Aedes-borne diseases are on the rampant rise despite continued application of chemical insecticide-based interventions. The appearance of high degree of insecticide resistance in Aedes species and noxious effects on environment and non-targets have raised further concerns. Among new chemical interventions, neonicotinoids are considered a safe and effective approach. The present study investigated the control potency of acetamiprid and development of resistance in Aedes aegypti larvae; and the involvement of CYP450 monooxygenases in inducing resistance. The early fourth instars of Ae. aegypti parent susceptible strain (PS) were selected with acetamiprid for 15 generations (ACSF strain) increasing the resistance to 19.74-fold in ACSF-10 and 36.71-fold in ACSF-15. The ACSF-10 larvae were assayed with acetamiprid combined with piperonyl butoxide (PBO) in three different ratios (1:1, 1:5 and 1:10) and selected for next five generations with 1:10 combination. Selection with synergized acetamiprid (APSF strains) reversed as well as reduced the rate of resistance development resulting in only 1.35-fold resistance in APSF-15. The APSF strains showed %monooxygenase dependency ranging from 86.71 to 96.72%. The estimation of the monooxygenases levels in parent and selected larvae showed increased monooxygenase level in the ACSF strains by 2.42–2.87-fold. The APSF-15 strains exhibited 57.95% lower enzyme production than ACSF-15 strain. The reduction and reversion of resistance by using PBO and the elevated levels of monooxygenases in ACSF and reduction in APSF strains recommend the involvement of CYP450-mediated mechanism in the development of acetamiprid resistance in Ae. aegypti. These studies could help in devising resistance management strategies in order to preserve the efficiency of pre-existing insecticides.

An Agar/Parafilm membrane system, developed for feeding tsetse flies, was evaluated by comparing membrane-fed and goat-fed female Glossina morsitans morsitans Westw. with respect to the following: fly weight, meal size, trypsin levels and amount of protein in the posterior midgut, and the portion of midgut protein which is in the posterior midgut. In flies having the same prefeeding history, the digestive physiology of membrane-fed flies was not significantly different from those fed on goats. The offspring of membrane-fed flies were lighter, took smaller meals, and had less trypsin and protein in the posterior section of the midgut than did flies from the stock animal-fed colony. However the relationship between trypsin levels and protein in the posterior part of the midgut was the same in flies from animal-fed and membrane-fed colonies.

Monitoring of oriental fruit moths (Grapholita molesta Busck) is a prerequisite for its control. This study introduced a digital image-processing method and logistic model for the control of oriental fruit moths. First, five triangular sex pheromone traps were installed separately within each area of 667 m2 in a peach orchard to monitor oriental fruit moths consecutively for 3 years. Next, full view images of oriental fruit moths were collected via a digital camera and then subjected to graying, separation and morphological analysis for automatic counting using MATLAB software. Afterwards, the results of automatic counting were used for fitting a logistic model to forecast the control threshold and key control period. There was a high consistency between automatic counting and manual counting (0.99, P < 0.05). According to the logistic model, oriental fruit moths had four occurrence peaks during a year, with a time-lag of 15–18 days between adult occurrence peak and the larval damage peak. Additionally, the key control period was from 28 June to 3 July each year, when the wormy fruit rate reached up to 5% and the trapping volume was approximately 10.2 per day per trap. Additionally, the key control period for the overwintering generation was 25 April. This study provides an automatic counting method and fitted logistic model with a great potential for application to the control of oriental fruit moths.

Studies were conducted in Zimbabwe to determine the nature and degree of sexual responses of males of Glossina morsitans Westwood and G. pallidipes Austen around host animals, traps and targets. Males of both species, after being attracted, appeared to accumulate around a stationary bait. This was supported by observations of concentrations of unfed males of G. m. morsitans on bait animals and unfed males of G. pallidipes on the surrounding ground. Nutritional analysis confirmed that traps attract males with a range of hunger states but catch mainly hungry males of both species. Movement of electrified targets significantly increased the catches of both sexes of G. m. morsitans but not of G. pallidipes. Artificial female-mimicking decoys made from black felt sewn onto electrified targets significantly increased the numbers of G. m. morsitans males caught when the targets were stationary and of G. pallidipes males when they were moving. The electrified targets caught a higher proportion of males of both species than traps, most probably as a result of their killing the males accumulating around the target in search of virgin females. The results show that the behaviour of relatively well-fed males attracted to host animals, traps and targets does appear to have a sexual component in both G. m. morsitans and G. pallidipes and that it may be possible to exploit the sexual responses of males to increase capture efficiency further. However, targets may have far greater potential for such manipulation than traps.

