Chrysomya megacephala (Fabricius) is shown to be a principal cause of loss of salted-dried fish in south-east Asia. Field and laboratory work conducted in 1982–1989 was aimed at reducing these losses. Field work at a small–scale fish processing site in Cirebon, West Java, showed that fully gravid C. megacephala females were highly differentially attracted to fish at the salting stage, which means that the salting tanks must have properly designed fly-tight lids to prevent infestation. C. megacephala counts and ovary examinations showed that females with various stages of immature ovaries (stages I–IV) were predominent during the drying stage after the fish had been removed from the salting tanks, with numbers usually greater on the first day of drying than the second. C. megacephala counts were high during the dry season, although numbers fluctuated enormously depending on weather, among other factors. Physically screening fish during the initial drying period effectively controlled infestation, although problems associated with the screen design were identified. In laboratory cultures adult sex ratio was approximately 1:1 and longevity in both sexes, over three generations, ranged from 47 to 55 days (maximum induced longevity, 98 days) at c. 29°C, 30–60% r.h.; under similar conditions, 10% of females had mature (stage V/VI) oocytes after one week, 40% after two weeks and 90% after three weeks. Mean number of ripe oocytes in gravid flies was 221 (range 151–228).

Aponephus lentiformis, a new genus and species of Coccinellidae, is described from southern India and placed in the tribe Scymnini. It was found during searches for natural enemies of Rastrococcus spp.

Tick populations were observed on zebu cattle (Bos indicus) over an 18 month period at Patiko in northern Uganda. Monthly collections were made of all stages of ticks from five cattle and six sheep (Ovis aries). Collections of adults of Rhipicephalus appendiculatus Neumann were also made from the ears of about 30 cattle on several occasions. The species recorded on cattle, in order of decreasing abundance, were R. appendiculatus, Amblyomma variegatum (Fabricius), Boophilus decoloratus (Koch) and R. evertsi evertsi Neumann. Far fewer ticks were collected from the sheep. The adults of R. appendiculatus were randomly distributed over the herd. There was a distinct seasonal incidence of R. appendiculatus and A. variegatum on their hosts, which could be related to rainfall and to the emergence of new cohorts during the long rainy season. In addition, adult females of R. appendiculatus were collected daily off the ears of cattle at Entebbe following an infestation with 200 adult males and females. Measurements of the growth of the ticks were used to define the sizes of ‘standard’ ticks which would complete engorgement in the following 24 h. Such ticks provide a means of sampling to estimate the number of ticks engorging daily. Comparison of the frequency distributions of each stage and species in the Patiko collections were then used to infer the sizes of standard ticks for other species.

Chlorphoxim resistance is found in forest strains of Simulium sanctipauli Vajime & Dunbar, in some areas of the Onchocerciasis Control Programme in West Africa. There is an increase in esterase activity in both adults and larvae in the resistant compared to the susceptible strain with the general esterase substrate 1-naphthyl acetate. This appears to be associated with the temephos and chlorphoxim resistance which are found in the same resistant strain. It is possible that one or more esterases are qualitatively and/or quantitatively changed in the resistant strain compared to the susceptible. Preliminary studies indicated that esteratic hydrolysis and oxidative cleavage were both involved in chlorphoxim metabolism in S. damnosum Theobald sensu latu. There was evidence of an increase in detoxication by both these routes in the resistant compared to the susceptible strain of the cytospecies S. sanctipauli. The increase in oxidative detoxication seen in the resistant strain was associated with a slight, but non-significant increase in cytochrome P450 as measured by the sodium dithionite reduced carbon monoxide difference spectra.

