Egg production by two scarabaeine dung beetles, Onthophagus binodis (Thunberg) and Onitis alexis Klug, was measured in the laboratory in relation to seasonal changes in the characteristics of the cattle dung on which they fed. Dung was collected in two areas of south-western Australia monthly between September and May. Egg production was high on dung from green annual pasture from September to November and on green irrigated perennial pasture from December to May and low on dung from dead annual pasture from December to May. O. alexis was somewhat less affected by these seasonal changes in dung characteristics than Onthophagus binodis.

The chalcidoid parasites associated with galls on mango leaves and branches caused by Cecidomyiidae (mainly Procontarinia spp. in India) are taxonomically treated and keyed out. They include ten species belonging to five families (plus one treated elsewhere). The following taxa are described as new: in Torymidae, Mangostigmus gen. n. for Neomegastigmus amraeus Kurian; in Ormyridae, Ormyrulus gibbus gen. et sp. n.; in Pteromalidae, Gastrancistrus (Mangistrus subgen. n.) cherryi sp. n.; and in Eulophidae, Aprostocetus sankarani sp. n., Mangocharis longiscapus gen. et sp. n. and Chrysonotomyia obesula sp. n. The name Gastrancistrus mangiferae Subba Rao is placed in synonymy under G. muneswari Yadav. Two probable new synonymies are suggested under Chrysonotomyia.

The sensitivity of males and females of Glossina morsitans morsitans Westwood to the vapour phase of bisazir was tested in the laboratory in a moving air stream at temperatures ranging from 12 to 20°C. Similar tests were conducted in still air in closed systems. Bisazir was used in its granular form or absorbed onto silicone rubber or cellulose fibre surfaces from solution in dichloromethane. As a crystalline solid, it lost only 5% of its weight in a moving air stream over 12 days. However, even in relatively still air, bisazir absorbed onto cellulose fibre discs lost 70% of its weight at 20°C and 80% at 30°C in 24 days. Estimations of the amounts of bisazir present on a surface by weight difference were higher than those estimated by gas chromatographic analysis. Hence, in addition to being volatile, bisazir must be regarded as somewhat unstable. Nevertheless, sufficient active ingredient remained over a long enough period for it to be considered as a practical means of sterilizing tsetse in the field. Females were found more sensitive to bisazir than males, but exposure times required to produce total sterility in both sexes did not affect survival. Exposure times of only a few minutes were sufficient to induce a significant reduction in female fecundity or male fertility at 30–35°C, temperatures which might be expected under field conditions in a device to sterilize automatically tsetse attracted to traps in the field. The degree of sterility induced was permanent, and at these short exposure times the temperature had no effect on female fecundity.

There is a growing body of evidence to suggest that low density populations of Spodoptera exempta (Walker) in the solitary-phase can persist during the dry season in certain localities in eastern Africa. Moths were caught in simple pheromone traps for several months after the estimated dates of emergence of larval outbreaks in central Tanzania in 1980 and from 1982 to 1984. This provided evidence for the occurrence of a shifting population between the Uluguru Mountains and the swampy coastal areas, in east-central Tanzania, for a large part of the year. Central Tanzania is an important area for the development of the first outbreaks of the season in eastern Africa and for any control strategy. It has been suggested that S. exempta fits the criteria for an r-selected species. However, the low migratory capacity of low-density populations indicates rather that the species spreads out its risks in space and time. A theoretical genetic mechanism controlling the distance flown by moths may enable the species to exhibit both migratory and non-migratory strategies. Thus both ephemeral and continously favourable habitats may be exploited.

F2 traps of 53 different colours, selected from measurements of spectral reflectivities in the colour range visible to Glossina, were tested in a field study against G. morsitans morsitans Westwood and G. pallidipes Austen in Zimbabwe. Trap effectiveness depended mainly on reflectivity in four different wavelength bands, two of which, blue-green and red, were positively correlated with trap score; and two of which, ultraviolet and green-yellow-orange, were negatively correlated with trap score, the most important effects coming from the blue-green and green-yellow-orange bands. The ‘best’ trap material was a royal blue cotton, which reflected blue-green strongly but very little ultraviolet or green-yellow-orange. This material together with the lowest-scoring colours (green and yellow) gave results outside the range of a set of grey traps, indicating that the flies employ colour information and not intensity-contrast information alone in trap- orientated behaviour. No significant differences in colour preferences were found between sexes or species.

