The use of long-term forecasts of pest pressure is central to better pest management. We relate the Southern Oscillation Index (SOI) and the Sea Surface Temperature (SST) to long-term light-trap catches of the two key moth pests of Australian agriculture, Helicoverpa punctigera (Wallengren) and H. armigera (Hübner), at Narrabri, New South Wales over 11 years, and for H. punctigera only at Turretfield, South Australia over 22 years. At Narrabri, the size of the first spring generation of both species was significantly correlated with the SOI in certain months, sometimes up to 15 months before the date of trapping. Differences in the SOI and SST between significant months were used to build composite variables in multiple regressions which gave fitted values of the trap catches to less than 25% of the observed values. The regressions suggested that useful forecasts of both species could be made 6–15 months ahead. The influence of the two weather variables on trap catches of H. punctigera at Turretfield were not as strong as at Narrabri, probably because the SOI was not as strongly related to rainfall in southern Australia as it is in eastern Australia. The best fits were again given by multiple regressions with SOI plus SST variables, to within 40% of the observed values. The reliability of both variables as predictors of moth numbers may be limited by the lack of stability in the SOI-rainfall correlation over the historical record. As no other data set is available to test the regressions, they can only be tested by future use. The use of long-term forecasts in pest management is discussed, and preliminary analyses of other long sets of insect numbers suggest that the Southern Oscillation Index may be a useful predictor of insect numbers in other parts of the world.

Solutions of dieldrin, γ BHC, p, p′DDT and Baytex were applied topically to pregnant females of Glossina morsitans Westw. and also, in most cases, to fertilised flies over 21 days old and not noticeably pregnant, to virgin flies over 21 days old, and to males over 18 days old. Pregnant flies required about nine times as much dieldrin as young flies for comparable mortalities, and non-pregnant fertilised flies about four times as much. It was not possible to determine proper regression lines for other insecticides and classes of flies but significant increases in tolerance, as compared with that of young flies, were shown by pregnant flies to γ BHC and DDT, by old virgins to dieldrin and DDT but not γ BHC, and by fertilised flies to γ BHC and DDT. Pregnant flies and virgins showed no increased tolerance to Baytex, and old males showed none to dieldrin, γ BHC or DDT.

These results are discussed in relation to aerial spraying of tsetse habitats and it is suggested that they explain some unexpected past results.

A parasitoid community on agromyzid leafminers from Cordoba, Argentina was analysed in terms of parasitoid assemblage size and host ranges of parasitoid species. Samples were taken during 1991–1995 at natural, urban and agricultural habitats. The system consisted of 69 parasitoid species and 51 leafminer species on 109 plant species. On average, 12 species parasitized each host, when only numerically well represented leafminer species were considered for analysis. Each parasitoid species exploited on average seven species and three genera of agromyzid leafminers. Both parasitoid assemblage size and parasitoid host range were notably high when compared with similar systems from other regions.

The taxonomy of 39 species of mealybugs (Pseudococcidae) attacking sugar-cane, rice and sorghum is discussed. Twenty-seven species are described, eight of them as new. Some aspects of the biology derived from the literature are added, together with a key to the 39 species, and host and distribution records of each.

Factors affecting the persistence of deposits from aqueous suspensions of insecticides have been studied.

There is an inverse relationship between particle size of insecticides and the initial contact toxicity to mosquitos. The influence of particle size on effectiveness decreases as the intrinsic toxicity of the insecticide increases. The compounds investigated can be arranged in order of immediate contact toxicity to mosquitos (Aëdes aegypti): dieldrin ≥ gamma-BHC > aldrin > DDT.

