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 possibility of density dependent feeding success in the African malaria vectors Anopheles gambiae Giles (sensu lato) and A. funestus Giles was investigated by examining the gonotrophic status of mosquitoes from 423 collections made in a Tanzanian village. Up to 500 mosquitoes were caught in any single 35 minute indoor resting collection. Estimates of the total numbers of mosquitoes resting were made by removal sampling. These indicated that the efficiency of resting collections decreased with increasing mosquito population. Of 1904 mosquito blood meals tested by ELISA, 95% were of human origin. There was no decrease in the proportion of mosquitoes fully fed at high population densities and the only demonstrable avoiding action by hosts in response to high densities of mosquitoes was the increased use of bednets during the wet season. The late biting cycle of these mosquitoes precludes many other density-dependent host defence mechanisms because the hosts are asleep at the time of attack. African malaria vectors have evolved with man and perhaps their evasion of density-dependent host responses has reinforced their preference for human blood.

Radar, aerial netting and ground sampling were used to study the autumn migration of Nilaparvata lugens (Stål) in Jiangsu Province in east central China. Emigration of macropterous adults increased from late August until late September as the main rice crop matured and was harvested. In early and mid September, the resulting windborne migrations carried the planthoppers mainly towards the west, although the migration directions ranged (within the western sector) from south to north. By late September, however, displacements were predominantly to the south-west on the then prevailing north-east monsoon winds: migration was particularly rapid when the north-easterlies were reinforced by typhoons. Although in late September such movements to more southerly latitudes are essential for the survival of the planthoppers' progeny, we found no definite evidence for preferential emigration on winds blowing towards the south. There were, however, indications that when winds towards the north occurred, the duration of migratory flight was curtailed. Irrespective of any possible preference for migration on northerlies, a large proportion of the N. lugens population would normally be carried in an adaptive southwards direction, because the advent of the north-east monsoon occurs at a time when the number of flight-ready planthoppers approaches its peak.

The diversity and abundance of wild bees ensures the delivery of pollination services and the maintenance of ecosystem diversity. As previous studies carried out in Central Europe and the US have shown, bee diversity and abundance is influenced by the structure and the composition of the surrounding landscape. Comparable studies have so far not been carried out in the Mediterranean region. The present study examines the influence of Mediterranean landscape context on the diversity and abundance of wild bees. To do this, we sampled bees in 13 sites in olive groves on Lesvos Island, Greece. Bees were assigned to five categories consisting of three body size groups (small, medium and large bees), the single most abundant bee species (Lasioglossum marginatum) and all species combined. The influence of the landscape context on bee abundance and species richness was assessed at five radii (250, 500, 750, 1000 and 1250 m) from the centre of each site. We found that the abundance within bee groups was influenced differently by different landscape parameters and land covers, whereas species richness was unaffected. Generally, smaller bees’ abundance was impacted by landscape parameters at smaller scales and larger bees at larger scales. The land cover that influenced bee abundance positively was olive grove, while phrygana, conifer forest, broad-leaved forest, cultivated land, rock, urban areas and sea had mostly negative or no impact. We stress the need for a holistic approach, including all land covers, when assessing the effects of landscape context on bee diversity and abundance in the Mediterranean.

Bemisia tabaci (Gennadius) populations, collected from cassava and other plants in major cassava-cultivation areas of Sub-saharan Africa and from elsewhere around the world, were studied to determine their biotype status and genetic variation. Random amplified polymorphic DNA–polymerase chain reaction (RAPD–PCR) markers were used to examine the genetic structure of the populations. The dendogram obtained using the neighbour joining method (NJ) split the cassava-associated populations from the non-cassava types with a 100% bootstrap probability. Analysis of molecular variance (AMOVA) of the RAPD fragments revealed that 63.2% of the total variation was attributable to differences among populations, while the differences among groups (host) and within populations accounted for 27.1 and 9.8% respectively. Analysis of the internally transcribed spacer region I (ITS 1) of the ribosomal DNA confirmed that the cassava populations of B. tabaci populations were distinct from non-cassava populations. Experiments to establish whitefly populations on various host plants revealed that cassava-associated populations were restricted to cassava only, whereas B. tabaci from other hosts were polyphagous but did not colonize cassava. Hence, populations of B. tabaci from cassava in Africa represent a distinct group.

