The distribution and species composition of lepidopterous maize borers was studied in six locations in southern Nigeria during the second planting season (August-November) of 1985 and 1986. Sesamia calamistis Hampson (Noctuidae) and Eldana saccharina Walker (Pyralidae) were the stem borers most abundantly found in the locations sampled. S. calamistis was the dominant species up to eight weeks after planting in all locations. E. saccharina was the most abundant species from nine weeks after planting onwards, except at Umuahia where S. calamistis always comprised over 50% of the borer population. Mussidia nigrivenella Ragonot (Pyralidae) was found attacking maize ears in all locations, while Busseola fusca Fuller (Noctuidae) was found only at Idah and Alabata, and even there constituted only a small proportion of the population. Other borer species found were Coniesta (= Acigona) ignefusalis (Hampson) (Pyralidae) and Cryptophlebia species (Olethreutidae).

Laboratory investigations were conducted into factors affecting oviposition, larval growth and mortality in the blowfly Chrysomya megacephala (Fabricius), an important cause of losses of salted dried fish in south-east Asia. When presented with a choice of fish spiked with recently laid C. megacephala eggs and unspiked fish, the flies preferentially oviposited on the spiked fish. Subsequently choice experiments indicated that the attraction exerted by the eggs was mainly olfactory in nature. When presented with oviposition media of a range of salt concentrations, C. megacephala preferentially oviposited on the medium of lowest concentration. In the absence of choice, C. megacephala readily oviposited on fish that had been salted to levels of up to 40% dry weight basis (dwb). Trials investigating the effects of feeding medium salt concentration on larval growth and mortality indicated that a high salt concentration of about 40% (dwb) is necessary to effectively control infestation of salted fish by C. megacephala. Such high salt concentrations are rarely obtained in commercially produced salted dried fish in south-east Asia and would be unlikely to gain consumer acceptance.

The parasitoid Aphidius rhopalosiphi De Stefani-Perez was imported into New Zealand as a biological control agent against the rose-grain aphid (Metopolophium dirhodum (Walker)) in 1985. In 1988–89, the rate of parasitism by A. rhopalosiphi was studied by rearing fourth instar M. dirhodum collected from barley at Lincoln and other sites in Canterbury. The rate of parasitism at the time of peak aphid numbers at Lincoln was approximately 50% in winter barley and 100% in spring barley. In spring barley, peak numbers did not exceed five aphids per tiller, and regulation of aphid population density below this level was attributed to parasitism following a large immigration of adult A. rhopalosiphi. Suction trap catches of A. rhopalosiphi increased between 1984, prior to release, and 1989, while catches of M. dirhodum showed a corresponding decline.

Two field experiments examined the effect of dung fauna on the breeding success of Haematobia irritans exigua DeMeijere at Rockhampton, Australia, and Haematobia thirouxi potans (Bezzi) at Hluhluwe Game Reserve, Republic of South Africa. Dung pads naturally infested with Haematobia eggs were produced by cattle at Rockhampton and by Cape buffalo at Hluhluwe. Pads were either exposed to, or protected from, all dung fauna for various periods up to four days. The effect of dung fauna on the immature stages of Haematobia spp. was estimated from differences in the numbers and size of flies that emerged from treated and control pads. In the first experiment, pads produced during the morning and afternoon were exposed for one, two or four days on seven different occasions. At Rockhampton, fauna-induced mortality was substantial but did not increase significantly after the pads had been exposed for one day. At Hluhluwe, in pads produced during the morning, fauna-induced mortality rose substantially with duration of exposure; in afternoon pads the increase was not statistically significant. Fly size, indicated by the mean headcapsule width of surviving females, decreased as exposure of pads to dung fauna increased from zero to four days, except in the afternoon pads at Rockhampton. In the second experiment, pads produced in the afternoon were exposed in the field for four days on 16 occasions at Rockhampton, and on 17 at Hluhluwe. Fauna-induced mortality averaged 79% and 84%, respectively. The activities of the dung fauna reduced the headcapsule widths of surviving flies by an average 2% at Rockhampton and by 7% at Hluhluwe, despite similar levels of dung dispersal. The dung fauna associated with the highest mortality of H. irriatans exigua at Rockhampton were Scarabaeinae and Macrocheles spp., while there were no significant associations between fly mortality and particular fauna in the Hluhluwe data.

