An analysis of the population changes of Glossina palpalis palpalis (R.-D.) during and after two insecticide trials in Ivory Coast revealed that the effects of insecticide application depend very strongly on the characteristics of the population ecology of the fly, which showed considerable local variation. At sites with high fly populations and low natural mortality rates, the populations declined rapidly during the spray period as the insecticide killed a large proportion of the local, mainly resident, population. The high resilience of the populations, however, permitted rapid recovery, largely through reinvasion from neighbouring areas, so the reduction in fly numbers lasted for only 3–4 months at a time of year when, in the absence of insecticide, the population showed a significant seasonal decline lasting for up to three months. At other sites, with low populations and high natural mortality rates, the local populations were supported chiefly by immigrants and therefore insecticides only affected a very small proportion of the total population and thus did not cause an immediate decline in fly numbers. The low resilience of these populations, however, means that any repeated low additional mortality (such as that caused by removal trapping or deterioration of environmental conditions) would cause the populations to decline. Thus at both types of site, but for rather different reasons, single or short-term insecticide applications had a limited effect on the populations, and longterm, repeated control procedures are considered to be the only ones likely to reduce the populations significantly; through economic necessity these must rely on low-technology devices such as insecticide-impregnated screens or traps.

In studies in Nigeria, all instars of Zonocerus variegatus (L.) were found to be strongly attracted to flowers of the common exotic composite weed Chromolaena odorata. Experiments in the field and with caged nymphs suggested that the attraction is due to a volatile compound(s) concentrated in the conspicuous stigmas and released when the buds open. Although very palatable, the flowers seemed inadequate as food, and most of the nymphs roosting on C. odorata even during the flowering season had fed on leaves of C. odorata or other plants. Feeding diminished the attraction to the inflorescences in experimental cages, and of the field nymphs attracted between 11.00 and 15.00 h, a significantly higher proportion than on other plants had relatively empty foreguts. The numbers of field nymphs attracted were maximal at 08.00–10.00h and minimal at 11.00–12.00 h. Both in the cages and in the field, interest in the inflorescences diminished after about 17.00 h, when the highest points within reach are being looked for as roosting sites. Reduction of C. odorata around plantations is unlikely to lessen crop damage by Z. variegatus, but insecticides for Z. variegatus control could be applied conveniently to the tops of C. odorata at roosting time during the flowering season.

In populations of overwintering pupae of Delia radicum (L.) collected from ten sites in England and Wales, parasitism varied from 0% at Newcastle to 42% at Evesham. Unlike their hosts, few of the parasites were in extended diapause. Irrespective of when collected at Wellesbourne, emergence of 50% of the ichneumonid parasite Phygadeuon trichops Thoms., the eucoilid parasite Trybliographa rapae (Westw.) and the staphylinid parasite Aleochara bilineata Gylh. occurred after 14, 21 and 28 days, respectively, at 20°C. Early-emerging populations of D. radicum were more heavily parasitised than intermediate- or late-emerging populations. During the winters of 1979–80, 1980–81 and 1981–82, T. rapae and A. bilineata emerged in similar numbers from 37% of the field-collected pupae from Wellesbourne. Less than 1% of the pupae were parasitised by P. trichops. D. radicum adults emerged from a further 25% of the pupae, and the remainder, approximately 38%, were dead. Most dead pupae were recovered from heavily parasitised populations. When parasites were present in high numbers, many of their progeny probably died from multiple parasitism and superparasitism. Comparison with earlier studies indicated that parasitism should be expressed as a percentage of the total pupae, and not just as a percentage of the living insects, if the data are subsequently to be of use for studies on the population dynamics of this pest.