Lactic acid, carbon dioxide and human sweat stimuli were presented singly and in combination to female Aedes aegypti (Linnaeus) within a wind-tunnel system. The take-off, flight, landing and probing responses of the mosquitoes were recorded using direct observation and video techniques. The analyses determined the nature of the response to different stimuli and the concentration ranges within which specific behaviours occurred. A threshold carbon dioxide concentration for taking-off of approximately 0.03% above ambient was detected. Lactic acid and human sweat samples did not elicit take-off when presented alone, however, when they were combined with elevated carbon dioxide, take-off rate was enhanced in most of the combinations tested. Flight activity was positively correlated with carbon dioxide level and some evidence for synergism with lactic acid was found within a narrow window of blend concentrations. The factors eliciting landing were more subtle. There was a positive correlation between landing rate and carbon dioxide concentration. At the lowest carbon dioxide concentration tested, landing occurred only in the presence of lactic acid. Within a window of low to intermediate concentrations, landing rate was enhanced by this combination. At the highest carbon dioxide concentration, landing was however inhibited by the presence of lactic acid. The sweat extract elicited landings in the absence of elevated carbon dioxide. This indicated the presence of chemical stimuli, other than lactic acid, active in the short range. Probing occurred only at low carbon dioxide concentrations and there was no probing when lactic acid alone was tested. There was however probing in the presence of combined stimuli, the level of response seemed to be positively correlated with the ratio of carbon dioxide and lactic acid concentrations.

Ovarian ages were obtained for tsetse flies Glossina morsitans morsitans Westwood and G. pallidipes Austen caught in Zimbabwe using a stationary bait ox, an odour-baited trap in the presence or absence of humans, a mobile ox fly-round and a vehicle-mounted electric net. The biggest daily catches were obtained from the electric net and the unacccompanied trap, but while for G. m. morsitans the ratio of the catches from these two methods was 7:1, for G. pallidipes it was 0.7:1. Evening catches were 1.3–5.5 and 2.9–18.8 times higher than morning catches for the two species, respectively; the differences were greater for stationary than for mobile baits. The sample age structures differed significantly (P < 0.05: x2) between methods in six of the ten possible contrasts between pairs of methods in G. m. morsitans and for all ten in G. pallidipes. The differences in age distribution and mean catch levels are attributed to increases in flight activity with age; at each age G. pallidipes is more active than G. m. morsitans. Man's presence in the trapping system reduced catches significantly (P < 0.05: t test) but this effect was small in the youngest and oldest flies. Odour-baited traps are biased in favour of G. pallidipes and, for both species, in favour of older flies; mortalities calculated from age distributions of trap samples therefore underestimate the true value.

The arthropod community associated with irrigated rice grown in five sites in Luzon Island, Philippines, was analysed using guild categories. Phytophages and predators were predominant in all sites. The phytophage species were mainly Homoptera and dominated by Nephotettix virescens (Distant), N. nigropictus (Stål) (Cicadellidae), and Nilaparvata lugens (Stål) and Sogatella furcifera (Horváth) (Delphacidae). Predators were mainly Heteroptera with Microvelia douglasi atrolineata Bergoth (Veliidae), Mesovelia vittigera (Horváth) (Mesoveliidae), and Cyrtorhinus lividipennis Reuter (Miridae) as the most abundant species. Spiders were the next dominant group with Pardosa pseudoannulata (Böesenberg & Strand) and three species of Tetragnatha the most common. Differences in species diversity between the sites were easily differentiated using diversity indices. The relative differences in arthropod abundance, species richness and diversity may be attributed to the median temperatures, cropping patterns, and diversity in crop stages and germplasm in the sites. Predator-Homoptera correlations were significant in all cases. High positive correlations were obtained for veliids, spiders and Cyrtorhinus lividipennis, in most sites.

