In south-west Saudi Arabia two forms of leishmaniasis occur. Visceral disease (VL) due to Leishmania infantum affects humans (mainly infants) in lowland areas and cutaneous disease (CL) due to L. tropica affects a broader age group in highland areas. Leishmania infantum is common in dogs and may occasionally infect man. Longitudinal sampling of sandflies in two foci with matched sticky and light traps inside and outside houses demonstrated that, although the species composition was very similar, the dominant species in the highlands (Phlebotomus sergenti Parrot) was different from that in the lowlands (P. bergeroti Parrot). In both habitats there was a marked seasonal variation in abundance, peak levels in the lowlands preceding the highlands, as did sandfly numbers inside houses compared to outside houses.

Phlebotomus sergenti were found infected with L. tropica in June and July which, together with its endophilic behaviour, incriminated this species as the vector of cutaneous disease. The vector of visceral disease in humans is suspected to be either P. alexandri Sinton or P. orientalis Parrot, but not P. arabicus Theodor as previously suggested.

The potential role of oviposition deterrents in the egglaying behaviour of Neodiprion sertifer (Geoffroy) females was studied by investigation of natural egg distribution, and by a laboratory study of potential oviposition deterrents. Pine shoots were sampled from different whorls on the sun-exposed and the shaded side of trees. More shoots with eggs from two or more females were found than would be expected if each female laid eggs on a randomly chosen shoot. The anti-predatory larval oral secretion of N. sertifer had no effect on N. sertifer egglaying but acted as an oviposition deterrent to Diprion pini in laboratory experiments. The different responses may be due to differences in the species' life-cycles. In other experiments, the effect of the presence of N. sertifer eggs, extracts obtained from eggs or from needles with eggs, were all tested on N. sertifer egg laying. None of the treatments had any inhibitory effect on egglaying. Thus, neither the natural pattern of egg distribution nor the results of the laboratory experiments indicated that an oviposition deterring pheromone is used by N. sertifer. Results from earlier studies, showing a deterrent effect of larval oral secretion in D. pini, were confirmed.

Investigations were carried out in southern Benin on the annual flight cycle and the effects of weather variables on the flight activity of Prostephanus truncatus (Horn) and its natural enemy, Teretriosoma nigrescens Lewis. Two seasonal peaks in flight activity of P. truncatus were observed, one between the end of December and the beginning of January and a second one between May and June. Teretriosoma nigrescens showed a single delayed peak in June, approximately six weeks after the major peak of P. truncatus. Flight activity of P. truncatus was only weakly associated with weather characteristics (standardized regression coefficient for mean daily temperature b = 0.18, t = 2.87, P < 0.05)), whereas for T. nigrescens it was associated with precipitation (standardized regression coefficient for accumulated rainfall during the trapping period b = 0.38, t = 4.76, P < 0.05). The possibility that one of the P. truncatus peaks was associated with dispersal from crowded maize stores and the other with the search for natural woody host plants is discussed.

The flight activity of each of the three major leafhopper vectors of rice tungro viruses, Nephotettix virescens (Distant), N. nigropictus (Stål) and Recilia dorsalis (Motschulsky) was closely associated with rice cropping periods and was influenced by crop growth stage and season. Leafhopper flight was influenced by changing levels of illumination at dusk and dawn and, for R. dorsalis only, was significantly affected by moon phase. Recilia dorsalis was the dominant species caught in suction traps at 0.75 m and 1.5 m and an upwardly-directed light trap at 4.0 m, whereas N. virescens was the most abundant species caught on sticky yellow traps at the height of the canopy. Infectivity tests on migrant leafhoppers caught in upwardly-directed light traps showed that N. virescens was the most common transmitter of rice tungro viruses. Infective leafhoppers were recorded at the end of dry seasons and during wet seasons in 1991 and 1992. The risk of tungro disease incidence was very low early in the 1991 dry season, when aerial abundance of leafhoppers was small and no infective individuals were recorded.