Transgenic Bt maize expressing the Cry1Ab toxin is poorly effective for suppressing populations of two non-target Lepidoptera, Mythimna unipuncta and Helicoverpa armigera. In order to determine the mechanisms that may be involved in this poor effectiveness, last instar larvae of the two Lepidoptera were fed with a diet containing lyophilized leaves with Bt vs non-Bt toxin for different periods; additionally, some larvae fed on Bt diet were transferred to non-Bt diet for an additional period. In the experimental larvae, we measured the growth (weight) gain from just before treatment to after the end of the treatment, and the Cry1Ab contents in the hemolymph, the peritrophic membrane and its contents and midgut epithelium. Effects of the treatments on the midgut epithelium were observed by light and transmission electron microscopy. It was seen that multiple mechanisms can be involved in the low susceptibility of the two Lepidoptera. The low content of the toxin within the peritrophic membrane 48h after ingestion indicates a high rate of toxin elimination in this space. Moreover, M. unipuncta larvae fed on the Bt diet displayed a similar growth gain index to those fed on the non-Bt diet, and showed an increasing elimination rate during the experiment. Little toxin reached the midgut epithelium, indicating a low permeability of the peritrophic membrane or a low affinity at the binding sites. Larvae fed on the Bt toxin showed rapid recovery in weight gain and in the midgut epithelium, and also showed overcompensation mechanisms.

Many studies in population ecology have shown that related species have different dispersal behaviours. Species with sedentary and migratory behaviour exist in butterflies. While the genetic responses to population isolation are well studied, the effects of different dispersal behaviours of species are widely unknown. Therefore, we analysed 19 allozyme loci of two lycaenid butterflies, Cupido minimus as a sedentary butterfly and Aricia agestis as a mobile and expansive species. We collected 594 individuals (280 of C. minimus and 314 of A. agestis) in a western German study region with adjacent areas in Luxembourg and northeastern France. The genetic differentiation among populations of A. agestis (FST=3.9%) was lower than in C. minimus (FST=5.6%). Both species built up an isolation-by-distance system, which is more pronounced in A. agestis than in C. minimus. The genetic diversity in C. minumus populations (e.g. Ptot=73.5%) is higher for all analysed parameters than in A. agestis (e.g. Ptot=52.1%). Both species show specific genetic characteristics fitting with their different dispersal behaviours and respective ecological strategies. In the light of conservation genetics, we deduce that highly fragmented populations do not necessarily have a high extinction probability, but this risk depending much more on specific population genetic structures. In the studied species, C. minimus preserves a complex genetic constitution by high population densities. The patchily distributed A. agestis represents less rare alleles, present only in some populations, and holds up genetic diversity by high mobility.

Amblyomma lepidum Dön., previously incriminated as a vector of heartwater (caused by Rickettsia ruminantium) among sheep and goats, and possibly camels, in southern Kassala Province, Sudan, is apparently the only Amblyomma species in this area. Systematic collections of all ticks infesting domestic animals were carried out in November 1959, just after the rains, in five ecologically differing areas in the region most severely infected with heartwater. Though rare in desert scrub (north of 16°N. latitude) and only moderately numerous in semidesert grassland (Butana area), incidence of A. lepidum is high in wooded savannah (River Atbara) and in the cultivated Gash Delta, and highest (15·5 per host) in the Acacia seyal savannah of the River Gash. Chief hosts of adults are cattle. Sheep are secondary hosts, and camels, donkeys, and goats are less heavily infested. Two males were taken feeding on humans. Mating (breeding) activity is only slight following the rains (November). Few larvae and nymphs were found during this period; those present were mainly on sheep and goats, with a few on cattle, and these were usually feeding on the hoofs of their hosts.

Rhipicephalus s. sanguineus (Latr.), the most numerous and widely distributed tick here, infests chiefly sheep and goats, is common on cattle, and also occurs on camels and donkeys. Mating activity of this species is high in November. Hyalomma dromedarii Koch is equally widely distributed and follows R. s. sanguineus in numbers, but is most frequent on camels, common on cattle, and rare on donkeys and sheep; goats were uninfested. Mating is moderately active at this season. The incidence of H. impeltatum Schulze & Schlottke, which occurs in each zone, equalled that of A. lepidum. Cattle are the chief hosts and camels are secondary hosts; donkeys, sheep, and goats are less frequently infested. Mating activity is moderate in November.

