The administration of dieldrin in the larval diet of Lucilia cuprina (Wied.) killed susceptible females with no pre-emergence mortality of males in a strain which contained a Y–autosome translocation linking dieldrin-resistance to the male sex. Laboratory assays of flight activity, sexual competitiveness and visual sensitivity revealed no significant differences between treated and untreated males. The life-span of treated males was slightly reduced at the highest dieldrin concentration used. In field releases, however, the recapture rate of treated males was much lower than for untreated males, indicating a major deficiency in the performance of dieldrin-treated males in the field that was not suspected from the laboratory tests.

A laboratory bioassay technique was used to compare the susceptibility to a granulosis virus of 16 field populations of Phthorimaea operculella (Zell.) in Australia. A difference of 11·6× was found between the most and least susceptible population, while a laboratory strain was over 30 × as resistant as some field populations. It is suggested that this variability might reflect the past history of exposure of different populations to the virus, which appears to be endemic. The implications for the use of this virus as a microbial control agent are discussed.

The Rhyzobius (or Lindorus) ventralis frequently referred to in the literature of biological control is shown to be a mixture of two distinct, though similar, species. The origin of the confusion is traced to the nineteenth century searches in Australia for insects to control scale insect infestations on citrus and other crops in California. Adults of the two species are defined and illustrated, and a key is provided for their separation. Lectotypes are designated for R. ventralis (Erichs.), its synonym Scymnus restitutor Sharp and for S. halli Broun, newly synonymised with R. ventralis. A lectotype is designated for Platyomus forestieri Muls., the second species of the complex, here transferred to Rhyzobius, and for S. circularis Sharp, newly synonymised with R. forestieri. Distribution data for both species, based on actual specimens examined, are listed, and their Australian distribution is summarised in a map. Past usages of ‘ R. ventralis’ as a biological control agent are reviewed in the light of the revised taxonomy. The taxonomy and nomenclature of Rhyzobius Stephens is discussed in order to establish the correct generic placement of and binomina for R. ventralis and R. forestieri.

Life-cycles and voltinism are described for Rhyzobius ventralis (Erichs.) and R. forestieri (Muls.) living in the region of Sydney, Australia, and also the role each plays in its particular biocoenosis. Colour variation and wax production are described for the larvae, prepupae, pupae and adults of both species, also the defensive and feeding behaviour. New and known host records are listed for both species. Reasons are suggested for the success, partial failure or failure of the species as biological control agents in various parts of the world.

Light-trap catches of Dysdercus bimaculatus Stål and weekly phenological records of its host-plants over a period of three years on Barro Colorado Island, Panama, are discussed in relation to a year-long study of population growth at selected plants. Population build-up of D. bimaculatus occurred on a sequence of seed crops from wild host-plants in the dry season. Each year, the largest number of bugs caught in the light-trap occurred after a drop in vapour pressure deficit marked the end of the dry season. Thus, the population appears ‘poised’ to attack cotton crops maturing in the late wet season. A stepwise linear regression indicated that each year, the variance in size of Pseudobombax septinatum crops (maturing at the end of the dry season) explained the largest proportion of variance in the light-trap capture of D. bimaculatus. However, estimates from the field study indicated that Ceiba pentandra crops were more important than P. septinatum in building up numbers of adult cotton stainers. The discrepancy between the field study and the longterm phonological monitoring survey would be resolved if D. bimaculatus adults experience a dispersal flight at the end of the dry season. This flight would enable the insect to locate better-quality seed crops in drier habitats that mature in the late wet season, such as Sterculia apetala or cotton. Light-trap captures at the end of the dry season in areas such as Barro Colorado Island where Ceiba and Pseudobombax occur, could be an index to the intensity of attack on cotton crops in nearby drier areas.

More adult males of Glossina morsitans morsitans Westw. were caught with hand nets in Tanzania from a man-carried dark screen baited with surrogate female decoys impregnated with synthetic 15,19,23-trimethyl-heptatriacontane (the G. m. morsitans sex pheromone) than from a screen bearing unimpregnated decoys or from a screen alone. A similar pattern was obtained with G. pallidipes Aust., but the variations in numbers of both species caught within and between fly-round sectors were large. Although many G. m. morsitans males attracted to the screens visually were seen to engage in copulatory activity with pheromone-impregnated decoys, none of the G. pallidipes so attracted was seen to do so. It is therefore concluded that catches of G. m. morsitans were not improved by the presence of pheromone-baited decoys on visually attractive screens. Copulatory behaviour was frequently interrupted by other flies and/or the flies flew off as soon as the screen ceased to move. Of the G. m. morsitans males attracted to a baited screen on the back of a slowly moving vehicle, 51% were seen to have alighted on the impregnated decoys and 42% were engaged in copulatory behaviour with the decoys immediately after the vehicle stopped. Copulatory responses of wild male G. m. morsitans to pheromone-impregnated decoys in glass tubes approximated those of laboratory-reared males only after confinement for several hours at low light intensity. Contamination of laboratory-reared male G. m. morsitans with synthetic pheromone elicited prolonged male:male copulatory behaviour. Prospects for the use of the G. m. morsitans sex pheromone in population studies or control programmes are discussed.

