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 life cycle of Strobilomyia anthracina (Czerny) which exploits Norway spruce seed cones was investigated in 1992 and 1993 in the Alps at c. 1800 m at Torgnon (Valle d'Aosta, Italy) and Lac de Tseuzier (Valais, Switzerland) by sampling cones at fortnightly intervals. Oviposition occurred primarily singly in the basal third of cones at the beginning of June when cone scales were open for pollination. Infestation rates were higher when cone crops were poor. Most larvae left the cones in August to pupate in the litter beneath trees, usually at a depth of 1–4 cm. Prolonged diapause of pupae coincided with failed or poor cone crops. Parasitism was investigated at these two and 27 additional sites in the Swiss, French and Italian Alps. Among several hundred host eggs only one was parasitized by Trichogramma sp. (Trichogrammatidae). Among the larval-pupal endoparasitoids, the figitid Sarothrus areolatus Hartig was more common than an ichneumonid, Atractodes sp., but parasitism by both was commonly below 10%. Parasitism by an ichneumonid larval ectoparasitoid, Scambus sp., also rarely exceeded 10%. Puparia of S. anthracina that were buried in the litter to detect pupal parasitoids revealed the gregarious pteromalid Tritneptis sp. near lophyrorum (Rushka). This is the first record of a pupal parasitoid of Strobilomyia species. Information on the biology of the three larval parasitoids is presented. The potential for biological control of North American Strobilomyia neanthracina Michelsen and S. appalachensis Michelsen by importation of natural enemies of S. anthracina appears limited.

Delayed and immediate oocyst rates; parous rates and sporozoite rates were obtained in Anopheles gambiae Giles, A. arabiensis Patten and A. funestus Giles from two villages in the Kilombero Valley, southern Tanzania during the wet season of 1991. Collection methods included light trap, indoor resting collection and nets with holes cut in their side. Mosquito survival estimates from parous rates obtained from light trap collections, were compared with estimates from capture–recapture experiments and from that obtained during a population decline. Methods of estimating the proportion of feeds infectious to mosquitoes, K, were also compared. This proportion varied between villages and species and was highest in the village with the greatest proportion of A. gambiae. We propose that absolute estimates of K should be obtained by determining the immediate oocyst rate and measuring the parous rate using the same host seeking mosquitoes. This estimate was only available from one village and ranged from 1.9% for A. gambiae s.l. to 3.4% for A. funestus.

The southern African shrubs Chrysanthemoides monilifera monilifera and C. m. rotundata (Compositae) are serious weeds of native vegetation in Australia and are targets for classical biological control. In host specificity tests using 69 species from 25 families, two leaf-feeding chrysomelid beetles, Chrysolina picturata (Clark) and Chrysolina sp. B, were able to complete development on only Chrysanthemoides monilifera and C. incana. The subspecies Chrysanthemoides m. monilifera was the superior host for both Chrysolina picturata and Chrysolina sp. B. Feeding and limited development of both species occurred on Calendula officinalis; limited development by Chrysolina picturata larvae occurred on Helianthus annuus, Tussilago farfara and Cymbonotus priessianus. Chrysolina picturata and Chrysolina sp. B are considered to be Chrysanthemoides-specific and have been approved for release in Australia. Potential release sites for both Chrysolina species were chosen by comparing the climate of the insects' African distribution with climate stations within the range of Chrysanthemoides monilifera in Australia. Chrysolina picturata and Chrysolina sp. B are suited for release within the western distribution of Chrysanthemoides m. monilifera in coastal areas of south eastern South Australia.

New Zealand is currently the only major fruit producing country in the world that is free of economically important fruit flies. As part of the effort to maintain this status, there is a need to supplement quarantine decision-making procedures with a means of rapidly identifying immature life stage infestations to the species level. Here we describe a molecular method that achieves this, using simple restriction patterns of ribosomal DNA (rDNA) as diagnostic markers. The 18S and 18S plus internal transcribed spacer (ITS) regions were amplified from larval DNA by the polymerase chain reaction (PCR). Nineteen species, spanning four genera (including five subgenera of Bactrocera) were analysed. Restriction analysis of the 18S PCR product provided poor resolution, even at the generic level. Digestion of the 18S + ITS PCR product, however, generated thirteen diagnostic haplotypes as defined by the composite restriction patterns from RsaI, Sau3a HaeIII and AluI. No variation was detected at these restriction sites within or between populations. Twenty two restriction enzymes have been screened, but diagnostic RFLPs have yet to been found for six out of the ten Bactrocera (Bactrocera) species; B. passiflorae (Froggatt) cannot be distinguished from B. facialis (Coquillet), nor B. kirki (Froggatt) from B. trilineola (Froggatt) or B. neohumeralis (Hardy) from B. tryoni (Froggatt). Geographic origin could assist in distinguishing the first four species, but the latter pair are very closely related with overlapping origins, hosts and adult morphology. All six species, however, are considered high risk with respect to their likely establishment in New Zealand. Therefore diagnosis based on this molecular technique would support the same quarantine decision. We consider this method could be useful as a diagnostic technique and discuss directions for further development.

