The status of the different cytological variants of Simuliumsanctipaulisensu stricto Vajime & Dunbar (sensu b8Post, 1986) found in Ghana and Côte d’Ivoire is cytotaxonomically evaluated in view of recent revisions of the S. sanctipauli subcomplex. Three geographical variants designated as ‘Pra’, ‘Comoé’ and ‘Sassandra’forms of S. sanctipauli are described. The ‘Pra’ form is genetically differentiated from the other two forms by a distinct sex-determining system. The ‘Comoé’ and ‘Sassandra’ forms are considered as the two ends of an interspecific stepped cline with the River Bandama basin as the zone of contact. The possibility that the ‘Comoé’ form populations breeding in southwestern Ghana could serve as reinvading S. sanctipauliinto the Onchocerciasis Control Programme (OCP) area in West Africa is discussed.

Flight by Listronotus bonariensis (Kuschel) in Canterbury, New Zealand varied greatly both within and between seasons; no winter flight was detected between mid-May and mid-August. Predisposing conditions for flight were found to be >19degC, rh <81% and windspeed <10.8 km h–1. Three flight phases with different characteristics were identified when approximately equal numbers of weevils were trapped. These were between mid-August and early December (overwintered weevils), between early December and mid-March (first summer generation weevils) and mid-March and mid-May (first and second generation weevils). The proportion of individuals with developed flight musculature was c. 8% in the first phase and 30% in the last phase; muscle development was delayed in the mid-phase. First phase weevils with flight muscles were c. 20 times more likely to fly than those in the last. A very weak inverse relationship was observed between developed flight musculature and the presence or absence of eggs. Similarly, there was a very weak inverse relationship between weevil ground densities and the proportion with developed flight muscles. Levels of parasitism by Microctonus hyperodae Loan amongst trapped weevils were far less than that on the ground, indicating that it inhibits flight and may explain the relatively slow dispersal of the parasitoid. It was concluded that the adaptive implications of flight could be linked to escape responses from desiccating microclimates rather than dispersal from crowded habitats.

Common house flies, Musca domestica Linnaeus, were reared to pupation with exposure to ivermectin, washed, and then exposed to parasitism by Muscidifurax zaraptor Kogan & Legner. Pupae exposed to ≥ 0.25 ppm ivermectin produced 63% fewer parasitoids than did control pupae. Pupae exposed to 0.01 ppm ivermectin produced 23% more parasitoids. Exposure to 0.10 ppm ivermectin had no detectable effect. Treatments did not affect the developmental time of male or female F1parasitoids. Treatments did not affect the production of adult F2 progeny by F1 females, nor the sex ratios of these offspring. This study documents an indirect effect of ivermectin residues across trophic levels. It identifies altered host quality as another mechanism by which faecal residues of ivermectin may affect insect activity in dung of treated cattle. The importance of this phenomenon under field conditions is undetermined.

Termites were sampled using randomized soil pits in 64 cropping plots, each 25 x 25 m, forming an experimental agrisilvicultural system in both a 6- and an 18-year-old Terminalia ivorensis plantation, in which canopy cover, crop, cropping system and land preparation were the principal treatment variables. The treatments were established in April 1995 and sampling was carried out in November 1995, February 1996 and July 1996. A total of 82 termite species were found, of which 67 were soil-feeders. Overall termite abundance and the abundance of soil-feeders increased between November 1995 and July 1996, reaching a mean of nearly 6000 m-2. Pooling termite data from these sampling dates, in the old plantation, the high canopy cover treatment (192 stems ha-1) had a greater abundance of termites, compared with the low canopy cover treatment (64 stems ha-1) and this effect was independent of crop type (plantain or cocoyam), cropping system (single stands or mixed crops) and land preparation (mulch retained or burned, plantain only). The young tree plantation (same tree densities as in the old plantation) showed no significant difference in termite abundance between high and low canopy (levels of tree foliage) densities, though the high canopy sheltered a greater number of termites. Analysis of covariance showed that crop yield (both plantain and cocoyam) was not directly linked to the abundance of all termite populations, but that the cocoyam yield was positively correlated with the abundance of soil-feeding termites (the majority in the assemblage) in the young plantation. This may be due to the beneficial conditioning of soil resulting from the foraging and construction activities of soil-feeders.

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.

Lutzomyia lichyi (Floch & Abbonenc) is a suggested secondary vector of Leishmania in Colombia. Taxonomically, L. lichyi is very closely related to the L. longipalpis (Lutz & Neiva) species complex. Male members of the complex can be distinguished by their sex pheromones which are produced in papules found grouped together in pale patches on tergites 3 or tergites 3 and 4. Male L. lichyi also have papules, very similar in appearance to those of the L. longipalpis species complex but distributed on tergites 4, 5, 6 and 7. Chemical analysis of male L. lichyi hexane extracts has revealed the presence of two novel oxygenated methylsesquiterpenes. The two major oxygenated terpenes found in the extract of L. lichyi males are tentatively characterized as a primary and tertiary alcohol. The mass spectrum of the proposed primary alcohol is very similar to the published mass spectrum of 3-methyl-α-himachalene, the sex pheromone produced by the Jacobina chemotype of the L. longipalpis complex. The mass spectrum of the proposed tertiary alcohol also has similarities to the 3-methyl-α-himachalene sex pheromone.

