A method for identifying the members of the endemic genus Wiseana Viette from New Zealand is described. Seven species have been described in the genus: W. cervinata (Walker), W. copularis (Meyrick), W. fuliginea (Butler), W. jocosa (Meyrick), W. mimica (Philpott), W. signata (Walker) and W. umbraculata (Guenée). No morphological characters have been identified to distinguish between the larvae of each species and adult females exhibit high levels of intra and interspecific morphological variation making identification difficult or impossible. Adult males can be distinguished by a combination of scale, antennal and genital characters, but this requires considerable taxonomic experience. Molecular markers were generated via amplification of the cytochrome oxidase subunit I and II (COI and II) of the mitochondrial DNA by the polymerase chain reaction (PCR). Amplified DNA was digested with restriction enzymes to give characteristic fragment patterns. Fourteen restriction enzymes were surveyed and a combination of four of these distinguish all Wiseana taxa except W. fuliginea and W. mimica.

Pretreatment of first instar larvae of 28 resistant strains of Lucilia cuprina(Wiedemann) with the inhibitor of microsomal oxidases, piperonyl butoxide, resulted in a biphasic response to the phosphorothioate insecticide diazinon. Analysis of the data revealed a complex response in which both synergist-dependent and independent effects occurred. The responses varied markedly from strain to strain. A laboratory susceptible strain and field strains with resistance factors of less than 20-fold exhibited, in the presence of piperonyl butoxide, an increased LC50 with respect to diazinon whereas those strains with > 20-fold resistance were synergized by the compound. We conclude tentatively that microsomal mixed-function oxidases play a contributory role in the development of resistance and that the variation in synergist effect from strain to strain may be attributed, at least in part, to the two-fold effect of these enzymes on phosphorothioate insecticides such as diazinon.

The factors that set broad-scale limits on the species ranges of ticks have not been clearly defined, despite their potential importance for the study and control of ticks. A database of 33,989 published collection records for African ticks is used to test the hypothesis that the outer limits to tick species ranges are determined by the distributions of their hosts. Distribution maps for many of the more economically important tick species are given. Direct comparisons of the known ranges of ticks and their hosts show that the hypothesis of a host-determined species range is supported for only one tick species, Amblyomma rhinocerotis (de Geer), which has been constrained by the near-eradication of its rhinoceros hosts. At least 97 other species are not host-limited; the quality of available host-use and distribution information is insufficient to draw strong conclusions about the (approximately) 132 remaining species. In general, the boundaries to tick species ranges are more likely to be set by factors such as vegetation and climate.

The times for knockdown of resistant and susceptible strains of both Anopheles stephensi Liston (DUB234 and BEECH) and A. gambiae Giles (RSP and KWA), on exposure to a permethrin impregnated net were determined to evaluate the effect of age on susceptibility to permethrin. The mean knockdown times of pyrethroid resistant strains of A. stephensi and A. gambiae were significantly shorter if they were 10 days old (either fed or unfed), as compared with those of newly emerged mosquitoes. Based on KT50 values, the resistance ratios between resistant and susceptible A. stephensi were 3.5 and 2.2 for the newly emerged and 10-day-old mosquitoes, respectively. After 1 h exposure to paper impregnated with 0.25%permethrin, mortality of newly emerged individuals of the susceptible and resistant strains of A. stephensi was significantly less than when they were 10 days old. Irritability by permethrin was less with the resistant strain of A. stephensi. In the other strains irritability declined significantly with age. Pre-exposure of susceptible mosquitoes of BEECH and IRAQ strains of A. stephensi for a short time to permethrin did not increase tolerance when the mosquitoes were re-exposed 24 h later. Because of the age effect and the possibility of an effect of pre-exposure under some circumstances, confirmatory tests on newly emerged F1 individuals reared from wild collected mosquitoes are recommended in monitoring for resistance in wild populations.

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 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.

