A country-wide survey of the distribution of tsetse flies Glossina morsitans submorsitans Newstead and G. palpalis gambiensis Vanderplank was carried out in The Gambia, during 1989–1990, using box traps at 1654 sites over an area of 10,000 km2 The general distribution of tsetse had changed little during the last 45 years. G. m. submorsitans was present in dry, canopied woodland throughout most of the country, but was absent from an area south of the River Gambia stretching from the coast to some 100 km inland. G. p. gambiensis occurred in evergreen forest and woodland near the coast, and in riparian habitats along the length of the River Gambia and its major tributaries. Nowhere in the country was more than 20 km from tsetse-infested areas. Five major foci of G. m. submorsitans infestation were identified. Demographic, climatic and environmental factors affect tsetse populations in The Gambia, but it is expected that these foci of infestation will persist for at least the next 5–10 years. The numbers of tsetse trapped, expressed as relative densities, were used to assess the extent and severity of losses from trypanosomiasis to different categories of livestock. Survey results such as these could be used to assess whether control measures to reduce tsetse challenge are likely to be economically viable by using techniques such as insecticide-impregnated targets, pour-ons or chemotherapy.

The two spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is a pest of cotton in Australia yet has received little attention. To develop sampling strategies for pest management the seasonal abundance and intra-crop distribution of T. urticae on cotton was studied. T. urticae colonized cotton crops at seedling emergence in October. Populations declined through November/December then increased progressively thereafter, at varying times and rates. Higher initial infestation levels were correlated with earlier, potentially more damaging, mite outbreaks. Survival of T. urticae through November/December appears crucial in determining the extent to which this potential is realized. Nodes 3 to 5 below the terminal were most heavily infested and should be used as the sampling unit for mites. The within plant distribution of T. urticae was unaffected by cotton variety or insecticide applications. T. urticae was more abundant on the edges of fields than in the interior early in the season (October and November) indicating colonization from an external source. The edge effect diminished with time, suggesting a lack of continuous colonization. The only exceptions to this pattern occurred when T. urticae migrated from senescent maize crops into the nearby cotton crops in early January. A simple sampling technique, based on the presence or absence of mites on leaves was developed for pest management purposes.

Culex quinquefasciatus Say from Peliyagoda, Sri Lanka, has elevated esterases A2 and B2. In vitro insecticide metabolism studies on the temephos-selected Sri Lankan Cutex quinquefasciatus strain, Pel RR, showed that fenitrothion was hydrolysed more rapidly than malathion. A significantly larger amount of fenitrothion was metabolized in Pel RR compared to the insecticide susceptible Pel SS strain, but the amount of malathion metabolized in the two strains was not significantly different. There was more esterase hydrolysis of fenitrothion than oxidase or glutathione S-transferase metabolism in Pel RR, which suggests that the elevated esterases in this strain have both metabolic and sequestering functions and that the relative importance of the two roles depends on the insecticide used. Genetic crosses of the temephos resistant and susceptible strains, showed that both resistance and elevated esterase activity were inherited as semi-dominant multi-genic characters. Hydrolysis of 2-naphthyl acetate was highest in the Pel RR strain, lowest in the Pel SS and intermediate in the F1 cross of the two strains. A minor maternal effect on resistance occurred with backcrosses involving resistant (F1) females, which gave consistently and significantly lower mortalities than those involving resistant (F1) males.

Fourteen wild species of Arachis (Leguminosae) were investigated under field and laboratory conditions to evaluate their effect on the survival and development of the larvae of Spodoptera litura (Fabricius). All of the species studied were observed to be resistant compared to the susceptible control, Arachis hypogaea (genotype TMV2). Overall, the mortality and development of larvae recorded in the field were similar to those recorded for larvae on excised leaves of the same species in the laboratory. When neonate larvae were exposed to excised leaves of A. batizogaea, A. kemph-mercadoi, A. appresipila, A. paraguariensis, A. stenophyla and A. villosa mortality was greater than 94% compared to less than 20% on TMV2. Third stadium larvae lost weight when exposed to both field plants and excised leaves of eight of the wild species, whereas larvae feeding on TMV2 gained weight. When third stadium larvae were fed pulped leaves they gained more weight than when exposed to intact leaves, except in the case of A. chacoensis and Arachis spp. 30007. A penetrometer was used to determine the relative toughness of the leaves. The leaves of most of the wild species were shown to require a greater biting effort for feeding than the leaves of TMV2. There was a negative correlation between toughness of whole leaves and larval development. Observations of larval behaviour indicated that, overall, larvae were deterred from feeding on the leaves of the wild species. Diets containing the chemical extracts of dried leaves of A. kemph-mercadoi, A. paraguariensis, A. appresipila, A. chacoensis, A. glabrata and A. pseudovillosa resulted in low larval weight gain. The physical quality of the leaves and foliar chemicals are implicated as being responsible for the observed resistance. The implications and potential applications of these results are discussed.

Research on aphid-parasitoid associations was carried out in Chile in 1979–80 and 1991–92 on the biological control of the cereal aphid pests Metopolophium dirhodum (Walker), Sitobion avenae (Fabricius), and Diuraphis noxia (Mordvilko). The introduced parasitoid species, Aphidius ervi Haliday, A. rhopalosiphi De Stefani Perez, A. smithi Sharma & Subba Rao, A. uzbekistanicus Luzhetski, Ephedrus cerasicola Starý, E. nacheri QuilisPerez, E. plagiator (Nees), Monoctonus nervosus (Haliday), Prnon gallicum Starý, P. volucre (Haliday) were all recovered in cereal and other ecosystems. Most of the parasitoids had adapted well and some of them had even extended their host range; ecological relationships were all found to extend beyond those of the target pests. The parasitoid complex, which had developed from the indigenous and introduced species, was found to be successful in preventive biocontrol and the endemic fauna of Chile was not affected.

