Two strains of Helicoverpa armigera (Hübner), resistant to synthetic pyrethroids, were isolated from field populations collected in the irrigated cotton growing areas of northern New South Wales: an isofemale strain, Mfo, and a composite field strain, Field. A series of crosses were undertaken between the Mfo and susceptible strains to determine the genetic basis of the resistance. Dose-responses were obtained by bioassay using topical application of fenvalerate in acetone. Considerable variation in tolerance was observed in both resistant and susceptible strains. In the Mfo strain, the major shift in resistance phenotype (33-fold resistance) was due to a single major gene with incomplete dominance. The resistance phenotype was not diluted by 23 generations of backcrossing. The major resistance phenotype could be eliminated almost completely by the addition of piperonyl butoxide which affects oxidative breakdown of the pyrethroids by mixed function oxidase (mfo) enzymes. Similar results were observed in the Field strain. Monitoring for resistance in field populations will be imprecise because a true discriminating dose does not exist for susceptible and heterozygous resistant individuals.

The sexual behaviour of Heliothis peltigera (Denis & Schiffermüller) was studied in the laboratory. Calling activity was very low during the first five hours of scotophase and then increased sharply, particularly in six-to eight-day old females. Peak activity was observed, in all ages tested, between eight and nine hours into scotophase. Calling in six-day old females was significantly higher than in two-day old females but no significant differences were detected between four-to eight-day old females. Maximal amounts of pheromone were found in the pheromone glands of five-to eight-day old females in the second half of scotophase. Male activity was monitored in a wind tunnel. There was no response to pheromone lures during the first two days, then flying activity increased sharply and maintained its high level until the eighth day. Peak activity was observed between six and eight hours into scotophase. Mating activity was very low during the first five hours of scotophase and then increased sharply, with 61.8% of the observed pairs mating between six and eight hours into scotophase. The sexual behaviour of H. peltigera was very similar to the reported behaviour of the sympatric species Helicoverpa armigera (Hübner) indicating that the reproductive separation of the two species is not affected by temporal factors, but depends mainly on the species-specific pheromone blends.

A description is given of the life history, biology and feeding habits of the cetoniine beetle Pachnoda interrupta (Olivier) (Coleoptera: Scarabaeidae) studied in pearl millet (Pennisetum glaucum) fields in north-west Mali. The third instar larva of this beetle, reared from the progeny of field captured adults, is also described and figured. Yield losses to a range of beetle densities (1–5 and 10 beetles/head) on millet heads have been estimated to range from 9 to 48% in caged trial experiments. The regression equation generated from these data may be used to establish economic injury thresholds and predict losses resulting from varying beetle densities.

Adult grasshopper (Orthoptera: Acridoidea, Tetrigioidea Tettigonioidea) assemblages were sampled at four localities in south-eastern Shoa, around Debre Zeit, Ethiopia, between August 1986 and September 1988. Three localities were followed for the whole period but the fourth locality was followed only between August 1986 and July 1987. Samples were taken fortnightly from both black and light soil fields of tef and wheat crops, each in three replicates. The fauna consisted of twenty-nine taxa of both short- and longhorned grasshoppers, twenty-six of which are identified to species. Over 70% of the species belong to Acrididae and most of them are either pests or potential pests of cereal crops. Species richness, diversity and dominance within and between sites and seasons did not differ much during the two year period. The composition and structure of the assemblage was relatively constant. Despite fluctuation in abundance, dominant and common species remained common and rare species rare. Aiolopus longicornis Sjöstedt was most dominant. Some species are more abundant on black soil than on light soil and vice versa. The results are compared to grasshopper assemblages studied elsewhere.

A new species of gall midge, Procontarinia schreineri Harris, which attacks mango foliage in Guam, is described and the results of field observations on its pest status, biology and population fluctuations are reported. Eggs are laid on young mango leaves and larvae, which develop rapidly over about 5 days, induce blister galls before leaving to pupate. Secondary damage to infested foliage is caused by the fungus Colletotrichum gloeosporioides, which invades damaged leaf tissue and causes mango anthracnose disease. P. schreineri population fluctuations on mangoes were assessed at four localities on Guam over three years by counting the numbers of galls. It was concluded that the main factors affecting populations were rainfall and location. More galls were present during rainy periods, possibly because high humidity improves larval and pupal survival. Gall populations were generally low and unlikely to have direct effects on fruit yields but the introduction of new improved varieties of mango might increase susceptibility to damage. In addition, old galls on damaged leaves may provide reservoirs of anthracnose inoculum.

A trial was carried out using experimental huts to determine whether mosquitoes deterred from entering a building where a person slept under a permethrin-impregnated bednet would enter neighbouring dwellings where people used untreated nets. In each of the six experimental huts a man slept under a bednet for six weeks during the dry season in The Gambia. One bednet was impregnated with permethrin, the other five nets were untreated. The design of the trial was based on a series of Latin squares, so that both men and nets were rotated between huts on different nights. At the end of the trial each man had slept under each net in each hut. Mosquitoes collected from the huts each morning were used to estimate the total number of mosquitoes which had entered each hut during the night. Fewer Anopheles gambiae Giles (sensu lato), A. pharoensis Theobald and Mansonia spp. entered a hut with an impregnated bednet than those with untreated nets. However, there was no evidence that mosquitoes deterred from entering a hut with a treated net entered neighbouring huts with untreated nets. Thus it appears unlikely that people using untreated bednets in a community where most use impregnated nets would receive more bites than if everyone had an untreated net. However, the responses of mosquitoes to permethrin-impregnated bednets were found to depend both upon their species and nutritional condition since A. rufipes Gough, banded Culex spp. and non-human bloodfed A. gambiae (sensu lato) freely entered huts with a treated net.