A series of experiments was undertaken to examine the relative concentration of cotton flea-beetles (Podagrica puncticollis Weise and P. pallida (Jacoby), Halticinae) within cotton fields in the Sudan Gezira in 1954 and 1955. Assessments were carried out on the flea-beetle populations and on the damage done by them, and evidence is produced to show that the use of a damage assessment in the first three weeks of the life of the cotton plant is more satisfactory in a large-scale experiment than beetle counts. The assessment lasted for between three and four weeks after the emergence of the seedling cotton.

It appeared that the beetles tended to leave cotton 19 days after sowing. Damage within the cotton field was at first in accord with the sowing differential, but then shifted against this as the flea-beetles moved on to the later-sown cotton as this became more attractive.

The peak population of flea-beetles occurred during the last few days of August and the first few of September when the first-sown cotton was 14–18 days old, and this suffered more damage than the later-sown and less attractive cotton. Differences in the level of attack on the four sowings tended to even out, but did not do so completely as the flea-beetle population was declining.

An Ichneumonid, reared from egg-masses of weevils (Entypotrachelus meyeri Kolbe and E. micans Hust.) harmful to tea culture in Kenya, is placed taxonomically and is described under the name Sozites kerichoensis.

In experiments covering many successive generations of Musca domestica L. (strains NS and WHO/SRS/MHSCO domestica/1), sublethal doses of p,p'DDT applied topically to adults or fed to larvae or adults had no effect on the numbers of abnormal follicles, but the numbers of normal follicles increased in F1–3 when larvae were fed with diet containing 10 parts per million of DDT. These results conflict with those of previous workers. Other possible causes of abnormal oogenesis were examined. Sublethal doses of o,p'DDT and DDE (an impurity and metabolite, respectively of p,p'DDT) had no effect, whereas inbreeding and high-density rearing caused the numbers of normal follicles to fall; the latter caused the numbers of abnormal follicles to increase. There were also heritable differences in oogenesis among three strains of house-fly.

The small collection of CERATOPOGONINAE described in this note was made by me last December (1923) during a short voyage on the Nile from Cario to Assuan and back. The steamer on which the voyage was made anchored at night, and being brightly lit, attracted large numbers of midges which congregated on the woodwork in the neighbourhood of lamps and were thus easily secured. The collection, which was brought home to England before being examined, was not rich in CERATOPOGONINAE, but an account of such species as were contained in it may be of some interest, because little appears to be known about the occurrence of these midges in Egypt.

Genetic systems have been developed in several insect species for separating males and females prior to releasing sterilized males in pest control programmes using the sterile insect technique. The systems generally depend on translocating a readily selectable gene onto the Y chromosome. A potential source of instability in such a system is genetic recombination in the male. Although such recombination was originally thought to be absent in most cyclorrhaphous Diptera, low levels have recently been found. We have developed a computer model which simulates the progression of instability in the presence of male recombination, which can be used to assess the influence of rate of recombination in combination with a range of associated genetic and biological parameters. Male recombination alone or fitness of the Y-linked translocation were found to contribute relatively little to the rate of progression of instability. By contrast reduced fitness or mating competitiveness associated with the selectable gene had a strong effect. The sex ratio and the ratio of carriers to non-carriers of the selectable gene showed patterns characteristic of the parameters modelled. The relevance of such data to the development of suitable strains for genetic sex-separation and the replacement of strains under mass rearing conditions are discussed.

