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 diversity of macromoths in the various fast-growing exotic tree plantations and natural secondary forest in Brumas, Sabah, Malaysia was assessed by means of an annual cycle of light-trap samples. The moth diversity in the forest plantations, viz. Acacia mangium, Gmelina arborea, Paraserianthes (=Albizia) falcataria, Pinus caribaea, and in particular Eucalyptus deglupta, was unexpectedly high. Eucalyptus deglupta showed moth diversity as high as that in the natural secondary forest, a finding attributed to the fact that the E. deglupta plantation had a very diverse understorey both in terms of plant species (secondary regrowth species) and architecture, and thus supported a more diverse moth fauna. Subsidiary samples showed that primary natural forest in the neighbouring Danum Valley does not show higher moth diversity compared to the disturbed forest habitats in Brumas, though moth diversity at Danum is lower than that recorded in other Bornean primary forests. The value of plantation forests for conservation of invertebrate diversity is discussed, together with the implications for plantation management strategy.

Four species of the psylloid genus Trioza damage Persea americana in Central and South America; two of these species, T. aguacate and T. godoyae are described as new; an identification key is provided for the six Trioza species known to develop on Persea species in the New World. A review is given of the psylloid species associated with the plant family Lauraceae.

Four possible biochemical mechanisms of organophosphate resistance were examined in populations of Rhyzopertha dominica (Fabricius) collected from eight locations in the states of Minas Gerais and São Paulo in Brazil and from seven locations in northeast Kansas, United States. Results from insecticide bioassays with synergists (triphenyl phosphate, diethylmaleate, and piperonyl butoxide) suggested that metabolic detoxification mechanisms might be involved in organophosphate resistance in some of the populations of R. dominica. However, overall low synergism, non-synergism or even antagonism presented by these synergists in all 15 resistant populations suggested that carboxylesterases, cytochrome P450 monooxygenases and glutathione S-transferases were not likely to play a major role conferring organophosphate resistance in R. dominica. This hypothesis was strongly supported by our biochemical studies showing no significant difference in these enzyme activities, as well as cytochrome b5, P420, and P450 levels between the susceptible and resistant populations. In contrast, all resistant populations of R. dominica showed higher acetylcholinesterase activity than the susceptible population both in the presence and absence of malaoxon. Furthermore, acetylcholinesterase from the resistant populations was less sensitive to inhibition by malaoxon than that from the susceptible. These results suggested that quantitative and qualitative changes in acetylcholinesterase might contribute to organophosphate resistance in these populations of R. dominica.

Carbon dioxide, carbon monoxide, chloroform, hydrogen, methane and nitrous oxide emissions were collected from within several mound colonies of the subterranean termite Coptotermes lacteus (Fgottatt) and the surrounding habitat of a dry sclerophyll forest in central Gippsland, Australia, following treatment of the termite mounds with mirex-treated bait blocks. All the mirex-treated colonies died within two weeks of commencing active feeding on the bait blocks. The flux measurements of the gaseous emissions were calculated before, during and after treatment with the mirex-treated decayed wood bait blocks. Carbon dioxide, methane and hydrogen all declined after colony death.

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 efficacy of abamectin (AgrimecR) and teflubenzuron (NomoltR) was assessed by leaf-dip bioassay against larvae of the diamondback moth, Plutella xylostella Linnaeus from a population (SERD3) collected originally in lowland Malaysia in December 1994. Evidence for resistance to both abamectin and teflubenzuron was found in the F7 generation (LC50 ratio of 60 and 24 respectively compared with a laboratory, insecticide-susceptible strain). Selection of sub-populations of SERD3 (F7–F9) with abamectin and teflubenzuron increased the LC50 ratio to 220 and 360 respectively and estimates of realized heritability [h2] were high (c. 0.8 and 0.9) for both compounds. There was no cross-resistance between these compounds in the abamectin and teflubenzuron-selected sub-populations but some indication of negatively-correlated resistance. Topical application of the synergists piperonyl butoxide, S,S,S-tributylphosphorotrithioate and maleic acid diethyl ester to the laboratory strain had no significant effect on the toxicity of abamectin or teflubenzuron in subsequent leaf-dip assays. In contrast, pre-treatment with piperonyl butoxide and S,S,S-tributylphosphorotrithioate significantly increased the toxicity of abamectin (c. 4- and 3-fold) and teflubenzuron (c. 7- and 19-fold) in the abamectin and teflubenzuron-selected sub-populations of SERD3, suggesting that microsomal monoxygenases and/or esterases may be involved in resistance. Pre-treatment with maleic acid diethyl ester only increased the toxicity of abamectin by c. 2-fold and had no significant effect on the toxicity of teflubenzuron, providing limited evidence for the involvement of glutathione-S-transferases in resistance to the former compound alone.