The range of the moth Zeiraphera diniana Guénée and the regions where high population densities are infrequent and unpredictable are thought to be determined by high temperatures during egg pre-diapause. Exposure of eggs to incubation temperatures known to be optimal for Z. diniana elsewhere resulted in a pre-diapause mortality of 13% which corresponds to known rates of egg mortality in British forests. Evidence suggests that high temperature and its duration are both important determinants of pre-diapause egg mortality which, if experienced in forest conditions, may prevent populations from reaching outbreak levels. Historical records of outbreaks were associated with lower than average August temperature. However, high temperatures on their own are unlikely to determine the range of the insect in Britain since a high proportion of eggs survives extremes; more than 70% of British eggs survived 24 h exposure to a temperature of 30°C. Variations in egg mortality among families of moths suggests a genetic basis for differences in thermal tolerance. Furthermore, there may be selection for thermally-tolerant eggs in British forest environments and this could be connected with other forms of genetic differentiation in budmoth populations.

Variation in the sheep blowfly, Lucilia cuprina (Weidemann), mitochondrial DNA (mtDNA) was assessed using restriction endonucleases. Ten individuals from 13 localities throughout New Zealand and Australia were examined using 18 restriction endonucleases. Only two localities exhibited polymorphism, suggesting historical events have contributed to this low level of mitochondrial variability in L. cuprina from these regions. A 472 base pair region of the mitochondrial cytochrome oxidase I gene (COI) was sequenced from six Australasian regions and samples from South Africa and Malaysia. Phylogenetic analyses using both parsimony and neighbor-joining methods indicates possible multiple introductions of L. cuprina in New Zealand.

Trypanosome infections in approximately 110,000 tsetse of 12 species or subspecies, at sites in six African countries, were studied over various periods from 1983 to 1994. Infection rates ranged from 0.2% in Glossina fuscipes quanzensis Pires at a site in Zaire, to 18% in Glossina tabaniformis Westwood at a site in Gabon. Statistical models were fitted to data for nine species or sub-species of tsetse (G. pallidipes Austen, G. morsitans morsitans Westwood, G. morsitans submorsitans Newstead, G. fuscipes fuscipes Newstead, G. fuscipes quanzensis Pires, G. palpalis palpalis Robineau-Desvoidy, G. palpalis gambiensis Vanderplank, G. tachinoides Westwood and G. tabaniformis Westwood), recorded across eight sites. The prevalence of mature trypanosome infections increased with age, as determined by wing-fray category, for both Trypanosoma vivax- and T. congolense-type infections, although for G. palpalis, G. tabaniformis and G. tachinoides the rate of T. vivax-type infections decreased in older age categories. Infection rates for T. brucei were very low and statistical analysis was not possible for this species. Overall prevalences of Trypanosoma vivax-type infections were significantly higher in female than male flies in four tsetse species; G. pallidipes, G. palpalis, G. tabaniformis and G. tachinoides. At sites where ovarian ages were also determined, close correlations between wing-fray category and ovarian age were found.

Nucleotide sequence variation and morphological characters were used to study the evolutionary relationships among nine tetranychid mites species. A phylogenetic study of this family based on mitochondrial cytochrome oxidase subunit I (COI) sequences had previously placed the species Tetranychus viennensis Zacher outside the other species analysed in the genus. Phylogenetic relations within the genus were re-examined with the addition of the species Tetranychus quercivorus Ehara & Gotoh, which is morphologically close to T. viennensis. Another region of the genome, the second internal transcribed spacer (ITS2) of ribosomal DNA, was also studied and proved to be of considerable interest at this taxonomic level. Both COI and ITS2 sequences indicated a close relationship between T. viennensis and T. quercivorus, which are grouped together and distinct from the other Tetranychus examined. The two species display morphological characteristics such as the absence of a medio-dorsal spur on all empodia of the legs of both sexes and the presence of anastomosing peritremes. This distinguishes them from the other members of the genus Tetranychus. The convergence of molecular and morphological data suggests that T. viennensis and T. quercivorus should not be classified in the genus Tetranychus. It is proposed that the genus Amphitetranychus Oudemans should be restored for classification of these species. Finally, a key to the Tetranychini tribe genera with one pair of para-anal setae is presented.