Populations of the blowfly Lucilia sericata Meigen in sheep pastures were monitored for three years (1990–1992) using sticky targets. A simulation model, developed previously from detailed analyses of the effects of temperature on the component stages of the life-cycle of L. sericata, was used to predict the pattern of seasonal abundance expected during these years at the temperatures observed. After inclusion of the effects of temperature over each catching interval, the model was able to explain 67%, 52% and 49% of the variance in catch in 1990, 1991 and 1992, respectively. The model was validated by using regression coefficients and constants derived from data collected over previous years to predict the expected catch in the following year. Up to 50% of the variance in catch was explained by this analysis. The results confirm value of the day-degree modelling approach for this blowfly species and suggest that such predictive models may play an important role in the development of strategic control for flystrike prevention.

An experimental hut trial of bednets was undertaken in The Gambia to compare six different permethrin treatments, including a wash-resistant formulation, and to test the effect of thorough hand washing of the nets. The wash-resistant formulation on nylon and cotton nets deterred Anopheles gambiae Giles (sensu lato) from house entry. All treated bednets killed a significantly higher number of A. gambiae (sensu lato) than untreated nets. The ability to kill mosquitoes was not diminished with the wash-resistant and Wellcome formulations after washing unlike the normal ICI formulation, this result being consistent with the permethrin residues found by gas liquid chromatographic (GLC) analyses to persist on the nets after washing. The mortality on treated cotton nets was significantly less than on treated nylon nets. Of the unwashed nets only the cotton net was significantly repellent. Both washed and unwashed treated nets significantly reduced the proportion of human bloodfed mosquitoes that survived and were potentially able to transmit malaria. Although the wash-resistant formulation might prove more efficient at killing mosquitoes with time, as compared to the other treatments, in The Gambia, where women wash their nets frequently, we suggest that the cheapest and most readily available formulation is used on nylon nets where possible.

The potential of carabid beetles as natural control agents of slugs was investigated using a quantitative indirect enzyme-linked immunosorbent assay (ELISA). The crop contents of two species, Abax parallelepipedus (Piller & Mitterpacher) and Pterostichus madidus (Fabricius) collected between May and December 1990, were analysed using an anti-mollusc haemolymph antiserum. The mass, immunological reaction and calculated mollusc content of each beetle crop was determined. Mollusc content was calculated as ‘fresh mollusc equivalent’, and the probable quantities of degraded material present are discussed in relation to predator and prey species. 89.5% of A. parallelepipedus and 42% of P. madidus were found to contain mollusc proteins. Although approximately the same proportion of male and female A. parallelepipedus tested positive, females contained greater quantities of mollusc remains. Approximately 39% of male and 45% of female P. madidus tested positive, and overall female crops contained significantly more material. The calculated amount of mollusc remains found in females was also greater. Over time, the immunological reactivity of A. parallelepipedus crop samples varied significantly. However, when crop weight was taken into consideration, the calculated quantity of mollusc found in strongly reacting samples was not significantly different between months in either species. Neither the immunological response nor the quantity of mollusc remains varied over time in P. madidus, although significant differences were found in overall crop weights. A significant correlation was found between the proportion of mollusc in beetle crops and crop mass in A. parallelepipedus, but not in P. madidus. Correlations between soil temperatures and crop mass, immunological reactivity and mollusc content were not significant in either species. The improved methods of quantifying predation from ELISA data, employed in this study, were an important part of a larger on-going investigation of the role of predation in slug population dynamics within agricultural systems.

Following the examination of 53 Lutzomyia spp., seven Phlebotomus spp. and five Sergentomyia spp. (Diptera: Psychodidae) new observations are recorded on the presence of pheromone disseminating structures on the tergites of male phlebotomine sandflies. Descriptions are given of 11 of the species which include structures such as simple cuticular pores in craters, pores with emergent spines, and mammiform papules with or without spiny processes. Pheromone papule distribution on the tergites of Lutzomyia pessoai (Coutinho & Barretto) is plotted and gas chromatography and GC-mass spectroscopy have been used to demonstrate the presence of a diterpene compound similar to a sexual attractant pheromone observed in some L. longipalpis (Lutz & Neiva) populations.

This review examines the recent literature on tsetse (Glossina spp.) metamorphosis behaviour and its regulation. The behavioural events associated with metamorphosis are highly specific and most occur only once during the life of the fly. The review begins with the larva's commitment to metamorphosis and then discusses the behaviour associated with parturition, wandering of the third instar larva, pupariation, pupation and adult eclosion. While certain aspects of tsetse metamorphosis behaviour are common to the higher Diptera, the peculiar reproductive strategy of tsetse has dictated many modifications. Most notable of the tsetse peculiarities are the larva's late commitment to metamorphosis, the contribution by the mother in deciding the onset of the wandering period, the brevity of the wandering period, the involvement of the nervous system in co-ordinating puparial tanning, the tight pack aging of the pupa within the puparium, the long duration of pharate adult development, and the great expansion of the body that occurs following eclosion. A final section discusses the potential for disrupting tsetse metamorphosis.

A brief review is given of species of Coccoidea found on sugarcane (Saccharum officinarum) in the island of New Guinea. A key and comments on all the species of Aulacaspis that have been recorded on sugarcane and other Saccharum spp. throughout the world is presented. The scale insect Aulacaspis neoguineensis Williams & Watson sp. n. is described from specimens on sugarcane intercepted at Washington, DC, USA from Papua New Guinea because it is a potential pest of sugarcane. It is compared with A. madiunensis (Zehntner), a closely-related species often injurious to sugarcane in southern Asia, Australia and Africa.