Wind tunnel studies were conducted on the influence of pheromone dose and wind speed on the response behaviour of the larger grain borer, Prostephanus truncatus Horn to its male-produced aggregation pheromone. The pheromone did not increase the proportion flying and non-optimal dosages reduced flight initiation. Beetles flew at progressively lower airspeed and net upwind velocity as the pheromone dose was increased from 0.02 mg to 4 mg. Also, at the higher doses, the latency of take-off was longer. However, at the intermediate dose of 0.2 mg, take-off latency was significantly shorter, and the proportion of beetles exhibiting phototaxis at this dose was at a minimum. Wind was necessary for the beetles' orientation to pheromone, supporting the pheromone-induced anemotaxis hypothesis. Flying beetles increased their airspeed and net upwind velocity and therefore flew faster at the higher wind speeds. These results suggest that pheromone dose and wind speed are major influences on the flight behaviour of P. truncatus, and the implications of this on the interpretation of field pheromone-baited trap catch data are discussed.

The insect growth regulator buprofezin was tested using a leaf-dip assay on immatures of Bemisia tabaci (Gennadius). The method was robust and repeatable, and baseline data were calculated for a laboratory strain and a number of field collections from Pakistan where the insecticide has not been used. A baseline LC50 of 0.53 ppm buprofezin was defined and compared to other field collections. Populations known or suspected to have been intensively selected with buprofezin showed substantial tolerance to the insecticide at both the LC50 and at specific diagnostic doses, with the highest resistance factor of 47 fold in a population from the Netherlands. Reasons for the variation between populations, biotypes and geographical areas are discussed and the dangers of human-assisted movement of resistance genes are highlighted.

The genus Stenobracon Szépligeti which contains species of economic importance for biological control of lepidopterous borers of sugarcane, rice and other graminaceous crops in Asia, is revised. Principal components analysis was employed to help delineate species. Six species, distributed from Pakistan to Australia, are recognized. Stenobracon brevis, S. clarus and S. malensis are described as new and Stenobracon nicevillei (Bingham), S. deesae (Cameron) and S. oculatus Szépligeti are redescribed. Illustrated keys for males and females are provided. Phanaulax levituberculatus Cameron is a new junior subjective synonym of S. nicevillei and S. trifasciatus Szépligeti is a new junior subjective synonym of S. oculatus. Elphea flavomaculata Cameron is synonymized with Ischnobracon (Bracon) laboriosus Cameron (comb. n). Host records are summarized.

Two experiments were conducted at Galana Ranch, Kenya, which examined, under natural conditions, the relationships between the number of tsetse flies (Glossina pallidipes Austen) attracted to cattle, the rate at which the cattle made defensive movements, and the feeding success of the tsetse. The most frequent defensive movements were skin ripples and tail swishes, while leg kicks were of intermediate frequency, and head and ear movements were infrequent. In one experiment, the rate of skin ripples, but no other type of defensive movement, was significantly correlated with the number of tsetse attracted to the cattle. The proportion of tsetse that engorged was significantly (P < 0.004) correlated with the rate of leg kicks, more weakly with the rate of head movements (P < 0.07), and uncorrelated with the rates of other types of defensive movement. In the second experiment, the rates of skin ripples, tail swishes and leg kicks were significantly correlated with the number of tsetse attracted to the cattle. The proportion of tsetse that engorged was again significantly correlated to the rate of leg kicks (P < 0.03), more weakly to the rate of head movements (P < 0.04), and unrelated to the rates of other types of defensive movement. In neither experiment was there a significant relationship between the number of tsetse attracted to the cattle and the proportion that engorged, suggesting that any density-dependent feeding success was too weak to be detected. In experiment 1, the relative fat content of the male G. pallidipes that fed decreased as the rate of leg kicks increased, suggesting that when hosts are more active the sub-sample of tsetse that feed, out of those that approach, is both smaller and hungrier. There was no detectable effect of host defensive behaviour on the bloodmeal size of male G. pallidipes.

Salivary oxidation has been hypothesized as a possible means by which spotted alfalfa aphid (Therioaphis trifolii maculata (Buckton)) deals with deleterious phenolics in the susceptible host plant, lucerne (Medicago sativa). In this study, some basic questions about this hypothesis were examined. Constitutive flavonoids and a crude phenolic extract from lucerne leaves were shown to be deterrent to the aphid in a choice test. Phenolics were oxidized by phenoloxidase in the saliva of the aphid. Fresh sap expressed from aphid-infested, oxidatively-reactive leaves was phagostimulatory to the aphid, compared to that from non-infested healthy leaves. Oxidative reaction was responsible for at least part of the phagostimulation, since addition of ascorbic acid into the sap deleted the phagostimulatory activity. Ascorbic acid was itself not deterrrent and its titre decreased in leaves after aphid feeding. The results provide further information on the Oxidative interaction between spotted alfalfa aphid and lucerne plants and support the previous suggestion that oxidation of phenolics and anti-oxidation by reductants affects feeding activity of this aphid.