A time series analysis of noctuid and sphingid moths caught at light traps in East Africa revealed the existence of sources of periodic variation in catch with three different wavelengths: lunar, annual and four-year. A comparison of catches of Spodoptera exempta (Walker) at different sites showed that site characteristics influence a light trap’s catch and confirmed the northward advance in flight period with season in the early part of the year. This species apparently goes through periods of increased abundance every four years. Of eight other species examined, all but one showed signs of a four-year cycle in abundance, although the peaks occurred in different years. Catches of all nine species were reduced by moonlight, but not equally. The size of the insect influenced its susceptibility to interference by moonlight. This was apparently mediated by the height of flight. High and low flying moths were more strongly influenced by moonlight than those at intermediate heights.

Isolates of Serratia marinorubra and S. liquefaciens pathogenic for Costelytra zealandica (White) were artificially cultured and applied to field populations of larvae of C. zealandica in New Zealand in the late summer and autumn of 1984. In four trials, when bacteria were applied from February to late March, high levels of disease transmission were recorded. Three months after application, significant (P<0·05) reductions of 30–59% in the larval populations were obtained, and 47% of the remaining larvae in the treated plots were diseased, suggesting the long-term effect would be greater. Treatment resulted in a 30% increase in dry matter production in the pastures. There was no consistent difference between the bacterial isolates tested. Application of the bacteria in May had no effect on the larvae, suggesting that they were no longer susceptible. It is concluded that these pathogenic isolates should be developed further as microbial insecticides for control of C. zealandica.

Parasitoids of Aonidiella aurantii (Maskell) on citrus in South Africa were monitored using two types of yellow sticky trap. One of these traps was highly efficient, being fluorescent with peak reflectance at about 530 nm. Aphytis spp. populations were low before February and high thereafter. Citrus surrounded by natural bush was an isolated reservoir of high host and parasitoid population levels. Aphytis spatial distribution within the orchard was extremely patchy, with over 100-fold differences in population levels over a distance of a few metres. This patchiness mirrored that of its host. This contagious spatial pattern was maintained despite 1000-fold seasonal changes in population levels. These temporal changes were characteristic and general throughout an orchard, and independent of patchiness. Initial Aphytis population levels did not dictate the final population level at the end of the season. Comperiella bifasciata Howard and its hyperparasitoid Marietta javensis (Howard) also showed clear seasonal population trends, but not of the same magnitude as those of Aphytis. There was no statistically significant correlation between the spatial distribution of one parasitoid with that of another, even between C. bifasciata and M. javensis. The patchiness of these two species was not correlated with overall host density. Aphytis and C. bifasciata were partially mutually exclusive. Aphytis was by far the most economically important of the parasitoids. Pest management practices, therefore, should aim at conserving the pool of Aphytis within the orchard as far as practicable.

Some flightworthy alate exules of Aphis fabae Scopoli reproduce before taking off while others do not. This difference in behaviour is influenced by crowding and has previously been taken as an indication of the urge to migrate, although it has never been conclusively demonstrated. In this study, the flight performance of those aphids depositing some nymphs before take-off (‘flyers’) was compared with those which did not (‘migrants’). In fact, no significant difference was found between migrants and flyers in any of the aspects of post-take-off flight or settling behaviour tested. In tethered flight, large alatae flew for longer than small ones, irrespective of their pre-flight reproductive behaviour. In free flight, however, large alatae flew for a shorter period before actively landing on a plant. Large alatae were also subsequently more reluctant to leave the plant than small alatae, spending more time in sedentary activities such as probing and less time preparing to take off. It is concluded, therefore, that migratory urge is related more to aphid size, a product of plant nutritive quality, than to take-off urge, as measured by pre-flight reproductive behaviour. However, as high population densities tend to occur when the nutritional quality of the host is declining, take-off urge and migratory urge are likely to be synchronized in the field.

Ultraviolet-light and fermentation trap catches of adults of Mythimna convecta (Walker) in Victoria, Australia, could be related to the times of various stages of larval development in oat crops by means of a day-degree accumulation model. Mated females were more attracted to fermentation than ultraviolet-light traps, and predicted oviposition times closely coincided with fermentation trap catches. The phenological model successfully mimicked the observed larval instar development in the field. Peak moth flights occurred within three periods. The first peak period (October to mid-November) usually contained mated moths which generated larval populations in maturing oat crops; in 1983, these moths probably occurred in late August. The second (mid-November to December) contained unmated females; in 1983–84, moth flights during this period could be related to the emergence of moths from crops 70–130 km north of the trap site. The third peak period (January to February) also comprised unmated moths which had usually emerged locally and were probably emigrating.