Possible sources of adults of Spodoptera exempta (Wlk.) giving rise to outbreaks in East Africa at the beginning of the season were estimated by assuming downwind displacement and using the technique of backtracking. The accuracy of backtracks was limited by the availability of suitable weather data, but they provided a reasonably objective means of analysis. Eastern Kenya and eastern Tanzania were found to be the most likely source areas for moths. Migration from Ethiopia was very unlikely. Immigration from southern Somalia into Kenya, and from Malawi, Zambia or northern Mozambique into southern Tanzania was possible in a few years. In most years, there were likely to be sources in Kenya or Tanzania, probably of low density and in places suitable for the larvae to survive the dry season.

Insects migrating above the surface boundary layer were efficiently and economically sampled over long periods using a large diameter tow net suspended beneath a kite. In a series of trials in Australia, sequential samples were obtained by day and night at predetermined altitudes, in the range 50–500 m. The net was raised and lowered independently of the kite, so that when conditions were calm in the lower atmosphere the kite could remain aloft in the geostrophic airflow. Potential contamination of insects flying below the sampling height was minimised during net ascent, by reducing the airflow through the net. A radio-operated net-closing and releasing mechanism prevented contamination during the free fall of the net. The catch was converted to absolute values of aerial density and migration rate or flux. Aerial sampling was originally developed to identify upper air migrants under observation by the CSIRO entomological radar and to provide quantitative measurements of those species too small to be individually detected by radar. The technique was subsequently operated independently of radar to quantify microinsect migrations, but not those of macroinsects because of their relatively low catch rate.

A population of the coconut pest Segestidea uniformis (Willemse) was monitored on a small island 2° from the equator in Papua New Guinea between 1973 and 1978. Totals of 54 000 first-instar nymphs were caught on sticky traps on palm trunks and 8750 other nymphs and adults were recovered from the crowns of palms. Generations were completely overlapping, and there was no evidence of seasonality in population fluctuations. The sex ratio was 50:50 in the first six instars, but 90% of seventh instars and 30% of adults were female. Explanations for these variations are given. The population declined from an annual mean of 24 individuals of all ages per palm crown in 1973 to 9 in 1976 and increased again to 29 in 1978. Most post-hatching mortality occurred as first instars climbed from the ground to the crown of palms, probably due to the lizard Gehyra oceanica and rainfall. The number of adults was more sensitive to mortality occurring after the first instars had arrived in the crowns. This mortality appeared to be related to the duration of periods without rainfall, supporting earlier observations that damaging outbreaks of S. uniformis populations do not occur in places which experience a regular dry season. Production of coconuts appeared to be inversely related to the population density of S. uniformis, which did not rise above a level estimated to cause 20% defoliation of the palms during the study. Nut production also seemed to be related to the number of hours of sunshine received in the preceding 12 months. Biological control aimed at nymphs and adults in palm crowns is suggested as an option for controlling S. uniformis which deserves investigation.

Sitona discoideus Gylh., an introduced pest of lucerne in New Zealand, exhibits univoltine, aestivatory seasonality in Canterbury and Otago, with each generation appearing in late December. Some two weeks after the December emergence of adults, flights to aestivation sites commenced. These sites were commonly remote from the lucerne stands and included such places as under stones or at the base of trees, fence posts, etc. At the commencement of aestivation, the indirect flight muscles atrophied rapidly, only to redevelop some 6–8 weeks later when autumnal post-aestivatory return flights to lucerne began. During the winter, S. discoideus fed on lucerne foliage and became reproductively mature. By October, age-related adult mortality had begun, and for about two weeks in December no adult weevils were present at all in one Canterbury site. In Otago, there was a distinct generation overlap of 2–3 weeks. The eclosion of new generation weevils was closely synchronised; it is suggested that this may have been the product of differential egg development and egg-laying temperature thresholds and a high fourth instar and pupal develoment threshold. Synchronised emergence of adults tended to accentuate the problem of defoliation caused by their feeding.

