Emergence of coffee berry borer, Hypothenemus hampei (Ferrari), from infested coffee berries (Coffea arabica) was studied in the laboratory under controlled temperature and relative humidity (RH) regimes. Low humidities (<60% RH, 25°C) provoked rapid evacuation of adults. Emergence was at a minimum at 90% RH. A steady increase in emergence occurred at values from 90 to 100% RH. Emergence was low below 20°C (90 and 100% RH) and increased markedly between 20 and 25°C. There was no significant increase in emergence above 25°C. Using a simple flight event recorder, emergence flight times were found to peak at the time of maximum daily ambient temperatures on successive days. Under constant temperature conditions successive peaks of emergence were not seen. Results are discussed in relation to control and sampling procedures.

We have used a new technique to identify discrete genetic markers in aphids, a family in which biochemical and morphological genetic polymorphisms are rare. The new technique uses the polymerase chain reaction (PCR) to amplify random regions of aphid genomes (random amplified polymorphic DNA) and has been termed RAPD-PCR. We demonstrate the use of the technique in revealing genetic variation in four aphid species, the greenbug (Schizaphis graminum (Rondani)), the Russian wheat aphid (Diuraphis noxia (Mordvilko)), the pea aphid (Acyrthosiphon pisum (Harris)), and the brown ambrosia aphid (Uroleucon ambrosiae (Thomas)). In contrast with allozyme surveys, RAPD-PCR revealed large amounts of genetic variation among individuals in each of these species. Variation was detected among biotypes, populations, colour morphs and even individuals on a single plant. We also explored the utility of RAPD-PCR in the detection and identification within aphid bodies of two endoparasitic wasps, Diaeretiella rapae (McIntosh) and Lysiphlebus testaceipes (Cresson). The use of RAPD-PCR in species diagnostics, parasitoid detection, and population studies is discussed.

The electrophoretic mobility of the enzyme glutamate oxaloacetate transaminase (GOT) on cellulose acetate plates was compared among sibling species of the Myzus persicae (Sulzer) group (M. persicae, M. nicotianae Blackman, M. antirrhinii (Macchiati)). M. persicae itself is monomorphic for GOT-1 (genotype ff), whereas European populations of M. nicotianae are polymorphic for this enzyme, with two forms of slightly different mobility (alleles s, f). In the samples of M. nicotianae examined, M. persicae-likeff genotypes were rare and heterozygotes (sf) were in large excess, even in samples from Greece where M. nicotianae has a regular holocycle (i.e., annual sexual reproduction). In North America, where M. nicotianae is probably entirely anholocyclic, samples of both red and green colour morphs of this species were found to be heterozygous for GOT-1. The enzyme difference can thus provide a means of distinguishing most individual specimens, including trapped alatae, of M. persicae and M. nicotianae. The anholocyclic taxon M. antirrhinii appears to be a fixed heterozygote for GOT-1 and thus resembles most M. nicotianae, but can be distinguished electrophoretically from both M. persicae and M. nicotianae by its distinctive pattern of esterases.

Seasonal changes in the distribution of the tsetse flies, Glossina pallidipes Austen and G. longipennis Corti, along a transect from riverine thickets out into open plains were monitored along with tsetse density, climatic factors, vegetation and host abundance. Dispersal of tsetse into open country was quantified using the mean spread. During and after the rains both species extended their distribution out into open country up to at least 3.5 km from riverine thicket areas. The mean spread of G. longipennis was greater than that of G. pallidipes. The spread of males and females was very similar, as was the spread of different age categories of parous females, but nulliparous flies and females carrying second instar larvae were under-represented in samples from open areas. This seasonal dispersal can be accounted for by random diffusion with an average root mean square displacement of about 175 m per day. Observed degrees of spread were best correlated with humidity conditions prior to sampling, but multiple regression models suggested that host abundance, vegetation as measured by Normalised Difference Vegetation Indices (NDVI), and, in the case of G. longipennis, tsetse density, were also factors in determining the degree of spread. The significance of these findings in relation to tsetse control is discussed.