The dung fly Neomyia cornicina (Fabricius) fed on either control dung or dung containing 0.15 μg g−1 ivermectin were mated in the following combinations: (a) control male × control female, (b) control male × ivermectin-fed female, (c) ivermectin-fed male × invermectin-fed female and (d) ivermectin-fed male × control female. Frequency and duration of mating attempts by males during 10 min mating trials were significantly higher when males were placed with control females, irrespective of male treatment. There was no significant difference between groups in the frequency and duration of all other behaviours observed. There was a significant effect of mating combination on the percentage of females that laid eggs, with most laying in groups where females were controls (groups a and d). There was also significant effect of mating combination on the time to first oviposition, with control females mated with control males (group a) laying earliest. Egg batch size was unaffected by treatment group. At the end of the experiment, all females were dissected and the number, size and yolk content of the terminal oocytes were measured. There was no effect of treatment group on any of these parameters. Results of this study indicate that female exposure to ivermectin was of greater importance than male exposure in altering male mating behaviour and reducing fecundity. Ivermectin in cattle dung could therefore lower reproductive output of this species even when only one of a pair was exposed to the drug.

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.

Rice green leafhopper Nephotettix virescens (Distant) populations were collected in 1985 from fields planted with a leafhopper resistant rice, Oryza sativa cultivar IR64 in South Cotabato, Philippines. The populations were reared on IR64 for eight generations and tested on six cultivars, including susceptible TN1, moderately resistant IR26 and IR36, and resistant IR54, IR62, and IR64. Leafhoppers excreted larger amounts of basic honeydew, efficiently transmitted two tungro associated viruses, and showed greater population increase and lower nymphal mortality on all cultivars except IR62 than a greenhouse population reared on TN1. Nephotettix virescens were transferred and maintained on TN1, IR26, IR36, IR64, or a mixture of the four cultivars plus IR54 and IR56 in equal proportion. When the TN1-maintained colony was tested at the third generation, its feeding behaviour and tungro transmission rates on test cultivars were similar to those of the original population but amounts of basic honeydew excretion and the transmission rate on the resistant test cultivars were greatly reduced at the seventh or later generations. When the IR26-maintained colony was tested at the sixth, ninth, or 13th generation, it exhibited lower amounts of basic honeydew excretion on the resistant test cultivars but exhibited similar transmission efficiencies on other test cultivars. When the colonies maintained on IR36, IR64, or the cultivar mixture were tested similarly, their population characteristics and virus transmission efficiency were similar to the original population. These results indicate that N. virescens retain their ‘virulence’ to resistant cultivars when maintained on resistant cultivars, but quickly lose their ‘virulence’ when maintained on a susceptible cultivar. Colonies continuously reared on IR26, IR36 or IR64 showed ‘cross-virulence’ to many cultivars possessing a variety of genes for N. virescens resistance but often differed in feeding behaviour, virus transmission efficiency, and nymphal mortality on cultivars with the same genes for leafhopper resistance.

The developmental rate of Frankliniella occidentalis (Pergande) was determined on cucumber Cucumis sativus cv. Sandra over a range of constant temperatures. The lower developmental threshold (LDT) and the sum of effective temperatures (SET) for the pre-imaginal development were 10.7°C and 231.1°C, respectively. The rate of population increase was assessed as the sum of effective temperatures above the lower developmental threshold by monitoring the numbers of thrips on individual leaves of cucumber under commercial greenhouse conditions. Population growth was characterized by an early stochastic phase, corresponding to pre-imaginal development of the first generation, and followed by an exponential phase starting with the second generation, the rate of which did not vary between plants. Throughout the exponential phase, the rate of population growth increased with time/age of plant. As significant damage to cucumber may occur during the exponential phase of population increase, the sum of effective temperatures of 231°C can be used to predict when damage is likely to start to occur.

