Samples of engorged outdoor-resting females of the complex of Anopheles punctulatus Dönitz, primarily A. farauti Laveran, were obtained from villages in Madang Province, Papua New Guinea, in 1981–83 and their blood-meal sources identified. The proportion of the population feeding on man varied considerably from village to village according to the number of animals, particularly pigs, available as alternative hosts. Using a unique host in a mark–release–recapture experiment, the distance flown by engorged females of A. farauti was found to be generally less than 50 m. In one village, the gonotrophic age of a subsample of 1523 females of A. farauti was obtained and in 503 of these the electrophoretic pattern of the enzyme phosphoglucomutase (PGM) determined. Tests of association were per formed on the data. However, no significant relationship was found between host source, gonotrophic age and allelic type of PGM. Thus, separate subpopulations of A. farauti were not identified within this village. The relevance of the results to the epidemiology of malaria is discussed.

Ways in which the bionomics and dynamics of populations of Musca domestica L. can influence the development of insecticide resistance, and how resistance genes spread within and between farms was investigated in a three-year study of the biology and movement of flies on 63 pig-rearing farms in south-eastern England. House-flies survived winter only on 12 ‘overwintering’ farms where they bred in heated pig-rearing houses (‘closed buildings’) throughout the year. In late spring they appeared out doors, and their descendents founded populations on neighbouring ‘summer’ farms where pigs breed only in unheated (‘open’) buildings. There, flies reached peak numbers in August–September and died out by mid-November. Gene flow within and between farms was studied indirectly by mark-release-recapture of colour-marked adults, and directly by monitoring the diffusion of the visible marker gene bwb (brown body) introduced into indigenous house-fly populations. Although movement between open buildings within a farm was unrestricted, dispersal between farms was limited, and gene flow between even adjacent closed buildings was indirect, and required more than one generation. Likewise, indirect and gradual gene flow during summer probably accounted for the similarity in type and frequency of other independent genetic markers of local overwintering populations. Thus closed buildings played a key role in house-fly ecology and population genetics. Unfortunately, control with persistent insecticides in these buildings ensures efficient resistance selection, ultimately resulting in its spread to all pig farms. Less selective control practices are needed at these sites.

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.

Wavelength dispersive X-ray fluorescence spectrometry was used to make quantitative determinations of the elemental composition of adults of Agrotis segetum (Denis & Schiffermüller) that had been reared on one of eight soil-plant combinations or a semi-synthetic diet. Robust-means principal components analysis (RMPCA) of the data for eight elements and all treatments (except for the semi-synthetic diet) separated the means of the groups by soil type, irrespective of host-plant. However, individuals could not be separated until the data were grouped into the two host-plant sub-sets. The main discriminant, Al, was of doubtful validity and was therefore excluded from the data which were reanalysed by RMPCA. This failed to discriminate either group means or individuals until each host-plant sub-set was analysed separately; then, individuals could be differentiated by soil type although not as distinctly as when Al was included in the data. There was, however, a clear separation of the sexes because of a higher content of K and lower content of Ca in females; these two elements, together with S and Cl, were the main discriminants of soil type. It is concluded that larval host-plant is a significant factor in the elemental composition of adults of A. segetum but limiting and confounding in respect of identification of soil type and, therefore, geographical source. This conclusion probably applies also to other similar polyphagous species, but specific differences in biology and behaviour may influence the applicability of the technique to field studies.

