Examination of the polytene chromosomes and cross-breeding data confirmed the specific status of Anopheles dirusPeyton & Harrison within the complex of A. balabacensis Baisas. The data also strongly suggested that A. dirus itself is a complex of at least two species, one of which, a hitherto unrecognized species, provisionally designated A. dirus species B, previously known as the Perlis form, occurs in northern Peninsular Malaysia. A distinct population from Thailand was designated A. dirus species A. The mosquitoes studied also include material from natural populations in Sabah, here provisionally designated A. balabacensis s.s., and may represent the first genetic analysis of this species. The Sabah material is distinct from either of the A. dirus forms. Hybrid males from crosses of A. balabacensis × A. dirus species A and of A. dirus species B females × A. dirus species A males were sterile. Chromosome studies also showed that reproductive isolation was accompanied by genetic changes in both the autosomesand X chromosome in the hybrid larvae.

The hymenopterous parasite, Aphidius sonchi Marshall, has been introduced into Australia as a biological control agent of the sowthistle aphid, Hyperomyzus lactucae (L.), the principal vector of lettuce necrotic yellows virus disease. Some aspects of its biology were studied in the laboratory. Females reared at 22°C contained a mean ± s.e. of 179·4 ± 10·26 eggs on emergence, and more eggs were formed during adult life. Unmated females produced male progeny only; mated females produced progeny of both sexes. At 22°C, both males and females mated within 12 h of emergence. Virgin females could mate successfully after having commenced oviposition and switch to producing progeny of both sexes. At 20°C, both virgin and mated females started oviposition within 7 h of emergence. The female oviposited in all nymphal instars and both apterous and alate adults of the host. Only one egg was laid per insertion of the ovipositor. Superparasitization was common, but only one parasite per aphid survived to the adult stage. Females at 22°C and LD 12:12 oviposited during both the photophase and the scotophase; the proportion of eggs laid in the scotophase was correlated with the availability of hosts. Adult females lived longer in the absence of hosts than in their presence and lived longer than males, and those supplied with water and honey lived longer than those without. Facultative diapause occurred. The integumental coloration of adults varied according to the temperature during their immature stages. Females of A. sonchi oviposited readily in Macrosiphum euphorbiae (Thomas), but their progeny did not develop beyond the egg stage. A. sonchi was parasitized by Alloxysta ancylocera (Cameron), Pachyneuron aphidis (Bouché) and Dendrocerus carpenteri (Curtis) in the field.

In the Zambezi Valley of Zimbabwe, the numbers of Glossina morsitans morsitans Westwood and G. pallidipes Austen electrocuted on grids placed across their flight paths as they arrived at various natural and synthetic odour sources demonstrated that ox odour comprises two broad fractions of attractants. One fraction can be trapped by a charcoal filter and, in part, consists of 1-octen-3-ol. A more volatile fraction passes through the filter and, in part, consists of carbon dioxide and acetone. Levels of acetone and 1-octen-3-ol in ox odour varied considerably, up to maxima of 24 mg/h and 0·025 mg/h, respectively. Catches were roughly doubled when octenol at 0·5 mg/h was added to ox odour, but declined when the dose was increased to 50–500 mg/h. A synthetic odour consisting of 2 litres of carbon dioxide/mm, 5 mg of acetone/h and 0·05 mg of 1-octen-3-ol/h, was nearly as effective as ox odour for G. m. morsitans but only half as effective as ox odour for G. pallidipes. Increases to the doses of each attractant in the synthetic odour increased the catches, to roughly double those with ox odour. Data for other Diptera are also presented.

In Zimbabwe, the catches of Glossina morsitans morsitans Westwood and G. pallidipes Austen in traps were increased by up to three times by releasing 1-octen-3-ol at 0·05–50 mg/h or acetone at 5–5000mg/h near traps, but in some circumstances 1-octen-3-ol at 5–50 mg/h reduced catches. Carbon dioxide at 0·02–20 litres/min increased catches by up to ten times. A mixture of all three chemicals increased the catches by up to 60 times. Each of the three chemicals attracted both species of flies from a distance; carbon dioxide also enhanced trap-entering and alighting responses. Acetone with 1-octen-3-ol can increase by several times the numbers of flies that contact visual baits suitable for exposing them to insecticide. Data for other Diptera are also presented.