An insecticide impregnated fabric (IIF) trap was developed at the Vector Control Research Centre, India. The mosquito sampling efficiency of this new trap, relative to hand catches of indoor resting mosquitoes, was evaluated in human dwellings and cattle sheds in a filariasis endemic area. The predominant species collected in human dwellings was Culex quinquefasciatus Say, a vector of bancroftian filariasis; whereas mosquitoes of the Culex vishnui group Theobald and Anopheles subpictus Grassi were caught in relatively greater numbers in cattle sheds. The numbers of mosquitoes in the trap were significantly correlated with the numbers caught in hand catches, and the numbers of mosquitoes collected per two traps per day in the three habitats during the study period were 1.79, 0.95 and 2.27x those collected by hand-catches. The number of occasions on which mosquitoes were detected by both methods was comparable. There was no evidence for a systematic difference in the age-structure and parasite distribution between the two sampling methods, suggesting that the trap is able to monitor both insect vectors and parasite infections. Therefore, the calculation of infection and infectivity rates necessary to monitor filariasis transmission should be possible from the IIF trap in filariasis endemic areas where control measures are being taken.

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.

Delphacodes kuscheli Fennah is the vector of maize rough dwarf virus, that affects maize production in central Argentina. The spatial and temporal abundance pattern of the insect vector was studied from October 1992 to November 1994, within endemic and non-endemic areas of the crop disease. Insect density was estimated every 7–15 days during spring and summer (maize season) or monthly during autumn and winter from high (6 m) and low (1.5 m) sticky traps placed at eight sampling stations along a 300 km transect. Each year, D. kuscheli density increased from October, peaked in December, to decrease afterwards and disappear in May. Density was lower in the nonendemic area and higher in the endemic one. The average absolute difference of density between sampling station pairs increased with the distance between the sampling stations (R2=0.85), and the correlation of density changes decreased with the distance between the sampling stations (R2=0.78), suggesting that the population dynamics were affected more by local than by regional factors. There was a significant correlation (with a 36 days lag) between the normalized difference vegetation index (NDVI) (calculated from 15 days maximum value composites images of NOAA-11 meteorological satellites) and D. kuscheli abundance. Based on this regression model, and using the time series of the satellite derived NDVI values, maps of the distribution and abundance of D. kuscheli within the study area for the spring and summer of 1992 were produced.

Limburger cheese, previously shown to attract female Anopheles gambiae Giles, was solvent extracted and chemically fractionated into acid and non-acid fractions. The extracts and aliquots of headspace odour of the cheese were analysed by gas chromatography and electron impact mass spectrometry. Nineteen saturated and unsaturated aliphatic fatty acids, ranging in carbon chain length from C2 to C18, were detected. The most abundant acids (>1 mg/g of cheese) identified in the acid extract were ethanoic, propanoic, butanoic, hexadecanoic and 9-octadecenoic acid. The same compounds were identified in analyses of headspace samples but only trace quantities of the less volatile acids (C10 to C16) were present, whilst C18 acids were absent. Behavioural responses of female A. gambiae towards a range of dilutions of the acid extract (in diethyl ether) were recorded in a windtunnel bioassay. The undiluted extract was found to be repellent, but became highly attractive (P «0.001) at lower doses, and was still significantly attractive (P<0.001) when diluted 106times. A synthetic mixture of 12 of the more abundant aliphatic acids identified in the acid extract was found to be significantly attractive (P<0.001) when diluted 108 times. Electroantennographic (EAG) studies showed significant and reproducible responses to (saturated) Limburger cheese headspace. At doses higher than 0.1%, the synthetic mixture of 12 acids elicited significantly higher EAG amplitudes than the solvent control (paraffin oil). EAG responses were recorded from mosquitoes stimulated with C5 to C8 acids, that were characterized by significant dose-dependencies. Weaker, though significant EAG responses were obtained with the less volatile acids (C9 to C14). Only hexadecanoic acid did not elicit a detectable response. The electrophysiological and behavioural responses obtained with fatty acids isolated from Limburger cheese suggests that together they could act as a kairomone for female A. gambiae. The implications of this are discussed together with the occurrence and bacterial production of these compounds on human skin.

