Field studies with Glossina morsitans morsitans Westw. in Rhodesia showed that hand-net catches can reduce slightly the responses of males to mobile baits and can reduce female responses by three-quarters. Description is given of methods of operating baits in the absence of men and of methods of electrocuting flies as they fly near baits, alight on baits and respond to decoy tsetse. These techniques are more efficient and objective than hand-net catching.

Biodiversity relevant to pest management of tropical irrigated rice pests is discussed in terms of variation within rice plants, rice fields, groups of rice fields and rice associated ecosystems. It is concluded that, in the unique cropping conditions and stable water supply of tropical irrigated rice, the manipulation of a relatively few manageable components of diversity can confer stability such that pests are mostly kept at levels which do not justify the use of insecticides. Durable rice plant resistance, including moderate resistance, together with ability to compensate for damage by certain key pests, are regarded as fundamental to successful biological control by the natural enemy complex. Reliable natural enemy action is also considered to depend on all-year-round continuity of prey or hosts made possible by the relatively short fallow periods between staggered two to three rice crops per year and by proximity of certain non-rice habitats, notably the vegetation-covered bunds (levées) surrounding each field. In contrast, synchronous cropping could upset stability by destroying the continuity needed for natural enemy success. Such conclusions are supported by the experience of farmers who use little or no insecticide. Much evidence on destruction of natural enemies by certain insecticides supports the contention that insecticide use, especially early in the crop season, upsets natural enemy control of insects such as Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) and also creates heavy selection pressure for strains of pests that can overcome previously resistant rice cultivars. Such circumstances create outbreaks of secondary pests and impair biological control of some key primary pests such as stem borers. It is concluded that pest management of much tropical irrigated rice must be based on natural controls rarely supplemented by insecticides. The success of this approach depends in particular on further research on dynamics of natural enemy and pest communities in rice ecosystems, especially where climatic conditions and water supply are marginally stable. Much more needs to be known about the nature and utilization of rice plant compensation for damage, particularly by defoliators and stem borers. The justification for, and supplementary use of, insecticides needs to be radically reassessed. There is no evidence that a natural control-based approach, as recommended in this review, is incompat ible with farmer practicability or with future developments in rice production technology, except perhaps the possible mechanization-driven increase in field size which would decrease bund area. In contrast, the insecticide-based approach is not only harmful to natural controls but is costly and mostly demands impracticable decision making by farmers on need-based use.

The biology and pest status of the common species of Sitobion, Metopolophium and Rhopalosiphum found on wheat, barley and oat crops in Europe is critically reviewed. After preliminary sections on species and sampling, the factors that induce the production of the different morphs of cereal aphids are considered. Basic life-cycles are described and the importance of migration and dispersal considered. Host-plant preferences, survival and reproduction on different Gramineae, and feeding site preferences are considered, particularly in relation to the type and amount Of damage caused by the aphids. The effects of constant temperatures on the biology of some species have been investigated, but little is known about the effects of weather in the field. There have been few quantitative studies on the effects of natural enemies on cereal aphids, but the evidence suggests that they may be important in reducing their numbers. Side-effects of pesticides and fertilisers on aphids are also discussed. Aphids may reduce grain yield and quality. Direct damage may result from reductions.

Anopheles funestus Giles has been implicated as a major malaria vector in sub-Saharan Africa where pyrethroid insecticides are widely used in agriculture and public health. Samples of this species from northern Kwazulu/Natal in South Africa and the Beluluane region of southern Mozambique showed evidence of resistance to pyrethroid insecticides. Insecticide exposure, synergist and biochemical assays conducted on A. funestus suggested that elevated levels of mixed function oxidases were responsible for the detoxification of pyrethroids in resistant mosquitoes in these areas. The data suggested that this mechanism was also conferring cross-resistance to the carbamate insecticide propoxur.