Other more or less common tick species on these domestic animals are Boophilus decoloratus (Koch), R. e. evertsi Neum., R. simus Koch, H. anatolicum excavatum Koch, H. truncatum Koch and H. marginatum rufipes Koch, evidence for the status of which as a subspecies of H. marginatum Koch is to be presented in a subsequent paper. Several other rare species are also recorded.

The frequency of DDT resistance in Anopheles culicifacies Giles in Sri Lanka remained relatively constant from the cessation of DDT use for malaria control in 1975 until 1982. From 1983 to 1986, the frequency of resistance decreased slowly but significantly. In contrast, the resistance gene frequency in A. subpictus Grassi declined between 1980 and 1983, after which the trend was reversed, and there was a significant increase in DDT resistance in 1984–86. This rise in DDT resistance cannot be attributed to positive DDT selection pressure as there has been little or no agricultural use of DDT during this period. It is also unlikely that the rise in resistance is due to pyrethroid selection as the quantity of pyrethroids used on the island is low and there is no evidence of pyrethroid resistance from WHO susceptibility tests. Studies with the synergists FDMC (4-chloro-α-(4-chlorophenyl)-α-(trifluoromethyl)benzenemethanol) and piperonyl butoxide indicated the involvement of DDT-dehydrochlorinase rather than oxidase in the resistance. This was confirmed by metabolism studies, as DDT-resistant adults of both A. culicifacies and A. subpictus showed an increase in the rate of DDE production, which was also correlated with an increase in glutathione transferase activity.

Wild adults of Glossina morsitans morsitans Westw. and G. pallidipes Aust. were caught in a trap baited with carbon dioxide and acetone near Chimotsi Dam in the Zambezi Valley, Zimbabwe. The design of the trap was such that flies were induced to move into a sterilising chamber, where they were treated with a spray of the chemosterilant metepa, after which they were automatically released back into the environment. Exposure to a spray of 0·2 s duration produced between 94 and 100% sterility, with very low mortality. The sterilising unit, its action and performance are described.

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.

The Simulium sanctipauli Vajime & Dunbar subcomplex of the West African S. damnosum Theobald complex is cytotaxonomically revised for the western part of the Onchocerciasis Control Programme area. The subcomplex is defined and a chromosomal key provided for the identification of the sibling species and forms recognized. Two sibling species are newly described, S. leonense Boakye, Post & Mosha (Sierra Leone) and S. konkourense Boakye, Post, Mosha & Quilleévéré (Guinea and Sierra Leone). Detailed chromosomal data are provided as warranty for the conclusions about the specific or infraspecific status of the taxa recognized.

The distribution of introduced parasitoids of Phthorimaea operculella (Zeller) in Victoria is described. Apanteles subandinus Blanchard and Orgilus lepidus Muesebeck were most abundant, but Copidosoma koehleri Blanchard was also recorded from several sites. Detailed analysis of data obtained through regular monitoring revealed that, in an area free from insecticides, parasitoids were a major factor in controlling P. operculella. This result differs from previously published opinions on the effect of parasitoids, and is attributed to the analysis of data, in this study, on a generational basis. The effect of insectide applications on P. operculella and its parasitoids is discussed.

Tsetse flies Glossina pallidipes Austen and G. morsitans morsitans Westwood deposit their larvae in warthog burrows, in August–November, at Rekomitjie Research Station, Zambezi Valley, Zimbabwe. Artificial burrows, made from 200–l steel drums, were used to sample these flies and to collect their puparia. Sand-filled plastic trays in the burrows served as a substrate for larval deposition. The sand was covered with c. 2 cm of leaf litter after it was shown that only 3% of larvae were deposited on bare sand if both substrates were available. Other burrow modifications – artificially shading the burrow entrance, increasing the relative humidity inside the burrow, or reducing the size of the burrow entrance – significantly decreased deposition rates. The use of burrows in the hot season results in a reduction in the temperature experienced by the puparium towards an assumed optimum level of 26°C. Artificial burrows maintained a mean temperature of 28.5°C during October-November 1998, c. 2.5°C cooler than ambient; earlier work has shown that natural burrows can be c. 5°C cooler than ambient at these times. This may explain why natural burrows in full sunlight were used for larviposition, whereas artificial burrows were used only when they were in deep shade, and why significantly higher proportions of G. pallidipes were found in natural (66%) than in artificial burrows (34%). Better-insulated artificial burrows might produce more puparia with higher proportions of G. pallidipes. Burrows become waterlogged during the rains and may be too cool for optimum puparial development during the rest of the year. The percentages of G. m. morsitans in catches of females from artificial burrows, refuges and odour-baited traps were 34, 26 and < 10% respectively. Traps are biased in favour of G. pallidipes; artificial burrows may show a bias in favour of G. m. morsitans that is a function of temperature. Artificial warthog burrows provide a convenient way of studying the puparial stage in tsetse and for the first time facilitate the capture of females as they deposit their larvae.

