The swollen-shoot virus of cacao is transmitted in the Gold Coast by mealybugs, of which Pseudococcus njalensis Laing is the most important, and these are tended by ants of the genus Crematogaster, which build carton tents over the colonies, thus affording them protection against contact insecticides. An account is given of an investigation which was carried out at Tafo, Gold Coast, between 1950 and 1953, of the possibility of controlling mealybugs and thus the spread of the virus, by the use of systemic insecticides. Dimefox, schradan, paraoxon and parathion were tested, although the two last are not strictly systemic in action.

The egg production and development of Trogoderma anthrenoides (Sharp) has been studied over a range of temperatures from 17·5 to 37·5°C. and in relative humidities of 70 per cent, and near 0 per cent.

At 70 per cent. R.H., the minimal temperature for development was between 17·5 and 20°C. and the maximum between 35 and 37·5°C. Adult females, which apparently required no food, lived on average 18 days at 37·5°C., this period increasing with falling temperature to 146 days at 17·5°C. The greatest number of eggs, a mean of 54 per female present, were laid at 27·5°C. The quickest development occurred at 35°C., females taking a mean of 44.7 days (egg 6; larva 34·3; pupa 4·4). Male larvae developed slightly faster and male adults died a little earlier than females.

Near-zero humidity shortened adult life, reduced egg production and prevented the development of larvae.

Some larvae entered a condition that is probably a facultative diapause resembling that of T. parabile Beal. The diapause was terminated by an increase in volume of food combined with a change of temperature.

The biology of T. anthrcnoides resembles that of two minor pests, T. parabile and T. inclusum Lee., more than that of the important pest T. granarium Everts. The first two species show no signs of becoming serious pests. It is concluded that T. anthrcnoides probably has the potential only of a minor pest.

Scolytus intricatus (Ratz.) is a potential vector of oak wilt and is distributed throughout Europe wherever oak (Quercus) occurs. Its biology was studied in England in Monks Wood National Nature Reserve, Cambridgeshire, Alice Holt Forest, Surrey, and the New Forest, Hampshire, in 1977–83. S. intricatus was univoltine. Oviposition occurred from June to September in the bark of cut or weakened oak (Q. robur) over 5 cm in diameter. Eggs were laid in a single batch in maternal galleries cut across the grain of the cambium and phloem. The mean egg batch size was 17–36. Eggs hatched after 10–14 days, and the larvae ate the phloem and underwent five, or occasionally six, instars. The beetle overwintered as third-fifth-instar larvae, which were cold hardy and were located in cells in the phloem or outer xylem. Pupation occurred in spring, in cells in the bark or outer xylem. Emergence occurred between mid-May and mid-July and spanned a period of 3–4 weeks. The sex ratio was 1:1. Males and females differed externally by the presence of a tuft of setae on the frontal-clypeal suture of the head of the male. Newly emerged adults fed on twigs of live oak, but twig feeding was not obligatory for sexual maturation. Mating was observed during attacks on new hosts, which occurred in June-September. The eulophid Entedon ergias Wlk. was an endoparasite of larvae while larvae of the dolichopodids Medetera and Dolichopus and woodpeckers were predators.

The movement of weevils in a mass of grain was investigated using metal pipes 4 ins. in diameter. These grain columns were broken down into samples. It was found that the predominant movement of weevils was towards the bottom.

The major factor affecting movement was tightness of packing but although tight packing restricts movement it does not prevent oviposition. Small insects move more easily in grain than bigger ones and also show a greater tendency to move downwards. Increase of moisture content which increases the amount of airspace also increases the ease of insect movement.

The results of experiments giving the weevils a choice of moisture content were somewhat contradictory. This is partly due to the choice of the weevil being affected by the humidity it experienced prior to the test and partly due to the moisture choice being overridden by the greater attraction of the end of the grain column. On the whole, however, damper grain appears to be preferred to dry grain.

In the field, owing to the tighter packing, movement is likely to be more restricted than in these experiments. The tight packing will prevent much of the downward penetration of weevils observed in these experiments but some such movement may occur on the walls and posts. Where insects are originally placed in the centre of a bulk of grain they will often be immobile but will lay eggs and be liable to cause heating. It is clear that the insects will tend to move toward the edges of the bulk and remain there.

A survey of an empty granary was undertaken to assess the size and composition of itsinsect fauna, and the possible importance of such insects as a source of infestation of stored goods. The most important feature of the building in this connection was the presence of boarded-up cavities in the walls.

Samples were taken at random from behind all walls, from parts of the grain-distributor system, and from certain other areas.

