Gene flow between field populations of the cereal aphids Sitobion avenae (Fabricius), Sitobion fragariae (Walker) and Rhopalosiphum padi (Linnaeus) is examined using statistical analyses of allozyme frequency data (both Slatkin's and F statistics). Analysis using Slatkin's method confirms the conclusions previously drawn from earlier analyses. Thus there is found to be high gene flow between subpopulations of S. avenae and R. padi, and a more restricted level between local S. fragariae subpopulations, especially when infesting the secondary host (cocksfoot grass, Dactylis glomerata). The value of Nm (number of immigrants per generation) calculated for S. avenae was approximately 2 and is indicative of high gene flow i.e. Nm>1.0. Also, as previously found by x2 genetic contingency testing, the F statistical analysis confirms that S. fragariae subpopulations infesting D. glomerata are genetically more heterogeneous than those infesting the primary host, blackberry, Rubus fruticosus agg. Hence, there may be less gene flow between populations on the secondary host compared with that on the primary. The results obtained are compared with the flight behaviour of these particular aphid species and to their respective host plant abundances. The advantages and disadvantages of both Slatkin's method and F statistics for analysing insect population genetic structure are noted.

The susceptibility levels of Mansonia bonneae Edwards larvae to Bacillus thuringiensis israelensis (B.t.i.) SkeetalR, B.t.i. BactimosR briquettes and Bacillus sphaericus RB80 were evaluated under field conditions. Satisfactory control of larvae was achieved during 24 h–48 h post-treatment. At 72 h after treatment with a 48 h exposure period, over 90% reduction was achieved by SkeetalR at both applied dosages and by B. sphaericus RB80 at the higher applied dosage. BactimosR briquettes achieved less control at both applied dosages, due to slow, sustained release of B.t.i. spores. SkeetalR and B. sphaericus RB80 released their toxic ingredients as early as 2 h after treatment, after which the spore counts (CFU/ml) increased steadily in the middle and bottom water layers and reached maximum level at 72 h post-treatment. However, SkeetalR displayed very little residual activity as evidenced by the drastic decline of spore counts as well as larval reduction at one week post-treatment. By contrast, BactimosR briquette and B. sphaericus RB80 prolonged their residual toxicity throughout the four week period. The peaks of spore counts in the middle and bottom water layers for SkeetalR and B. sphaericus RB80 preceded the corresponding peaks for larval reduction rates by 24 h and 48 h and 1 week to 2 weeks, respectively. The spore counts of BactimosR briquette at the high applied dosage fluctuated closely with the reduction rates of larvae throughout the four week period.

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.

The taxonomy and host-records of 11 Telenomus species recorded from eggs of ten species of pyralid pests in Africa are reviewed. Three species, T. bini, T. creusa and T. nemesis, are described as new. Primary type material of nine previously described species was examined: T. applanatus Bin & Johnson, T. etielliphaga (Risbec) (comb. n.), T. nephele Nixon, T. procas Nixon, T. soudanensis (Risbec), T. thestor Nixon, T. tolli Risbec, T. ullyetti Nixon and T. versicolor Bin & Johnson. A lectotype is designated for T. etielliphaga (Risbec), which is transferred to Telenomus from Micromymar. Lectotypes are also designated for T. soudanensis and T. tolli. The monotypic genus Micromymar Risbec is synonymized with Telenomus. A method for the preparation, mounting and identification of Telenomus specimens reared from eggs of African pyralid pests is given. Host-records based on previously misidentified Telenomus spp. are corrected, and records in which the host has been apparently misidentified are commented upon. The relevance of Telenomus spp. to biological control and integrated pest management of African pyralid pests is discussed.

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.

Immature stages of bush fly, Musca vetustissima Walker, were reared at constant temperatures ranging from 18°C to 39°C. Mean egg to adult development times ranged from 7.0 to 25.8 days. Eggs, larval instars I, II and III, and pupae averaged, respectively, 3.1, 4.4, 5.5, 36.4 and 50.6% of the total development time. Mean development rate was a non-linear function of temperature. A non-linear development rate model accurately estimated mean development times of immature stages under both constant and fluctuating temperature regimes. Simulation of dung pad temperatures, from air temperature and solar radiation records, predicted development times of soil- and dunginhabiting stages of M. vetustissima to within 4% of those observed under field conditions.

Phlebotomus perfiliewi perfiliewi Parrott and Phlebotomus perniciosus Newstead (Diptera: Psychodidae,) known vectors of Leishmania infantum were caught in light traps in five different sites in Italy. Sandflies were cryopreserved and transported to the laboratory where they were thawed and aqueous extracts of the crushed flies were analysed for their carbohydrate content using high performance liquid chromatography. Several sugars were detected, including significant amounts of the trisaccharide melezitose, known to be available as a natural source from aphid or coccid honeydew. There was no difference between the analyses of sugar meals of P. p. perfiliewi from different sites within its range, or between P. p. perfiliewi and P. perniciosus. The results indicate that both males and females of P. p. perfiliewi and P. perniciosus feed on honeydew.

Anagyrus mangicolasp. n., an encyrtid parasitoid of Rastrococcus species on mango in India, is described and compared with related species. The parasitoid has been the subject of laboratory studies and may be introduced into West Africa to supplement the activities of previously introduced natural enemies of the mango mealybug (R. invadens Williams).

Laboratory apparatus and techniques are described for the rearing and insecticidal treatment of whitefly, Bemisia tabaci Gennadius, under simulated field conditions. Insects were reared on cotton plants inside large population cages and treated from an overhead sprayer. The effects of these treatments were assessed accurately, without interfering with insects or plants, by monitoring adult numbers with an endoscope over one or more generations. Examples of single-generation and multiple-generation tests with cypermethrin are described. The apparatus is suitable for testing strategies for delaying the selection of resistance (e.g. using insecticides applied singly, alternately, or in mixture, at various application rates and frequencies), for controlling populations already resistant to insecticides, and for integrated pest management using chemical and biological control agents together.