The development of a bee species as a new crop pollinator starts with the identification of a pollination-limited crop production deficit and the selection of one or more candidate pollinator species. The process continues with a series of studies on the developmental biology, pollinating efficacy, nesting behaviour, preference for different nesting substrates, and population dynamics of the candidate pollinator. Parallel studies investigate the biology of parasites, predators and pathogens. The information gained in these studies is combined with information on the reproductive biology of the crop to design a management system. Complete management systems should provide guidelines on rearing and releasing methods, bee densities required for adequate pollination, nesting materials, and control against parasites, predators and pathogens. Management systems should also provide methods to ensure a reliable pollinator supply. Pilot tests on a commercial scale are then conducted to test and eventually refine the management system. The process culminates with the delivery of a viable system to manage and sustain the new pollinator on a commercial scale. The process is illustrated by the development of three mason bees, Osmia cornifrons (Radoszkowski), O. lignaria Say and O. cornuta (Latreille) as orchard pollinators in Japan, the USA and Europe, respectively.

Research on Lepidopterous stem borers of Nigerian cereals began in 1951. Preliminary surveys finished in 1954 and from 1955 to 1961 the author studied these pests in Northern and Western Nigeria.

Guineacorn (Sorghum vulgare) and millet (Pennisetum typhoides) are the most important cereal crops in Northern Nigeria, and maize (Zea mays) is the only cereal of any importance in Western Nigeria. The crops are sown early in the wet season, which alternates with a dry season of two to seven months, and mature in three to five months. They are cultivated by hand and few farmers grow more than one acre of any one cereal.

The host ranges of all the known species of Nigerian cereal stem borers (viz., Busseola fusca (Fuller), Sesamia calamistis Hmps., S. penniseti Tams & Bowden, S. poephaga Tarns & Bowden, S. nonagrioides botanephaga Tams & Bowden, Manga basilinea Bowden, Coniesta ignefusalis (Hmps.), Chilotraea sp. ? argyrolepia (Hmps.), Chilo sp. ? phaeosema, Martin, Maliarpha separatella Rag. and Eldana saccharina Wlk.) are summarised and their distribution in Nigeria and relative importance there are discussed.

B. fusca and Coniesta ignefusalis are the most important stem borers of guineacorn and millet, respectively, and detailed accounts of their life-cycles and seasonal cycles are given, together with observations on adult activity, light-trap catches, larval migration, larval morphology and the effects of larval feeding patterns on plants of guineacorn and millet. Differences between the pupae of the three Noctuid genera (Busseola, Sesamia, Manga) and all stages of C. ignefusalis are illustrated. Some information on the biology of S. calamistis, S. poephaga and M. basilinea is also given.

At Samaru, the life-cycles of B. fusca and G. ignefusalis are completed in about two months under field conditions and in the absence of diapause. Three generations develop during the growing season, larvae of the third entering diapause until the next season. Many diapause larvae survive the dry season in crop residues, and the local practice of stacking stems for later use in building, etc., ensures reinfestation of subsequent crops, particularly near villages. The diapause ends between late April and early June, so that adults of the diapause generation emerge about three weeks after millet and guineacorn have germinated. Experiments indicate that diapause is terminated when larvae are provided with moist food or drink water. The relative abundance of B. fusca and C. ignefusalis in guineacorn, millet and maize largely reflects host selection by ovipositing females. C. ignefusalis lays freely only on millet and is therefore mainly confined to this crop, whereas B. fusca, though favouring guineacorn, also lays on the other two crops. Experiments indicate that more eggs are laid on larger plants.

Early millet and maize are harvested before borer populations reach their highest level. Guineacorn tolerates the considerable damage done by the high populations present at the end of the season but late millet and second-crop maize do not. Any factor hindering normal crop development tends to increase the damage done.

A provisional list of 14 primary parasites, three hyperparasites, one predator and four diseases is given. Tetrastichus atriclavus Wtstn., Apanteles sesamiae Cam., and Pediobius furvus (Gah.) were always present on B. fusca at the end of the season. Syzeuctus sp. was the most important parasite of C. ignefusalis and was regularly reared from diapause larvae, and other common parasites of this species later in the season were Sturmiopsis parasitica (Curran), T. atriclavus and Hyperchalcidia soudanensis Steffan. The over-all rate of parasitism seldom exceeded 10 per cent, of all larvae and pupae collected. Bacillus thuringiensis killed many diapause larvae of B. fusca and was the most important disease recorded.