A wild-type black-eyed strain (PALA DR) and a mutant white-eyed strain (S104) of Anopheles gambiae Giles were used to determine whether nulliparous mosquitoes of this species are polyandrous. White-eyed females were given the opportunity to mate with black-eyed and white-eyed males. As the white-eye gene is recessive and is located on the X chromosome the presence of both white- and black-eyed females in a female's egg batch denotes that she mated with males of both types. Three out of 52 egg batches gave rise to both white-and black-eyed females. Only a proportion of multiple matings can be detected in this way; those involving males of only one type go undetected. It is estimated that, under the conditions prevailing during the experiment, 12% of nulliparous A. gambiae are polyandrous.

The juvenile hormone mimic, pyriproxyfen, applied topically to female tsetse flies, Glossina morsitans morsitans Westwood and G. pallidipes Austen, effectively sterilizes them by arresting development of their offspring in the pupal stage. Between July and November 1989, 41 odour baited traps treated with pyriproxyfen were deployed near Rekomitjie Research Station, Zambezi Valley, Zimbabwe, in a 12.3 km2 block of woodland habitat of G. m. morsitans and G. pallidipes. Tsetse entering the traps brushed against material dosed with 2 mg/cm2 pyriproxyfen and were then allowed to escape. Emergence rates from pupae of the two species collected in the block fell to 30% and 2.7%, respectively, of control levels after three months. Of more than 750 pupae of each species dissected 78% and 94%, respectively, showed incomplete development. The average ovarian age category of female G. pallidipes sampled in the block doubled during the trial. This was due to immigration of older flies and the declining birth rate which, if sustained over a large area for a year, was estimated as sufficient to cause a population reduction to 10−6 of its original level.

Studies were carried out at Nguruman, south-west Kenya to develop an effective trap/odour bait system that could be used for sampling and possibly controlling the tsetse Glossina longipennis Corti. Neither acetone nor cow urine increased trap catches significantly when used alone, but together they increased catches by about four to five times. Used with a target and electric screens, acetone with p-cresol, 3-n-propyl phenol and 1-octen-3-ol gave a significantly higher index of increase than did acetone and cow urine. The use of odour baits did not affect the age composition of the catch. The standard F3 trap was about three and a half times more effective for females than was the biconical trap and about eight times more effective when used without its blue floor. The NG2B was the best of the NGU series of designs, and caught about four times more females than did the biconical trap. Neither the F3 nor the NG2B caught significantly more males than the biconical trap. The NG2B caught a significantly higher proportion of parous female flies than the biconical. Either the F3 or the cheaper NG2B, baited with acetone and cow urine or phenols, is recommended as a sampling tool for G. longipennis. Electric screen experiments showed that the NG2B caught less than 10% of the flies that approached it. Despite this, it might still be effective for control of G. longipennis given the high mobility of this species and the consequent likelihood of encountering traps.

Areas in Argentina, Bolivia, Brazil and Paraguay were searched for the cassava mealybug, Phenacoccus manihoti Matile-Ferrero. The mealybug was located in the Paraguay River basin in the Santa Cruz de la Sierra area of eastern Bolivia, the Mato Grosso do Sul state in South-Western Brazil and in Paraguay east of the Paraguay River. Mealybug populations were extremely low in all areas but there was a period of increase from August to December. Eighteen species of natural enemies were found attacking P. manihoti: the most abundant and also most important were a solitary, internal parasitoid, Epidinocarsis lopezi (DeSantis) (Hymenoptera: Encyrtidae), Hyperaspis notata Mulsant and Diomus spp. (Coleoptera: Coccinellidae), and Ocyptamus spp. (Diptera: Syrphidae). Collections of a closely related mealybug, Phenacoccus herreni Cox & Williams yielded two additional encyrtid parasitoids, Epidinocarsis diversicornis (Howard) and Aenasius sp. nr vexans Kerrich, but they did not survive on P. manihoti. Four parasitoids (E. lopezi, E. diversicornis, Parapyrus manihoti Noyes and Allotropa sp.) and four predators (H. notata, Diomus sp., Sympherobius maculipennis Kimmins, and Exochomus sp.) were sent for quarantine. With the exception of Parapyrus manihoti, all mentioned natural enemy species were forwarded to the International Institute of Tropical Agriculture at Ibadan, Nigeria for mass rearing and subsequent release.