Crosses were made between the three subspecies of the complex of Glossina morsitans Westwood and the hybrid females backcrossed. Hybrid female fecundity was highly ‘reactive’ to foreign male genes when the mother was G. morsitans centralis Machado compared with the reciprocal crosses and backcrosses. Hybrid F1 males were unable to inseminate females successfully, and although in nearly a quarter of the dissections sperm was transferred to the uterus, it did not migrate to the spermathecae. Heterozygosity between the X- and Y-chromosomes and most of the autosomes led to high frequencies of sterile males, but homozygosity between the X- and Y-chromosomes could still yield 30–50% sterility. Successive backcrosses of hybrid females between G. m. morsitans and G. m. centralis to the latter subspecies continued to increase the frequency of fertile males. Interactions between X-chromosome and autosomal gene seemed to be responsible for hybrid male sterility, and the number of sterility genes involved appeared to be very few. Crosses involving G. morsitans submorsitans Newstead generally agreed with those between the other two subspecies, but the distortion in the sex ratio of emergent adults limited the application of the data to this subspecies. Competition experiments using sterile hybrid males and fertile males in population cages (30 cm cube) showed that suppression was possible, especially when the ratio of sterile:fertile males was 2:1. The value of stetile hybrid males in tsetse control programmes and the evolution of reproductive isolation in the complex is discussed.

The black markings on larvae of Cactoblastis spp. can be used to separate different biotypes or species. These markings are figured, together with host and locality records for ten distinct biotypes or species, at least five of which are undescribed. Past introductions of C. cactorum (Berg) and Cactoblastis spp. to Australia and elsewhere are reviewed, and it is suggested that some of the undescribed biotypes might be of value in the biological control of Opuntia spp.

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.

Energy dispersive X-ray spectrometry was used to make quantitative determinations of the elemental composition of plasma-ashed apterous and alate individuals of Metopolophium dirhodum (Walker) and Rhopalosiphum padi (L.). Both morphs of M. dirhodum were reared on wheat grown in potting compost as were the morphs of R. padi but the latter were reared also on oats, free from or infected with barley yellow dwarf virus (BYDV), grown in potting compost. The data were statistically analysed by various multivariate methods, which demonstrated that alatae of both species were more readily separated by their chemoprints than were apterae. There were also clear differences, again in both species, between the two morphs from wheat and the two from oats; the main discriminant elements for R. padi were Fe, Al and Mn, and for M. dirhodum they were Cl, Ca and Al. Alatae of R. padi from healthy and BYDV-infected oats were clearly differentiated from each other and from their apterae; both groups of apterae could also be separated but not as distinctly as the alatae. The discriminant elements for these separations were Fe, Zn and Mn, and possibly Al. The differences between alates, and between alates and apterae, may reflect fundamental differences in homeostatic and metabolic processes in alate and apterous morphs of R. padi.

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.

Questing individuals of Ixodes ricinus (L.) on a naturally infested moorland in Wales were censused every fortnight from January 1981 to October 1982 by blanket-dragging, and feeding ticks were counted on the sheep hosts. The seasonal activity patterns for ticks in all three stages were unimodal, with nymphs and adults active between March and July, and larvae active between April and August. This unimodal, as opposed to the usually described bimodal, pattern is explained in terms of the long cold winters and short summers of this field site. The survival time of questing nymphs was calculated from an analysis of their changing lipid content during the activity season to be a maximum of four months, which is consistent with the other field observations. The precise identification of the pattern of activity, as well as being essential for the application of appropriately timed control procedures, is necessary for the interpretation of the tick-host interactions under various control regimes that were applied.

Genetic (electrophoretic) variation was examined in the two pest species of Heliothis found in Australia, H. armigera (Hübner) and H. punctigera Wallengren. They could be differentiated by seven loci which enabled identification of individual eggs and small larvae not normally distinguishable by their morphology. The traditional criteria for distinguishing the larger larvae of the two species were shown to be unreliable. The genetic distance between the two species was 0·34 ± 0·02. The percentage of loci polymorphic in both species, 32%, and the mean heterozygosities, 11·3% for H. armigera and 10·8% for H. punctigera, are lower than those reported in the American species, H. virescens (F.) and H. zea (Boddie). Populations throughout Australia were differentiated from each other, but there did not appear to be a marked geographic pattern to the variation. Genetic distances between populations of H. armigera were low (<0·01). It was concluded that the effective population size of Heliothis is large and that significant gene flow probably occurs between widely separated regions.