Insects and mites associated with each species in the Salvinia auriculata complex were recorded in Trinidad, Venezuela, Guyana, Brazil, Uruguay, Paraguay and Argentina. There was a consistent pattern of herbivore-plant association throughout the range of the complex. Field studies showed that three insects, the curculionid Cyrtobagous sp., the pyralid Samea multiplicalis Gn. and the pauliniid Paulinia acuminata (Deg.), together contained Salvinia molesta at a density slightly below the carrying capacity of the environment in coastal areas of Brazil.

In a field study of Sitobion avenae (F.) in winter wheat at Cranfield in southern England, the main predators were found to be the larvae of the staphylinid Tachyporus sp. and syrphids. Most predation occurred overnight. These predators were active during the period when the wheat crop was most suitable for aphid population increase, and in 1982 were apparently responsible for preventing an outbreak at Cranfield.

Resistance of cocoa to Planococcoides njalensis (Laing) was assessed in the laboratory in Ghana by rearing the mealybug from birth until death on seven cocoa progenies, and determining survivorship, duration of reproduction, gross reproductive rate and live weight. Field evaluation was by sampling both P. njalensis and Planococcus citri (Risso) on the tree trunks and in terminal buds. Progenies 85D/176A × M7/537 and T12/116 × T62/977 were judged the most resistant using the parameters determined in the laboratory. The resistance factor is attributed to antibiosis. The mealybug populations in the field did not show any significant differences among the progenies, but the trend followed the laboratory results. It is suggested that the laboratory method reported here is adequate in assessing resistance, has the advantage of being faster than the field technique and can be used in combination with existing methods for assessing cocoa progenies for resistance to the virus disease.

A non-technical description is given of a new, powerful, low cost field system (Infra-red Active Determination of Insect Flight Trajectories or IRADIT) for detailed and automatic remote sensing studies of natural insect flight behaviour. The special requirements and difficulties of the detection problem are defined. A series of examples of field devices and techniques are presented to illustrate the key factors of the optical sensing and tracking of insects in flight. In the finally adopted IRADIT system, flying insects are differentially illuminated, under all natural light conditions, by an intense beam of pulsed near-infra-red radiation and detected using a shuttered image intensifier linked with a video camera operating at a rate of 50 frames per second. Immediate fully-automatic determination of the flight trajectories of several simultaneously detected insects was achieved, at this same high rate and in the presence of sky background photon noise, by processing the video signals with electronic circuits and a microcomputer. Flight trajectories are influenced by the local wind, whose vector must be subtracted to study insect flight behaviour. This was achieved by the use of a specially developed sensitive three-vector vane anemometer, providing digital data to the microcomputer at a minimum rate of 5 Hz. In tests of the prototype IRADIT-anemometer system in the field, insects with wing area of only 1·5 mm2 and flying against the midday sky were readily tracked at ranges up to 15 m. A range of at least 100 m is expected for nocturnal moth tracking.

Brood care in Copris diversus Waterh. enhanced survival of progeny. Reallocation of dung from brood balls with no live progeny to brood balls containing live progeny was. a typical behaviour pattern in this species and resulted in fewer, larger brood balls. The advantage of this behaviour is that larger brood balls produced larger progeny, which in turn produced a greater number of offspring.

An account is given of changes in nocturnal illumination at the spring and autumn equinoxes and summer and winter solstices at latitudes between 50 and 60°N. A Relative Trap Index (RTI) was devised to describe changes in light-trap effectiveness and used to adjust catches of Noctuidae and Geometridae for change in trap effectiveness caused by seasonal and latitudinal change in nocturnal illumination at latitudes between 50 and 58°N. When so adjusted, catches were frequently larger in northern than in southern latitudes, not smaller as unadjusted catches show. It is clear that unless light-trap catches are adjusted to allow for changes of illumination, comparisons over time and space, particularly those which involve assumptions about sample constancy, are suspect. Because of the large differences in RTI that may exist between northern and southern traps, particularly in summer and between the summer solstice and other times, it may be necessary to use different light sources at different times of year to maintain a consistent trap sample.