A prerequisite to studying the specific interactions involved in the persistent transmission of luteoviruses such as the potato leafroll virus (PLRV) is the characterization of both the virus and its vectors. A range of techniques was used to assess genetic differentiation among 27 clones belonging to the Myzus persicae complex (M. persicae (Sulzer), M. antirrhinii (Macchiati) and M. nicotianaeBlackman) and showing different efficiencies in transmitting PLRV isolates. All M. persicae/M. nicotianae clones belonged to one of two karyotypes, both 2n = 12, either normal or carrying an autosomal translocation (A1,3), and all M. antirrhinii clones had 13 or 14 chromosomes. Amplified esterase 4 genes were detected by PCR–REN assay in M. persicae/M. nicotianae taxa, with gene expression being modified by methylation. Similarly, amplified E4 genes were revealed in M. antirrhinii but they all showed unmethylated. Two allozyme and 11 microsatellite loci discriminated 10 different genotypic classes among the 27 clones. Analysis of genetic relatedness between these genotypic classes revealed that M. nicotianae clones were very closely related to M. persicaeclones, whereas the genetic differentiation between M. antirrhinii and M. persicae was greater. The implications of these results for the taxonomic status of these genotypes within the complex, and the transmission of PLRV, are discussed.

Studies were made of the behaviour of Glossina pallidipes Austen and G. morsitans morsitans Westwood during the hot season (September–November) in Zimbabwe, and attributes of samples of tsetse from refuges, odour-baited traps, targets and mobile baits were compared. Various arrangements of electric nets were used to study tsetse as they entered or left artificial refuges. The peak time of entry into a refuge varied between 0800 h and 1400 h and coincided with the time when the air temperature reached 32°C; the response was stronger if 32°C occurred earlier in the day. The peak time of exit varied between 1500 h and 1700 h, being significantly later on hotter days, but did not show a clear temperature threshold. Micro-meteorological measurements showed that refuges were significantly cooler than the surrounding riverine woodland during the day but warmer at night. There was no significant difference between the air temperatures in leafless mopane woodland and semi-evergreen riverine woodland during the day but at night the riverine woodland was significantly cooler. Combining the micro-meteorological data with the estimated local movements of tsetse suggested that during the hot season, tsetse experienced temperatures 2°C cooler than the daily mean in a Stevenson screen located in mopane woodland. Compared with the catches of tsetse from traps, refuges had higher proportions of G. m. morsitans, males, young flies and females in the later stages of reproduction, and it is suggested that during the hot season, samples from refuges were less biased than traps with respect to species and sex composition, age and reproductive status. During the hot season, tsetse populations declined by c. 90% and although air temperatures exceeded lethal levels (c. 40°C), the refuge-entering responses meant that adult flies probably experienced a maximum of only c. 35°C. It is suggested that the decline in numbers is not due to direct mortality effects of temperature on adults but may be due, in part, to a doubling in the rates of reproductive abnormality during the hot season and an increase in adult mortality related to a temperature-dependent decrease in pupal period.

A total of 4420 male Glossina morsitans morsitans Westwood were captured on man fly-rounds in Katete District, Eastern Province, Zambia between February 1991 and December 1993. Of these flies, 1680 were captured before June 1992, during which period 989 flies were also captured on odour-baited electric screens operated in the same area. Non-teneral flies were analysed for fat, haematin and residual dry weight and their wing-vein length was measured. There were well marked annual cycles in wing length, fat and residual dry weight. Flies were biggest at the end of the rainy season, and smallest at the end of the hot dry season. Fat levels were lowest before the onset of the rains and highest in the cool season. Residual dry weight was a function of haematin content and the degree of wing-fray; these factors were used to correct the residual dry weight to zero haematin. Corrected residual dry weight and wing-vein lengths were most highly correlated with relative humidity in the month prior to capture (r > 0.8 and 0.6 respectively). Correlations with saturation deficit were weaker; temperature accounted for <20% of the variance. Fly-round flies had a consistently higher residual dry weight than those from the electric screen, but their fat levels were lower. The distributions of log haematin levels differed little between the two sampling methods and were adequately described by a model where capture and feeding rates increased exponentially after each meal. The increase in the feeding rate after each meal differed little with season and was closely similar to that estimated for female G. pallidipesAusten in Zimbabwe.