Wolbachia are intracellular, maternally transmitted bacteria considered the most abundant endosymbionts found in arthropods. They reproductively manipulate their host in order to increase their chances of being transmitted to the offspring, and currently are being used as a tool to control vector-borne diseases. Studies on distribution of Wolbachia among its arthropod hosts are important both for better understanding why this bacterium is so common, as well as for its potential use as a biological control agent. Here, we studied the incidence of Wolbachia in a broad range of insect species, collected from different regions of Brazil, using three genetic markers (16S rRNA, wsp and ftsZ), which varied in terms of their sensitivity to detect this bacterium. The overall incidence of Wolbachia among species belonging to 58 families and 14 orders was 61.9%. The most common positive insect orders were Coleoptera, Diptera, Hemiptera and Hymenoptera, with Diptera and Hemiptera having the highest numbers of Wolbachia-positive families. They included potential human disease vectors whose infection status has never been reported before. Our study further shows the importance of using quantitative polymerase chain reaction for high-throughput and sensitive Wolbachia screening.

In British East Africa Oecophylla longinoda (Latr.) var. textor Santschi is locally common in the costal region. Inland it is absent from higher altitudes and from areas where there is a pronounced dry season.

In Zanzibar Island, O. longinoda at least 89 species of trees and shurbs; the largest populations occur on the clove (Jambosa caryophyllus), Citrus spp., Bridelia micrantha and Canthium zanzibaricum.

The nesting habits and colony composition of O. longinoda are such that one colony may spread over a number of adjacent trees; it contains only one gravid queen.

Winged virgin sexual forms are released at the beginning of the wet seasons and new colonies are initiated by a single queen, who uses her food reserves to bring the first batch of brood to maturity.

In Zanzibzr, O. longinoda tends a wide range of Homoptera that produce honey-dew, but apparently “ prefers ” certain Coccids, notably Saissetia spp.

The degree of attention afforded by an ant species determines the species of Homoptera which it is able to attend.

The insect species preyed upon by O. longinoda include the honey bee, Apis mellifera, and the driver ant, Dorylus nigricans, of which large numbers may be destroyed.

O. longinoda is of undoubted value for controlling certain coconut pests, notably Theraptus sp. (Coreidae), and its efficiency in coconut plantations could probably be much enhanced.

The relationships between the predatory mites, Amblyseius swirskii (Athias-Henriot) and Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae), and their prey, western flower thrips (Frankliniella occidentalis Pergande) (Thysanoptera: Thripidae), were investigated to determine the effects of predation on intra-guild or extra-guild prey and predator preference. Life history characteristics of both predatory mites were measured when fed eggs and larvae of the other predator species and compared to data obtained when the predators were fed thrips larvae. In addition, choice tests were conducted to determine if the predators had a preference for different prey or if they were indiscriminate predators. Amblyseius swirskii appears to be an important intra-guild predator of N. cucumeris juveniles because of a high predation rate and a preference for N. cucumeris juveniles over thrips. Neoseiulus cucumeris is also an intra-guild predator of A. swirskii juveniles; however, it has a lower predation rate than A. swirskii. Contrary to intra-guild predation theory, intra-guild prey was an equally good or better food source than thrips (extra-guild prey) for both predators, based on high oviposition rates and fast development times. The results of this study indicate a high potential for negative interactions between A. swirskii and N. cucumeris when used together in biological control of thrips.

The effect of a range of temperatures (15–42°C) and relative humidities (40–80%) on growth of populations of Liposcelis entomophilus (Enderlein), Liposcelis bostrychophilus Badonnel and Liposcelis paetus Pearman infesting a rice-based medium was investigated. These species are often found infesting stored cereal grains in the tropics. Both L. entomophilus and L. bostrychophilus bred most rapidly at 30°C, 70–80% r.h. Neither survived at temperatures of 36°C and above. In contrast, L. paetus bred most rapidly at 33–36°C, 70% r.h., and was able to breed at 42°C, 80% r.h. No species survived humidities below 60%. As well as consuming mould growth, Liposcelis spp. also caused visible damage in rice grains. Implications of these findings in the understanding of pest status and geographical distribution of severe outbreaks of Liposcelis spp. are discussed.

The use of chromosome translocations for the control of pests, with particular reference to Glossina, is proposed. A translocation arises if two non-homologous chromosomes in the same cell undergo breakage and the fragments re-join with the wrong partners. At meiosis in an individual heterozygous for a translocation, gamete nuclei with several different combinations of chromosomes are produced. Some of these are diploid for one part and lack completely another part of the normal chromosome set; when such unbalanced gametes fertilise normal gametes inviable embryos are produced. It has been found in a number of organisms that about half the gametes of translocation heterozygotes are of the unbalanced type and such heterozygotes are described as semi-sterile. If an individual inherits the same translocation from both parents it is described as a translocation homozygote; this is often inviable but, if not, its fertility is usually normal.