An assay based on recovery rates of released laboratory-reared flies was used to compare the field performance in Australia of a series of strains bearing compound chromosomes with that of wild-type strains of Lucilia cuprina (Wiedemann). The compound chromosome strains tested all performed less well than the wild-type strains. Four of the former were recovered on average 0·37 times as readily as the average wild-type strain, and one was recovered 0·65 times as readily. The compound chromosome strains differed in the selection pressure they had been exposed to in the field, which had selected among the various compound chromosomes in an original strain and in the extent to which their non-compound chromosomes had been replaced by recently collected field material. The strain that performed best had been exposed to the most severe selection pressure, overwintering in the field, and had had much of its non-compound genome replaced. Among the group of strains with similar performance, some had had their non-compound genome replaced with field genetic material.

The genus Isozulia is re-characterized and compared with Aeneolamia. Two species are transferred from Aeneolamia to become I. astralis (Distant) comb. n. and I. christenseni (Lallemand) comb. n., and I. flamen Fennah is reduced to a subspecies, I. astralis flamen, stat. n. Two populations from Ecuador and Peru are described as new species, I. minor sp. n. and I. charaxus sp. n., respectively, and a population of I. christenseni in Jujuy Province, Argentina, is recognised as a distinct subspecies, I. c. jujuyana subsp. n. Both this subspecies and I. minor are reported as attacking sugarcane.

Ferrisia meridionalis sp. n. is described from Paraguay on cassava and from Argentina on ragweed (Ambrosia tenuifolia). Characters are given to separate it from F. virgata (Cockerell) with which it may easily be confused in life in South America on cassava.

Simple one- and multi-generation models are used to show the essential features of the dynamics of selection for resistance to one insecticide or two unrelated insecticides in insect populations, part of which are unexposed to either compound. The use of a mixture appears advantageous provided that resistance is not fully dominant, but, if it is, linkage disequilibrium builds up rapidly and nullifies the advantage of the mixture

The sawfly Cephalcia lariciphila (Wachtl) is a pest of larch (Larix spp.) that has recently become widespread in Britain. Before taking measures to control the sawfly the status of parasites in the infestations was investigated. The only insect parasite species found was the ichneumonid Olesicampe monticola (Hedwig), which is new to Britain. As this insect is taxonomically so poorly known it is redescribed from specimens collected in South Wales. The preliminary biological observations show O. monticola to be well-adapted to its host and that it can significantly reduce an infestation.

Insecticide-impregnated blue cotton targets 70 × 110 cm weretested for the control of Glossina palpalis palpalis (Robineau-Desvoidy) and G. tachinoides Westwood in riverine fringing forests in central Nigeria, under wet-season conditions. Following exposure to treated cloth for 1·5 min, delta-methrin caused 100% mortality of G. p. palpalis for six weeks at 0·05% and for 13 weeks at 0·1%. Dieldrin at 5% was not very effective. At 4%, endosulfan initially caused a high mortality, but rapidly lost its activity, especially against females. By chemical analysis, 43% of deltamethrin applied to the fabric was found to have been lost within 12 weeks, in which 230 mm of rainfall was recorded. Placed 150 m apart in a fringing forest, targets impregnated with 0·05% deltamethrin caused a rapid decline in the G. p. palpalis population, and after 12 weeks only 5% of the original density was recorded. No further reduction or significant increase was observed during the following six months, though it appeared that flies caught during this period had immigrated from an adjacent undisturbed riverine forest. The effect on G. tachinoides was less dramatic, but this may have been due to the low initial density of this species, and to its greater mobility, giving rise to reinvasion from elsewhere.