The taxonomic status of Phylacteophaga Froggatt is re-evaluated using the independent techniques of allozyme electrophoresis and detailed morphological comparison. Analysis of 45 scorable loci showed highly significant fixed differences (46–51%) among two currently recognized subspecies, P. eucalypti eucalypti Froggatt P. e. froggatti Riek, and a previously unrecognized taxon from Tasmania, demonstrating that they are different species. In addition to colour, significant variation is revealed among P. e. occidens Benson, P. rubida Riek and the three electrophoretically defined species, in body size, structure of the antennae, the shape of the crest, dorsal spines and saw teeth of the ovipositor, and in male genitalia. Based on these results there is substantial justification in recognizing P. occidens and P. rubida as separate species, distinct from P. eucalypti, P. froggatti, and P. amygdalinisp. n. Further, comparison of the holotype of P. e. tasmanica Riek shows it to be conspecific with the lectotype of P. eucalypti (designated here) so that the former species is considered a junior synonym. The distribution of P. eucalypti and P. froggatti is extended to include Tasmania, and a key is presented to distinguish the males and females of all five species. The biology and host plant relations of the species concerned are discussed, along with their pest status and potential to spread to other regions of the world where eucalypts are grown.

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.

The seasonal variation of adult populations of Haematobia irritans Linnaeus was monitored at Santa Fe, Argentina from August 1992 to August 1994 by weekly counts of flies on grazing heifers. Each year, flies were recorded at a density of more than two flies per heifer from August/September to the following June, with peaks of abundance in mid to late spring and late summer to mid autumn. The seasonal trend of fly numbers was best correlated with the mean temperature 4 weeks prior to each fly count (correlation indices of P<0.01 in six of the nine fly periods) followed by the previous 4 week mean saturation deficit. Rainfall and relative humidity correlated poorly with the seasonality of H. irritans. Temperature appeared crucial at the beginning (late winter) and at the end (early-mid autumn) of the fly season while its relevance diminished in the middle of the season. The percentage of heifers that were infested decreased from 80–100% in the fly season to 0–55% between fly seasons but H. irritans never disappeared from the heards, indicating that if diapause occurs at the latitude of the study area, part of the fly population was not sensitive to diapause inducing factors.

The UK glasshouses in which the western flower thrips Frankliniella occidentalis (Pergande) is prevalent offer protection from adverse winter conditions. As such, F. occidentalis may not have been exposed to selection for cold tolerance that would allow successful overwintering in the field. In this study, the cold tolerance of larval and adult F. occidentalis has been assessed in the laboratory. Both age groups show pre-freeze mortality in chronic and acute cold exposures though adults are more cold hardy. Larvae and adults are both able to increase their cold tolerance in response to a combination of lower temperatures and decreased photoperiod. Field experimentation confirmed that F. occidentalis is unlikely to survive for the duration of a harsh UK winter, but a level of cold tolerance that would be adequate for survival in mild winters or for short exposures at sub-zero temperatures was observed.

The oviposition aggregation pheromone of six species or forms of the Simulium damnosum Theobald complex (Diptera: Simuliidae) from different sites in West Africa, was investigated by gas chromatographic analysis of hexane extracts of the ovaries from wild-caught flies, bloodfed and maintained until gravid in the laboratory. The two compounds previously shown to be released from fresh eggs and associated with mediation of oviposition aggregation were found in S. leonense Boakye, Post & Mosha (Sierra Leone), S. yahense Vajime & Dunbar (Ghana), S. sanctipauli Vajime & Dunbar (Ghana), S. sqnamosum; Enderlein (Cameroon), S. sirbanum Vajime & Dunbar (Ghana) and the Bioko form (island of Bioko, Equatorial Guinea). Coupled gas chromatography–mass spectrometry of the S. leonense, S. sanctipauli and the Bioko form extracts showed the two compounds to be identical in all three. Volatile emissions from freshly laid eggs of S. sanctipauli were similar to those previously described from S. leonense, and identical in chemical composition to gravid ovaries. No new compounds were detected in any ovary extracts or volatile emissions examined, demonstrating that the composition of the aggregation pheromone is similar throughout the S. damnosum species complex. Analysis of S. leonense adults of different age groups and physiological states showed that the compounds are detectable only in gravid ovaries at 2 or more days following the bloodmeal, suggesting that production of the pheromone occurs during egg development. Demonstration of an oviposition aggregation pheromone common throughout the species complex raises the possibility of developing an odour-baited trapping system for blackflies, which could be employed across the large area of Africa where they are the vectors of onchocerciasis.