The foraging behaviour of the redlegged earth mite, Halotydeus destructor (Tucker), in annual pasture was documented and the relative numbers of individuals foraging on subterranean clover, Trifolium subterraneum (Leguminosae), capeweed, Arctotheca calendula (Compositae) and grasses (mainly Lolium rigidum (Gramineae)), estimated in winter and spring in south-western Australia. The main feature of H. destructor foraging behaviour was the presence of aggregations ranging in size from 3–36 individuals on the adaxial surfaces of the upper canopy of the pasture. Most aggregating individuals were feeding, while most solitary and paired individuals were searching. There was no evidence that individuals aggregated for reproductive behaviour; the adult sex ratio was similar to that of the population even though immatures were under-represented in aggregations. During winter the distribution of numbers of H. destructor on subclover, capeweed and grasses in the upper canopy of pasture was similar to the estimated ground cover of these plant species. However, individuals showed host-plant selection for subclover when feeding. During spring, when the pasture plants were flowering, there were more H. destructor in capeweed flowers than in aggregations on subclover foliage. The capeweed flowers were shown to enhance the rate of H. destructor reproduction in a laboratory experiment. Most H. destructor were on or near the soil surface, with 10% at any one time on the upper canopy of the pasture. H. destructor is polyphagous, and behaved in pasture as a selective opportunist feeder.

The ovipositional behaviour of the mirid predator Macrolophus caliginosus Wagner, a potential biological control agent of glasshouse pests, was studied in detail using a modified video camera technique. In the laboratory, females laid their eggs in the leaves of tobacco plants. They remained generally motionless on the main veins of the leaves, raised their body, folded the rostrum towards the thorax and extended their ovipositor when selecting a site in which to oviposit. The ovipositor was inserted into the plant tissue by a downward and forward thrust of the body and contractions of the abdominal muscles. After a period of immobility, the ovipositor was retracted and the insect's body and organs returned to their initial positions. This behaviour was preceded and followed by extensive rostral exploration of the oviposition site. In most females the same area was explored before and after egg-laying and the ovipositor was inserted approximately in the middle of the selected area. The sequence and pattern of ovipositional behaviour varied between females.

An estimate of the inbreeding coefficient, FIS, of the coffee berry borer, Hypothenemus hampei Ferrari, was calculated from genotype frequencies of endosulfan resistance in beetles collected from berries in 41 different fields on the East Coast of New Caledonia. Two different estimates were obtained as a function of sampling date: FIS=0.491 ± 0.059 (s.e.) for samples collected in September, and FIS=0.215 ± 0.108 for samples collected in April. These values of FIS are very high in comparison to those of most insects, but surprisingly low given current understandings of H. hampei mating patterns. The difference between April and September FIS estimates is discussed in terms of insecticide regimes and seasonal variability of sib inbreeding levels. The high level of inbreeding in the coffee berry borer increases frequencies of homozygotes relative to heterozygotes. Inbreeding will accelerate resistance evolution whenever the fitness of homozygous resistant insects exceeds that of heterozygotes, and will undermine any high-dose strategy to control resistance evolution.

During translocations of black rhinoceros (Diceros bicornis Linnaeus) in Kenya, we studied the relationships between the rhinoceros and biting flies. In trapping experiments, rhinoceros waste products (urine or dung) were substituted for known attractants such as cow urine, l-octen-3-ol or acetone. Catches of Glossina pallidipes Austen, Glossina longipennis Corti, Stomoxys spp., and Haematopota spp. were not affected by these substitutions. NG2G and Vavoua traps sited near captive animals caught similar numbers and kinds of flies as traps set without animals. Any minor attractive properties of rhinoceros odours were probably due to the presence of known attractants such as 4-cresol and 3-n-propylphenol, which were confirmed to be present through gas chromatography—mass spectroscopy. In feeding trials with laboratory-reared tsetse, Glossina brevipalpis Newstead and Glossina morsitans centralis Machado fed well on immobilized animals, whereas G. longipennis fed reluctantly. Catches of G. brevipalpis were doubled in one trapping experiment when rhinoceros urine was used as odour bait. Philoliche spp., Haematopota spp. and other Tabanidae fed on captive rhinoceroses. Many species of Stomoxyinae were associated with rhinoceroses. Of these, the most frequent association was with Rhinomusca dutoiti Zumpt, a species found previously only in South Africa. Rhinomusca dutoiti was found in two highland rhinoceros sanctuaries, Nairobi National Park and Solio Ranch Game Reserve.