The integrated use of biconical traps, insecticide-impregnated targets and the sterile insect technique was developed for the eradication of Glossina palpalis palpalis (Robineau-Desvoidy) in a 1500-km2 area of central Nigeria. Six weeks or more of continuous removal trapping, using biconical traps, reduced the target tsetse population by more than 90% but failed to eradicate it. Males sterilized by irradiation from a 60Co source that were then released weekly induced significant sterility in target females and were successful in helping to eradicate the target population. A minimum ratio of 10:1 of sterile to wild males was required to achieve eradication in a central area of 300 km2. In marginal habitats, insecticide-impregnated targets were found adequate to control the tsetse population. The targets were also efficient as barriers to prevent reinvasion of the area. The combined effect of removal trapping and sterile male release is expected to eradicate G. p. palpalis from the entire study area.

Various ketones and 1-octen-3-ol were used as odour attractants with biconical traps at Nguruman, south-western Kenya, to assess their effects on the catch size and composition of Glossina pallidipes Austen. Acetone, methyl ethyl ketone and 1-octen-3-ol were found to be effective in increasing catch size by up to 2–4×, but the two ketones differed in their dose-response curves. Acetone was more effective for males than females, as was 1-octen-3-ol. The age composition of samples from baited and unbaited traps differed only slightly. The level of variability between traps was reduced by the use of odour. Acetone with cow urine produced increases in catch of 9–25×, and significant differences were found between samples in sex ratio and age composition. The index of increase for cow urine plus acetone, when used with a biconical trap, was correlated with temperature changes during the day. This could only be partially accounted for by variability in dose rates. Cow urine with acetone is considered to be a potentially useful combination of baits for community participation tsetse control schemes.

A deterministic simulation model for Glossina spp. based upon a simple life-history analysis was used to test a variety of effects designed to cause a decline in population numbers. Average daily survival values for pupae were varied to make populations grow at different rates. All age classes were then updated for all life stages each day for a 12-month period. As expected, the population remained stable when Ro = 1·0, and the population doubled in 105 days when Ro = 2·0. Sub-routines were added to test the effects of trapping 0·5 to 2·5% of the population per day and killing both sexes, sterilizing and releasing both sexes or sterilizing and releasing males only, the females not being trapped. Results suggest that killing or sterilizing both sexes is always superior to sterilizing males only and leaving the females unharmed but that this superiority is diminished when either population growth rates are low (<1·0) or trapping rates are high (>2·0% per day). As population growth rate increases or trapping rates decline, there is a proportionately greater advantage to be gained by sterilizing both sexes than by adopting either of the other two strategies. A situation is illustrated where for a trapping rate of 1% per day within a population that is doubling at close to its optimal rate (Ro = 2·0) sterilization of both sexes is the only strategy which will cause a population decline. Results are discussed in terms of development of low technology, cost-effective methods of tsetse control which are non-polluting and therefore environmentally acceptable.

The biology and development of immature stages of summer (SR) and winter rainfall (WR) strains of Onitis caffer Boheman were studied in South Africa in a summer rainfall area (Pretoria). A pair of adult beetles buried up to 650 ml of dung from one dung pad, and females laid an average of 1 egg for every 62 ml of dung buried. Broods were buried at an average depth of 50 cm in watered soil and 24 cm in unwatered soil. Eggs laid in June (winter) hatched 10 weeks later. The third instar was reached by late October. WR larvae suffered higher mortality (82%) with the onset of summer rains than did SR larvae (53%). By the following June, 6% of surviving WR individuals had emerged as adults, 12% were adults in faecal shells and 82% were diapausing third-instar larvae. Of the SR individuals, 67% emerged by June and 33% were diapausing third-instar larvae. In a second experiment, two groups of broods of the SR strain of O. caffer of different ages were set out in the field in June. One group, equivalent to broods produced early in the season (March), entered diapause as third-instar larvae, and adults emerged the following autumn. The second group represented broods produced later in the season (May); the majority did not diapause, but adults also emerged the following autumn. A field population of SR adults of O. caffer was sampled for two years. Adults were first recorded at the end of February (late summer), and newly-emerged specimens were caught up until the end of April. Maximum numbers were recorded in late March to early April (autumn), and activity ceased in June-July (winter).

Sitophilus oryzae (L.) is a serious pest of stored cereal grains, but recently a few populations have been found able to feed and breed on certain legumes also. Legumes contain many toxic phytochemicals. A technique is described to generate data suitable for probit analysis, enabling a dose- response line to a toxic food to be constructed. The toxic effects of two legumes, yellow split-pea and adzuki bean, on adult survival and reproduction in three geographical strains of S. oryzae were examined. The strains were shown to vary in their abilities to tolerate legume phytotoxins, but there was no correlation between the abilities to survive on different legumes in the same strain. Yellow split-pea was shown to have residual effects on adult survival and reproduction, but performance was enhanced rather than impaired. It is suggested that improved performance results from induction of certain enzymes by substances within yellow split-pea. The use of legumes mixed with cereals as a control measure against S. oryzae is also discussed.