Many grain pests were found associated with the residues. In the wall cavities large populations had been built up, reaching in one case over 2,000 insects in the food material behind a foot length of wall (the average concentration over all cavities examined was 266 insects per foot of wall).

The largest populations were behind the north and south walls and, in general, the numbers of insects increased on descending the warehouse. The difference in size of population of the different walls and stories depended largely upon the volume and quality of the débris present in the cavities. The increase in numbers was due to increase in number of species and to increase in individuals of some species.

Effects of constant rearing temperature and the plant species fed upon by its hosts were investigated for several developmental parameters of Diadegma semiclausum (Hellén), an important parasitoid of the diamondback moth, Plutella xylostella (L.). Temperature had highly significant effects on all developmental parameters measured, and effects were usually both linear and quadratic with increasing temperature. Host plant species, comprising Brassica napus L., Brassica rapa L. ssp. pekinensis and Brassica oleracea L. var. capitata, also affected development of the parasitoid, and significant interactions were observed between plant species and rearing temperature for all developmental parameters measured. Development of D. semiclausum occurred successfully on all host plant species tested for the temperature range of 10 to 25°C. However, when its P. xylostella hosts consumed leaf tissue of B. napus, no specimens survived to pupate at 30°C, whilst pupation and adult eclosion occurred at 30°C on B. rapa ssp. pekinensis and B. oleracea var. capitata. At high ambient temperatures, such as those characteristic of tropical or subtropical regions (especially at low elevations) or regions that undergo temperature increases due to climate change, P. xylostella is predicted to occur at a higher range of temperatures than its biocontrol agent, D. semiclausum. Effects of high temperatures are expected to be more profound on the parasitoid for some host plants than others, with greater developmental limitations for the parasitoid on B. napus than on B. rapa or B. oleracea.

These species, together with A. brunnipes, Theo., have been referred to the Neocellia group of the subgenus Myzomyia on account of the broad mesonotal scales, and (in the case of the first two species mentioned) of the broadly white-tipped hind tarsi. The three species, however, differ from the other members of the Neocellia group in the possession of a distinct propleural hair, whereas the other African species (A. maculipalpis, Giles, and A. pretoriensis, Theo.) agree with all the Oriental species of the Neocellia group in having no propleural hair. It is therefore probable that the first three species are to be regarded as members of the Myzomyia group in which the ornamentation is unusually well developed. This conclusion, arrived at from an examination of the adults, is confirmed by a study of the larvae ; Christophers informs me that the larvae of A. theileri, which have been examined by himself and Puri, have pleural hairs of the Myzomyia type. It is also suggestive that A. rufipes and A. theileri are both variable in wing-markings and thoracic scaling, and as in the case of A. marshalli, some variations appear to be definitely fixed. Some of these variations are described below as new varieties.

The effects of conspecific adult interference on the reproductive output of an aphidophagous ladybird, Propylea dissecta (Mulsant) were investigated. Ovipositing females were subjected to physical interference with conspecific adults (0 to 4 males or females) in Petri dishes and the effects on egg cannibalism, oviposition and egg viability were recorded. The absence of interference was related to the lowest egg cannibalism (0.00%) and higher fecundity (336.30±32.16 eggs) and egg viability (95.83±1.60%). Fecundity decreased with increasing physical interference from either sex. Egg viability declined with increasing male density, but was not influenced by conspecific females. In a second experiment, evaluating the role of conspecific adult chemical tracks on fecundity and egg viability, it was observed that adult chemical track density (fresh and ten-day-old) was negatively correlated. Egg viability was not affected by the presence of adult chemical tracks. The decrease in fecundity was not affected by the sex of the adults making the tracks, thus revealing that the chemical constitution of these deterrent compounds was not sex-specific. Conspecific interference in a Petri dish reduces reproductive output, as a result of physical interference and response to what seem to be oviposition-deterring pheromones present in adult tracks.