Descriptions are given of six hypogeic mealybugs forming the genus Geococcus. A key to species and illustrations of five species are included. G. johorensis is described as new from Malaya where it is reported as damaging oil palms. Another new species, G. lawrencei, is described from the Solomon Islands. The history of G. coffeae Green is discussed together with its present distribution.

The impact of Sahelian grasshopper species on short cycle pearl millet (Pennisetum glaucum) was studied at two sites in north-west Mali and techniques of crop loss assessment were investigated. At one of these sites an onfarm study was carried out with the co-operation of seven village farmers. The grasshoppers Diabolocatantops axillaris (Thunberg) and Kraussaria angulifera (Krauss) were the principal destructive species, primarily causing grain loss through their feeding upon millet heads. Leaf damage was found to be sustainable to a high level before influencing yield, although direct grain loss through head damage was shown to be an important determinant of final yield. It was concluded that the best means of determining the yield loss attributable to grasshopper attack for late-season patterns of damage was to estimate head damage immediately prior to harvest. In this estimate, heads were assigned to one of ten classes according to the severity of the damage. Studies at a second site demonstrated the existence of a linear relationship between estimates of head damage and actual grain weight loss. On the basis of these findings it is concluded that the average loss of yield incurred as a result of grasshopper attack in the study village, Mamaribougou Freybe, was 25.7% + 3.0, −2.5. A system is proposed by which such village-level crop loss estimates may be undertaken.

The rainfall of the Blue Nile valley diminishes towards the north, and the number of mosquitos tends to do the same, but the natural state of affairs has been somewhat altered by irrigation works in the shape of the Sennar reservoir and the watering of cotton, sorghum and sunt trees (Acacia arabica, Willdenow), and will be further altered when the proposed dam at Roseires is constructed.

The latter dam will form a large reservoir in the Kiri-Roseires area where conditions are likely to differ from those of the Sennar reservoir. Anopheles funestus Giles and many other species occurred in the stretch downstream between Roseires and Abu Hugar in which riverside basins, overgrown with sunt trees, were flooded when the river was high.

Farther downstream, between Karkoj and Sennar, breeding conditions were affected by the Sennar dam, water at full storage level reaching different heights in the basins according to their distance from Sennar. Near Sennar the dualpurpose dam had a particular effect on the aquatic vegetation and the mosquitos.

A. gambiae Giles bred among Najas pectinata (Parl.) Magnus which, however, only occupied a small area in the reservoir, A. rufipes (Gough) bred in small numbers in various places, and A. pharoensis Theo. in a large area of creeping grass growing on silt under conditions which caused it to form a raft that rose and fell with the water. Adults of A. pharoensis, which was by far the commonest Anopheline, rested near houses by day at certain times of the year. Control of the grass was difficult and liable, to favour more dangerous species of mosquitos. Differences between the Sennar and Jebel Auliya reservoirs are discussed.

In the riverain area between Abu Geili and Soba, A. gambiae bred in residual pools in the river-bed in the dry season and in flooded sunt basins in the rains. Control of larvae was very difficult in these basins and much reliance was placed on residual sprays against adults in houses.

Breeding conditions in the Gezira irrigated area are described with particular reference to the type of clay soil. There were many larvae of A. gambiae in field channels at the end of the rains when irrigation began, and in March when the summer started. The latter increase was not reflected by any increase in the number of adults, probably owing to the reduction in length of life of the latter in the very hot dry weather. A. rufipes was sometimes found in houses. Control measures are briefly described.

Some mosquitos of Khartoum and a few other areas within the Blue Nile valley are briefly considered.

The coffee leaf-miners Leucoptera meyricki Ghesq. and L. caffeina Wshbn. are serious pests of arabica coffee in Kenya. At the present time sprays containing parathion, methyl-parathion or diazinon are used extensively for their control.

To facilitate preliminary investigations into various aspects of insecticidal control of the larval stages of these pests, a laboratory bioassay technique was developed. Larvae were reared on detached coffee leaves placed on moist filter paper in plastic boxes. When the larvae were in their third instar, the leaves were sprayed in a Potter tower and then kept in a moist air stream for three days before the mines were dissected to enable mortality counts to be made.