The pattern and cause of mortality of the early stages of Helicoverpa armigera (Hübner) on cotton was investigated in both field and glasshouse situations for two seasons. In 1987, egg losses were high (32–88%) over days 1–3 following oviposition, more so from the lower than upper leaf surface. The mortality of first instar larvae was 93–100% over days 4–5 following oviposition, and losses were higher from seedling stage than squaring cotton. Wind, rain (or watering), aerial predators, dispersal of first instar larvae, and host plant effects (including leaf orientation) were important mortality factors. In 1988 trials, egg losses over days 1 to 3 after oviposition on plants in glasshouse and field situations, respectively, were 0–1% and 5–6% due to changing leaf orientation alone; 4–22% and 16–32% due to rain/watering and changing leaf orientation combined; 14–31% and 12–31% for wind and changing leaf orientation combined; and 4–38% and 23–52% for the combination of wind, rain/watering and changing leaf orientation. Mortality of first instar larvae on day 4 was 32% and 29% on plants in glasshouse and field, respectively, from which the action of such mortality factors had been excluded. Mortality on plants with changing leaf orientation alone was 30% and 68%, with rain/watering and changing leaf orientation combined 48% and 74%; with wind and changing leaf orientation combined 40% and 63%; and with all factors combined 45% and 69%, respectively. The highest losses (of eggs) occurred on day 1 after oviposition, and similarly for first instar larvae on day 4, which coincided with hatching.

In Zimbabwe, cotton cloth dyed phthalogen blue attracted three times more Stomoxys spp. than Alsynite fibreglass panels. A single F3 trap caught nearly six times as many Stomoxys spp. as four Williams traps. The host odour component l-octen-3-ol (released at 0.6 mg/h) increased catches of Stomoxys spp. in an F3 trap (P < 0.05), but 4-methylphenol (0.7 mg/h) and 3-n-propylphenol (0.15 mg/h) did not (P > 0.05). Insecticide-impregnated targets did not appear to control a population of Stomoxys spp. attacking cattle. However, it is concluded that there is scope for the improvement of trapping and control systems for use against Stomoxys spp.

Dispersal of apterae from their natal plant was monitored for three aphid species (Myzus persicae (Sulzer), Brevicoryne brassicae (Linnaeus) and Megoura viciae Buckton), each on a different host plant. Some movement off the plant occurred even in the initial parental and second generations, when the plant appeared to be growing normally and when crowding was unlikely to be the cause. However, in most experiments the most marked increase in apterous dispersal coincided with a reduction or even cessation of plant growth. In nearly all the experiments this dispersal occurred when the population on the natal plant exceeded about 20 adults and their offspring per plant. The main emigrants were fourth instar apterae and prelarviposition adult apterae. The implications of this behaviour are discussed, and it is argued that apterous dispersal might be common in aphids, allowing a fuller utilization of the environment than would be likely by alate dispersal alone.

Rice plants, infested with eggs of Nilaparvata lugens (Stål) or Nephotettix spp. in laboratory cultures, were used to trap egg parasitoids in rice fields at two sites over a period of four days in Sri Lanka. Levels of egg parasitism per plant varied from 0 to 54% in N. lugens and 45 to 100% in Nephotettix spp. Egg predation was a minor cause of mortality, but attack by a species of Panstenon (Hymenoptera: Pteromalidae) killed up to 18% Nilaparvata lugens eggs. N. lugens eggs were parasitized by Anagrus sp. nr flaveolus Waterhouse, A. optabilis (Perkins) (Hymenoptera: Mymaridae) and Oligosita sp. (Hymenoptera: Trichogrammatidae). Nephotettix spp. eggs were parasitized by two species of Gonatocerus (Hymenoptera: Mymaridae) and one of Paracentrobia (Hymenoptera: Trichogrammatidae). There was no overlap in field host range between the two parasitoid assemblages. Gonatocerus spp. and Paracentrobia spp. seldom attacked the same Nephotettix sp. egg batch, suggesting the possibility that these species compete in the field. Overall egg parasitism of Nilaparvata lugens was positively related to host egg density at the spatial scale of the rice plant, but unrelated at the tiller or batch scale. Nephotettix spp. egg parasitism showed a negative density dependent relationship at the spatial scales of the tiller and plant and no relationship at the batch level. The potential role of these egg parasitoids in preventing outbreaks of hopper pests in Sri Lanka is discussed.

The thermal preference of adults of the reduviid bug Triatoma infestans (Klug) was investigated along a temperature gradient by means of video recording. The preferred temperature varied with a daily rhythm, reaching the highest value at the onset and the lowest at the end of the dark phase. The daily range of preferred temperatures depended on the starvation level. After feeding it was about 28–29°C, and after 12 days of starvation 25–26°C. The number of eggs laid showed a bimodal pattern, with maxima at 29°C and 26°C. Along a gradient of relative humidity, the bugs were always found around 40% r.h.