An open wind tunnel, down which air was blown from over a bait animal, was used in the field in the Gambia to measure the flight speed of host-seeking mosquitoes. Insects were trapped on an electrocuting grid fitted halfway up the tunnel. As the speed of air movement through the electrocuting grid was increased from 0·5 m/s, catches of Mansonia spp. fell off steeply, reaching negligible levels above 1·4 m/s. At air speeds lower than 0·5 m/s, catches at the grid were greatly reduced. Similar results were obtained for Anopheles ziemanni Griinb. and other species of Anopheles. It is concluded that the maximum flight speed of hostseeking females of all these species was in the range 1·4–1·8 m/s.

The dark-scaled form of Culiseta longiareolata (Macq.) was found near Bloemfontein in South Africa. Breeding took place in various kinds of flooded pools, small containers and drinking troughs. It was multivoltine and overwintered as hibernating second-, third- and fourthinstar larvae and adult females. Laboratory colonisation was easily accomplished. Adults were maintained alive at 23°C and 70% relative humidity, and survival rates were high for 40–50 days. Starved females fed readily on blood from pigeons at night or on a 3:1 mixture of human blood and 10% sucrose solution from cotton-wool pads. Mating swarms were not observed in the field, but swarming activity occurred in laboratory populations provided with simulated dawn and dusk conditions. The fact that mating activity could be readily induced at any time was taken to show that it is not governed by a rigid endogenous rhythm. Egg-rafts varied in shape from round to oblong. Oviposition was invariably nocturnal. Some substance, probably emitted by bacteria, served as an oviposition attractant. The anterior pole of each egg lacks an exochorion and is hydrophilic. The posterior pole bears a lipid droplet. The exochorion is sculptured, the sculpturing consisting of bosses connected to one another by bridges constituting the outlines of a series of pores. The exochorial pattern varies in different regions of the egg. Pupation and emergence occurred mainly at night, and there was an approximately normal sex ratio.

Pregnant females of Glossina morsitans morsitans Westw. were offered choices of larviposition sites in the vicinity of various models and patterns. Ground-level surfaces of black, green, white or red were not attractive. Vertical surfaces did not attract a majority of flies, but 50% of those that settled on them gave birth in that region of the chamber. Shade cast by horizontal surfaces was attractive, but shade cast by vertical objects was not. Models with an enclosed space were attractive, but larviposition rarely occurred within the model, probably because flies do not readily enter cavities unless the temperature is very high. Among patterns presented at a distance, a simple unbroken area of black was more attractive than equivalent areas in the form of stripes, etc. No distinction was made between stripes presented vertically, horizontally and at an angle. Models representing logs or trees with rot holes were not attractive. Models with subterranean cavities, even a simple trench, were attractive. Loose sand was not more attractive than sand glued to a substrate, but there was an indication of a preference for larger particles. No evidence was obtained for the hypothesis of Nash et al. (1976) that a larval pheromone attracts gravid females to larviposition sites.

Between June 1976 and November 1977, man-baited and truck-trap collections of haematophagous Diptera were made on the foreshore of Las Cuevas Bay, north Trinidad, close to a fishing village where Mansonella ozzardi infections are prevalent in man. Culicoides phlebotomus (Will.) predominated in all collections, forming 96·1% of the total catch. Analysis of blood-meals from engorged C. phlebotomus collected by truck trapping at sunset indicated frequent feeding on mammals, with feeds on man comprising 47% of those identified. Filarial larvae were found in 0·8% of 6767 females of C. phlebotomus captured on man, and five (0·08%) had infective larvae of M. ozzardi. Similarly, 1·3% of 7028 females obtained by truck trapping were infected, including nine (0·13%) with infective larvae. Growth rates of M. ozzardi in C. phlebotomus were determined by experimental infection and were used to estimate daily survival rates of wild-caught females of C. phlebotomus based on filarial growth stages found in them. The daily survival rate varied from 85 to 95% in flies 1–3 days after infection to 69% in flies six days after infection. It was estimated that a person spending one hour on the beach every morning would receive 38 infective bites from C. phlebotomus per annum.