Of 22 new insecticides screened, only Sumithion (O, O–dimethy1 O–(3–methy1–4–nitrophenyl) phosphorothioate) and fenthion gave mortalities higher than those achieved with diazinon. Parathion gave somewhat higher mortalities than methyl-parathion, and emulsifiable formulations of these insecticides were more effective than wettable powders. The inclusion of additional wetting agents increased the efficiency of commercial formulations of these two insecticides. These results are subject to confirmation in field trials.

The mode of action of parathion was investigated. Dosage/mortality lines were constructed for parathion, methyl-parathion and diazinon so that resistance to these insecticides by L. meyricki could be detected should it develop at some future date. L. caffeina was found to be apparently more susceptible to these insecticides than L. meyricki and this was believed to be due to its greater rate of feeding.

This paper is concerned firstly with the standardisation of a technique for the estimation of the speed of action of insecticidal sprays and deposits on adult houseflies (Musca domestica), as indicated by their speed of knock down, and secondly with the application of this technique to the assessment of the biological efficiency of insecticidal solutions. The main conclusions are:—

The speeds of action of both sprays and deposits are greatly affected by the duration and intensity of illumination to which the flies have been exposed before treatment and by the ratio of the sexes in the treated population. The first factor was eliminated by conditioning the flies to an intensity of illumination of 20 foot-candles overnight, i.e. at least 17 hours, and the second was minimised by estimating the median knock down time for 50c per cent. instead of 50 per cent, where 50c=0·67x+0·y, and x and y represent the percentages of males and females respectively in the treated population. This relationship appeared to be independent of the technique as it was the same for 0·05 per cent. gammexane in petroleum distillate used as a fly spray and for deposits of pure p.p. DDT put down from petroleum distillate. The experimental evidence, on which this correction is founded, is set out in full.

It was found that there was a separate straight line relationship between the percentage knock down in terms of probits and the time after spraying (or the time of exposure) in minutes for male and female M. domestica. It follows therefore that such a relationship is not true for a population of mixed sexes. The method of calculating the corrected median knock down time (K.D.50c) is detailed.

The speed of knock down of solutions of pyrethrins, the gamma isomer of BHC and the para para isomer of DDT were proportional to the concentration of the insecticide in the solution. This conclusion has been applied to the estimation of gammexane in solutions of unknown strength and examples are given in which the calculated and actual values are compared and some conception is obtained of the accuracy of the method.

Experiments with DDT deposits on aluminium plates showed that:—

(a) The speed of action was independent of the deposit providing that this was above 2 mg. p.p. DDT/sq. ft. Although when the deposit was applied to paper-covered panels the speed of action varied with the magnitude of the deposit.

(b) A deposit of p.p. DDT from a solution of pure (100 per cent.) p.p. DDT acted more quickly than an equal p.p. DDT deposit from a solution of technical (80 per cent.) p.p. DDT.

(c) The action of a deposit was more rapid when the deposit was in a form which could act both as a stomach and contact poison and hence the ball milled technical DDT applied as a suspension acted more quickly than an equivalent deposit of technical DDT from petroleum distillate because the crystals of the latter were too tightly adherent to the panel for the flies to ingest them.

The significance of these results is discussed under the appropriate section.

Helicoverpa zea (Boddie) is a damaging pest of many crops including soybean, Glycine max (L.), especially in the southern United States. Previous studies have concluded that oviposition and development of H. zea larvae mirror the phenology of soybean, with oviposition occurring during full bloom, younger larvae developing on blooms and leaves, intermediate aged larvae developing on varying tissue types, and older larvae developing on flowers and pods. In a field trial, we investigated the presence of natural infestations of H. zea larvae by instar in determinate and indeterminate soybean varieties. In complementary experiments, we artificially infested H. zea and allowed them to oviposit on plants within replicated cages (one with a determinate variety and two with an indeterminate variety). Plants were sampled weekly during the time larvae were present. In the natural infestation experiment, most larvae were found on blooms during R3 and were early to middle instars; by R4, most larvae were found on leaves and were middle to late instars. In contrast, in the cage study, most larvae were found on leaves regardless of soybean growth stage or larval stage. Determinate and indeterminate growth habit did not impact larval preference for different soybean tissue types. Our studies suggest H. zea larvae prefer specific tissue types, but also provide evidence that experimental design can influence the results. Finally, our finding of larval preference for leaves contrasts with findings from previous studies.

