molesta ranged from 1·18 to 1·82% of dry weight. Establishment was effected by releasing 200 adults, and the shortest time for extensive damage to be caused to the weed was four months. Cyrtobagous sp. dispersed in undamaged S. molesta at rates of a few metres per month. The pyralid Samea multiplicalis Gn. was released, and became established, at three sites and spread at least 170 km north and south in 20 months. At the sites colonised, air temperatures ranged from less than 0°C to more than 45°C and the mean nitrogen concentration in Salvinia molesta ranged from 1·34 to 3·30% of dry weight. Establishment was effected by releasing 800 larvae, and the shortest time for extensive damage to be caused to S. molesta was three months. Contrasts in the biology and ecology of the two species of insects are discussed briefly as is competition between them for food. In late 1983, Cyrtobagous sp. had achieved control of S. molesta at five sites, while Samea multiplicalis had achieved control at none. It is suggested that S. multiplicalis might perform better in locations which experience maximum temperatures lower than those in the present distribution.

Homoptera were assessed by examining branches from mature cocoa trees in an Upper-Amazon 3 × 33 shade × nitrogen, phosphate and potash fertilizer experiment at Tafo, Ghana. Trees in territories of the ants Crematogaster clariventris Mayr and Acantholepis capensis Mayr were sampled. Planococcoides njalensis (Laing), Planococcus citri (Risso), Phenacoccus hargreavesi (Laing), Pseudococcus concavocerarii James, Maconellicoccus ugandae (Laing) and Mesohomotoma tessmanni (Aulm.) were more abundant on unshaded trees than on shaded ones. Steatococcus sp. and Stictococcus sjostedti Ckll. also occurred most frequently on unshaded trees. The abundance of five other infrequently recorded species was unaffected by overhead shade. A species of Gascardia near G. zonata (Newst.) was more common as shade increased. Planococcus citri increased with increasing nitrogen where A. capensis was dominant, and decreased with increasing potassium on heavily shaded trees where C. clariventris was dominant. M. tessmanni decreased with increasing potassium both on unshaded trees where A. capensis was dominant and on trees which had received most phosphate where C. clariventris was dominant. No responses to fertilizers were detected among other species. An estimated 100, 99 and 83%, respectively, of unshaded, lightly and heavily shaded trees were infested with mealybugs, vectors of cocoa swollen shoot virus. These estimates presage little change in the rate of spread of virus due to the continued shade thinning over cocoa in Ghana.