A significant relationship between pteridine content of the head, fly age and fly size, which was independent of temperature, was found for adult females of Simulium sirbanum Vajime & Dunbar using flies maintained at different constant temperatures after eclosion. Similar relationships for flies maintained at varying temperatures within the species' natural ranges were obtained in experiments with the Beffa form of S. soubrense Vajime & Dunbar (sensu Post, 1986), S. sanctipauli Vajime & Dunbar (= S. soubrense sensu Post, 1986), S. squamosum (Enderlein), S. yahense Vajime & Dunbar and S. damnosum sensu stricto. Common slopes for the effects of age and size could be fitted to all these species. Relations between pteridine concentration in the head, fly size and age, with the common slopes but with species-specific intercepts, were used to estimate the age structure of wild-caught populations of the Beffa form of S. soubrense, S. squamosum and S. yahense. A dry season sample of S. squamosum was estimated to be older than a wet season sample. The mean age of the S. soubrense population, sampled one week after its presumptive breeding sites were treated with larvicides, was estimated to be 13.5 days. The maximum was 30.9 days and a frequency distribution of the estimates had distinct peaks, at three day intervals between 8 and 21 days. The significance of the results is discussed in relation to fly longevity and gonotrophic cycle lengths.

The increase of air transport and the potential dangers therefrom, together with the related problems are investigated.

The introduction of a malarial vector from one faunal region to another, and the effects thereof are discussed.

The literature of the epidemiology of yellow fever, particularly the work done on the insect vectors and the susceptible animals is reviewed, and the implications thereof in connexion with air transport are considered.

The air communications of the world are shown as a map; maps of Africa and South America showing the air routes and yellow fever areas are presented.

The control of air ports and aerodromes is discussed, in connexion with which the literature on the flight-range of insects, the dissemination of insects by wind, and insects and the upper air is reviewed.

A comparison is made between the insects collected from the terrestrial zone of the atmosphere and those from the upper air.

The work done upon insects found in aircraft is reviewed, and the results incorporated together with those from Khartoum in a “World List” table. The work done in Khartoum is described, and this, together with other workers' results, is analysed.

A comparison is made between insects found in the terrestrial zone, the upper air or “Plankton zone” and those found in aircraft.

The medical, veterinary and agricultural aspect of insects found in aircraft is discussed.

The control of insects in aircraft is considered and suggestions made for future research.

A raster or grid-based Geographic Information System with data on tsetse, trypanosomosis, animal production, agriculture and land use has recently been developed in Togo. This paper describes the generation of area-wide digital tsetse distribution and abundance maps and how these accord with the local climatic and agro-ecological setting. Results include: (i) a spatial demarcation of ecologically distinct areas, producing a seasonal cluster map based on seasonal weather data and temporal series of satellite derived National Oceanic and Atmospheric Administration (NOAA) AVHRR and METEOSAT variables: (ii) tsetse distribution maps of Glossina tachinoides Westwood, G. palpalis palpalis (Robineau-Desvoidy), G. morsitans submorsitansNewstead, G. longipalpis Wiedemann, G. medicorum Austen and G. fusca fusca (Walker); and (iii) tsetse abundance or ‘risk’ maps, corrected for within database seasonal fluctuations, for G. tachinoides and G. p. palpalis. It is concluded that grid-based sampling is the ideal method for rapid assessment of the current vector and disease situation within any country or region, and that remote sensing has an important role to play in planning such a sampling system.

This paper reports on the performance of an atmospheric numerical model called BLAYER which has been adapted to forecast the movement of migrant brown planthopper Nilaparvata lugens (Stål) and white-backed planthopper Sogatella furcifera (Horvarth) populations from China to Korea. Comparison of model forecasts with trapping data for the 1987 and 1988 migration seasons indicated: (i) that the model is capable of successfully simulating the movement of planthoppers to Korea; (ii) that the model has sufficient detail to simulate insect movement into different regions of Korea; (iii) the source region for early season migrants is most likely to be south-eastern China (i.e. south of 25°N and east of 115°E); (iv) later season migrants may not necessarily always originate from an expanded northward region (south of 30°N); (v) the flight level of migrants may vary from about 500 to 2000 m altitude from one migration episode to another; and (vi) flight times ranging between 24 and 45 h are required to explain the migratory influxes. The results reported here have led to BLAYER forecasts of planthopper migration being produced on an operational basis within Korea.

A laboratory bioassay was developed to allow blind testing of panels of odours for their effect on target-orientated behaviour of tsetse (Glossina spp.) in the laboratory. Landing responses of G. m. morsitans Westwood on black and blue targets were increased up to four-fold in the presence of carbon dioxide, but no significant effect of any other odours could be demonstrated. 2-methoxy phenol gave an apparent increase in landing behaviour in the laboratory, but this substance diminished rather than increased landing of G. pallidipes Austen and G. m. morsitans on targets in the field, as well as repelling tsetse from the target vicinity. Black, blue and red targets elicited strong landing behaviour in male G. m. morsitans in the laboratory, and white and yellow targets elicited little or none, whether carbon dioxide was present or not. In the field, high ultraviolet reflectivity increased landing behaviour of G. pallidipes, but only when there was a proportion of transmitted light through the target. Ultraviolet reflectivity always reduced overall attraction of tsetse to a single-coloured target. Two-coloured targets incorporating ultraviolet-reflecting white cloth obtained strong landing on the white panels, but caught fewer flies overall than all-black, or blue-and-black targets.