The parasitoid complex and apparent parasitism of Choristoneura murinana Hübner were investigated in relation to the relative abundance of budworm larvae at several sites in Europe. A single outbreak population was sampled, while other sites supported varying but much lower host population abundance. Sampling at Sion in Switzerland from 1984–89, indicated that the species richness of the parasitoid complex was correlated with relative host abundance and in general more polyphagous parasitoids were represented in sites with greater budworm abundance. Of the specialized parasitoids, Apanteles murinanae Čapek & Zwölfer (Hymenoptera: Braconidae) was dominant in less abundant host populations and both Cephaloglypta murinanae (Bauer) and Dirophanes maculicornis (Stephens) (Hymenoptera: Ichneumonidae) were supported only at greater budworm abundance. These findings are discussed in relation to the use of Choristoneura murinana parasitoids in the biological control of native Choristoneura spp. pests in other continents.

The coccinellid biocontrol agent Chilocorus nigritus (Fabricius) can be established on the non-target scale Asterolecanium sp. (Hemiptera: Asterolecaniidae) on giant bamboo Dendrocalamus giganteus. When these sites are adjacent to citrus orchards, the coccinellid readily moves across to reduce population levels of the target prey, red scale Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae). C. bipustulatus (Linnaeus) and C. infernalis Mulsant are potential new biocontrol agents against A. aurantii in South Africa. Each life stage of C. nigritus, C. bipustulatus and C. infernalis has advantages and disadvantages for field introductions. This paper investigates different methods of introduction of the different life stages for field establishment. A number of synthetic materials were tested as egg pads for C. infernalis without success. Introduction of eggs adhering to stiff paper cards was unsuccessful and impractical for all species. Eggs, young larvae (first and second instars), older larvae (third and fourth instars) and adult C. nigritus were introduced into stands of bamboo. The adult was the most suitable life stage for establishment followed by older larvae, then younger larvae, with the least suitable being the egg stage. Adults of the three species were released on to scale-infested bamboo at two sites to evaluate the viability of such introductions and to compare their persistence at these sites. C. nigritus and C. infernalis persisted at one release site through the winter and the hottest period of the summer.

From 1986 to 1989, the factors that determined the abundance of Metopolophium dirhodum (Walker) on cereals were studied in western Czechoslovakia. Forty seven sites were selected within cereal fields, mainly of winter wheat. Host plant size and leaf area varied between sites. The maximum abundance of M. dirhodum per tiller varied annually and with host plant stature. The main factor determining maximum abundance was the length of time for which the aphid population grew. M. dirhodum populations differed both in the time of the onset and termination of their growth. On stunted plants population growth started, with little variation, 200 day degrees later than on well developed plants. Within years, nearly all populations ceased growing simultaneously. In years of low or medium aphid abundance it was 40 to 90 day degrees earlier than in aphid outbreak years, and this extension of the population growth was the principal cause of the outbreak. Population growth rates varied slightly with plant quality and differed little between years. They were not important factors determining maximum abundances. 55–75% of the aphids occupied the flag leaves. The lower leaves of well developed plants were more heavily populated than nutritionally and water stressed smaller plants. The population growth rates on particular leaves were related to leaf nitrogen content, but not water content. A relationship for calculating the maximum abundances from a census made during the middle phase of population growth was proposed.

Toxoptera victoriae sp. n. is described from Hong Kong. The economic importance of the genus Toxoptera is discussed. Separate keys are provided to adult and first instar larvae of the species of Toxoptera.