Genetic methods to eliminate females prior to releasing sexually sterilized males in sterile insect technique programmes generally involve the translocation onto the Y chromosome of a readily selectable gene (here designated F). However, such strains often show instability with regard to sexual dimorphism. Concerted attempts to determine the most probable causes of such instability have rarely been successful, and appropriate countermeasures have generally not been implemented. We have developed a computer model which simulates the progression of instability in such strains. Here we simulate the effects of contamination in association with a range of genetic and biological parameters and assess the patterns and rates of progression of the ensuing instability. A single event of contamination alone was found to contribute relatively little to the progression of instability and invariably resulted in an equilibrium within the population. However, strong effects were produced by reduced fitness and mating competitiveness of both the f/f genotype and the translocation carriers, a reduction in the parameters involving the f/f genotype resulting in the virtual elimination of f/f, while a reduction in the translocation parameters had the opposite effect of virtually eliminating the F/ – phenotype. The sex ratio was affected only by a change in the relative fitness of the f/f genotype and the translocation. Several characteristic patterns contributed to distinguish clearly the effects of contamination from those of male recombination in unstable genetic sexing strains. With such knowledge appropriate measures may be taken to counter or alleviate the effects of instability in mass reared genetic sexing strains.

Megaselia chlumetiae Disney sp. n. is described from India. Its larva parasitizes larvae of Chlumetia transversa (Walker), a pest of Mangifera indica. Eggs are laid on the integument of the host larva. Newly emerged fly larva enter the host and develop by consuming the host's internal tissues. Pupariation normally takes place within the host's empty skin.

A seed-feeding weevil, Melanterius servulus Pascoe, is considered suitable for release against the weed Paraserianthes lophantha. However, host specificity tests have indicated that M. servulus may also develop on the seeds of Acacia mearnsii (black wattle), which is both a weed and a crop plant in South Africa. Seed orchards, which supply the black wattle industry, may therefore need to be protected. The aim of this study was to determine whether the two pyrethroid insecticides presently used in wattle plantations against the wattle bagworm (Kotochalia junodi Heylaerts (Lepidoptera: Psychidae)) are effective against M. servulus. Since M. servulus has not yet been released in South Africa, field trials were not possible, and evidence that black wattle seed orchards can be protected from M. servulus was obtained indirectly, in two stages. Firstly, field trials showed that the two insecticides effectively protect the weed Acacia longifolia from a closely related weevil, Melanterius ventralis Lea, which has already been established as a biocontrol agent. Secondly, quarantine laboratory trials demonstrated that M. ventralis and M. servulus showed similar avoidance responses and similar levels of mortality when exposed to the insecticides. All the evidence indicates that the chemical protection of A. mearnsii seed orchards from M. servulus is possible.

The development and longevity of Amblyomma triguttatum triguttatum Koch were studied at temperatures of 15, 20, 25, 30, 35 and 40°C, and humidities with water staturation deficits of 2–3, 8–9 and 16–17 mm Hg. No stage developed at 40°C and the engorged larva was the only stage able to develop at 15°C. The rate of development was inversely related to temperature, with the exception of the pre-oviposition period of the engorged female which was longer at 35°C than at 30°C. The egg was the most vulnerable stage to high saturation deficit (low humidity) but some did survive in constant conditions of 16–17 mm Hg, showing an adaptation to harsh environments; A. t. triguttatum survives in a semi-desert habitat. The longevity of the unfed stages increased from the larvae, nymphs to adults. The longevity decreased with increase of temperature and decrease of humidity with the exception of adults maintained at 30°C and 16–17 mm Hg, which had a longer viability to the same saturation deficit at 20°C (50% mortality) and 25°C (50% and 100% mortality).

The cuticular hydrocarbon profiles of wild caught, male Phlebotomus argentipes Annandale & Brunetti from Kandy, Sri Lanka, and Calcutta, India, were significantly different. Using discriminant functions based on three peaks from a gas-liquid chromatogram, 89% of specimens were correctly allocated to their parent sample. These results correlate with previously reported morpho-metric differences in this species from different parts of its range. Following laboratory colonization of the Kandy strain, the cuticular hydrocarbon profiles showed a progressive change, so that wild-caught and F5 generations could be completely distinguished by discriminant function anaysis, with the F1 and F 2 as intermediates.

In a field of six hectares, the number of palms foraged by Anoplolepis custodiens (Smith) increased from January to December 1988 from 32 to 85% and the ant activity scores (0–3 system) from 0.5 to 2.0. During the same time, the population of the coconut bug, Pseudotheraptus wayi Brown (Heteroptera: Coreidae) as well as the damage it caused, decreased significantly. A significant relationship between low percentages of damaged nutlets and high ant scores of the palms could be established. The nut set of ant foraged palms was 2–3 times higher than that of comparable palms in an immediately adjacent field free of A. custodiens. Palms with high A. custodiens scores had invariably high scores of the coconut aphid, Cerataphis variabilis Hille Ris Lambers (Homoptera: Aphididae). The performance of the palms was not visibly affected by the aphids.