In the fragmented landscape of arable farmland, hedgerows and other non-crop habitats provide refuges of food and shelter for invertebrates, and corridors through which they can move to other habitats. Their role as corridors is likely to depend on their connectivity, both to each other and to other patches of suitable habitat. The effects of connectivity on the carabid beetle Nebria brevicollis (Fabricius) were analysed by observing movement between hedgerow intersections (nodes) and the linear section of the hedgerow, and across gaps in the hedgerow. Capture–mark–recapture of N. brevicollis revealed a uniformly higher activity at hedgerow nodes than at mid-section strips of comparable area. This is consistent with previous studies of hedgerow fauna including butterflies, plants and birds. Gaps in the hedgerows typically measured 7–9 m and functioned as a passage between fields for farm machinery. These were readily crossed by N. brevicollis as was the hedge bottom. Some movement along the hedgerow was found indicating their use as a corridor.

The effect of density of the Shin-Etsu twist-tie rope pheromone formulation (PBW rope L®) on mating of female pink bollworm, Pectinophora gossypiella(Saunders) was tested in Israel. The success of mating disruption was evaluated during 1997 by the mating table technique, comparing the percentage of mating of virgin sentinel females in pheromone-treated and control plots. Under low pest population pressure application of ‘long-life’ formulation of P. gossypiellapheromone, PBW rope L®, spaced 9 m, 11 m and 14 m apart, resulted in very high suppression of mating (96.5–100%) and complete shut-down of pheromone trap catch. These application rates were much lower than those now prevailing in Israel and elsewhere. Spacing of ropes 20 m apart resulted in less effective mating disruption of 65% only, and shut-down of pheromone traps was also incomplete. The tests during 1998 were carried out at high pest population and efficacy of treatments was assessed by the reduction of male capture in traps in pheromone-treated plots relative to catches in the control. The distance between pheromone sources proved to be the most critical factor determining success. In both years, any spacing significantly greater than 10 m gave markedly less than complete trap catch shutdown/mating suppression. Pheromone dosages and population density were also important in determining mating success. Results obtained in this study indicate the possibility of reducing the number of pheromone sources per unit area and the total amount of pheromone as compared with that in use today, only at very low pest populations. However at high population levels, dispensers closely-spaced, with increased dosages of pheromone, are required.

The effect of host availability at 6 h, 12 h and 24 h intervals on temporal variation in median host-biting frequency, oviposition and survival of the mosquito, Aedes aegypti (Linnaeus), was investigated under laboratory conditions. In each feeding interval, ten replicates containing five mosquitoes were assessed over 12 days. Median host-biting frequencies were 0.7 bites per female mosquito in the 24 h feeding interval, 0.54 bites per female in the 12 h feeding interval, and 0.47 bites per female in the 6 h feeding interval. Although the 24 h figure was comparable to previously documented levels, feeding increased by 1.5 and 2.7 fold in the 12 and 6 h feeding intervals over a 24 h period. Host biting and oviposition were observed to peak at dusk in the 6, 12 and 24 h feeding intervals, but substantial activity was also observed at dawn, noon and midnight. Daily feeding analysis showed that host biting decreased by approximately 50% in all feeding interval trials over the 12 day test period. Oviposition peaks coincided with biting decline, suggesting a three day gonotrophic cycle. Survival did not differ significantly between feeding intervals. The reported rate of 0.47 host bites per female mosquito per 6 h (≈ 1.9 per 24 h) is thus far the highest recorded for A. aegypti. The suggestion that A. aegyptiprobably feeds more regularly than once in a 24 h period in nature is consistent with the biting and oviposition results.

The influence of protein in the adult diet on first cycle gonotrophic development was examined in newly colonized screwworm flies, Cochliomyia hominivorax (Coquerel), reared on an artificial larval diet and bred in subsequent generations from females stimulated to oviposit only after all individuals in a colony were expected to have matured their eggs. This latter criterion was established with the goal of reducing selection for early ovarian maturity and increased autogeny. Under these conditions, supplementing the diet with raw meat during the first week after adult emergence hastened egg maturation by two to four days or more, increased the percentage of seven- to ten-day-old females that was gravid by 45%, and boosted the number of eggs per gravid female by c. 30%. The serous discharge from screwworm-infested sheep wounds, a casein–salt mixture, or casein in potassium hydroxide was as effective as raw meat. Addition of B vitamins to the casein–salt mixture was without further effect. The measures taken to reduce selection for altered gonotrophic development were not critically evaluated here, but they appeared successful in that age and protein affected ovarian maturation rates similarly in F2 and F27. Fecundity measured as eggs matured per gravid female differed between generations, but appeared correlated with size differences that were unrelated to colonization duration.

