1. Simple trials of the effect on mosquitos of single applications of DDT to the internal surfaces of houses were initiated in British Guiana during the period 27th January to 20th April, 1945.

2. The solution used in the first two trials was 4·6 per cent. DDT (72 per cent. para para) in kerosene applied at the rate of about 2 quarts per 1,000 square feet (i.e., approximately 100 mg. of crude DDT per square foot).

3. An apparent reduction in the house population of Anopheles darlingi, the chief malaria vector, followed the treatment. Reduction exceeded 99·7 per cent. over eight weeks in the treated houses on one estate and 98·8 per cent. over six weeks on another.

4. In a third trial with a small variety of simple formulations, promising results were obtained with a 6 per cent. emulsion and a 2½ per cent. solution. But mosquito catches over a short period suggest that mud walls, thatch and whitewash may interfere to some extent with the action of DDT.

5. The cost of applications was of the order of one shilling and sixpence for each room (or small hut) of about 1,000 sq. feet internal wall and ceiling surface. This estimate does not include European supervision or the initial cost and depreciation of apparatus.

1. Mosquitos often recover completely after showing the preliminary symptoms of DDT poisoning.

2. The effect of contact with DDT on the activity and distribution of mosquitos has been studied in a small cage, exposure times being kept below that necessary to kill the insects.

3. The duration of single resting periods on DDT-treated surfaces was several times shorter than resting periods on untreated surfaces, provided the mosquitos had had no recent access to DDT.

4. Mosquitos that had been in recent contact with DDT rested only slightly longer on untreated than on DDT-treated surfaces.

5. Mosquitos excited by DDT moved preferentially toward light.

An increased indoor population of Anopheles sacharovi at the start of hibernation is recorded.

Figures are given for dissections of A. sacharovi during the winter months, showing an infectivity rate (sporozoites) of 0·41 per cent.

Eggs of A. sacharovi laid at the end of hibernation are described.

An account is given of an area in Northern Persia where A. sacharovi is present in association with a lower endemicity of malaria than is usual.

We are indebted to Lt.-Col. D. N. Keys, R.A.M.C., Major J. Yofe, R.A.M.C., and Major R. Hillman, R.A.M.C., for their interest and help in these observations.

Investigations undertaken by the writer involved the determining and sexing of a large number of fleas daily, and it became clear that this would be a laborious process unless an apparatus could be designed which would facilitate separation and examination of the insects by making the process as automatic as possible. The technique finally used, though designed primarily for handling fleas, could be adapted for use with other insects of comparable size where examination under magnification is necessary.

At the end of June, 1942, large colonies of a black aphid, indistinguishable from Doralis fabae (Scop.), were found on foxgloves growing on a hillside in Westmorland. This aphid was found commonly in the mountainous districts of Westmorland and Cumberland in 1943, Caernarvonshire in 1945, and Anglesey in 1946. Observations to be described below have indicated that in nature, this aphid spends the whole of its life on foxgloves, and experiments have shown that it does not readily feed upon the economically, important host plants of D. fabae.

A bug identified as Aphanus littoralis, Dist., but believed to be synonymous with A. sordidus, F., was found infesting stored ground-nuts at Yola, Nigeria. It had not hitherto attracted attention in this country, but was found later to be recognised by native farmers as associated with ground-nut plants drying in the fields at harvest.

The nuts concerned were in war emergency mud and thatch stores which were much cooler than the (uninfested) corrugated-iron stores normally used. This difference is believed to have favoured the infestation.

The adults and nymphs cause damage by sucking the oil from the kernels. Loss of weight and germinative power, and development of free fatty acids and rancid and bitter taste follow. It was found, however, that bugs could not penetrate more than three inches or so into the bulked kernels, so damage was not extensive.

Myzodes, Mordv., 1914, type Myzodes tabaci, Mordv. (═ Aphis persicae, Sulzer) is a synonym of Nectarosiphon Schouteden, 1901 (nom. nov. for Macrosiphum, Del Guercio, 1900, nec Passerini, 1860). Following Baker's 1920 Generic Classification, Aphis convolvuli, Kalt. (which clearly is Aphis persicae, Sulzer) is the type of Macrosiphum, Del Guercio, and therefore of Nectarosiphon Schouteden, a subgenus of Myzus, Pass.