Bucculatrix parthenica Bradley sp. n., a moth native to Mexico, is described. It has been released and established in Queensland, Australia, as a biological control agent for its host plant, Parthenium hysterophorus. The moth oviposits on leaves of its host. First and second instar larvae are leaf miners, and later instars feed externally on the leaves. The life cycle occupies about 25 days under field conditions. B. parthenica was narrowly oligophagous in host-specificity tests. In Mexico the insect is scarce but in Queensland it has become abundant enough to cause extensive defoliation of its host plant at some sites. Its rapid increase in Queensland is attributed to the absence of parasitism.

Males of Tribolium castaneum (Herbst), T. confusum (Duval) (Tenebrionidae), Rhyzopertha dominica (Fabricius) and Prostephanus truncatus (Horn) (Bostrichidae) secrete aggregation pheromones attractive to both sexes. Responses of the four species to synthetic aggregation pheromones were investigated in relation to age, habituation, time of day, sex and previous mating experience in an olfactometer in which odour gradients were set up in moving air. Habituation reduced pheromone response in all the species tested but all recovered to pre-habituation levels after 48 h except Tribolium spp. males. Both sexes of T. castaneum and T. confusum were responsive to pheromone immediately upon eclosion, males reaching maximum response after 19 and 21 days and females after 21 and 16 days, respectively. Pheromone response was linearly related to age of the Tribolium spp. and T. castaneum males showed a greater response than the females. Sex or having mated did not affect the responses of T. confusum, P. truncatus and R. dominica. All the pheromones evoked periodicity of response, peaking between 10.00 and 18.00 h.

Adult male Tribolium castaneum (Herbst) secrete an aggregation pheromone that is attractive to both sexes. The responses of T. castaneum to different pheromone concentrations (0.5, 1.0, 2.0, 4.0 and 8.0 mg/septa) were tested in the laboratory. In general, pheromone-baited pitfall and probe traps were over 50% more effective than unbaited traps. A curvilinear relationship between numbers trapped and pheromone concentration indicated that 2.0 mg of pheromone per trap elicited an optimum response. The proportion of marked beetles released in 2.5 m × 0.3 m × 0.4 m trough, filled with wheat and caught by unbaited probe traps, declined with distance from release point, whereas pheromone traps captured a similar proportion up to 2.0 m from the traps. Tracks of T. castaneum responding to different pheromone concentrations in still and moving air in a 2.5 m × 0.4 m olfactometer indicated that the aggregation pheromone stimulated the beetles to walk faster at higher concentrations, to increase the frequency and magnitude of turning and to decrease track reversal distances and distances between turns. The behavioural responses of the beetles to the pheromone in still and moving air were similar, indicating chemotaxis as the major orientation mechanism used by T. castaneum to locate an odour source. The beetles showed greater orientation efficiency within a discrete pheromone plume than a diffuse plume.

Culex quinquefasciatus Say from Peliyagoda, Sri Lanka, has larval resistance to temephos, malathion, fenitrothion and chlorpyrifos. Biochemical assays on individual resistant and susceptible mosquitoes of this strain showed that there was a good correlation between this resistance and increased esterase activity with both 1-and 2-naphthyl acetate, which appears to be the major resistance mechanism in this multiple organophosphate resistant strain. There was no significant difference in malaoxon, bendiocarb or propoxur sensitivity of the acetylcholinesterase from the resistant and susceptible strains, indicating that the sensitivity of the target site has not been altered. Biochemical assays on mass homogenates of the resistant and susceptible strains showed no correlation between resistance and the level of glutathione s-transferase activity, or the amount of cytochrome P450 present.