A significant relationship between pteridine content of the head, fly age and fly size, which was independent of temperature, was found for adult females of Simulium sirbanum Vajime & Dunbar using flies maintained at different constant temperatures after eclosion. Similar relationships for flies maintained at varying temperatures within the species' natural ranges were obtained in experiments with the Beffa form of S. soubrense Vajime & Dunbar (sensu Post, 1986), S. sanctipauli Vajime & Dunbar (= S. soubrense sensu Post, 1986), S. squamosum (Enderlein), S. yahense Vajime & Dunbar and S. damnosum sensu stricto. Common slopes for the effects of age and size could be fitted to all these species. Relations between pteridine concentration in the head, fly size and age, with the common slopes but with species-specific intercepts, were used to estimate the age structure of wild-caught populations of the Beffa form of S. soubrense, S. squamosum and S. yahense. A dry season sample of S. squamosum was estimated to be older than a wet season sample. The mean age of the S. soubrense population, sampled one week after its presumptive breeding sites were treated with larvicides, was estimated to be 13.5 days. The maximum was 30.9 days and a frequency distribution of the estimates had distinct peaks, at three day intervals between 8 and 21 days. The significance of the results is discussed in relation to fly longevity and gonotrophic cycle lengths.

The osmolality and ion concentrations in the haemolymph and the body of lepidopterous larvae were studied under different experimental conditions. It was shown that the haemolymph osmolality of Aglais urticae (Linnaeus) larvae returned to normal three hours after the injection of 0.4 M sucrose or 0.4 M sodium chloride, despite the fact that in the latter case, the level of sodium was very high (to 53.1 mM vs 4.5 mM in control). The injection of 0.2 M or 0.4 M sodium chloride did not induce significant changes in the concentration of ions, other than sodium, in haemolymph. Treatment of Mamestra brassicae (Linnaeus) larvae with insecticides (DDVP, lindane, decis) led to a fast loss of body weight (up to 30%). This was due to dehydration, which was accompanied by a significant decrease of potassium content in body tissue, but not in the haemolymph. Study of the haemolymph parameters of Lepidoptera and insects taken from their natural environment indicates that the lowest values of variation coefficient related to osmolality and to the concentration of the dominant cation of the haemolymph (sodium, potassium or magnesium). These data suggest effective regulation of osmolality and ion concentration in the insect haemolymph.

Incubation of eggs of the African migratory locust, Locusta migratoria migratorioides (Reiche & Fairmaire), was examined in the Orange Free State (OFS) highveld of South Africa where the locust is a recurring pest of cereal crops. A minimum incubation time of 16±SE 0.97 d was recorded in summer and this progressively increased through autumn as temperatures declined. Eggs laid in autumn overwintered for 140±2.63 d until spring, when rising temperatures initiated hatching. Controlled laboratory studies established that the threshold for egg development was in the region of 15.6°C and that eggs required 5268 degree-hours to complete their development. Analysis of hourly soil temperature records, measured at egg pod depth in the field, showed that temperatures first dropped below this critical temperature threshold during mid-April, after which eggs became quiescent and overwintered until spring. There was no evidence of diapause in the field and overwintering eggs exhibited a wide range of embryonic development. Quiescence during winter on the OFS highveld was therefore a simple temperature-induced response. This is the first record of prolonged overwintering in the egg stage of the migratory locust in Africa.

A range of techniques was used to quantify the nocturnal flight behaviour of Helicoverpa armigera (Hübner) in pigeon pea (Cajanus cajan) crops near Hyderabad, in central India. These included visual observations in the field, the use of field cages and a vehicle-mounted net, optical and video imaging in the infra-red, and radar. Moth emergence from the soil was observed to start at dusk and recruitment continued steadily throughout the first half of the night. Little activity was observed in moths on the night of emergence, except for weak flying or crawling to daytime refuges. Flight activity of one-day old moths started about 20 min after sunset, peaked 15 min later and within about an hour of sunset had declined to a low level which persisted for the rest of the night. Flight of reproductively mature moths was most frequent about 1 h after sunset and at this time mainly comprised females searching for oviposition sites and nectar sources. By about 2 h after sunset, flight had decreased markedly, but there was a slight increase in activity in the second half of the night caused by males undertaking mate-finding flights. Under the conditions studied, the majority of H. armigera dispersed below 10 m, and there were no mass ascents to higher altitudes like those observed at outbreak sites of the African armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae). The contrasting migratory strategies of H. armigera and S. exempta are briefly discussed.