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.

Records of braconid parasitoids attacking bees (Apidae) are reviewed and their biology is discussed. The adult of Syntretomorpha szaboi Papp (Braconidae) is redescribed, the female for the first time. The final-instar larva is also described for the first time and the implications of interpreting larval characters are discussed. The Oriental honey bee, Apis cerana Fabricius, is recorded here for the first time as the host of S. szaboi.

Antibiosis of resistant melon lines to the carmine spider mite, Tetranychus cinnabarinus (Boisduval), was evaluated in the laboratory. Significant differences among lines were observed seven days after the inoculation of detached leaf disks. The most resistant lines, namely CHI-8, BUS-7 and BUS-3, reduced the average mite daily fecundity by 49%, 40% and 33%, respectively, as compared to the susceptible NY line. Resistance did not appear to be related to the growth habit. Selfing resistant melon parents resulted in a significant increase in the number of plants on which female mites produced less than one egg per day.

A new genus Mesobraconoides Sarhan & Quicke is described for the species M. psolopterus (Wilkinson) comb. n. (type species) and M. truncatus (Szépligeti) comb. n. Both species have been transferred from Mesobracon. M. psolopterus is here recorded from Sierra Leone as a parasitoid of the pyralid, white rice borer, Maliarpha separatella Ragonot, widespread in the Afrotropical region. M. psolopterus is redescribed and illustrated and a key provided to separate it from M. truncatus.

Extracts of different sesame plant (Sesamum indicum) Linnaeus organs inhibited the in vitro growth of the fungus Leucocoprinus gongylophorus (Möller) (=Rozites gongylophora Möller), which is cultivated by the leaf-cutting ants of the species Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae). The presence of the factor responsible for this inhibition was detected in methanol or chloroform extracts and is constant in the plant.

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.

Ovarian dissection of Glossina austeni Newstead, G. brevipalpis Newstead, G. morsitans morsitans Westwood and G. pallidipes Austen shows that there are significant interspecific differences in egg-follicle lengths. Differences between G. brevipalpis and G. pallidipes are slight as are those between G. austeni and G. m. morsitans, but the former two species have significantly larger eggs at all ages examined than the latter two. Egg-follicle length is positively related to species size (measured as wing vein length) but only weakly related to the size of individuals within a species. In the ovarian dissection technique for ageing tsetse flies, nulliparous females are usually divided into 0A (one to four days) and OB (five to eight days) categories, depending on whether the first egg follicle is less or more than 0.6 mm in length. The results presented, however, show that at four days the first egg follicle is about 1 mm in length in G. pallidipes and G. brevipalpis and 0.77 mm in length in G. m. morsitans and G. austeni. Thus, application of the 0.6 mm, four-day threshold will result in severe under-estimation of the proportion of females of the former two species of less than five days of age in a population.

In Zimbabwe, catches of Glossina morsitans morsitans Westwood and G.pallidipes Austen at odour baited traps were increased in the presence of residues of a solution of the skin secretions of oxen (hereafter sebum) by 80% and 29% respectively, and catches at F3 traps were significantly increased when sebum was presented on adjacent screens. Testing of fractions of sebum revealed active components(s) in the phenolic and non-acidic fractions but not in the acidic fraction. Furthermore, the activity of the phenolic fraction could not be explained by the presence of the known phenolic tsetse attractants. The effect of sebum was to attract more flies to the target rather than to induce a landing response in a higher proportion of attracted flies. Whether or not tarsal contact responses are involved remains conjectural. However, targets that were electrified over only one quarter of the surface caught more than one quarter the catch of targets electrified over all the surface both with and without sebum, indicating that many tsetse habitually alight more than once on baited targets. Data on the catches of other Diptera are also presented

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 effect of a range of temperatures (15–42°C) and relative humidities (40–80%) on growth of populations of Liposcelis entomophilus (Enderlein), Liposcelis bostrychophilus Badonnel and Liposcelis paetus Pearman infesting a rice-based medium was investigated. These species are often found infesting stored cereal grains in the tropics. Both L. entomophilus and L. bostrychophilus bred most rapidly at 30°C, 70–80% r.h. Neither survived at temperatures of 36°C and above. In contrast, L. paetus bred most rapidly at 33–36°C, 70% r.h., and was able to breed at 42°C, 80% r.h. No species survived humidities below 60%. As well as consuming mould growth, Liposcelis spp. also caused visible damage in rice grains. Implications of these findings in the understanding of pest status and geographical distribution of severe outbreaks of Liposcelis spp. are discussed.

A pilot field study, involving periodic augmentative release of predatory larvae of a dragonfly, Crocothemis servilia (Drury), to suppress a mosquito, Aedes aegypti (Linnaeus), was conducted during the rainy season in Yangon (Rangoon). More than 90% of pre-adult A. aegypti occurred in domestic water-storage containers. Evaluations of larval and adult numbers of A. aegypti were made half-monthly three times before, and seven times after, treatment began. Four laboratory-reared, three-week-old C. servilia larvae were placed in each major source of A. aegypti larvae immediately after the third evaluation and then monthly for three successive months. Such treatment reduced the larval population of A. aegypti to a very low level in two to three weeks and suppressed it progressively until the trial ended; the adult population was greatly reduced after about six weeks and was progressively diminished thereafter until the trial ended. The trial's success was ascribed to: the virtual confinement of pre-adult stages of the target mosquito to containers accessible to control operators; the behaviour, growth rate, survival and ready availability of the chosen species of dragonfly; and the awareness and enthusiastic participation of local householders.