Tambinia verticalis Distant, an Indian tropiduchid planthopper, has been found breeding on coconut in Zanzibar, Tanzania, and also in low numbers in mainland Africa. No Tambinia species has hitherto been recorded in Africa. A lectotype is designated for T. verticalis, and the species is redescribed and figured.

This new species of Aëdes (Stegomyia) was discovered while I was conducting a malaria and anti-Anopheline survey in Mauritius for the Colonial Office during 1922–1923.

Following heavy infestations of garden pea (Pisum sativum) by leadmining insects at an experimental farm near Baghdad in 1963, collections of infested leaves from crop plants and associated weeds were made in 1963–1965 in central and souther Iraq and teh insects emerging from them identified. These included the following six pieces of Agromyzid flies: Phytomyza atricornis Mg., Liriomyza congesta (Beck.), L. Brassicae (Ril), L. strigata (Mg.,) Liriomyza sp. and Agromyza nana Mg. Of these, P. atricornis was the most abundant and widely distributed, followed by L. congesta.

P. atricornis was found on a wide range of hosts, of which P. sativum and Taraxacum monochlamydeum wwre those most attacked. Six species of Hymenopterous parasites were recorded from P. atricornis and these are listed.

Experiments in south-east England are described in which insecticides were tested against the Carabid beetles Harpahis rufipcs (Deg.) and Feronia melanaria(111.), which cause damage to strawberry fruits.

In preliminary screening tests, the mortality of H. rufipex was low when adults were caged with fruits or straw treated with rotenone at 0·004 per cent, or with carbaryl, DDT, dimethoate, malathion, mevinphos, nicotine, TEPP, toxaphene and trichlorphon at one or more concentrations in the range 0–06–0–2 per cent. In small-scale field trials, γ BHC at 0·026 per cent, gave poor results but chlordane and dieldrin exhibited persistent toxicity.

In further tests with fruits, field-weathered deposits from sprays containing 0·1 or 0·2 per cent, dieldrin caused over 90 per cent, mortality for 7 and 21 days, respectively, but left residues at harvest of 0·5 p.p.m., which were considered too high for consumer safety.

Dieldrin applied to soil at 5 lb. per acre resulted in 100 per cent, mortality for 28 days in 1957, but gave very variable results in 1958. Conversely, aldrin at 5 lb. gave effective mortality for only 14 days in 1957 but for the maximum test period of 89 days in 1958; no satisfactory explanation was found for the seasonal differences. Aldrin at 10 lb. per acre gave 100 per cent, mortality for 77 and 89 days, respectively, in the two years. Tests of soils into which measured quantities of insecticide had been incorporated, resulted in 100 per cent, mortality, after 4 days' exposure, with aldrin and dieldrin at levels of 2–4 and 16–32 p.p.m., respectively; endrin at 64 p.p.m. was only slightly toxic.

In field trials in 1959–60, application of aldrin at 10 lb. per acre to the surface of the soil around the plants in sprays in late April immediately before flowering, or at 5 lb. per acre in late May before laying straw below the fruit, reduced fruit damage due to H. rufipes or F. melanaria by 66–94 per cent. Residues at harvest were of the order of 0·03 p.p.m., and no effect on flavour was detected in processed fruit from plots treated at either time of application.

Aneityum is the only Pacific island south of Latitude 20°S. from which Anophelines and autochthonous malaria have yet been reported. Both Plasmodium vivax and P. malariae were found there, the former species only being detected in the blood of children who had visited the nearby island of Tanna and the latter in that of children who had never left Aneityum. Autochthonous quartan malaria has not previously been reported from the New Hebrides. In the absence of any other Anophelines from this group, it must be assumed that Anopheles farauti Laveran is the vector of P. malariae at Aneityum.