Uscana lariophaga Steffan is an egg parasitoid of bruchid species in West Africa. The hosts are Callosobrucbus maculatus (Fabricius) and Bruchidius atrolineatus Pic, insect pests of stored cowpea. Experiments were carried out to study the selection between hosts of different ages and of different species in choice and no-choice situations. Results were obtained through parasitization studies and by direct behavioural observations. A description of the parasitization behaviour of Uscana lariophaga is given. At 30°C, C. maculatus eggs of 0–2 day old are readily accepted for parasitization, but in a choice situation the 0 day old eggs are preferred. Of the older eggs only those of 3 days old are parasitized but significantly less than those of 0–2 days. At 30°C, B. atrolineatus eggs older than 24 hours are significantly less parasitized than younger eggs also in the no-choice situation. When eggs are older than one day, the time needed for penetrating the egg increases with host age. Both bruchid species are suitable hosts for U. lariophaga. In a choice situation B. atrolineatus is the preferred host and especially so when U. lariophaga has been reared on this species. However, in a no-choice situation the highest rate of successful parasitization is obtained on hosts of the species from which they have been reared. The higher parasitization rate of C. maculatus in the field in Niger can be explained by the difference in the susceptible period between the two host species.

The effects of crowding and photoperiod during rearing of Mythimna convecta (Walker) on oocyte development in adult females were measured in the laboratory and field. Most larvae reared under isolated conditions in a Light 12 h: Dark 12 h photoperiod had mature oocytes within 72–84 h of eclosion. Females were slower to mature when reared under longer daylengths. The mean oocyte width in 3–10 days old females was significantly lower for moths reared under long (Light 16 h: Dark 8 h) than equal (Light 12 h: Dark 12 h) daylengths. Crowding of larvae also prolonged the pre-reproductive period. In the laboratory, 47% of females had arrested oocyte development of 3–6 days after eclosion and, in the field during late winter/spring, 48% of females required 3–9 days to mature. Larvae were collected from late spring/summer populations and caged under high and low density conditions. All females emerging from both treatments had arrested oocyte development of at least seven days. In catches from baited moth traps run over the same period, the proportion of immature female M. convecta was lower during spring (18–30%), than in summer (60%) and, in both seasons, mating commenced before oocytes had matured, but after oocyte arrest. Long daylength appears to be only one of several contributing factors causing delays in ovarian development during summer. Delays in achieving reproductive maturity, induced by either crowding or summer conditions, may assist M. convecta to emigrate from unfavourable habitats. This is particularly relevant in the winter rainfall areas of south-eastern Australia where most food plants senesce in summer and suitable habitats are usually confined to the coast.

Subperiodic filariasis (Brugia malayi) infections are endemic in the State of Sarawak, Malaysia, along the coastal villages and rural communities where the mosquitoes Mansonia bonneae Edwards, M. dives (Schiner) and M. uniformis (Theobald) are the main vectors. Two ecologically similar villages, Kampung Ampungan and Kampung Sebangkoi, were selected for comparison of the three Mansonia spp. in terms of their entomological baseline data, namely biting activity, survival and infective rates. Data obtained on their annual transmission potential (ATP), annual infective biting rate (AIBR) and vectorial capacity (C) showed M. bonneae to be the principal vector of B. malayi infections in Sarawak. Survival rates of M. bonneae and M. dives were estimated using both the exponential model of Macdonald which assumes an age-independent survival rate and the Gompertz model which assumes a decrease in the survival rate with advancing age of female mosquitoes.

In undisturbed annual pasture in a Mediterranean-climate region of Australia adults of the whitefringed weevil, Graphognathus leucoloma (Boheman), were present from summer to early winter (December–June), with upsurge in numbers of first instar larvae only occurring after the rains began in April. The G. leucoloma population was predominantly first instar larvae in high abundance throughout the winter period (May–August). Larval growth, with high mortality, occurred in the spring period (September–January). The survival of eggs during the dry summer when adults were most abundant, although only at times of unseasonal rainfall, indicated that low larval recruitment at that time resulted primarily from the absence of high-quality legume food essential for oogenesis. It was inferred that most larvae arose from heavy oviposition by the few adults present in autumn when rainfall germinated annual legumes. A steady year-round abundance of late-instar larvae indicated that not all individuals completed their development in the one year.