The results of experiments relating yields to stem-borer attack in maize, early millet, late millet and guineacorn are presented and discussed. Early-sown maize suffers little damage but second-crop maize at Ibadan suffers losses of stand which, in local farms, generally exceed 20 per cent. In experiments, loss of stand did not always result in loss of yield, and evidence is presented that, under certain conditions, loss of stand is compensated for by the production of heavier cobs. At Samaru, the development of single larvae of B. fusca in otherwise healthy stems reduced their yielding capacity by 28 per cent, of the mean cob weight of healthy stems (P <0·001).

In six experiments on early millet, little reduction in yield occurred, even when infestations were much higher than those normally experienced, but late millet suffered almost complete loss of yield in two experiments and more than 90 per cent, of the stems were bored in. two other experiments, in which yields were low. These results and general observations indicate that stem borers, particularly C. ignefusalis, play a major part in limiting yields of late millet.

In six experiments on guineacorn, significantly so in three of them, the yield per bored stem was higher than that per unbored stem, and it appears that borers concentrated on or were concentrated on the larger, higher-yielding stems, possibly as a result of selective oviposition. In one other experiment, stems bored by first-generation larvae yielded significantly less than unbored stems but neither in this nor in any other experiment was over-all borer attack related to a reduction in yield and it is generally true that excellent yields of guineacorn can be obtained in the presence of high populations of borers.

Reduction of the carry over of diapause larvae, by destroying or composting crop residues or removing them from the field, has given good control on the experimental farms at Samaru but it is difficult to extend these measures to local farms. Farmers should clean up their fields before the beginning of the rains and stems that are to be used for building should be exposed in the open during the dry season; to reduce populations of diapause larvae. Insecticidal control has as yet shown little promise and plant breeding for resistance has not begun.

The necessity for further work to confirm the general conclusions drawn here is stressed and possible lines of investigation are indicated.

From March to October 1984, targets consisting of black cloth and netting, baited with 1-octen-3-ol (released at about 0·5 mg/h), and acetone (about 100 mg/h) or butanone (15 mg/h), and coated with deltamethrin, were deployed at 3–5/km2 in 600 km2 of the Zambezi Valley of Zimbabwe where Glossina morsitans morsitans Westwood and G. pallidipes Austen were initially abundant. About 3 000 000 adults of G. pallidipes and 200 000 of G. m. morsitans originally present in the area as adults or pupae were killed by targets or removed by sampling procedures between March and December. At the end of this period, the tsetse populations in the centre of the block had declined by at least 99·99%. The targets dealt adequately with a strong invasion pressure from initially dense infestations nearby, partly because the targets reduced the abundance of tsetse up to 5–10 km outside the block. At 18 months after the start of the study, the targets were badly faded; this was corrected by spraying them with a black dye and an ultraviolet-light absorber that protected the dye and insecticide, but by then the targets had deteriorated and were without adequate odour attractant, and many were no longer being maintained. Tsetse then invaded further into the block, but only in small numbers. Tabanids and muscoids were not strongly attracted to targets; their population densities in and near the block did not change greatly. Targets offer a simple and ecologically clean method of controlling tsetse and preventing invasion.

A generation of Glossina morsitans was artificially isolated by allowing emergence for three days in the habitat of G. swynnertoni and G. pallidipes.

Most teneral flies (with chitin unhardened before their first meal) were active on day 2 to 4 from emergence. The non-teneral flies first appeared in numbers when a week old. It is possible that they were somewhat inactive while still fairly young, that is, up to two or three weeks, but this was not proved. They are definitely inactive between the first and second meals. The females, on the other hand, are much more active in the first three weeks of life than later on.

The teneral males contained about 12 mg. water, which was increased after several meals to a maximum of about 18 mg. by day 17. Fat started at a mean of 1 1/2 mg., declining to 1 mg. at the first meal, then rising to about 3 mg. at day 17, after which there was no further increase. Residual weight behaved like the water, except that it was relatively very low in teneral flies. The hungry flies which reappear after the first meal have also a relatively low residual weight.

In this experiment there was no evidence that smaller flies were at a disadvantage, as has been suspected from other work.

With reservations concerned with differences in place and time, the mean age of samples of male flies can be accurately deduced from the wear on the trailing margin of the wing. The females do not wear out their wings so quickly.