Throughout the world, wheat bran seems to have been the most popular carrier for locust and grasshopper baits. Wheat bran has, however, always been difficult to obtain in East Africa in sufficient quantity for large scale campaigns, and wartime conditions coinciding with a large outbreak of Schistocerca gregaria have made the position even more acute.

Whilst investigating the biology of parasites of the frit-fly (Oscinella frit, L., Diptera, Chloropidae) in North America with a view to introducing possible species for the biological control of this pest in Great Britain, extensive experimental work was done with one species of Chalcid, Spalangia drosophilae, Ashm. (Spalangidae), a parasite of frit puparia. During this work conditions inducing a state of diapause in the mature larvae were investigated. As with many other species, it was found that low temperatures during development favoured entry into diapause, whilst high temperatures favoured emergence of the progeny without arrest in development. However, other factors were found to have some important bearing in this respect. Some individual females produced progeny, all of which entered a state of diapause in the full-grown larval stage, others bred and ovipositing under identical conditions produced progeny all of which emerged without arrested development, others produced progeny that were mixed in this respect. This effect did not seem to be inheritable. The history of each individual female with respect to environmental conditions was found to have an important influence on the propensities of her progeny for entering diapause. These effects will be dealt with more fully at a later date. There was, however, one striking effect which has apparently not been noted before, and which it was felt was of sufficient interest to be recorded separately.

The investigations were carried out in the Inland Savanna Forest Zone of the Northern Territories of the Gold Coast, the climate of which is characterised by extreme variations in rainfall and relative humidity between the wet and dry seasons.

Glossina palpalis and G. tachinoides are widely distributed along the waterways throughout the zone. They come into intimate contact with the human population and are, in consequence, the most important vectors of human and animal trypanosomiasis.

G. morsitans submorsitans occupies unpopulated and thinly populated regions and so, coming more rarely into contact with man and cattle, is a less important vector of trypanosomiasis.

A pandemic of sleeping sickness, with 30,000 square miles of heavily infected country, lies across the upper reaches of the Volta rivers and involves parts of the north of the Gold Coast. In the areas studied high rates of infection (4–7 per cent.) were found associated with serious population declines which have given rise to secondary evils, the invasion of G. morsitans into depopulated parts and the concentration of populations on the watersheds between infected river valleys, with resultant over-farming, erosion and lowering of the standard of living.

The results of two methods of controlling G. palpalis and G. tachinoides were studied : (1) “ Protective Clearings ”, aimed at breaking the contact between the tsetse and man or cattle at certain points only ; (2) “ Eradicative Clearing ”, aimed at the complete removal of tsetse throughout an area.

The effects of protective clearings on the fly were as follows : Clearings less than 300 yards in length are considered useless, and may cause an increase in fly-incidence by forming artificial feeding grounds. Clearings of 440 yards can effect up to 70 per cent, reduction in fly-incidence measured over a long period, but for several months of the year show no reduction or may even show an increased incidence. Clearings up to 880 yards long can bring about 60–90 per cent, fly reduction, but at two periods during the year, at the end of the dry season and in the middle of the rains, their effectiveness is considerably lowered by the invasion of hungry flies into the clearings. Clearings over a mile in length exclude all but a few vagrant flies, but even five miles of clearing are traversed by occasional flies.

A study of the effects of various applications of protective clearings on the incidence of sleeping sickness led to the following conclusions. To have any value protective clearings must be made in as many places as possible over a wide area. They effect no general reduction in the disease if applied at a few places only. Small clearings, averaging 400 yards in length, if made consistently over a large area, can effect up to 40 per cent, reduction in sleeping sickness in 4–5 years, after which the disease tends to become stabilised at the lower level. Long clearings, averaging 1,000 yards, almost double the rate and amount of reduction, effecting 70 per cent, reduction in three years, but the tendency for the disease eventually to become stabilised remains. Clearings over a mile in length at each village caused a reduction of 85 per cent, in one area.