Wolbachia bacteria are among the most common endosymbionts in insects. In Wolbachia research, the Wolbachia surface protein (wsp) gene has been used as a phylogenetic tool, but relationships inferred by single-locus analysis can be unreliable because of the extensive genome recombination among Wolbachia strains. Therefore, a multilocus sequence typing (MLST) method for Wolbachia, which relies upon a set of five conserved genes, is recommended. In this study, we examined whether the alnus ambrosia beetle, Xylosandrus germanus (Blandford), is infected with Wolbachia using wsp and MLST genes. Wolbachia was detected from all tested specimens of X. germanus (n=120) by wsp amplification. Five distinct sequences (i.e. five alleles) for wsp were found, and labeled as wXge1–5. MLST analysis and molecular phylogeny of concatenated sequences of MLST genes identified wXge3 and wXge5 as closely-related strains. The detection rate of wXge4 and wXge1 was 100% and 63.3%, respectively; wXge2, wXge3 and wXge5 were detected from less than 15% of specimens. We performed mitochondrial haplotype analyses that identified three genetic types of X. germanus, i.e. Clades A, B and C. Wsp alleles wXge1, wXge2 and wXge4 were detected in all clade A beetles; wXge2 allele was absent from Clades B and C. We concluded that (i) five wsp alleles were found from X. germanus, (ii) use of MLST genes, rather than the wsp gene, are more suited to construct Wolbachia phylogenies and (iii) wsp alleles wXge2 and wXge3/wXge5 would infect clade A and clade B/C of X. germanus, respectively.

Natural enemies are exposed to insecticide sprays for herbivorous species and may evolve field resistance to insecticides. Natural enemies selected for resistance in the field, however, are welcome for pest control. The susceptibility of 20 populations of Eriopis connexa from various crop ecosystems to λ-cyhalothrin was tested. Three bioassays were conducted: (i) topical treatment with lethal dose (LD)50 previously determined for populations considered standard for susceptibility (LD50S) and for resistance (LD50R) to λ-cyhalothrin at technical grade; (ii) dose–mortality assay to calculate the LD for populations exhibiting significant survival to the LD50R; and (iii) determination of survival when exposed to dried residues at field rates. Among the 20 tested populations, seven populations did not survive or survival rates were lower than 10% when treated with LD50R; three populations survived >20%, but lower than 50%; while ten populations exhibited equal or greater survival rates compared with the 50% expected survival for the LD50R. Thus, these ten populations were subjected to dose–mortality response, and the LD50 values varied from 0.046 to 5.44 µg a.i./insect with resistance ratio of 8.52- to 884.08-folds. Adults from these ten populations that were ranked as resistant according to the LD50R exhibited survival from 44.5 to 100% exposed to the lowest and from 38.8 to 100% exposed to the highest field rates of λ-cyhalothrin, respectively. Otherwise, the remaining ten populations ranked as susceptible according to the LD50R showed survival from 3.3 to 56% exposed to the lowest and from 0 to 17.7% exposed to the highest field rates of λ-cyhalothrin, respectively. Therefore, 50% of the tested E. connexa populations exhibited field-evolved resistance to λ-cyhalothrin and the use of a discriminatory LD50 for resistance matched the survival obtained when exposed to the insecticide field rates.