The possibility that mosquitoes are diverted from protected people sleeping outdoors in a bednet to an unprotected person immediately adjacent was investigated during field trials conducted in an Afghan refugee village. The presence of an untreated bednet covering three people sleeping adjacent to the subject did not cause a significant rise in the biting rate on that subject. At the dose rates studied, biting rates in the presence of an ImperatorR treated bednet fell slightly (although not significantly). K-OthrineR treated bednets had no discernible effect on biting rates. Similar studies conducted within giant net traps showed that the ImperatorR treated bednet, and to a lesser extent the K-OthrineR treated bednet, did repel mosquitoes. Within these net traps, biting on the unprotected subject decreased considerably in the presence of the imperatorR treated bednets (P < 0.05 for both culicines and Anopheles stephensi Liston in the presence of the ImperatorR treated bednet). The net traps held in volatile components from the treated bednets in much the same way as the walls of a well ventilated room. We conclude that while sleeping next to a treated bednet may be of considerable benefit inside, where one sleeps in relation to a bednet outside is of little importance. Further studies revealed that for each mosquito species, insecticide induced mortality was highest when the bednet contained the preferred host of that species. This suggests that selection for pyrethroid resistance by bednets may be relatively slow to develop in areas where the primary vectors of malaria are zoophilic.

The taxonomy of three species of Smicronyx that are potential biocontrol agents of witchweeds (Striga spp.) in West Africa is revised. The two most abundant species are identified as Smicronyx(Afrosmicronyx) umbrinus Hustache and S. (Smicronyx) guineanus Voss. A third species is described as Smicronyx (Afrosmicronyx) dorsomaculatus Cox, sp. n. Diagnostic descriptions and a key, to separate adults of the three species from each other and from Sharpia bella Faust, are presented. Mature larvae of the three Smicronyx species are separated through a key and diagnoses. A lectotype is selected for Smicronyx umbrinus. All available host and distribution data are summarized for each species.

The status of pyrethroid resistance in some field populations of Helicoverpa armigera (Hübner) from Pakistan was determined using an IRAC leaf-dip method. Resistance factors varied between populations, and the general trend was for a moderate to high resistance to cypermethrin and cyfluthrin; a low to moderate resistance to deltamethrin and alpha-cypermethrin; and a comparatively low resistance to bifenthrin, lambda-cyhalothrin and zeta-cypermethrin. Depending on which physiological mechanisms are shown to be present in Pakistani field strains, the latter group of pyrethroids may serve as useful tools in the management of insecticide resistance.

Reproduction of Varroa jacobsoni Oudemans has been extensively studied in colonies of the mite's recently acquired host, Apis mellifera Linnaeus. However, data on reproduction in colonies of its original host, A. cerana Fabricius, are still fragmentary. In order to compare reproductive success in naturally infested brood cells of A. cerana and A. mellifera, freshly capped worker and drone cells (0–5 h after capping) were marked and opened 9 days later. When one or more foundress Varroa mites were found, the number and stage of the offspring were recorded. In colonies of A. cerana, V. jacobsoni reproduced almost exclusively in drone cells. Surprisingly, however, these drone cells proved to be better suited for reproduction than drone (and worker) cells of A. mellifera. Firstly, in drone cells of A. cerana, 97–100% of the mites produced daughters and 98–99% of these mites also produced a son. In drone and worker cells of A. mellifera only 70–80% produced daughters and only 74–86% of these mites produced a son. Secondly, if a mite produced daughters, she produced more daughters in drone cells of A. cerana than in drone cells of A. mellifera: 4.5–4.6 vs 2.9–3.7 daughters per mite, respectively. Finally, infestation by two foundress females negatively affected reproduction per mite in drone cells of A. mellifera, but not in drone cells of A. cerana. Thus, V. jacobsoni seems to be better adapted to A. cerana than to A. mellifera, although population growth of mites in A. mellifera colonies is higher due to the exploitation of worker cells besides drone cells.