Gravid females of Culex quinquefasciatus Say from a laboratory strain originating in Nigeria orientated to a source of the main volatile pheromone component, erythro-6-acetoxy-5-hexadecanolide, isolated from the apical droplets of the egg rafts. Significantly more egg rafts were laid around polystyrene discs treated with the synthetic compound than around untreated discs, and modification of the chemical structure destroyed its biological activity. The response was found at a dose of 0·02μg of the synthetic compound, which is equivalent to one-sixteenth of the total acetoxyhexadecanolide found in an egg raft, and above. Although the apical droplets were contaminated by bacteria, these did not contribute to the production of the acetoxyhexadecanolide, which was present in the eggs before they were laid. It is concluded that the pheromone is released slowly from the apical droplets into the air above the water surface, attracting other gravid females to oviposit around previously laid egg rafts, and there is evidence of attraction over a distance of 5·5 cm.

Multilocus electrophoresis was used to study the genetic variation of field samples of Culex quinquefasciatus Say from Mali, Burkina Faso, Nigeria and Mozambique, and a laboratory strain from Senegal. Phallosome morphology (the DV/D ratio) was used for the taxonomic identification of the males. The proportion of individuals with a highly active esterase pattern, indicating resistance to organophosphorus insecticides, ranged from 0 to 0·75 in the field samples and was 1·00 in the Senegal strain. The following 17 loci were genetically analysed: α-Gpdh, Mdh-1, Mdh-2, Me-1, Me-2, Idh-1, Idh-2, 6Pgdh, G3pdh, Got-1, Got-2, Hk-1, Adk, Pgm, Aid, Tpi and Gpi. Comparisons made with published data for C. pipiens L. from the Old World and C. quinquefasciatus from the USA revealed similar levels of genetic variability in C. quinquefasciatus from Africa (H e = 0·06, P = 0·44, A = 1·47) and the USA, but considerably higher variability in C. pipiens (H e = 0·14, P = 0·52, A = 1·64). C. quinquefasciatus populations appeared genetically much more homogeneous than those of C. pipiens (average Nei's D = 0·004 within the former taxon, about ten times more within the latter) and the genetic divergence between African and USA samples of C. quinquefasciatus was very low (D = 0·003). Comparison between C. quinquefasciatus from Africa and C. pipiens showed that the former is genetically more related to C. pipiens s.s. from Italy (D = 0·145) than to C. pipiens form molestus Forskål from Italy (0·186) or Egypt (0·165). The average genetic distance found between C. quinquefasciatus and C. pipiens was 0·17, a value observed for some pairs of mosquito sibling species. Allele frequencies at some loci (Me-2 and Got-2) appeared to be remarkably differentiated between C. quinquefasciatus and C. pipiens, with fixed alternative allozymes at the Me-2 locus: 106 in C. quinquefasciatus, 100 and 108 in C. pipiens. These findings provide a basis for the investigation of gene flow between contiguous or overlapping populations of these two taxa in order to ascertain their relative taxonomic status.

Tanaostigmodes cajaninae LaSalle sp. n., the larvae of which feed in pods of pigeon pea (Cajanus cajan), is described. This insect, which also feeds on the weeds Atylosia spp. and Rhynchosia spp., has reached pest status on ICRISAT's research farm in Andhra Pradesh, India, where more than half of the pods on the late-maturing pigeon pea crops may be infested. However, surveys of the crops in farmers' fields in India showed that, although this insect is widespread, it is not yet a serious pest. The abnormal populations of this insect on the ICRISAT research farm appear to be associated with an abundance of its wild hosts, the availability of pigeon pea pods for many months in each year and the use of endosulfan, which does not control the pest but reduces its parasites. The potential for T. cajaninae to become a major pest in farmers' fields is discussed, and control measures are suggested.

