Mosquitoes were caught in bedrooms in Tanzanian villages by human-biting catches and in light-traps set close to occupied untreated bed nets. Catches by each method were carried out on pairs of nights in the same week at different seasons and in different villages. The pairs of adjacent catches by the different methods showed a strong correlation. Analysis of the ratio between the catches by the two methods on pairs of nights in the same week indicated that on average three light-traps caught about the same number of mosquitoes as a team of two human catchers. The ratio did not differ significantly between Anopheles gambiae Giles (sensu lato), A. funestus Giles, and Culex quinquefasciatus Say, nor between the villages, or between times when mosquito populations were high or low. The distribution of numbers of ovarian dilatations differed significantly between catches in different villages and seasons but not between pairs of catches by the two methods. Similarly, the parity and sporozoite rates agreed between pairs of light-trap and house-resting catches, but differed markedly between villages and seasons. Thus it is concluded that light-traps used in conjunction with bed nets catch a representative sample of the vectors which would have bitten humans in bedrooms in this area.

The durations for development for immature stages of the fruit piercing moth, Eudocima salaminia (Cramer), were determined at constant temperatures ranging from 15°C to 27°C and at ambient temperatures at a field site in southeastern Queensland over a 16 month period. At constant temperatures average heat requirements for: 50% eclosion of eggs were 62.4 day-degrees above 11°C, development of larvae to pupation were 246 day-degrees above 12°C, development of pupae to eclosion were 233 day-degrees above 12°C. For each stage there was no difference between day-degrees calculated at constant temperatures or at those in the field indicating no diapause in the immature stages. For adults, temperatures below 16°C during the activity period after dusk prevented feeding, mating and oviposition. Failure of E. salaminia to overwinter in south-eastern Australia in most years, was explained by the effects of low temperatures on egg hatch, larval, pupal and adult survival, reduced adult feeding, mating and cessation of oviposition.

The distribution of Rastrococcus spp. within mango trees (Mangifera indica) was studied at Bangalore, India. Population densities of R. invadens Williams, R. iceryoides (Green) and R. mangiferae (Green) were significantly higher on the abaxial leaf surface compared with the adaxial surface. Mealybug density was also higher from ground level up to 2 m compared with above 2 m. Significant variations in Rastrococcus spp. populations among trees and species composition per tree were observed. As populations built up on leaves, migration to other leaves occurred, more predominantly in R. mangiferae than in R. invadens. As the population of R. iceryoides increased on leaves, migration to twigs occurred.

The new age determination technique for tsetse flies based on the accumulation of fluorescent pigments in the head capsule has the minor problem that it is not possible to accurately identify very young flies. In this paper we describe a technique for the identification of very young Glossina morsitans morsitans Westwood based on their high levels of abdominal fluorescence. Under our holding conditions these fall back in a linear fashion to a minimum at five days post-emergence. The variability in the levels of head fluorescence at eclosion is mainly influenced by the size of the emerging fly, with the number of blood meals taken by the female parent, and intra-uterine larval and puparial periods of the emerging flies also playing a part.

The spatial distribution of five lepidopterous pests, Sesamia calamistis Hampson (Noctuidae), Eldana saccharina Walker (Pyralidae), Spodoptera exempta (Walker) (Noctuidae), Mussidia nigrivenella (Ragonot) (Pyralidae), and Cryptophlebia leucotreta (Meyrick) (Tortricidae), on maize in West Africa is described using Taylor's power law and the relationship of proportion of infested plants to the mean density. All five species showed a highly aggregated distribution, with Taylor's indices of aggregation ranging between 1.23 for C. leucotreta and 1.52 for Sesamia calamistis. Enumerative and binomial sampling plans that incorporate Taylor's power law are proposed to estimate mean densities of S. calamistis, C. leucotreta and the species complex consisting of E. saccharina, M. nigrivenella and Spodoptera exempta which showed similar spatial distributions, with a predefined reliability level.