The spectral sensitivity of the compound eye of the cabbage root fly, Delia radicum (Linnaeus), was measured using the electroretinogram (ERG) technique, at fifteen selected wavelengths between 340 nm and 670 nm. The form of the ERG was found to be diphasic in nature. A primary peak of spectral sensitivity in the UV (340–350 nm), and a smaller secondary peak in the blue-green region (460–546 nm) were found, together with a shoulder of sensitivity, representing a ‘pseudo-peak’ as reported for other Diptera, in the red region (630 nm). No significant differences were found between the dorsal and ventral regions of the eye. The peak response in the green region (546 nm) agrees well with existing behavioural data on colour attraction and visual discrimination of host plants by the cabbage root fly.

Adult Bemisia tabaci (Gennadius) were tested with imidacloprid in a bioassay method using systemically treated cotton leaves. The method was simple, robust and repeatable and provided baseline data for a laboratory and a number of recently collected field strains. The LC50 for imidacloprid susceptible strains was calculated to be 1.7 ppm and a concentration of 16 ppm determined as diagnostic for imidacloprid resistance. Ten strains of B. tabaci collected from the Almeria region of Spain showed significantly less mortality at the diagnostic dose than the susceptible strains. The intensive use of imidacloprid in the Almeria region is considered the reason for the occurrence of resistance in this locality. Resistance to organophosphates, pyrethroids and endosulfan in B-type and non-B type B. tabaci did not confer resistance to imidacloprid.

Rainfall records for 23 years at 21 selected stations in Kenya were summarized and compared with the numbers of outbreaks of armyworm Spodoptera exempta (Walker) reported in the following season. The numbers of outbreaks were found to be negatively correlated with the rainfall of the 6–8 months preceding the start of the season. Stations in south-eastern Kenya, including the coastal belt which harbours the most extensive off-season source populations of S. exempta, were identified as key stations for forecasting whether to anticipate local or countrywide armyworm outbreaks next season. A scheme is suggested that would enable a provisional forecast to be made as soon as the long rains (April–May) rainfall records were available, and confirmed or revised subsequently in the light of the June–October rainfall at stations in south-eastern Kenya.

Previous studies have shown the sandfly Lutzomyia evansi to be the vector of Leishmania chagasi in northern Colombia. A longitudinal survey during seven months on the host preference of Lutzomyia evansi was conducted in the visceral leishmaniasis focus of San Andrés de Sotavento, Colombia. Host preference was determined by presenting sandflies with a choice of three baits (human, and the reservoirs dog and opossum) and a blank control in specially designed cone traps. A rotational experimental design involved 56 trap nights in which the effect of bait, proximity to forest and season could be distinguished from the potentially confounding factors of site and day to day variation. From a total of 598 sandflies caught during all experiments, females and males of Lutzomyia evansi accounted for 93.8% of the captures in the baited traps. Overall, human attracted the greatest number of sand flies, followed by the other two baits. Attraction and feeding success showed significant differences (P < 0.0001) between baits.

Laboratory nests of the leaf-cutting ant Atta sexdens rubropilosa Forel fed daily with leaves of Ricinus communis showed a gradual decrease in fungal garden volume, a higher ant mortality rate, and fungal garden extinction after 6 weeks. The mean oxygen consumption rate of these ants was higher than that of control ants collected from nests fed with leaves of Eucalyptus alba (Myrtaceae) suggesting one or more components of the leaves of R. communis had a direct physiological effect on the ants, in addition to inhibiting fungal garden growth.

Twelve strains of German cockroach, Blattella germanica (Linnaeus) were collected from various locations in Peninsular Malaysia and tested for their susceptibility to three groups of insecticides applied topically. The levels of resistance were low to high (2.8 to 92x) for carbamates (propoxur and bendiocarb), low (2.0 to 7.6x) for organophosphate (chlorpyrifos) and low to moderate (1.0 to 23x) for pyrethroids (cypermethrin and permethrin) when compared to a susceptible strain. Five strains, resistant to both cypermethrin and permethrin, were also resistant to DDT, phenothrin and deltamethrin. Propoxur resistance in ten strains was suppressed with the synergists, piperonyl butoxide (PBO) and S,S,S-tributylphosphorotrithioate (DEFR), suggesting monooxygenase and esterase involvement in the resistance. However, the levels of resistance for cypermethrin and permethrin were not affected when using either PBO or DEFR.