Records are given of the species of mosquitos captured at Mombasa in the years 1943–44 and 1949–52. They were caught by four different methods, namely: (1) day-time net catches in the bush, (2) window-trap catches, (3) diurnal (bait) biting catches in the bush and (4) twenty-four hour (bait) biting catches in three different situations. Sixty-six species were taken in the day-time net catches and nine others which did not figure in the net catches were taken in one or other of the remaining three methods.

The habits of the commonest species, as indicated by these catches, are discussed in some detail.

Culex pipiens fatigans Wied. occurred in large numbers in biting catches, net catches and window-trap catches. In 24-hour catches most biting occurred after midnight, but, in the window traps, activity was greatest between 18 and 21 hr.

Aëdes simpsoni (Theo.) was not taken in window traps or houses. Seasonal occurrence, as indicated by larvae in banana axils, net and biting catches in the bush, is discussed. Twenty-four hour catches confirmed earlier findings that this mosquito bites almost solely during daylight.

Aëdes pembaensis (Theo.) occurred throughout the year with little seasonal variation; this is thought to be connected with its breeding in crab-holes. It is often found in fair numbers in houses when these are near the breeding grounds. Window-trap catches show that most activity takes place at night though some also occurs during the day. The biting rhythm as shown by 24-hour catches in houses, bush and on tree platforms is discussed.

Aëdes albicosta (Edw.). Previously this mosquito may have been confused with Aëdes albothorax (Theo.) and Aë. lineatopennis (Ludl.). It can occur at times in great numbers when it may bite viciously both indoors and outside.

Anopheles gambiae Giles and A. funestus Giles were not evident in large numbers. In window traps most activity took place at night although some also occurred during the day. In 24-hour catches, A. gambiae fed mostly just before dawn though biting occurred also from midnight onwards. A. funestus appeared suddenly and in fair numbers in window traps but was absent for much of the year.

Aëdes aegypti (L.), though fairly common, is recorded only in Tables and in one figure as its bionomics have already been discussed elsewhere.

Notes are given on other species, which include Culex duttoni Theo., C. nebulosus Theo., C. tigripes Grp., Aëdes metallicus (Edw.), Aë. albocephalus (Theo.), Eretmapodites subsimplicipes Edw. and E. quinquevittatus Theo.

Laboratory and field trials were conducted to evaluate the effect of plant species (maize, sorghum), plant age (young, middle, old) and four different nitrogen fertilization levels (N0–N3) on the bionomics of the invasive crambid Chilo partellus and the performance of its braconid larval parasitoid Cotesia flavipes. Plant N varied significantly between N0 and N1–N3, but the differences among the latter were not significant. Intrinsic rates of increase and net-reproductive rates of C. partellus followed the same trends: they were lowest with N0 and similar among the other treatments. On maize only, mortality of C. partellus and parasitism by C. flavipes tended to decrease with age of the plant while the percentage of borers reaching adulthood (i.e. pupation) increased. Borer mortality and parasitism was lower and pupation higher on sorghum than on maize. On both host plants, percent dry matter content of frass, which could affect ingress of the parasitoid into the borer tunnel, did not vary with nitrogen level but varied with age of the host plants: on maize, it was highest on young plants and on sorghum on old plants. Tunnels were shorter on young maize and sorghum plants; longer tunnels on older plants indicated compensatory feeding by the larva as a result of lower nutritive value of the food source. Consequently, larval weight was lower on older than younger plants. The level of nitrogen fertilization had no effect on food conversion efficiency of C. partellus. Nitrogen did not affect number of C. flavipes progeny while egg load of progeny increased significantly with nitrogen level, on both plant species. Differences in egg load between sorghum and maize were mostly not significant. It was concluded that on depleted soils only, an increase in nitrogen via mulching, rotation with a leguminous crop or fertilization would increase survival of C. partellus on both maize and sorghum and an increase in acreage of maize and in application of nitrogen fertilizer in an area would also increase the parasitism of C. flavipes.