Adult males of G. austeni Newst. have been irradiated and each of their progeny are being screened for the occurrence of semi-sterility. Any individuals found to be semi-sterile would probably be translocation heterozygotes and their progeny will be inbred to try to produce a viable stock, homozygous for a translocation. If this can be done, large numbers of such translocation homozygotes could be reared and released into a wild population, where matings with wild types would produce heterozygotes, and hence a reduction in the fertility of the population.

Using simple assumptions, the effects of releasing translocation homozygotes were computed. Provided the numbers released were such that the translocation frequency approached the optimum value of 50 per cent., the reduction in population fertility would be prolonged for many generations after the releases had finished. It is shown that it would be more efficient to release the translocation homozygotes at successive generations rather than all at once and that the homozygotes released could with advantage be of both sexes. For this reason, and because of the prolonged effect of releases of translocations, it is concluded that the number of individuals that would have to be reared to achieve a given result by the translocation method might be considerably less than if the sterile-male method was used. However, the reduction in population fertility at each generation that can be achieved with the translocation method is limited, and the method would therefore be ineffective against populations whose size was strongly buffered by density-dependent factors.

Several methods, including the use of serology, are available for evaluating prey-predator relationships. Two basic methods involving precipitation and agglutination reactions have been utilised, both of which depend on the production of specific antisera with high titres. A critical account is presented of methods of preparing antisera, with particular reference to the amount of antigen required, the route of inoculation and testing antisera, together with a review of the five precipitation and two agglutination techniques available. The main limitations of serological methods are tje specificity of the arrtisera and the difficulties in quantifying results unless assumptions are made as to the number of prey eaten at each feed. Details of studies employing serological techniques to identify the predators of specific prey and the food od invertebrates are given intwo tables. The value of serological techniques is discussed in relation to the ecology of invertebrates by considering, as examples, te insect fauna on broon (Sarothamnus scoparius), predation of mosquitoes and the food of triclads. Errors in the quantification of predation may occur by including positive reactions resulting from carrion feeding or material ingested acidentally on plants by phytophagous arthropods.

The effects of vegetative cover and soil type on the abundance and distribution of 50 species of scarabaeine dung beetle were examined during three successive days in January 1979 in Hluhluwe Game Reserve, South Africa. Pitfall traps baited with bovine dung were set at intervals of 20 m in a transect across a 20–ha patch of grassveld surrounded by Acacia bushveld. One end of the transect was on clay–loam soil and the other on sandy loam. In all, 32 936 specimens were caught, representing 71 species from 22 genera. Thirty–two species were diurnal and 18 were crepuscular or nocturnal. Twenty–six species were more abundant in bushveld than in grassveld, and eight species were more abundant in grassveld than in bushveld. Soil type influenced the relative abundance of 23 species. The degree of habitat specificity varied widely between species. During overcast weather, both bushveld and grassveld species became abundant in the transitional zone between bushveld and grassveld where the light intensity was similar to that in bushveld on a clear day. It is suggested that light intensity is one characteristic by which beetles recognise bushveld and grassveld.

Insect chemosensory proteins (CSPs) are supposed to transport hydrophobic chemicals to receptors on sensory neurons. However, CSPs are broadly expressed in various insect tissues, suggesting their involvement in the physiological processes beyond chemoreception. So, the exact physiological roles of CSPs in insects still need to be unraveled. In this study, three full-length of CSP genes from Spodoptera exigua have been cloned and characterized. The deduced amino acid sequences of SexiCSP1, SexiCSP2 and SexiCSP3 revealed open reading frames of 128, 128 and 126 amino acids, respectively, with four conserved cysteine residues. The expression patterns of the three SexiCSPs were further investigated by real-time PCR. Three SexiCSPs were expressed in antennae, heads, legs, wings, thoraxes, abdomens, testes and ovaries, with the highest expression level in female and male antennae. Furthermore, all three SexiCSPs mRNA were distributed extensively in the tested development stages with the highest expression level in pupae. RNAi-based gene silencing study resulted in a dramatic reduction of corresponding mRNA in female S. exigua after injection with dsRNA of all three SexiCSPs. Consequentially, 42.5% of mortalities, 68.3% (compare to DEPC water injected control) and 71.4% (compare to uninjected control) oviposition inhibition, and significantly effected egg hatching were observed in the female S. exigua injected with dsSexiCSP3 as compared to control treatments. On the other hand, dsSexiCSP1 and dsSexiCSP2 injected female adults did not show effects on survival and reproduction. Our study confirms the utility of RNAi approach to functional characterization of CSP genes in S. exigua and provides a starting point for further studies on female survival and reproduction in this insect. It also reveals the potential pest controlling method, as insect behavior regulation agent that disrupts the expression of chemosensory proteins.