Field strains of housefly collected from animal units were exposed to the insecticide baits, Golden Malrin and Alfacron in laboratory cage tests. Flies were exposed to each bait alone in no-choice tests and to the bait plus sugar in choice tests. Golden Malrin was generally effective against the strains tested in no-choice tests; the lowest recorded knockdown after exposure for 48 h was 82%. Eight strains, however, gave a reduced knockdown when exposed in choice tests (between 60 and 87%). Golden Malrin was ineffective against one strain in choice tests with 7% knockdown at 48 h. With Alfacron 12 strains exhibited knockdown responses between 57 and 87% at 48 h in no-choice tests. In choice tests, 17 strains gave knockdown responses of less than 50% at 48 h. Correlation coefficients were calculated for results from cage tests and levels of resistance to the active ingredients assessed using topical application and feeding test methods. There was a positive correlation between cage and feeding test results. Correlation was, however, less significant with choice test results than with no-choice results. There was no correlation between cage test and topical results. It is suggested that behavioural resistance was responsible for the reduced responses shown by some strains in choice tests compared to no-choice tests. The results demonstrate the importance of using a laboratory method which allows for behavioural differences when monitoring for resistance to insecticides formulated as baits. Behavioural differences in housefly strains should be considered when testing the efficacy of new bait formulations. It is also suggested that insecticide baits should not be used continuously and exclusively to control houseflies in intensive animal units.

The cibarial armatures of Anopheles albitarsis Lynch Arribálzaga, A. aquasalis Curry, A. bellator Dyar & Knab and A. homunculus Komp are described for the first time. Ten to 15 minutes after blood feeding, higher levels of blood haemolysis were observed among A. bellator (14.9%) and A. homunculus (14.0%) mosquitoes which possessed type C cibarial armatures than among A. albitarsis (3.3%) and A. aquasalis (3.2%) which possessed type B cibarial armatures. In contrast, there were no significant differences among the four species in levels of extra-erythrocytic haemolysis when measured immediately and after one hour. The blood processing physiology observed for the four anopheline species is discussed at the enzymatic, mechanical and taxonomic levels as it relates to innate vector competence.

Based on the fact that in haematophagous Diptera, the basal bodies, groups of six to nine specialized epithelial cells in the calyx wall within the ovariolar sheath, become granular after ovulation, a method for rapidly determining parity of the females has been developed. After supravitally staining intact ovaries with fresh neutral red solution in physiological saline (1:3000–1:5000) for one to three minutes, granular basal bodies in parous females can be clearly recognized under a stereo-microscope or a compound microscope with a raised condensor. The advantages of the method are its speed, accuracy and simplicity.

Trajectory analysis of the windfields at 10 m and 1.5 km was used to determine the direction and extent of windborne movements of insects trapped in spring and summer in south-eastern and eastern Asia for the period 1968 to 1985. Approximately 2500 trajectories, depicting the movements of airborne particles, were constructed where temperatures were high enough (>=10°C) to allow flight and where wind speeds (> =5 kmh−1) were expected to lead to downwind displacements. Trap catches were dominated (97%) by delphacid species (e.g. Nilaparvata lugens Stål and Sogatella furcifera (Horváth)), with Cicadellidae (1.1%) and Diptera (0.7%) as the next most numerous. Very few Lepidoptera were reported. Most trajectories were less than or equal to 40 h in duration. The previously recognized northwards migration along a broad front in prevailing Summer Monsoon and Trade winds was confirmed, as was the important role of frontal depressions in the windborne migration of insects in temperate areas. Nearly 50% of the trajectories were constructed in mobile weather systems which both disturbed and strengthened the prevailing winds and led to pronounced differences in the direction and distance of sources for insects caught at any catching site. Similarly, fluctuations in position of quasi-stationary fronts induced considerable mixing of populations from different sources and influenced the northern extent of each phase of rice pest migration. The results supported earlier findings that migrations occurred between the tropics and temperate areas during the spring and summer, but also indicated that migrations within the tropics at this time of year were a more frequent occurrence than had been considered previously.

The Kerala isolate of Oryctes baculovirus (OBV-KI) was introduced into the Andaman Islands in May 1987 for the population suppression of Oryctes rhinoceros (Linnaeus). The virus was released initially at four locations along the island chain. In all the places of virus release, damage to coconut palms was reduced by about 90% within 43 months of release. At one place of virus release, Sipighat, the adult beetle population in the field was reduced by 80% within 18 months and by 96% by the end of 55th month of release. Sixty per cent of the adult beetle population in the field showed symptoms of infection 30 months after virus release. The decline in the numbers of breeding sites at Viper Island and Sipighat were 100% and 98% respectively at the end of 43 months of virus release. The rate of spread of the virus in the field was estimated to be about 1 km/month. The beetle population remained at low levels after the establishment of the virus in these islands.