Heifers were treated with the recommended doses of ivermectin: 0.2 mg/ kg bw by subcutaneous injection or 0.5 mg/kg bw by pour-on. An analytic procedure is described and used for the detection of ivermectin residues excreted in dung. A large amount of the higher pour-on dose was excreted during the first five days after dosing due to a more rapid distribution to intestinal contents. Later faecal concentrations after the pour-on treatment were lower than those found after subcutaneous injection. No degradation of ivermectin was detected in pats exposed in the field for up to 45 days. Ivermectin excreted in dung voided 1–2 days after both treatments significantly reduced the number of dung inhabiting larvae of Aphodius spp. (Coleoptera: Scarabaeidae), but no effect was seen in dung deposited 13–14 days after treatments. Development of cyclorrhaphan larvae was inhibited in dung deposited up to 28–29 days after subcutaneous injection treatment, but only inhibited in dung deposited up to 13–14 days after pour-on treatment. The numbers of Nematocera larvae were not affected. In a laboratory bioassay the Diptera Musca autumnalis DeGeer and Haematobia irritans (Linnaeus) suffered higher mortality in dung from heifers treated by the subcutaneous injection 13–14 days earlier than in dung from heifers treated by pour-on at the same time. After subcutaneous injection, a significant reduction in the rate of decomposition was found in dung from heifers treated 1–2 days earlier, whereas pour-on led to a delayed decomposition in dung collected up to 13–14 days after treatment.

Avermectins administered to cattle for control of parasitic infections by injection or slow-release bolus are excreted in the faeces and have a variety of harmful effects upon Diptera and Coleoptera that develop in cow-pats: these effects are reviewed. Diptera Cyclorrhapha are severely affected, the extent of the response depending on the drug concentration in the dung. At high levels, larvae are killed or paralysed while at lower levels their metamorphosis is inhibited. At very low levels, adult emergence is reduced and a significant number of imagines show morphological abnormalities. These responses are induced by concentrations of avermectins well below levels occurring in faeces after routine treatment. Diptera Nematocera are less sensitive than Cyclorrhapha but larval and pupal development are affected at higher dose levels. Larval dung beetles and some immature adults cannot survive in the pats of recently dosed livestock. Mature adult beetles are more resistant, but contact with treated dung leads to impaired reproduction. Dung eliminated up to 5 weeks after cattle have been treated with a single injection or up to 14 days after topical dosing shows harmful activity against dung insects, and ivermectin-containing pats retain much of their toxicity after several weeks exposure on pastureland. The impact on dung insects is more pronounced and of longer duration when ivermectin is delivered daily at 40 μg per kg cow by sustained-release bolus. Following topical or injection treatments, the rate of cow-pat degradation (measured by actual loss of biomass) is significantly delayed. When cattle are treated with a bolus delivering 40 mg ivermectin per kg cow per day, their dung remains intact on grassland for at least three months. The conclusions drawn from the various papers on these effects are compared and contrasted. In particular, attention is drawn to the general failure to recognize the importance of delayed reactions to non-lethal doses of avermectins, and to our lack of consideration of long-term consequences for cow-pat insects and the wider implications for ecology.

The taxonomic identity and synonymy of four serious fruit fly pests, one of olives in Europe, and three Oriental species, two associated with citrus fruits and one with cucurbit fruits and vegetable, is clarified. Polistomimetes Enderlein is a new synonym of Tetradacus Miyake, which was originally described as a subgenus of Dacus, but is newly placed as a subgenus of Bactrocera. Heterodaculus Hardy is removed from synonymy with Polistomimetes. Mellesis citri Chen is a new synonym of B. minax (Enderlein); D. cheni Chao is a new synonym of B. tsuneonis (Miyake); and D. nubilus Hendel is replaced in synonymy with B. tau (Walker). Callantra splendida Perkins and D. discipennis Walker are transferred to the genus Bactrocera Macquart. The limits of the subgenera B. (Daculus) and B. (Tetradacus) are discussed; it is concluded that oviscape form separates those subgenera. B. (Daculus) includes the olive fly, B. oleae (Gmelin) and B. (Tetradacus) includes the Oriental citrus flies, B. minax (Enderlein) and B. tsuneonis (Miyake), plus three other species. It is also concluded that the presence or absence of anterior supra-alar setae and prescutellar acrostichal seatae should not be used in the diagnosis of Bactrocera subgenera. A lectotype of Polistomimetes minax Enderlein is designated.

The number of male tobacco budworm, Heliothis virescens (Fabricius), trapped on a daily basis in pheromone traps in individual cotton fields was compared to male and female adult densities measured by nocturnal field sampling. The decline of trap efficiency with increasing female density was demonstrated. A simple relationship for estimating H. virescens male density from the numbers trapped was derived as P♂ = (E2/13)2, where P♂ is density and E2 is the two-day exponential average of number trapped. The standard error for the regression translates to an accuracy ratio of 2:1. The results compare favourably with previous research using mark-release-recapture methodology. Application of the formula is discussed.