In Rhodesia from 1966 to 1970 Glossina morsitans Westw. and G. pallidipesAust. in natural and artificial refuges were studied by in situ counts or captured by a hand-net, mechanical, electric or sticky trapping, or a curtain drawn across the entrance. A modification of mechanical trapping permitted investigation of the pattern in whichtsetse vacated a refuge. Coolness and shade were features of effective refuges. Large numbers of tsetse utilised refuges only during the hot dry months of September, October and November. Entries occurred when temperatures reached 32°C in the morning and continued until mid-afternoon; exits occurred mainly in the evening. G. morsitansentering at 12.00–14.00 h were relatively abundant in fat; G. pallidipes entering at 12.00–16.00 h were relatively abundant in residual blood-meal. Greatest numbers of tsetse occupied refuges in naturally shaded situations such as riverine fringes. Few of the many tsetse marked in refuges and releasedwere found again at the refuge of marking. Artificial refuges were not used extensively for larval deposition. Comparisons between the catches from refuges, oxen, Morris traps and a fly round illustrate the problem of obtaining representative samples of tsetse populations. The application of insecticides to natural refuges is a policy of merit.

An analysis, using mathematical models, is presented of the ecological, genetic and economic factors that determine the optimal strategies for the long-term use of chemical control of Boophilus microplus (Can.) on cattle. As an illustration, the control of the tick in south-eastern Queensland is considered, but the approach is readily applicable in any other geographical area. It is suggested that optimal strategies take into account the need to delay the development of resistance to acaricides. The suggested strategies involve the use of tick-resistant Zebu-type cattle as a basis for tick control. High concentrations of acaricides are recommended to reduce seleotion of resistant ticks. Careful timing and moderation in the use of acaricides is also recommended to minimise the number of occasions on which resistant ticks are subjected to selection at times when they can successfully reproduce. As the spread of resistance is thought to occur primarily on moving cattle and before resistance is evident, stringent quarantine measures may slow down the spread.

Field and laboratory studies at Ibadan, Nigeria, showed that the young nymphs of Zonocerus variegatus (L.) normally reject cassava after biting it and die if they are confined on growing leaves. Later instars will eat cassava, especially when deprived of food for some time, but the adults progressively lose weight when restricted to feeding on growing cassava. On cut cassava, on the other hand, extensive feeding occurs and normal growth is maintained. The change from unpalatability to acceptability occurs within about an hour of cutting and is apparently associated with wilting. Cassava produces latex, but this was not distasteful to Zonocerus. The readiness to feed on growing cassava was associated with low levels of hydrogen cyanide production by the leaves; wilted leaves still produced hydrogen cyanide, but at a lower rate than turgid, growing leaves. In the area around Ibadan, Zonocerus regularly defoliates cassava in the latter part of the dry season, probably because a shortage of attractive foods forces the insect to eat cassava.

A panteles flavipes (Cam.) and A. sesamiae Cam. are important parasites of graminaceous borers in the Oriental and Ethiopian Regions, respectively. Both have been utilised for biological control. A. sesamiae has become the commonest parasite of Sesamia calamistis Hmps. in Mauritius (Anon., 1954), while A. flavipes has become remarkably successful against Diatraea saccharalis (F.) in Barbados (Simmonds, 1969a). In view of the interest engendered in these parasites, particularly the latter, by these successes, a general account is presented here of their biology, based on published data and on the author's observations at the East African Station (Kawanda, Uganda) of the Commonwealth Institute of Biological Control.