A population genetic study of Halotydeus destructor (Tucker) and H. anthropus Qin & Halliday was undertaken using allozyme electrophoresis. Allele frequency data were collected from five polymorphic loci (Gpi—glucose phosphate isomerase, G6pd—glucose-6-phosphate dehydrogenase, Idh — isocitrate dehydrogenase, Mdh — malate dehydrogenase, and Pgm–phosphoglucomutase) to determine genetic variability and levels of gene flow among Australian and South African populations. The two species could be distinguished by the most common allele at Gpi and usually Pgm. There was no evidence for subdivision among the Australian populations of H. destructor, but the levels of substructuring among the South African populations of H. destructor and those of H. anthropus were high. The geographic origin of H. destructor is discussed; the evidence suggests that the original source of the Australian populations of H. destructor was from Cape Town, South Africa.

Methods for dispensing tsetse attractants using sealed polyethylene sachets and bottles were studied in the laboratory and field. 1-Octen-3-ol (octenol), 4-methylphenol and 3-n-propylphenol were dispensed singly or as blends from sachets 25–200 cm2 in surface area and with a wall thickness of 0.06–0.32 mm; butanone was dispensed from polyethylene bottles. The release rates of attractants, assessed gravimetrically or by GC analysis of volatiles released, were independent of the amount present. The rates were related directly to surface area, inversely related to wall thickness and increased exponentially with temperature. With blends of the attractants, the release rates of the two phenols were directly proportional to the concentration present, but that of octenol showed an exponential dependence. A similar exponential effect was seen with blends of the attractants and an involatile diluent. For mixtures of chemicals, the ratio of the released components was not affected significantly by temperature, sachet size or wall thickness. Release rates from polyethylene sachets and bottles in the field varied 100-fold according to temperature differences related to the time of day, season, and degree of insolation. Day-degree models to predict the losses of attractants from a polyethylene sachet in shade or in full sunlight were highly correlated (r2 = 0.84 and 0.81 respectively) with observed losses. The practical implications of these findings are discussed.

Primers for DNA amplification using the polymerase chain reaction (PCR) were synthesized for a microsatellite locus isolated from a partial genomic library of the aphid parasitoid Aphelinus abdominalis (Dalman). Screening for genetic polymorphism at this locus in two laboratory strains of this wasp revealed the presence of two alleles different in the number of (GT) and (GGC) repeats. The relative frequencies of the two alleles were not significantly different between the two strains or between diploid females and haploid males. Heterozygosity at this microsatellite locus was estimated to be 0.40 which is within the range in other hymenopterous species. Given that A. abdominalis is a good candidate for augmentative release programmes in greenhouses against aphids, we suggest that microsatellite markers may have application in discriminating among aphelinid sibling species and strains. The markers provide a means for studying the performance and impact of selected parasitoid lines on pest dynamics in field release experiments.

Studies on the lepidopterous stem borer, Busseola fusca (Fuller) and its major larval parasitoid, Dolichogenidea fuscivora Walker were carried out in the field and the laboratory in eastern Ethiopia. Larvae of B. fusca are also parasitized in the field by the braconid, Bracon sesamiae Cameron and the sarcophagid, Sarcophaga sp., but in low numbers. Parasitism of B. fusca by D. fuscivora is as high as 71% during the dry season (November-March) and approximately 18% in the wet season (June-September). Dolichogenidea fuscivora is active throughout the year. In the laboratory it requires nearly 26 days at 24 ± 1°C to complete the development of one generation (egg to egg laying). Longevity of adults is affected by the availability of food and water. Mating and oviposition reduced the life spans of males and females, respectively. Sixty five to 75 larvae emerged from eggs laid by a single female. The sex ratio ranged from 1:1 to 7:1 (female:male), the average being 5:1.