Energy dispersive X-ray spectrometry was used to make quantitative determinations of the elemental composition of plasma-ashed apterous and alate individuals of Rhopalosiphum padi (L.). The aphids were collected as fundatrigenae at various localities in England and Scotland, mostly from their main overwintering host, Prunus padus, but at one site also from P. virginiana. Robust-means principal components analysis of the data confirmed that there were differences, unrelated to source, between the elemental composition of apterae and alatae, with lower concentrations of S, K and Cl in the alatae. There were, however, no clear separations of sources in either morph except between some extreme groups; it is possible that genetic uniformity limits variation in elemental composition and, therefore, the existence of detectable source-related chemoprints in R. padi. Elements that provided some discrimination were S, Cl, Ca, Zn and possibly Al, and, except for S, their mean concentrations were all less than 1% of weight of the sample examined; difficulties in detecting differences at these low concentrations may have prevented detection of source-related chemoprints in R. padi.

An antiserum was prepared against carboxylesterase E4, the enzyme conferring resistance in Myzus persicae (Sulzer) to a wide range of insecticides, and the immunoglobulin G (IgG) fraction was purified from it by affinity chromotography. Interactions of the antiserum and IgG with aphid homogenates and the purified esterase proteins were studied by immune diffusion, immunoelectrophoresis and enzyme-linked immunosorbent assay (ELISA). In M. persicae, the interactions were specific for E4 and its closely-related mutant form, FE4, and except for Phorodon humuli (Schrank), there was no cross-reaction with homogenates of the nine other aphid species examined. These studies confirmed the quantitative changes in E4 protein previously reported and established that the increased esterase activity in P. humuli also arises from the production of more protein, or proteins, homologous to E4. Resistance of M. persicae could be characterized by immunoelectrophoresis even after preservation of the insects in 30% ethanol. Although ELISA could also be used to identify resistance, a simpler immunoplate assay was developed based on measuring the esterase activity of E4 retained when the enzyme bound to IgG. This assay discriminates well between the three resistant M. persicae variants common in the field in the UK, and its simplicity allows the study of large numbers of insects.

An inexpensive and versatile method for maintaining age-structured Musca domestica L. populations for studies on the evolution of insecticide resistance is described. Adult flies are kept in spacious aluminium cages in which age-structuring is maintained by the thrice-weekly addition of pupae bred from eggs collected from within the cages. The population size is regulated in a density-independent manner by constraining the input of pupae to that necessary to maintain the required equilibrium density of adults within a cage. Adult numbers are monitored by photographing from outside the cage flies settled on a grid etched on the rear wall, and by converting this grid count to an estimate of population size using a calculated regression line. Observed changes in fly numbers in a cage accorded well with those predicted by a computer model using empirical data on larval productivity, and the emergence and survivorship schedules of adult flies. Since a variety of insecticide control regimes can be applied within the cage, this system enables an adequate yet tractable simulation of selection for resistance by insecticides under field conditions.

A chalcidoid wasp, Torymus apiomyiae sp. n., is described from material reared in southern Yugoslavia. The host is Apiomyia bergenstammi (Wachtl), a gall midge galling young fruit-bearing twigs of pear trees, which is locally a serious pest.

Seasonal abundance of fleas infesting small mammals was studied from July 1975 to August 1976 in a grassland in Lake Nakuru National Park, Kenya. Ten species of rodents and two species of shrews were live-trapped 935 times. The Nile grass rat (Arvicanthis niloticus) was the most abundant species, with 233 individuals captured 690 times, forming 73·8% of all captures. From these grass rats, 4247 fleas were collected, including Dinopsyllus lypusus Jordan & Rothschild (n = 2596), Xenopsylla bantorum Jordan (n = 1396) and Ctenophthalmus calceatus cabirus Jordan & Rothschild (n = 255). D. lypusus and C. calceatus cabirus were more abundant on Nile grass rats during the rains, while ×. bantorum became more abundant during the dry season and peaked during the early part of the rains. The potential for plague transmission by fleas between Nile grass rats probably exists all year. The potential for transmission to people living in close proximity to these rodents may be highest during the seasonal peak of X. bantorum, at the end of the dry season.