Four new species of Encarsia, E. lanceolatasp. n., E. paracitrellasp. n., E. pseudocitrellasp. n. and E. unicitrellasp. n. are described and illustrated. All four parasitoid species were reared from the Bemisia tabaci-complex and/or other whitefly hosts in the Neotropical region. Encarsia paracitrella, E. pseudocitrella and E. unicitrella are extremely closely related, to each other and to E. citrella (Howard). A diagnosis is therefore given for the E. citrella-complex, with a key to the four currently included species. For E. citrella (Howard) a lectotype is designated, the male is described and illustrated for the first time, and the female is redescribed and illustrated. A key and a modification to an existing key are provided to facilitate the identification of the five species treated.

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.

Apterous aphids need to move from ageing to younger leaves in order to survive UK winters. This behaviour was studied at low temperatures in field and laboratory trials using Myzus persicae (Sulzer) clones representing all five recognized categories of esterase-based insecticide resistance found in UK populations. Both studies showed that the tendency of aphids to move from deteriorating leaves was inversely related to their insecticide resistance level. This maladaptive behaviour associated with greater insecticide resistance could lead to increased risks of aphids becoming separated from plants after leaf fall, and subsequent death from starvation when adverse cold and wet conditions prevent return. Revertant clones, that had spontaneously lost extreme resistance to insecticides by ceasing to express their amplified esterase genes, tended to show similar behaviour to aphids that had retained their high resistance phenotypes. This implies that rates of movement were not related directly to esterase production.

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 observed mutualistic relationship between the black cocoa ant Dolichoderus thoracicus (Smith) and the mealybug Cataenococcus hispidus (Morrison) was examined. The importance of C. hispidus to D. thoracicus as a food source was investigated by giving D. thoracicus access to C. hispidus only, to C. hispidus and other food sources, and denying access to any obvious food sources. Dolichoderus thoracicus was seen to depend on C. hispidus alone as a source of food over an eight-week period of observation without showing ill effects. The role of D. thoracicus in spreading C. hispidus was studied in an experiment consisting of combinations of D. thoracicus and C. hispidus exclusion. It was shown that D. thoracicus was responsible for carrying C. hispidus across a ‘mealybug excluder’. Data on the frequency and duration of transport of C. hispidus by D. thoracicus were obtained by direct observation for a total of 90 h over 17 days. Both adults and nymphs of C. hispidus were carried by D. thoracicus with its mandibles in a brief and erratic manner, in the general direction of the trail. Such transportation is nevertheless considered to be important in view of the large number of individuals of D. thoracicus moving along a trail. The close mutualistic relationship between D. thoracicus and C. hispidus reiterates the necessity to manipulate both organisms for control of cocoa pests.

In the Esmeraldas focus of onchocerciasis in Ecuador, the larvae of the primary vector Simulium exiguum Roubaud are found in sympatry with the non-vector S. gonzalezi Vargas & Díaz Nájera. Distinguishing the pre-ultimate stage larvae of these two species usually relies on the pattern of markings on the cephalic apotome. These patterns appear either as dark spots against a pale cuticle (positive head pattern) or as pale spots within a darkened area of the cuticle (negative head pattern). Larvae of S. exiguum s.l. usually exhibit positive or no head patterns whilst those of S. gonzalezi usually have negative head patterns. The purpose of this paper was to investigate head pattern variation (scored in one of six categories) in (polytene) chromosomally identified larvae of the two species and cytotypes of S. exiguum from three collection sites in Ecuador (including one in the onchocerciasis focus). The head patterns of a total of 1183 larvae were studied. Chromosomal identification of penultimate instar larvae revealed only the presence of the Cayapa and Quevedo cytotypes of S. exiguum (n=208). Both cytotypes exhibited a wide range of head patterns from positive to negative. The results indicate that negative head patterns cannot be used to reliably distinguish between larvae of S. exiguum s.l. and S. gonzalezi. All except one larva with negative head patterns were females (n=53), suggesting that head pattern in this species complex might be a sex-linked character.