The feeding of Eupteryx melissae Curt. (Cicadellidae) on the leaves of ssge gives rise to the appearance of chlorotic spots, as a result of damaged mesophyll cells becoming filled with air. The length of the mandibular stylets in this species (as averaged from the adult and five nymphal instars) is 67 per cent. of that of the maxillaries, both types of stylet being slightly larger in females. The mandibular stylets when inserted do not penetrate much below the leaf surface where they are held by barbs and a salivary sheath, and the total extent of their insertion is only 29 per cent. of that of the maxillary stylets. The latter are the main penetrating organs; the stylets may move together or independently and are not surrounded by a sheath. Mandibular and maxillary penetration is greatest in fifth-stage nymphs, the mean (and maximum) distances being 97 (205)μ and 177 (340)μ respectively. It increases progressively from the first nymphal stage, and in the adult shows mean values near those of nymphs in the third or fourth stage. Rate and depth of stylet penetration is very variable, due to repeated maxillary protraction and retraction, and there is little correlation between the lengths to which the mandibular and the maxillary stylets are extended. Exuvial stylets, particularly the mandibulars of fifth-stage numphs, consistently show a graeter degree of extruction than is to be found in nymphs when feeding normally: such deeper insertion may help to anchor the insect more firmly during ecdysis.

Stylet insertion is by pressure, intracellular, and very rapid (attaining rates up to 115μ per minute). The sex of the individual insect and the leaf-surface attacked have no effect on depth of penetration, at least in certain nymphal stages, and all tissues of the lamina are available for feeding, even to first-stage nymphs, in consequence of the relatively greater development of the stylets in the younger insects. During penetration the mandibular stylets move alternately and initially lead, but quickly come to rest, and further penetration is by the maxillaries which follow a mainly intracellular path. Protrusion of one maxillary stylet beyond the other (up to a maximum distance of 112μ.) was observed in plant tissue and observations of feeding on stripped epidermis show that such a stylet can empty cells at its apex. Protoplasts are removed from a cell within a few seconds, and as this appears to be too short a time to allow digestion, it is assumed that chloroplasts must be mechanically fragmented on passage into the food canal. Removal may be a two-stage process, and if it is assumed that sometimes only the first stage is completed, and is accompanied by saliva injection, it is possible to explain the occurrence, as unimbibed residue, of plasmolysed degenerating chromophilic cells scattered throughout damaged tissue, which occurs mainly in the palisade and spongy parenchyma, and only seldom in vascular tissue. There is no evidence for diffusion of any salivary toxin from damaged cells or from the sheath. Stylet-tracks in damaged areas are unbranched and short and rarely give any indication of the cells fed upon or of the repeated probing by the maxillary stylets that is known to occur.

The overwintering of Heliothis armigera (Hb.) was studied in the Namoi Valley, north-western New South Wales, Australia. In field observations, over 80% of pupae formed during late April and May were found to be in diapause and did not resume development until September. Moth emergence from diapausing pupae occurred in a protracted period between September and November. Laboratory studies indicated the probability of two phases of diapause development, one completed under cool soil conditions of winter and a second requiring a temperature above about 17° C. The threshold of the second phase was higher than that for non-diapausing pupae and was not normally reached until late September. The times to diapause termination in populations of overwintering pupae were satisfactorily fitted to a geometric distribution, which was reflected in the protracted emergence period of moths in field cages. The limited availability of suitable host-plants for the overwintering generation and for emerging moths is discussed.

Many species of insects associated with cultivated rice do not over-winter in Korea and Japan, but migrate into these areas each year. To understand better the origins of these immigrations as well as the geographic structure of rice pests in Asian rice growing regions, intraspecific variation in two species of delphacid planthoppers, Nilaparvata lugens (Stål) and Sogatella furcifera Horvath, was examined. An 850 base pair region of mitochondrial DNA cytochrome oxidase-I (CO-I) was sequenced from a total of 71 individuals collected from 11 localities in seven countries: Korea, Philippines, China, Bangladesh, Malaysia, Vietnam and Thailand. In N. lugens, three haplotypes were found and all populations sampled shared a dominant haplotype. Localities in Korea contained two haplotypes and localities in China and the Philippines contained three. However, in samples from the Indochina peninsula no variation was detected either within or between populations, consistent with a hypothesis of regular migration and gene flow. These populations did not contain some haplotypes found in Korea, suggesting they were not the source of yearly immigration into Korea and, by extension, Japan. Populations from China did share haplotypes with Korea, which was consistent with the hypothesis that China was the source for yearly immigration into Korea. There was insufficient resolution to distinguish among populations in China. For N. lugens, the data suggested that populations south of the Red River Valley in Vietnam experienced regular mixing and were distinct from populations to the north which contributed to yearly immigrations. In S. furcifera, there was less differentiation among populations. Two haplotypes were found in all populations except Malaysia. The results for both species were consistent with seasonal weather data and indicated that more detailed analysis of DNA sequence data will be fruitful.