The biocontrol potential of a microsporidian pathogen, Vairimorpha sp., obtained from field collected diamondback moth, Plutella xylostella Linnaeus, was assessed in a laboratory colony of this insect. The pathogenicity was quantified using a standard bioassay procedure by infecting second instar larvae per os with variable dose levels of the pathogen. Vairimorpha sp. caused 100% mortality even at a dosage of 1.5 x 103 spores per larva. The median lethal dose (LD50) was 2.2 x 104 spores per larva on day 5 post-inoculation. The time taken to achieve 90–100% mortality was dose dependent and varied from 5 days with 1.5 x 106 spores per larva to 11 days with 1.5 x 103 spores per larva. The pathogen reduced the food consumption of P. xylostella larvae by 75%, 93% and 95% at doses 1.5 x 104, 1.5 x 105 and 1.5 x 106 spores per larva, respectively. Histological observations showed that the pathogen preferentially infected adipose tissue cells but spread to almost all tissues. The pathogen was transmitted transovarially as well as horizontally and had a marked influence on progeny performance. It was concluded that Vairimorpha sp. has sufficient potential to be tested in the field as a biocontrol agent for P. xylostella.

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.

Field sampling of grasses growing in and near rice fields at 12 sites in Nigeria during April/May 1994 recorded the presence of galls on Paspalum scrobiculatumat densities of up to 10.9 galls per m2. These galls were induced by Orseolia bonzii Harris, sp. n., which is described. This species is morphologically close to, but distinct from, the African rice gall midge, Orseolia oryzivora Harris & Gagné, with which it has been confused in earlier studies of that pest species. In host-transfer experiments O. bonzii did not transfer to rice, Oryza sativa. Six hymenopterous parasitoids were reared from galls of O. bonzii and the most abundant of these were Platygaster diplosisae Risbec, Aprostocetus nr. procerae (Risbec) and Neanastatusnr. cinctiventris Girault. Host-transfer experiments with the Platygasterand Aprostocetus species from O. bonzii on Paspalum indicated that the Platygaster may not transfer onto O. oryzivora on rice whereas the Aprostocetus does. The overlap between the parasitoid faunas of the two species of Orseolia is potentially useful as it may be possible to enhance the natural biological control of O. oryzivora by manipulating parasitoid populations on Paspalum.

The effectiveness of varying weekly release rates of the parasitoid Eretmocerus eremicus Rose & Zolnerowich for control of Bemisia argentifolii Bellows & Perring on poinsettias was determined. Two variable release rate strategies for E. eremicus were evaluated: a low–high and a high–low release regimen. In the low–high treatment, one female parasitoid was released per plant per week for seven weeks, then the release rate was increased to five female parasitoids per plant per week for the remaining seven weeks of the trial. In the high–low treatment, five female parasitoids per plant per week were released for the first seven weeks, then the release rate was reduced to one female parasitoid per plant per week for the final seven weeks of the trial. Both release rates averaged three female parasitoids per plant per week. Life-tables were made for B. argentifoliiin the presence and absence of parasitoids. In the absence of E. eremicus, egg to adult survivorship for B. argentifolii was 65%. In low–high release greenhouses, average egg to adult survivorship for B. argentifoliiwas 6% and parasitism was 28%. In high–low greenhouses, average egg to adult survivorship for B. argentifolii was 5% and parasitism was 16%. Average net reproductive rates for B. argentifolii in the absence of parasitoids was 17 indicating a rapidly increasing population. Net reproductive rates were 1.46 and 1.24 for low–high and high–low release greenhouses, respectively, indicating substantially reduced B. argentifolii population growth. At week 14 of the trial, densities of live nymphs and pupae were lower in high–low greenhouses when compared to low–high greenhouses. Better whitefly control is achieved with inundative releases of E. eremicus when this natural enemy acts as a predator as opposed to a parasitoid.