Differences in responses of males and females of Lucilia cuprina (Wiedemann) to carrion-baited traps were examined in Australia in relation to time of day, temperature, wind speed, relative humidity and solar radiation. The differences were small compared with responses obtained for the combined sexes (total catch), but the results were inconsistent over the four seasons of trapping. The seasons with most data (1975–1976 and 1981–1982) gave reasonably consistent results. Seasonal differences, although significant, were small enough to neglect for the purpose of standardizing trap catches. Time-of-day effects were also unimportant, except that males tended to be less active than females during the early morning (dawn-0900 h) and more active than females during the late afternoon (1500 h-dusk). Separate models are presented for standardization of male and female catch rates; the estimates differ from those obtained from total catches, but the differences are small compared to the observed day-to-day variation in catch rates.

The effect of constant and sinusoidally cycling temperatures on the durations of combined egg and larval development and of pupal development of Liriomyza trifolii (Burgess) was studied. The observed and estimated durations accorded well using 147·5 day-degrees above 10 1°C for eggs and larvae and 138·7 day-degrees above 10·8°C for pupae. A few pupae survived for 76 days in outdoor cages during a winter in southern England. Eggs hatched at 6–16°C (cycling), but larvae did not complete their development under this regime. Adults emerged from pupae at 6–16°C, and a few deformed adults emerged after 65 days at 11·5°C (constant). Some pupal development was detectable at 8°C. Pupae exposed to 1·1°C for 20 days all died, but some adults emerged at 14–26°C from pupae that had been kept at 1·1°C for 15 days.

Hollow-fibre, laminate-flake and microencapsulated formulations of the synthetic sex pheromone (a 1:1 mixture of (Z, Z)- and (Z, E)-7, 11-hexadecadienyl acetate) of Pectinophora gossypiella (Saunders) were compared in large-scale mating disruption trials in Egypt in 1982. Fifty-hectare blocks of cotton were treated at regular intervals throughout the season with the formulated pheromone as the sole means of controlling the pest. The pheromone treatments were compared with conventional insecticide spray treatments in other 50-ha blocks of cotton sited in the same localities. Comparisons of numbers of infested flowers and green boils, open boll counts, crop development, yield of seed cotton, lint quality and seed damage in pheromone-and insecticide-treated blocks, showed that adequate levels of control were achieved using the pheromone formulations, which were equal in effect to the insecticide sprays. Beneficial insects were found in greater numbers in the pheromone-treated areas than in areas treated with insecticides.

Bruchophagus muli sp. n. is described and compared to a similar Australian species, B. fellis (Girault). Both wasps attack citrus; B. muli galls the fruit of lime (Citrus aurantifolia) while B. fellis galls the twigs of a number of citrus varieties in Australia, including lemon, orange and grapefruit. B. muli appears to be restricted in distribution to the southern region of Papua New Guinea

An ecological study of summer populations of Metopolophium dirhodum (Walker) on winter wheat, was carried out near Bedford, UK, in 1978–80. Alate production (as percentages of alatiform fourth-instar nymphs) followed a consistent and synchronous three-phase pattern: with increases to 50% in early June in 1978–80 and 90% in late July in 1978–79. The proportions of winged offspring deposited by apterous parents also showed a similar increase, changing from 5% on 14–20 June to 91% on 5–11 July. Alate parents deposited mostly (75%) wingless offspring. Frequency distributions for nymph batch sizes were obtained for both morphs in 1979. Alate deposition was bimodally distributed. For apterous aphids, the fourth instar was the main dispersal stage. The numbers of adult apterae expressed as proportions of the total population were generally lower in 1979 than in 1978. The numbers of colonies increased sharply between 19 and 21 June in 1978 and 1979, and remained at similar levels to each other until at least 5 July. Colony and population numbers were highly significantly correlated over certain periods in 1978 and 1979. Colonies with >20 aphids increased sharply in numbers after 6 July, probably as a result of changing aptera dispersiveness. An estimate of mean colony size in 1979 showed a well-defined 14-day plateau phase. Changes in population alate production and changes in the proportions of winged offspring (from apterous parents) are discussed in relation to colony development. It is considered that increases in colony size produce colony-specific patterns of alate production.