Three species of Mesoclanis flies that attack the developing seeds of Chrysanthemoides monilifera in South Africa are being assessed for their potential as biological control agents of C. monilifera in Australia. Surveys in South Africa indicated that M. polana Munro is restricted to C. m. rotundata along the subtropical northern coast, M. magnipalpis Bezzi and M. dubia Walker occur on all three subspecies sampled (C. m. rotundata, C. m. monilifera, C. m. pisifera), although M. dubia is less abundant and has a more restricted distribution than M. magnipalpis. Mesoclanis eggs are laid into a wide range of flowerhead stages of C. m. rotundata over a period of approximately 12–14 days, from very small flowerheads with involucral bracts still completely closed, to flowerheads with the laminae of ray florets (petals) starting to elongate. Levels of oviposition by M. magnipalpis into C. m. pisifera are low in very young flowerheads, possibly as a consequence of a heavy layer of indumentum on young C. m. pisifera flowerheads. The pattern and location of feeding and pupation within flowerheads differs slightly for the three Mesoclanis species, but none of the species is associated with the formation of gall tissue. The effect of Mesoclanis activity on ovule development was assessed on four occasions. Mesoclanis destroyed all the ovules in some capitula, and the maximum level of ovule destruction recorded for a site was 64%.

Long term changes in the size of populations of the tsetse Glossina pallidipes Austen and G. longipennis Corti were monitored over a 12 year period at Nguruman in south-western Kenya. Tsetse populations were subject to droughts of varying intensity and, from 1987, to trapping, initially by a research organization, and later by a community-based development project. Populations were mainly sampled using odour-baited biconical traps, with data from other monitoring traps corrected accordingly. Mark–release–recapture studies were carried out to relate trap catches to absolute population size, and to quantify movement between subpopulations. Trypanosomiasis incidence rates in a herd of local cattle were also monitored for much of this period. Trap catches were shown to be well correlated with estimates of absolute population size, with no evidence of any seasonal change in trap efficiency. The intensity of trapping and level of seasonal immigration appeared to be the main determinants of population trends, with effective control being achieved when traps were well maintained. Movement between the two lowland subpopulations was shown to be greater for females, and to be inversely related to temperature. An analytical model was used to investigate the responses of a partially isolated population to trapping pressure. Predictions of a deterministic simulation model demonstrated that the observed changes are consistent with an adult trapping mortality of 4–8% per day, and immigration of 100,000 G. pallidipes females per month in the long rains (April and May), 5000 per month in the short rains (November), and about 500 per month during the dry seasons. Trypanosomiasis incidence in local cattle was greatly reduced during the period of community-based tsetse control. When tsetse were sampled exactly where the cattle were grazing, disease incidence was shown to be linearly related to G. pallidipes catches. Arguments for trap resistance and residual populations were examined, and found to be inconsistent with the data. The future for tsetse control by the Nguruman community is considered.

Although Aphytis lingnanensis Compère is an important parasitoid of California red scale Aonidiella aurantii Maskell, several ‘races’ of A. lingnanensis exist which parasitize white louse scale Unaspis citri Comstock. The reproductive status of a white louse scale ‘race’ of A. lingnanensis that originated in Thailand was examined in relation to several populations (from Queensland, California and the Philippines) that parasitize California red scale. None of the wasps from red scale mated with individuals from white louse scale in small cages within 10 min, whereas control crosses all mated in that time. The two ‘races’ would therefore constitute independent reproductive entities (species) in sympatry in the field, although no consistent anatomical differences could be found between them, even with the aid of discriminant function analysis on the number of setae on the delta region of the forewing and the mesoscutum.

Aphytis lingnanensis from California red scale in Queensland mated readily with wasps derived from the same host species in California and the Philippines, and mating took place at random among individuals in mate choice tests. Although such results are equivocal, there are no reasons for suspecting that these different populations of A. lingnanensis from California red scale also comprise more than one species. The results obtained indicate that cross-mating tests designed to quantify reproductive isolation between sexual populations are inappropriate. They should rather be designed to establish whether individuals recognize one another as potential mates. The design of cross-mating tests should therefore consider the usual time to mating, of known conspecifics, under the experimental conditions to be used.

What has previously been referred to in the literature as the African white rice borer Maliarpha separatella, is a complex of three closely related stemborers. These are described and the genus revised. The genera Biafra Ragonot and Ethitropa Hampson are synonymized with Maliarpha Ragonot. All primary types available have been examined. The revised genus Maliarpha is a monophyletic group defined by the apomorphic, tri-lobed form of the male gnathos. Six species of Maliarpha are treated, of which brunnella, fuscicostella and longisignumella are described as new. The species Biafra rhodinella (Ragonot), Singhalia haemocharis (Meyrick), Ethiotropa phromerella (Hampson) and Biafra taxiarcha Meyrick are synonymized with Maliarpha concinnella (Ragonot), and Biafra concinnella Ragonot and Saluria rosella (Hampson) are recombined with Maliarpha. The adult moths are illustrated and line drawings of the genitalia are provided for all species.