Culex quinquefasciatus Say from Peliyagoda, Sri Lanka, has larval resistance to temephos, malathion, fenitrothion and chlorpyrifos. Biochemical assays on individual resistant and susceptible mosquitoes of this strain showed that there was a good correlation between this resistance and increased esterase activity with both 1-and 2-naphthyl acetate, which appears to be the major resistance mechanism in this multiple organophosphate resistant strain. There was no significant difference in malaoxon, bendiocarb or propoxur sensitivity of the acetylcholinesterase from the resistant and susceptible strains, indicating that the sensitivity of the target site has not been altered. Biochemical assays on mass homogenates of the resistant and susceptible strains showed no correlation between resistance and the level of glutathione s-transferase activity, or the amount of cytochrome P450 present.

The summer and autumn migrations of the brown planthopper (Nilaparvata lugens) were observed in Southern China with a millimetric scanning entomological radar and a searchlight trap supplemented with capture in field cages, field surveys, and dissections of females. Nilaparvata lugens took off at dusk and dawn in summer, but in autumn there was sometimes only a dusk take-off. The variation of the area density of the radar targets indicated that flight durations were about 9–10 h. In summer, planthopper-size targets generally flew below 1800 m above ground level (AGL), although some insects reached 2000 m AGL; in autumn, they flew lower, generally below 1100 m although some insects reached 1700 m AGL. Multiple layer concentrations were seen every night in both summer and autumn. The depths of these layers in autumn were less than in summer. Nilaparvata lugens flew in strong winds; wind shear may be the main factor causing them to accumulate and form dense layers at certain heights. Nilaparvata lugens emigrating in summer from the vicinity of the radar site in the Northeastern Guangxi Zhuang Autonomous Region, and carried by the prevailing southwesterly wind, would have travelled northeastwards and reached Northern Hunan Province. In autumn, with the prevailing northeasterly wind, emigrants would have reached overwintering areas (south of 21°N).

A new electric trap for tsetse flies (Glossina spp.), based on a circuit producing the necessary high voltages from a small 2-V battery, is described. Power consumption is reduced to less than 1% of its level in other circuits designed for the same purpose so that in theory up to 300 h operation per charge is available from a single 2-V dry cell with a 7-Ah capacity (weight approximately 460 g). In practice this time is more likely to be limited by the shelf-life of the cell in tropical climates. The new circuit and a modified grid were tested against G. morsitans submorsitans Newst. during field trials in Ethiopia and the results are discussed. A high percentage of females was obtained only when a stunning capacitor was introduced across the output. The capacitor stores the charge from the circuit and gives a bigger impulse as flies land across the wires. It seems that, in the absence of the capacitor, females that visit the catching device escape from the electrified grid. When they are caught they are stunned for about the same length of time as male flies.

Flight ability of Ostrinia furnacalis Guenée was evaluated using a flight-mill in laboratory. Females flew most actively at 20–23°C, whereas the majority of the moths tested did not fly at 14–17°C. Temperature above 26°C inhibited their flight activity and survival. The age-specific flight ability of unmated males and females was similar from one to 12 days after emergence; it was highest at one day and then declined gradually. Females showed a pre-oviposition period of three to four days after emergence during which they were capable of longer continuous flight. There was no significant difference between the unmated and mated females in any aspect of flight ability at four days (commencement of oviposition) or at eight days old (peak of oviposition). In males, the flight ability of mated adults was reduced compared with that of unmated adults at both four and eight days old. Increased flight experience did not delay oviposition by mated females, but significantly reduced egg production. There was a significant negative correlation between flight duration and subsequent egg production. Ostrinia furnacalis is concluded to be an active flier that is able to male long-distance flights, because both mated and unmated adults displayed high flight ability for several days after emergence.

Canopy knockdown of arthropods using mist-blowing was carried out in Brumas, Sabah (north-east Borneo), in plantations of exotic (non-indigenous) tree species (Acacia mangium, Eucalyptus deglupta, Gmelina arborea, Paraserianthes [=Albizia] falcataria, and Pinus caribaea), plus secondary natural forest and dense understorey within E. deglupta stands. Each habitat had three 1 m2 samples taken four times in one year. The average arthropod species richness within the stands of the exotic tree species ranged from 27 in E. deglupta, to 68 in natural, secondary forest. The total number of individuals caught ranged from 137 in G. arborea to 1628 in secondary forest. The dense and plant-species rich understorey within E. deglupta stands yielded both higher numbers of species and individuals than the eucalypt trees themselves, indicating the importance of allowing the development of a luxuriant understorey for the enhancement of conservation and biodiversity. Though arthropod biodiversity is reduced by the conversion of tropical forests to plantations, abundance and richness are still substantial in the latter habitats.