Populations of African black beetle, Heteronychus arator (Fabricius), a subterranean pasture-dwelling pest of potatoes, were examined in pastures in geographically separated potato-growing areas covering 3½° of latitude in southwestern Australia. Abundance of all life stages was estimated by taking soil cores and the reproductive state of females was assessed from the stage of their ovarian development. H. arator adults emerged in late summer-early autumn (January–March), ovaries matured slowly during winter and oviposition occurred in spring (September–November). The interval between equivalent population events was about six weeks from the northernmost to the southernmost regions. Fecundity was estimated to be around 12 eggs/female and greatest natural mortality occurred late in the pre-adult development phase.

The attack rate of four parasitoids against different aphid species was investigated in the absence and presence of leaves from aphid food plants. The parasitoids used, Aphidius ervi Haliday, A. rhopalosiphi De Stefani, A. picipes (Nees) and Ephedrus plagiator Nees, varied in the extent of their host ranges. The presence of plant leaves significantly influenced the attack rate of A. ervi and A. rhopalosiphi, the two parasitoids with the most restricted host ranges, but did not appear to affect attack rates by the more polyphagous A. picipes and E. plagiator. Consideration of these results together with those from previous studies on the host preferences of laboratory populations of A. ervi and A. rhopalosiphi leads to the conclusion that genotype is probably determining the responses of individual parasitoids to semiochemicals involved in host recognition. It is proposed that field populations of oligophagous aphid parasitoids consist of a mixture of specialist and generalist individuals.

Cypermethrin, profenofos, and a mixture of these insecticides were evaluated against resistant and susceptible whitefly, Bemisa tabaci Gennadius, from Sudan using (a) laboratory technology which simulates the aerial spraying of whitefly infestations on cotton crops, and (b) standard residue-bioassays. Simulator tests in which adult cohorts were given a single insecticide treatment produced results that were unexpected on the basis of standard bioassay data. Resistance to cypermethrin, for example, was expressed in the bioassays but not in the simulator, resistance to profenofos was expressed both in bioassays and in the simulator, resistance to the mixture was expressed in the simulator but in the bioassay the chemicals acted synergistically and there was no resistance. Repeated treatment of resistant populations, comprised of all life stages, over three generations gave further unpredicted results: cypermethrin failed to contact larvae on the under surfaces of leaves and hence did not prevent population growth; profenofos sprayed at field rates controlled all life-stages (despite the expression of resistance) provided the insecticide vapour was not dissipated. An alternation of cypermethrin and profenofos – cypermethrin timed against maximum adult emergence and profenofos timed to coincide with high larval densities – gave the best control. The disparities between the simulator experiments and standard bioassays suggest that techniques simulating the field treatment of all life-stages are better suited for evaluating the practical significance of resistance and potential curative strategies.

Samples of Glossina longipennis Corti, taken over four days in traps (baited with acetone, cow urine and octenol) at half-hourly intervals during their restricted activity periods at dusk and dawn, were analysed for their nutritional condition. For both sexes, trap catches were highest at the end of dusk, between 19.00 and 19.30 h, associated with a significant increase in numbers with the low haematin content characteristic of flies estimated to have fed more than 60 hours previously. Also, the mean fat content of these flies was significantly lower than that of those trapped earlier. There was considerable day-to-day variation in the numbers of flies trapped, and in the numbers of low haematin and low fat flies. It is concluded that the nutritional condition of the fly probably influences the timing of the onset of activity, but possibly the fly's approach to the trap.

The majority of Chilo partellus (Swinhoe) males emerge within the first two hours of scotophase (20.00 to 08.00 h), females five hours later. The asynchrony of eclosion times facilitates mating during the last five hours of scotophase on the night of eclosion. Oviposition occurs during the first six hours of scotophase the following night but the majority of the eggs are deposited during the first two hours. No eggs are laid during photophase. A device for recording the timing of oviposition is described. Previous work is reviewed.