Bacillus thuringiensis Berliner isolates were detected in 57% of 801 samples of rice grain dust, soil, rice field arthropods, and miscellaneous habitats (rice straw compost and mammal faeces) collected at 100 sites in the Philippines. The collection yielded 3950 isolates of B. thuringiensis (8.7 isolates/positive sample). Grain dust from rice mills was the richest source (63% of the samples were positive, with 10.2 isolates/positive sample), followed by rice field arthropods, soil, and miscellaneous habitats. Polyclonal antibodies to six δ-endotoxin groups (Cry1A, Cry1B, Cry1C, Cry1D, Cry1E, and Cry3A) were used in enzyme-linked immunosorbent assays (ELISA) to characterize the toxins produced by each isolate. Subsamples of isolates representing the diversity of isolate sources and δ-endotoxin profiles were bioassayed against the yellow stem borer, Scirpophaga incertulas (Walker) and striped stem borer, Chilo suppressalis (Walker). Eighteen isolates highly toxic to both species were selected for characterization of δ-endotoxin genes by polymerase chain reaction (PCR) with primers specific to 14 genes or gene subfamilies, and Western blotting with Cry2A antibodies. At least two novel δ-endotoxin genes, related to cry1B and cry1F, were detected by DNA sequencing of PCR products.

Only a few individuals in the first generation of adults of Pieris brassicae (L.) reared in captivity will feed on artificially prepared flowers. By breeding from the eggs laid by these individuals and from a few others which have been helped to feed it is possible to maintain the stock. In each successive generation a few more individuals feed, and after about four generations most of the insects feed voluntarily. Finally, after many generations, all the insects use the flowers, and the experiments described are concerned with this adapted stock.

Many factors influence the attraction of the insects to the artificial flowers and the volume of food taken. Colour, blue or yellow, is responsible for attracting the adults to the flowers, and it is only when they are very close to the flowers and under the stimulus of colour that they show any detectable reaction to the odour of the honey solution in the flowers. Larger blue flowers are more attractive than smaller blue flowers.

The insects find the artificial flowers more easily, at first, if they are high in the cage. More honey solution is taken at 30 than at 20°C. and more in a large cage than in a small cage. When given a choice, the insects take more 10 per cent, (v/v) than 1 per cent, (v/v) honey solution and more 20 per cent, (v/v) solution than 10 per cent, (v/v) solution. When offered two of these solutions in separate cages the insects at first take less of the 1 per cent, solution than of the 10 per cent, solution. Later, presumably in an effort to obtain sufficient nutriment, they take more of the weaker solution than of the stronger solution. The insects live for a much shorter time on the 1 per cent, solution than on the 10 per cent, solution. Fresh honey solution is preferred to a solution 4–5 days old, and older honey solution is quite unsuitable as food. When the survival of adults fed on honey and sucrose solution is compared it is found that females, especially, survive longer when feeding on honey.

About 50 per cent, of the adults fed on 10 per cent, honey solution in the normal stock cage under glasshouse conditions live for 18 days. Very few survive for longer than 36 days. Starved insects all die by the llth day under similar conditions. When starved at 12·5°C. and 60 per cent, relative humidity, about half the males live for 17 to 19 days, but all are dead by about the 23rd day, whereas half the females live for about 29 days and some survive up to 40 days.

The eggs of Locusta migratoria migratorioides, R. & F., increase in size during development. The increase is due to the absorption of water from the surrounding moist soil.

The wet weight of a freshly laid egg is 0·0063±0·0008 gms, and of a fully developed egg 0·014±0·002 gms. The dry weight of a freshly laid egg is 0·003± 0·0004 gms. and of a fully developed egg 0·0024±0·0002 gms. The water-content of an egg increases from 51·92±3·53 per cent, of the wet weight in the freshly laid egg to 82·36±2·14 per cent, in the fully developed egg.

The egg-wall consists of an exo- and endochorion and a thick vitelline membrane. The latter has a felt-like structure in the freshly laid egg, but as the egg develops, this membrane increases in thickness and acquires a laminated character.

The micropylar apparatus consists of a ring of about 35–43 oblique, funnelshaped canals arranged round the egg near its posterior end.