A comparison was made between the cuticular hydrocarbons of five Palaearctic species of the Anopheles maculipennis Meigen complex; A. maculipennis sensu stricto, A. melanoon Hackett, A. messeae Falleroni, A. labranchiae Falleroni and A. atroparvus Van Thiel. Females of these species had their cuticular lipid removed and the hydrocarbons separated and quantified by gas chromatography. Discriminant analysis determined the degree of difference between the species. Wild caught adults of the complex had an average correct classification rate of 77.9%. A. atroparvus and A. labranchiae are homosequential and have no uniquely diagnostic isoenzymes, but expressed distinct hydrocarbon profiles enabling them to be separated in more than 86% of cases. Similarly, A. maculipennis sensu stricto and A. melanoon differ only by minor karyotype alterations, yet their hydrocarbon profiles could be separated with 83% correct classification. A dendrogram was drawn up, based on the hydrocarbons, using the Mahalanobis distances between species. A. maculipennis sensu stricto and A. melanoon were the two closest groups; A. messeae was next to join the cluster, followed by A. labranchiae and then A. atroparvus. These last two species were also very close to each other, but quite distant from A. maculipennis sensu stricto and A. melanoon. The species' relationships based on hydrocarbons thus reflect the tentative chromosomal phylogeny of the complex. In nature, hydrocarbon differences between species may be a device enabling the recognition of suitable mates. Studies showing that hydrocarbon dissimilarity is elevated between sympatric populations are also discussed in support of this theory.

The reproductive performance of the African migratory locust, Locusta migratoria migratorioides (Reiche & Fairmaire), was assessed in a cereal crop environment on the temperate Highveld of South Africa. Of the two principal crops involved on the Highveld, maize realized the highest reproductive potential during summer, wheat was successfully utilized for breeding in spring. The combined effects of food and temperature were the main factors influencing seasonal variation in clutch size. Green food was essential for continued reproduction, oviposition ceased for three to four months during winter when food resources deteriorated and was resumed in spring. Although locust size was shown to decrease significantly in early winter, this did not influence fecundity. The effects of egg resorption, female age and phase on clutch size are outlined. Despite the more adverse climate of the Highveld, the migratory locust realized higher individual natality in the cereal crop environment than that recorded previously and consequently achieved outstanding reproductive success in this alternative habitat.

The stages of bush fly Musca vetustissima Walker, killed by the dung beetles, Onthophagus binodis Thunberg and Onitis alexis Klug, at low and high densities were measured in cattle dung of low nutritive value. A high level of M. vetustissima mortality occurred in the presence of Onitis alexis and Onthophagus binodis in experiments both in the laboratory at a constant 25°C, and exposed to summer fluctuating temperatures outside. The K values for total eggpuparia mortality increased curvilinearly with increasing log10 beetle numbers. The mortality of older larvae, k3, was most closely correlated with total mortality, K, where b = 0.720 and r2 = 0.931, while a lesser but significant correlation was obtained with mortality of young larvae, k2, where b = 0.291 and r2 = 0.645, but no correlation was obtained with egg mortality, k1, where b = −0.010 and r2 = 0.058. It is predicted that in unfavourable dung which occurs during summer, mortality of older bush fly larvae will be the key mortality caused by scarabaeine dung beetles.

The estimation of tsetse fly mortality rates from life-table data is central to opulation dynamics studies and to the development of tsetse fly control programmes. For a population at equilibrium with a stable age distribution, the age-specific mortalities may be estimated directly from the number of individuals in each age class, but a correction must be applied when the population is growing or declining. Furthermore, if the mortality rates are changing with time, inaccuracies will be introduced into estimates of the mortality rates derived from the age structure of the population since the population will take time to reach a new stable age distribution. In this paper we use the Euler-Lotka equation, which relates the age-specific mortality and fecundity to the overall growth rate of the population, to study the loss rate of the tsetse fly Glossina pallidipes (Austen) as a function of pupal mortality, adult mortality and mortalities applied to each age class seperately. We then present a simulation model in order to quantity and to set limits on the precision of estimates of mortalities when the mortalities are themselves changing.