Density-specific sampling plans were developed under African conditions for the exotic spider mite, Mononychellus tanajoa (Bondar), a serious pest of cassava, Manihot esculenta. The within-plant distribution of Mononychellus tanajoa was found to favour new foliage, regardless of time of planting or plant age. Consequently, the first developed leaf near the top of the foliage was selected as the sampling unit and related to whole plant populations of M. tanajoa. The relationship between the mite population's variance and mean as measured by Taylor's Power Law proved to be stable over a range of planting dates, seasons and locations. Two binomial sampling plans, one based on Taylor's dispersion parameters and another based on direct field observations, were developed and compared. Binomial sampling, appropriate only for densities below 30 mites per leaf, was replaced by an enumerative procedure based on a ‘quick count’ protocol at higher mite densities.

The length of the intergenic spacer in the rRNA cistron varied within and among individuals of Schizaphis graminum (Rondani). Spacer lengths did not vary among offspring of a single maternal lineage (clone). The intergenic spacer was used as a molecular fingerprinting probe on individual aphids and to study spatial and temporal distributions of clones. A spatially nested sampling design was used in wheat and sorghum to estimate numbers of clones among aphids on leaves, among leaves on plants, among plants in fields, among fields in counties, among counties, and among dates. Each level of nesting added a level of clonal diversity to the entire population. 82.3% of the total population diversity was found among aphids on one sorghum leaf. Sampling additional leaves increased diversity slightly (5.4%), whereas plants (0.9%), fields (0.6% to 3.6%), and counties (1.2%) added very little. Sample dates contributed the highest increase in diversity (11%). Diversity rose and fell in wheat along with aphid numbers but remained constant in sorghum. Little variation in Mahalanobis distances could be explained by geographic distances. No genotypes were unique to any field, county, crop, or year. Kansas populations are made up of a large mixture of genetically diverse clones that recolonize wheat and sorghum each year. Sampling many plants, fields, or counties is an ineffective way to increase clonal diversity. Plant breeders developing crop resistance to S. graminum can expect plant entries to be exposed to most of the genetic diversity present in Kansas populations regardless of location.

Aphelinidae are all insect parasitoids, and most species are associated with nymphal stages of Homoptera: Sternorrhyncha, either as primary parasitoids or hyperparasitoids. The occurrence of egg parasitism in aphelinids has been recorded in eight of the 38 valid genera and these records are reviewed; it is particularly common in the genus Centrodora, which is shown to be the most polyphagous in the family. One species, C. darwini (Girault), is given special attention because of its occurrence in three recent surveys for biological control agents of crop pests. It is briefly redescribed, diagnosed, and shown to be the most polyphagous aphelinid known. A checklist of Australian Centrodora spp. is given, including the new combination Centrodora grotiusi (Girault) comb. n. The purported evidence for the classification of certain Encarsia spp. associated with eggs of Lepidoptera as ‘heterotrophic parasitoids’ is re-examined and dismissed.

Species of the chalcidoid genus Eurytoma associated with stone fruits are studied for the Palaearctic region. The eight species known to have such an association are: E. amygdali Enderlein, E. maslovskii Nikol'skaya, E. padi Veresh-chagin, E. samsonowi Vasiljev, E. schreineri Schreiner, E. turkestanica sp. n., E. paramygdali sp. n. and E. armenica sp. n. The first six species are phytophagous, developing in the stones, and the last two are entomophytophages, starting their development as parasitoids of a phytophagous species and completing development feeding on plant tissue. Four species, E. amygdali, E. schreineri, E. samsonowi, and E. maslovskii are of economic importance. Information is given on the economic importance, biology, distribution and taxonomy of these species, and includes several new records for hosts and distribution. A key is given to distinguish the species.

The taxonomy of the Oriental species of Helopeltis is revised and a review of the economic literature is given. An identification key is provided for the 14 recognized species, one of which, H. sulawesi, is described as new. A diagnosis and brief description is given for each species, as well as illustrations of useful taxonomic characters, information on distributions and host records, and a discussion of any known or suspected misidentifications. Lectotype designations are made for 13 nominal species and the following new synonymies are established: H. bradyi Waterhouse = H. ceylonensis De Silva, syn. n and H. romundei Waterhouse, syn. n;H. cinchonae Mann = H. brevicornis Poppius, syn. n.;H. clavifer (Walker) = H. australiae Kirkaldy, syn. n and H. niger Walker, syn. n;H. cuneata Distant = H. elegans Poppius, syn. n;H. fasciaticollis Poppius = H. pallidus Poppius, syn. n and H. pallidiceps Poppius, syn. n;H. theivora Waterhouse = H. oryx Distant, syn. n The somewhat obscure synonymy of H. theobromae Miller under H. theivora is confirmed. Two subgenera are recognized and diagnosed: Afropeltissubgen. n (type species Eucerocoris westwoodi White), including all African species of the genus, and Helopeltis sensu stricto, containing the Oriental and Australasian species.