Males dispersed, in any one direction, to a mean perpendicular distance of 365 yards in a week, 484 yards in two weeks, 772 yards in three weeks, and 941 yards in four weeks.

In spite of undoubted interference by G. swynnertoni, a considerable second generation appeared.

The females and pupae in nature experienced temperatures approximating to those obtained in a screen at a standard meteorological station: they did not live in specially cool eeoclimates.

Adding together all the hoppers listed above, we find that 637 individuals were reared in these experiments from 34 different pairs of adults; 394 were reared in complete isolation, and 243 under crowded conditions, but each crowd consisted of the progeny of one pair only. The majority of those isolated were placed in isolation on the day of hatching, but some first lived in a crowd for a week or two before being used to replace isolated individuals that had died.

Comparing the results in Tables XXI and XXII, we noted that the isolated hoppers acquired the solitaria characters, while those crowded tended to develop the gregaria characters, regardless of whether the parents had been gregaria or solitaria. Only two isolated hoppers from the pair L.p.352 showed gregaria characters, and one of these had lived in a crowd and had acquired gregaria characters before it was placed in isolation in its second instar. Table XXIII shows that crosses between gregaria and solitaria gave the same results.

In the second generation (Table XXIV) the progeny of the P1gregaria pair 352 reacted to isolation and crowding in the same way as all other hoppers, and the same was true of the F2 back-cross to gregaria (L.p.569).

Examining the hypothesis of Potgieter in the light of these experiments, we find that the data presented in Tables XXI to XXIV are in direct contradiction with the three phases enumerated above. Instead of giving a majority of gregaria, the matings of gregaria by gregaria produced both gregaria and solitaria according to the conditions under which the progeny were reared. According to the second thesis, the crossing of solitaria and gregaria should always result in a majority of gregaria, but Table XXIII shows that 90 isolated hoppers all became solitaria. Thirdly, the mating of solitaria with solitaria is supposed never to produce gregaria progeny; Table XXII shows that the progeny of these crosses developed gregaria characters when crowded and solitaria when isolated.

Psyllids are generally narrowly host specific and are restricted almost exclusively to perennial dicotyledenous plants. Psyllids are known vectors of plant diseases. In addition, the effects of salivary injection can be very severe, causing growth abnormalities in the plant. Psyllid development rates are related to the nutritive status of the host-plant and, as in aphids, the honeydew produced while feeding is low in nitrogen. Psyllids reproduce sexually and pass through five nymphal instars before becoming adult. The immature stages exhibit both morphological and behavioural adaptations to resist desiccation, and the life-cycle is often highly synchronised with host-plant phenology. Adult Psyllids are known to disperse up to eight miles on wind currents, although in general dispersal is less marked than in aphids. The mechanism of host-plant selection is probably chemo-gustatory. Capacity for population increase in Psyllids is more dependent on generation time than on female fecundity. Recorded Psyllid parasites include Diptera of the family Cecidomyiidae and a wide range of Hymenoptera. These parasite species are almost exclusively parasitic on Psyllids although there is little evidence for parasite–host specificity within the Psylloidea. Psyllid species from a wide range of geographical areas have similar predator complexes. Anthocorids, Syrphids, Coccinellids and Neuroptera larvae are the main predators. At high population densities nymphal mortality increases in a density-dependent manner with increasing density, whereas at low densities nymphal survival is enhanced by group feeding. Close parallels exist in the feeding biology of aphids and Psyllids, but aphids appear better adapted for the exploitation of unstable ephemeral food sources.

Filariasis is a mosquito-borne disease that causes lymphedema and the main vector is Culex quinquefasciatus. A simple measure was taken to eradicate the vector using nanoemulsion. Eucalyptus oil nanoemulsion was formulated in various ratios comprising of eucalyptus oil, tween 80 and water by ultrasonication. The stability of nanoemulsion was observed over a period of time and 1:2 ratios of eucalyptus oil (6%) and surfactant (12%) was found to be stable. The formulated eucalyptus oil nanoemulsion was characterized by transmission electron microscopy and dynamic light scattering. The nanoemulsion droplets were found to have a Z-average diameter of 9.4 nm and were spherical in shape. The larvicidal activity of eucalyptus oil nanoemulsion and bulk emulsion was tested and compared. Our nanoemulsion showed higher activity when compared to bulk emulsion. The histopathology of larvae-treated and untreated nanoemulsion was analyzed. Furthermore, biochemical assays were carried out to examine the effect of nanoemulsion on biochemical characteristics of larvae. The treated larval homogenate showed decrease in total protein content and a significant reduction in the levels of acetylcholinesterase. The levels of acid and alkaline phosphatase also showed reduction as compared to control larval homogenate.