Several methods for the bioassay of changes in cattle dung as insect food were defined and simultaneously assessed using Musca vetustissima Wlk. Size of emerging adults, in particular head width, was a reliable estimator of changes in the dung, but survival was not. Freezing of dung for 24 h had no effect. Flies of similar size emerged from dung placed on moist sand (field capacity moisture) and on an impermeable membrane; on dry sand, size was greatly reduced when the dung was coarse and less nutritious. The optimal method was deemed to be use of fresh dung on sand at field capacity moisture, leaving flies to emerge and die before measuring the head widths in a sample.

Population change in Myzus persicae (Sulz.) overwintering on spring cabbage in south-eastern England was studied in relation to meteorological and biological factors. Leaf surface wetness and temperature were correlated significantly with rate of population change, but rainfall and wind were not. Growth and development continued slowly throughout the winter, and the relationship with temperature is shown. Hymenopterous parasites, the fungus Entomophthora and predatory spiders did not affect winter survival.

Mylabris designata var. hacolyssa Rochebrune is a pest of a variety of crops, particularly okra, in the central and western provinces of the Sudan. A study is reported of the responses of the beetle to visually attractive traps which were used to measure daily and seasonal flight activity. Blue-coloured traps were more attractive than red, lavender, white or black traps. The catching efficiencies of Manitoba traps and sticky targets were recorded by direct observation: 43·3% of approaching beetles were captured by a blue Manitoba trap whereas the initial 50–80% efficiency of blue sticky targets decreased to 10–20% over three days due to an increasing close range olfactory repellent effect on the beetles. The potential for the use of such traps as a cheap and environmentally acceptable alternative to the use of insecticides for control of M. d. hacolyssa is discussed.

‘Blind’ trials using laboratory-bred females that had completed 0–3 gonotrophic cycles showed that Polovodova's method of assessing parity, by noting the presence of follicular dilatations, is applicable to Lutzomyia flaviscutellata (Mangabeira) and L. furcata (Mangabeira). However, at the resolution of the techniques used, classification is limited to a simple division into nulliparous and parous flies. The presence of granules in the ovarian accessory glands was found to be an unreliable indicator of parity for both species.

Five species of Muscidae were found to be commonly associated with dairy heifers in three areas in southern England. The biting flies Haematobosca stimulans (Mg.) and Stomoxys calcitrans (L.) were relatively rare and fed from the back, flanks and legs. The horn fly, Haematobia irritans (L.), was present in highest numbers; it rested on the back and fed on the legs, belly and occasionally on the teats. Musca autumnalis Deg. was found mainly on the head and had a restricted season. Hydrotaea irritans (Fall.) had a marked diurnal variation in activity, being most abundant in the morning and evening. It was found on the head but predominantly on the belly and teats. When judged by its site preference on cattle, it is the fly most likely to be involved in the transmission of summer mastitis.

Numicia gauhati sp.n., collected from rice in Assam, India, is described and illustrated. It is compared with other known species of Numicia from the Oriental Region. N. maculosa pusana Ghauri is raised to specific status.

The nature, frequency and causes of reproductive loss were investigated in populations of Glossina pallidipes Aust. in western and coastal localities in Kenya. Daily collections from biconical traps in which females were trapped for varying periods up to 30 h were followed by a series of hourly captures which gave less biased data. Ovarian abnormalities and insemination failure were rare, and abortion was the only major source of loss of fecundity. Total reproductive loss was within the range 1·60–1·97% (0·23% ovarian loss plus 1·37% abortions or 1·74% total empty uteri) in western Kenya (Lambwe Valley) and 0·99–1·71% from less comprehensive data at the coast. The incidence of empty uteri was higher in daily than in hourly collections, due mainly to premature parturitions brought about by the stressful effects of prolonged confinement in traps and handling. Abortions were significantly more frequent in females which had ovulated but were not yet parous than in older, parous flies. No relationship between the frequency of abortion and climate, tsetse density or pathogen or parasite infection could be demonstrated.