The dispersal of Microctonus hyperodae Loan, an introduced parasitoid of the South American grassland pest Listronotus bonariensis Kuschel, was measured in Canterbury, New Zealand. Considering all directions, the mean annual dispersive increment was 1.9 ± 0.9 km year–1 as measured in the winters of 1993, 1994 and 1995. The parasitoid’s ground distribution suggested that its movement was biased towards the south-west indicating probable wind-borne dispersal. The overall relatively low rate of dispersal was thought to be related to the inhibitory effects of M. hyperodae parasitism on L. bonariensisflight. A generalized linear model fitted to percentage of L. bonariensisparasitized took a simple form, with a quadratic increase in weevil infection, that with time, gradually decreased. The build-up of parasitism at the release site was significantly greater than the rates at the other sites measured in this study (P< 0.001) with a ratio of release site: dispersal site rates of 1.33: 1. The simplicity of the fitted generalized linear model indicated remarkable uniformity in both parasitism build-up and dispersal from one year to the next; this finding indicated that all dispersal was ‘natural’ and unassisted by human activity. Despite such modest dispersal rates, by the winter of 1996, five years after its release, the parasitoid had spread geometrically over an area of c. 140 km2.

Adults, larvae and pupae of the type material of Simulium (Edwardsellum) kilibanumGouteux from Zaïre, the important onchocerciasis vector Simulium (E.) damnosumcytoform ‘Nyamagasani’ from western Uganda and Malawi, and the closely related forms ‘Nkusi’ and ‘Sebwe’ from western Uganda were compared using morphological and molecular methods. Results support the assumption of synonymy of S. kilibanum and the cytoform ‘Nyamagasani’, which hitherto was based on weak evidence. The description of S. kilibanumis supplemented and detailed descriptive data are given of ‘Nyamagasani’and the cytoforms ‘Nkusi’ and ‘Sebwe’ all of which are taxa of the ‘Sanje’ group of the S. damnosum complex.

Three new prototype traps, (S1–S3), were developed during studies of the behavioural ecology of Glossina swynnertoni Austen in Kenya and Tanzania. The traps were compared in latin square experiments relative to the regular biconical trap as a standard and a selection of other conventional tsetse traps. Observations were also made on fly behaviour in the vicinity of traps using electric nets and sticky materials. When baited with acetone and 1-octen-3-ol, the S1 trap was 3.5 times as effective in catching G. swynnertoni in Kenya as the biconical trap. In Tanzania, the relative performance of the S1 and biconical traps differed; also, both traps were found to be inferior to an all-black, sticky 1-m2target. A second prototype (S2) performed slightly better than the biconical trap, but was still inferior to the black target. The final prototype (S3) was 2.9 times as effective as the biconical trap and performed as well as the black target. The potential for further improvement of traps for capturing G. swynnertoni and flies of the G. morsitans Westwood group is discussed.

Cattle were treated with cypermethrin and flumethrin pour-ons to determine possible adverse effects of residues in dung on the survival, fecundity and fertility of Euoniticellus intermedius (Reiche). Dung from both cypermethrin- and flumethrin-treated cattle was collected 1, 2, 3, 5, 7, 14, 21 and 28 days after treatment, with an untreated control for each. Mortality of adult E. intermedius exposed to dung collected from cypermethrin-treated cattle two to seven days after treatment ranged between 80% and 100%. Cypermethrin had no effect on adult and immature survival or on fecundity and fertility of E. intermediusexposed to dung collected 1, 14, 21 and 28 days after treatment. Dung collected from flumethrin-treated cattle had no apparent effect on adult survival, egg production, immature survival, adult emergence, fecundity and fertility of E. intermedius, except at seven days after treatment, when fewer brood balls were produced and consequently fewer adults emerged from dung from treated animals compared with the control.

The development period from birth to adult of alate and apterous virginoparae of the green peach aphid, Myzus persicae (Sulzer), reared on Brassica campestrisssp. chinensis, was measured at 13 constant and five natural temperature regimes. The day–degree model, the logistic equation, and the Wang model were used to describe the relationships between temperature and development rate at constant conditions. The constant temperature–development curves derived from the three models were used with a Weibull function describing the distribution of development times, to simulate the development of individuals of cohorts reared at natural temperature regimes. Comparison of the observed with simulated distributions of adult emergence indicates that all three models can simulate the development of M. persicaevery well when the temperature does not go below 4°C, the notional low temperature threshold of the day–degree model. When accumulation of temperatures below 4°C becomes substantial, only the logistic curve with a low temperature threshold of 0°C can offer accurate simulations; the other two models give falsely longer durations of development. Methods for accurately simulating the development of M. persicae in the field are suggested. The significance of modelling insect development at low temperatures by nonlinear models is discussed.

Experimental comparisons were made between samples of moths obtained by Rothamsted tungsten-filament and Robinson mercury-vapour light-traps operating in a lowland dipterocarp forest in Peninsular Malaysia. The Rothamsted trap gave more uniform and consistent samples and performed better in the tropical conditions than the Robinson trap. There were no significant differences between the overall measurement of diversity for the group Geometroidea between the two trap designs although the Robinson trap was much more erratic from night to night. The total catch of non-Geometroidea moths was remarkably similar in the two trap types. The choice of appropriate light-trap designs for biodiversity studies in tropical rainforest is discussed.