We have used a new technique to identify discrete genetic markers in aphids, a family in which biochemical and morphological genetic polymorphisms are rare. The new technique uses the polymerase chain reaction (PCR) to amplify random regions of aphid genomes (random amplified polymorphic DNA) and has been termed RAPD-PCR. We demonstrate the use of the technique in revealing genetic variation in four aphid species, the greenbug (Schizaphis graminum (Rondani)), the Russian wheat aphid (Diuraphis noxia (Mordvilko)), the pea aphid (Acyrthosiphon pisum (Harris)), and the brown ambrosia aphid (Uroleucon ambrosiae (Thomas)). In contrast with allozyme surveys, RAPD-PCR revealed large amounts of genetic variation among individuals in each of these species. Variation was detected among biotypes, populations, colour morphs and even individuals on a single plant. We also explored the utility of RAPD-PCR in the detection and identification within aphid bodies of two endoparasitic wasps, Diaeretiella rapae (McIntosh) and Lysiphlebus testaceipes (Cresson). The use of RAPD-PCR in species diagnostics, parasitoid detection, and population studies is discussed.

Mosquitoes were caught in bedrooms in Tanzanian villages by human-biting catches and in light-traps set close to occupied untreated bed nets. Catches by each method were carried out on pairs of nights in the same week at different seasons and in different villages. The pairs of adjacent catches by the different methods showed a strong correlation. Analysis of the ratio between the catches by the two methods on pairs of nights in the same week indicated that on average three light-traps caught about the same number of mosquitoes as a team of two human catchers. The ratio did not differ significantly between Anopheles gambiae Giles (sensu lato), A. funestus Giles, and Culex quinquefasciatus Say, nor between the villages, or between times when mosquito populations were high or low. The distribution of numbers of ovarian dilatations differed significantly between catches in different villages and seasons but not between pairs of catches by the two methods. Similarly, the parity and sporozoite rates agreed between pairs of light-trap and house-resting catches, but differed markedly between villages and seasons. Thus it is concluded that light-traps used in conjunction with bed nets catch a representative sample of the vectors which would have bitten humans in bedrooms in this area.

The Tsetse Investigation in N. Nigeria is being carried out under the auspices of the Imperial Bureau of Entomology, the expense being met by the Nigerian Government. The work was commenced by the present Investigators in 1921 and their Report dealing with the first year's work was published in the Bulletin of Entomological Research (xiii, p. 373, April 1923). This paper deals more fully with the trypanosome infection of tsetses in Nigeria and describes a method of estimating this with rapidity.

A survey was made to assess the biotype status of populations of the whitefly Bemisia tabaci (Gennadius) in Spain. The study involved observation of the squash silverleaf reaction, analysis of esterase patterns and application of a RAPD-PCR technique. The results obtained by the three methods were fully consistent and showed that the Spanish populations of B. tabaci were composed of two genetic types. One corresponded to populations of the B biotype, found in Tenerife (Canary Islands), Barcelona, Madrid, Malaga and Almeria. The other, showing a unique RAPD and esterase pattern, was found in Majorca (Balearic Islands), Seville, Valencia, Murcia and Almeria, as well as in the Algarve Region of Portugal. RAPD patterns of other populations from the rest of the world used for comparison showed that populations from Arizona (USA), Israel, France, Denmark, Italy, Netherlands and Japan have similar RAPD patterns typical of the B biotype. By contrast, populations from the Iberian Peninsula, Turkey, India, Pakistan and Arizona (A biotype), showed different and unique patterns.