To study life cycle variability in Rhopalosiphum padi (Linnaeus), the responses to short days (L:D 10:14) of 70 clones were tested at two temperatures (10°C and 15°C) in the laboratory. Three clones originating from spring populations on the primary host, bird cherry (Prunus padus), were holocyclic, producing gynoparae and then males in the second generation under experimental conditions. Of the other clones, all originating from Gramineae, 78.5% were anholocyclic and 21.5% androcyclic (male-producing) at 15°C, but at 10°C only 12.7% were anholocyclic, 82.6% were androcyclic, and 4.7% showed an ‘intermediate’ response (i.e., some of the alate females produced both sexual and parthe-nogenetic offspring). There was considerable interclonal and inter-individual variation in the numbers of males produced by androcyclic clones. These results are discussed in relation to field studies on R. padi in Britanny, which indicate that 1. primary hosts are rather rare, but nevertheless commonly develop spring infestations; 2. anholocyclic genotypes are regularly decimated every few years by severe winters. It appears that the preponderance of androcyclic clones is important for the maintenance of life cycle variability.

The Old World screw-worm fly, Chrysomya bezziana Villeneuve, occurs in Africa, the Middle East, Malaysia, Indonesia and Papua New Guinea, but it is not found in Australia. Introduction into Australia from any of these source areas would threaten the viability of much of the grazing industry in the northern part of the continent. Proposed control by the sterile insect release method (SIRM) would be compromised by the existence of sibling species within C. bezziana. This study examines the degree of genetic differentiation throughout the extensive range of the fly to assess if the degree of geographic differentiation indicates the existence of sibling species and, allows identification of the source of any introduced flies. Electrophoretic analysis of 23 loci from samples collected in southern Africa, the Middle East, Malaysia, Indonesia, and Papua New Guinea revealed 11 polymorphic loci. Overall, populations show remarkably little divergence given the geographic distribution of sample sites. None of the populations sampled were fixed for alternative electromorphs. There is no evidence from this study for the presence of sibling species within C. bezziana.

Field studies in Zimbabwe elucidated how trees might be enhanced as baits for controlling Glossina morsitans morsitans Westwood and G. pallidipes Austen. Catches from electrocuting devices at the bases of trees were near nil when sampling tsetse flies landing on the trunk but much greater when sampling them flying within 1 m of the trunk. Catches increased 5–8 times when 2 m2 of the trunk were blackened and given odour of acetone, 1-octen-3-ol, 3-n-propyl phenol and 4-methyl phenol, but were still only ca. 30% of the catches from an odour-baited, free-standing, 1 × 1 m screen of black cloth. The upright trunk of real and model trees hindered their attractiveness but leaves and branches 5 m above ground had no clear effect. Real and artificial stumps of trees were as effective as the screen if they were 1 m2, compact and sharply outlined. The practical and biological implications of the results are discussed, with particular reference to the use of insecticide-treated netting with modified tree stumps as baits for control.

Anopheles arabiensis Patton populations occur in those areas of Natal in which intra-domiciliary DDT is used for mosquito vector control and in the unsprayed areas. Indoor resting collections from the unsprayed area showed a human blood index >90%, in contrast to the indoor collections from the sprayed area where only 31% had fed on man. In exit trap collections from the sprayed area, 66% had fed on man. These trends of a high human blood index in the exit trap collections and a low human blood index in the indoor resting catches were unaffected, despite the close proximity of a cattle kraal to the majority of homesteads.