The insect fauna of a block of Amelonado cocoa trees at Tafo, Ghana, partly shaded by Gliricidia sepium and partly unshaded was sampled. Crematogaster clariventris (Mayr) and Oecopyhlla longinoda (Latr.) were the most numerous species of ants, the former occurring on 84% of the trees and the latter on 17%. There was a considerable overlap in the distribution of the two species. Thirty-two other species of ant were collected by pyrethrum knockdown sprays from the cocoa canopy, and 47 species were collected from leaf litter beneath the trees. More species of ant were recovered from litter on shaded plots than on unshaded ones. There was some avoidance of trees occupied by O. longinoda by certain canopy .ants. A greater number of Lepidoptera larvae, Orthoptera and the mirid Sahlbergella singularis Hagl were collected by pyrethrum knockdown sprays from unshaded plots than from shaded ones, whereas Diptera and Hymenoptera other than ants were more numerous on shaded plots. The most abundant coccid was Stictococcus sjostedti Ckll., a species tended for its honeydew by both dominant ants; it was more common on shaded plots. Mealybug species, of which Planococcoides njalensis (Laing) was the most common, were more abundant on unshaded plots.

The diurnal flight and biting activity patterns of Culicoides phlebotomus (Will.) were investigated during ten all-day (06·00–19·00 h) trapping sessions at Las Cuevas Bay, north Trinidad. A comparison was made of the results obtained by biting catches, paddle trapping (in which a piece of greased wire screen was swung in front of the collector's legs) and truck trapping. Biting activity persisted throughout the day, with peaks of activity one to two hours after sunrise and again at sunset. Truck trapping recorded little variation in flight activity of empty females during daylight hours, but that of engorged, half-gravid and gravid females was greater during the afternoon than in the morning. Male flight activity was high in the early morning and mid-afternoon but declined rapidly towards sunset. Paddle trapping alone recorded a substantial increase in the blood-seeking activity of parous females after sunset. The paddle-trapping technique was found to be a useful alternative to biting collections for the study of anthropophilic Culicoides.

A population of Aedes aegypti (L.) near the Kenya coast was monitored for nearly a year after a genetic control experiment. Two genetic markers that were carried by released males but unknown to the region persisted in the population during the entire period of observation. The endurance of introduced genetic material in a natural population is an important step toward the use of genetic control in insect management.

The behaviour of Myzus persicae (Sulz.) on plant surfaces treated with emulsions of saturated fatty acids was investigated in three types of test. Aphids showed no clear preferences for settling or larviposition when the acids were applied to whole Chinese cabbage plants or to leaf discs from several different plant species, but settling on halves of Chinese cabbage leaves treated with undecanoic, dodecanoic or heptadecanoic acids was significantly decreased.

The distribution and seasonal activity of Onthophagus granulatus Boh. was studied at two sites in eastern Australia. It is a univoltine species, with peaks of activity in spring and early summer. Breeding cycles and periods of stress were demonstrated by the proportions of newly emerged, nulliparous and parous beetles and those resorbing oocytes. The optimum temperature for brood production was 25°C. The threshold of development was 11·3°C, and 495 day-degrees C were required for development from egg to adult. Dung quality and drought were important factors affecting survival and brood production in the field. The distribution of the species in south-eastern Australia is limited by summer rainfall and temperature.

Resistance to chlorpyrifos and other commonly used organophosphate larvicides was found in Culex quinquefasciatus Say from several urban areas in Tanzania. Lower levels of resistance were found in laboratory strains of the complex of C. pipiens L. collected in Sri Lanka, Egypt, Liberia and Brazil. Crosses of the Tanzanian strains to a more susceptible strain gave results consistent with causation of the resistance by a single gene or closely linked group of genes. Electrophoresis of one of the Tanzanian stocks indicated two esterase bands of high activity. The resistance in Tanzania did not prevent larval killing by freshly sprayed chlorpyrifos, but it is suggested that a spraying would probably no longer remain effective for three months as reported in earlier field studies.

p. 329, column 1, line 5, for ‘ Cx.’ read ‘ Cs.’

p. 436, line 22, for ‘ no.’ read ‘ n.’

p. 669, line 9, delete ‘and egg survival remains high (7≥ 79%) for a wide range of saturation ’ and insert'. The response function, shown in Table III, was highly significant (P≤00001)’

p. 706, transfer figure but not caption to p. 712 as Fig. 10

p. 712, transfer figure but not caption to p. 706 as Fig. 5