The whitefly fauna of Europe and the Mediterranean Basin comprises 56 species that are considered to be native or naturalized, accommodated within 25 genera. Presented here are a check-list, an identification key to puparia, and a brief account of each species including its distribution and host-plant range. The puparium of each species is illustrated. One new nomenclatural combination (Aleuroclava similis, from Aleurotuberculatus) and two new synonymies (Parudamoselis kesselyakiwith Ceraleurodicus varus, Asterobemisia nigrini with A. paveli) are proposed. Three nominal species (Aleurodes capreae, A. fraxini, and Aleyrodes campanulae) are here treated as nomina dubia. Species which, in the study area, have only been recorded from glasshouses are discussed. Four additional species, not yet recorded from the region, are included in the discussion, two of them because a particular quarantine risk is perceived and two because they are notifiable pests in European Union quarantine legislation.

A diverse range of novel molecular (DNA) markers are now available for entomological investigations. Both DNA and protein markers have revolutionized the biological sciences and have enhanced many fields of study, especially ecology. Relative to DNA markers, allozymes are cheap, often much quicker to isolate and develop, even from minute insects (aphids, thrips, parasitic wasps, etc.), and subsequently easy to use. They display single or multi-locus banding patterns of a generally easily interpretable Mendelian nature, and the statistics for their analysis are well established. DNA markers are also suitable for use with small amounts of insect material and can be used with stored, dry or old samples. They have an expanding range of applications, many involving intra- and interspecific discriminations. Like allozymes, they can be single or multilocus, whilst methods for their statistical analysis have recently been published. However, they can be considerably more expensive than allozymes, require more complex preparatory protocols, expensive equipment, may involve lengthy development procedures (e.g. isolating cloned oligonucleotides to develop primers to detect microsatellite regions) and some have complex multi-locus banding patterns which may be of a non-Mendelian nature (e.g. RAPDs, randomly amplified polymorphic DNA), and are in some cases, not easily repeatable. In this review, we hope to inform the general reader about the methodology and scope of the main molecular markers commonly in use, along with brief details of some other techniques which show great promise for entomological studies. Thereafter, we discuss their applications including suitability for particular studies, the methods used to load and run samples, subsequent band detection, band scoring and interpretation, the reliability of particular techniques, the issues of safety involved, cost effectiveness and the statistical analyses utilized.

Simple one- and multi-generation models are used to show the essential features of the dynamics of selection for resistance to one insecticide or two unrelated insecticides in insect populations, part of which are unexposed to either compound. The use of a mixture appears advantageous provided that resistance is not fully dominant, but, if it is, linkage disequilibrium builds up rapidly and nullifies the advantage of the mixture

Attention has recently been focussed on the problem of why mosquitoes feed on some people more than others. In this paper, investigations of selective feeding by mosquitoes of the Anopheles gambiae Giles complex conducted in two villages in the Gambia are reported. Fed mosquitoes were collected from the bed nets of 35 groups of people who normally sleep together, for example mothers and infants or two children or two adults. A total of 2339 meals was analysed using haptoglobin or ABO typing to determine from which individual each meal had been obtained. The results showed that the proportion of feeds upon an individual in a group can be associated with the proportion of the total surface area or weight of the group contributed by that individual. The incidence of multiple feeding was between 3 and 6%. The results are discussed in relation to host selection by mosquitoes and their significance for models of malaria epidemiology.

Shortly after its invasion into Europe, the western flower thrips, Frankliniella occidentalis (Pergande), became a more severe pest of greenhouse crops than the onion thrips, Thrips tabaci Lindeman. To test whether this differential pest status was due to a larger capacity of population increase, a comparative life history study was carried out on cucumber (Cucumis sativus cv. Corona). Experiments at 25°C showed that the egg-to-egg period of F. occidentalis was shorter, but its peak ovipositional rate was lower and its offspring sex ratio more male biased. These differences resulted in a slightly lower intrinsic rate of population increase (rm) for F. occidentalis than for T. tabaci (0.166 vs. 0.176/day). It was shown experimentally that between 15 and 28°C, developmental rate of F. occidentalis is linearly related to temperature, with a theoretical threshold temperature similar to the value reported for T. tabaci (10.9 vs. 11.5°C). It is argued that the rm-value of F. occidentalis will not be higher than that of T. tabaci for any temperature within this range. Alternative explanations for the difference in pest status between the two thrips species are discussed.