Radar methods have been extended to measure the aerial density of small insects. Results obtained during an outbreak of the cereal aphid Metopolophium dirhodum (Walker) in south-eastern England were compared with simultaneous suction trap catches to study the sensitivity of trap effectiveness to windspeed. Two traps were studied: the Rothamsted Insect Survey trap (12·2-m) and a standard aerofoil trap. The Survey trap effectiveness is moderately sensitive to windspeed, decreasing exponentially by a factor of two for each 2·4 m/s (5 knots) of average windspeed. The two trap sensitivities did not differ significantly, but both results are very significantly different (P>0·001) from the published predictions, which were based upon a comparison of catches from suction traps and a combination of a rotary (whirligig) net and a tow net. These differences are discussed. The average catching rate is about 40% of that of an ideal trap. Seven-day catches could vary by a factor of 0·5—2·0 from average due to prolonged periods of extra strong or light winds. Systematic windspeed gradients can corrupt suction trap studies of insect dispersal in relation to vertical density profiles, diurnal flight patterns and geographical distribution. Absolute calibration of the aerofoil trap was achieved by using the remote-sensing IRADIT infra-red system to measure the aerial density of aphid-size insects near to the trap inlet in very light winds; the effectiveness was not statistically different from unity, and the Survey trap is expected to perform similarly.

The experimental manipulation of separate, but originally identical, populations of Ixodes ricinus (L.) by applying three conventional tick control measures in different enclosures on naturally infested moorland in Wales allowed the elements of the tick-host interaction to be analysed quantitatively and the effectiveness of the control methods to be compared. From the relationship between the sheep stocking density and the numbers of questing ticks picked up by fortnightly blanket-dragging in each enclosure, the death rate of ticks during their activity season and the rate of contact between sheep and ticks were calculated. From this, it was possible to investigate the effect of different stocking densities on the feeding success of ticks. A major factor determining the much lower contact rate for larvae than for nymphs was the different spatial distribution of questing ticks, clumped for larvae and random for nymphs. The non-random use by sheep of the three different vegetation zones in the paddock resulted in the highest contact rate between sheep and ticks in the pasture area, but tick survival was apparently highest in the bog area. Combining these factors resulted in the prediction that the bracken area was the least favourable habitat for ticks. In the two enclosures where the sheep were not treated with acaricide the mean tick loads on the sheep were similar, but the lower overall use of the pasture by the sheep in the low stocking density enclosure (2/ha) resulted in slightly lower tick loads there compared with those in the high stocking density enclosure (4/ha). The numbers of ticks counted in the second year showed that pasture spelling was the most effective control method, acaricide treatment was less effective, and the benefits of halving the stocking density were marginal. The implications of these results for control strategies are discussed.

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.

Experiments were carried out in a slow speed wind tunnel and in a moving air observation chamber on anemotactic and visual responses of Stomoxys calcitrans (L.). An increase in carbon dioxide concentration elicited an anemotactic response, which was enhanced by odours from expired human breath and odours from a live guineapig. Acetone vapour also elicited an anemotactic response, but acetic acid was repellent. The response to visual targets increased in proportion to the increase in flight activity induced by raising the concentration of carbon dioxide in the airstream. Cattle sebum had an arrestant effect but also elicited further searching activity.

Laboratory experiments were carried out to investigate the effect of carbon dioxide and breath odours on the flight activity of Stomoxys calcitrans (L.). The flies responded to an increase in carbon dioxide concentration by an increase in flight activity (measured as the number of flights or the number of take-offs). The extent of this response was dependent on the period of starvation before exposure and the level of the increase in the carbon dioxide concentration. Flies rapidly habituated or adapted to new levels of carbon dioxide. Expired human breath elicited a greater increase in flight activity than would be predicted from its carbon dioxide content, and it was shown that the increased activity was caused by breath odours acting synergistically with an increase in the carbon dioxide concentration.

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.