Trials for the control of soil pests, particularly of termites (Isoptera: Termiti-dae), in groundnuts (Arachis hypogaea) in India and Sudan used chlorpyrifos and isofenphos granules, chlorpyrifos, phorate, carbosulfan and carbofuran in controlled release formulations, and chlorpyrifos seed dressing. Their effects on foliar pests were also noted. Chlorpyrifos controlled release pellets were as effective as aldrin, used as a standard, in reducing root and pod attack and, like aldrin, doubled yields. Isofenphos and chlorpyrifos granules increased yields and reduced pod damage, but to a lesser extent. Other treatments were less effective. Carbosulfan and phorate controlled release and isofenphos granules reduced leaf miner attack. These trials establish the efficacy of controlling termites and other soil pests with controlled release formulations of otherwise non-persistent insecticides. However, the expensive formulation is unlikely to be cost-effective for rural farmers in developing countries and, in the case of chlorpyrifos, residue levels in kernels may be unacceptable. Future work should investigate other insecticides in the formulation and development of cheaper controlled release matrices.

The stem borer, Chilo aleniellus (Strand) (Lepidoptera, Pyralidae) is recorded for the first time as a pest of maize in the western part of the forest area of Côte d'lvoire. Descriptions are given of the larva (including chaetotaxy), the pupa, and adult genitalia. The geographical distribution of this species is presented, and its importance as a pest in Côte d'Ivoire is discussed.

The biology and biogeography of the economically important species of Heteropsylla Crawford, including H. cubana Crawford, are discussed. Heteropsylla comprises a group of legume-feeding neotropical psyllids within the subfamily Ciriacreminae. Taxonomic characteristics previously used to diagnose Heteropsylla and related genera are discussed and a new generic diagnosis is made using both adult and larval characters. Thirty-nine species of Heteropsylla are now recognized and each is described and illustrated. Of these, 21 are new to science. One species, H. boquetensis (Brown & Hodkinson), is transferred from Limbopsylla Brown & Hodkinson. Final instar larvae of 22 species are described and illustrated. Host-plants are recorded for 35 species, showing that Heteropsylla species are generally found on legumes belonging to the Mimosoideae. Three exceptions occur in the Caesalpinioideae. A checklist of species and keys to the identification of adult males, adult females and final instar larvae are provided.

The build-up of resistance to phosphine and methyl bromide in the developmental stages of Tribolium castaneum (Herbst) after six selections in successive generations was investigated in the laboratory at 25 ± 1°C. Responses of the life stages of the fumigant-selected insects were compared with those of untreated controls with a 24 h exposure and mortality was assessed after 14 days. Phosphine induced the development of resistance irrespective of the life stage chosen for selection. The onset of phosphine resistance was noted after the first selection but the levels of resistance attained in the different stages varied depending on the stage tested, and in each case the degree of expression was different in the four stages of T. castaneum. After selection, phosphine resistance was highest in the pupae followed by eggs, adults and larvae. Resistance to methyl bromide in the methyl bromide treated insects increased only slightly (less than × 2.0). Adults derived from egg, larva, pupa and adult-selected methyl bromide lines showed cross-resistance to phosphine (× 1.8 to 11.5 at LD95), while cross-resistance of adults to methyl bromide was noted only in adult-selected phosphine-resistant insects (× 1.5 at LD95).

The effects of ambient temperature on all component life cycle stages of the sheep blowfly Lucilia sericata Meigen were examined under controlled conditions. The critical base temperatures and the number of day-degrees required for completion of each stage were determined. Using these data a simple simulation model was developed to evaluate temperature effects on the seasonal pattern of L. sericata abundance. The number of flies estimated by the model to be available for capture, together with the temperature over each capture period determining adult activity levels, were able to account for 77% of the variance in L. sericata abundance observed over a season.

Four Old World blow flies (Diptera: Calliphoridae), Chrysomya albiceps (Wiedemann), C. putoria Wiedemann, C. megacephala (Fabricius), and C. rufifacies (Macquart), have recently invaded the New World. The interaction of Chrysomya rufifacies (Macquart) with native carrion flies in Texas, USA, was investigated by reducing oviposition by the invader on rabbit carcasses outdoors. These carcasses produced significantly more Cochliomyia macellaria (Fabricius) adults compared to carcasses on which the invader was not reduced. The results suggest that C. macellaria populations will decline where the two species co-occur. They also support the hypothesis that the carrion community is saturated with species, and provide a mechanism for the possible elimination of Lucilia caesar (Linnaeus) in Madeira and the reduction of C. macellaria in South America by Chrysomya albiceps (Wiedemann).