Protective clearings alone are considered unlikely to be able to effect complete control in areas of serious endemic sleeping sickness. They do not entirely exclude the fly, and they do not touch all the points where the transmission of infection takes place. Further disadvantages arise from the fact that, to attain maximum fly reduction, all vegetation, including tall trees, should be cut. This is expensive and difficult and may lead to erosion and the silting up of water-holes, thus driving the people back to uncleared parts of the river. Finally, animal trypanosomiasis can never be controlled by localised clearings, therefore improvement in animal husbandry, and consequently in agricultural practice and nutrition cannot be fully realised.

Eradication of G. palpalis and G. tachinoides is based on the consideration of the tsetse community of a complete river system as a natural biological unit. During the prevalence of the adverse climatic conditions of the dry season, the breeding and survival of tsetses are possible only in certain restricted habitats from which the flies spread extensively along the water courses during the rains. The dry-season habitats are confined to definite plant associations that are characterised by a limited number of species of trees and shrubs. The removal of only these species throughout a river system renders the habitats untenable during 4–6 months of the dry season and results in the disappearance of the whole fly community.

By the method of selective clearing, 1,050 square miles of country in the northwest corner of the Gold Coast were freed from tsetse between December, 1940 and March, 1945. On the main river of this region, the Kamba, which was cleared by 1942, routine catching after clearing showed 1–8 flies per year in places where the pre-clearing averages had been 2,700–7,500 flies per year. After the clearing of some neighbouring fly-belts, these occasional captures ceased. Wet-season migration from the uncleared Volta, however, brings small numbers of flies 5–9 miles up the lower reaches of the cleared river.

The incidence of sleeping sickness for the Kamba area fell by 92 per cent, between 1938, the year before the start of control measures, and 1944.

Along the Kamba, 160 square miles of land which had become depopulated through trypanosomiasis is being developed voluntarily by the natives, by farming, grazing, etc. Approximately 1,000 people have settled in parts of this area since clearing was finished.

In 1939 G. morsitans invaded the depopulated area, and increased greatly in numbers in the following years. The spread was checked, and finally a high degree of control was established by the disturbance of big game and its reduction in numbers. Settlement of the thinly populated country is needed to consolidate this control.

Selective clearing can be followed by the eradication of essential dry-season habitat vegetation which will enable maintenance to be put on a long-term rotation of about ten years. Permanent reclamation is a possibility that is now being studied.

The relative merits of medical and entomological methods of controlling sleeping sickness are discussed. Mass treatment can have great success, but fails to control under difficult conditions, and has not yet been found able to eliminate the disease. The addition of adequate tsetse control increases the effect of mass treatment. Eradication of the fly is capable of eliminating the disease and does not require the addition of mass treatment to bring this about.

The removal of tsetse throughout the river system, as in selective clearing, has the following additional advantages : It makes possible a sound agricultural development based on the possession of good quality livestock; this reflects also on nutrition. It enables the population to live with impunity in the vicinity of permanent water and, by spreading out at a density optimum for their type of agriculture, to avoid concentrations at local clearings or on dry, hilly country away from rivers; thus the possibilities of over-farming and erosion are avoided and the watersheds and headwaters can be reserved for afforestation. By these means, instead of ground being abandoned to the tsetse, the fly is replaced by a healthy agricultural population.

A detailed quantitative study of the incidence and development of an attack of wheat bulb fly on a field in East Yorkshire is described. The numbers of larvae, puparia, plants, and shoots, and the percentage of plants and shoots attacked, were estimated on various dates. This information is graphically summarised in fig. 1. Similar information was obtained from other fields in 1944 and 1945. No single factor could be correlated with the effect of the attack on the crop.

The number of larvae ranged up to nearly 600,000 per acre, but high numbers did not invariably result in a poor crop. A high percentage of plants or shoots attacked was not necessarily associated with crop failure. The number of shoots per plant at the time the larvae hatch was important and in some cases attack stimulated tillering. It is suggested that a study of the rate at which damage occurs would lead to a better understanding of the reaction of any crop to pest attack.

1. An onchocerciasis area in South Kavirondo, Kenya Colony, 65 square miles in extent, has been freed from Simulium neavei.

2. The fly was eliminated by the periodical application of DDT emulsion to all infested rivers and streams in the locality. Details of technique are described.

3. Most aquatic life, other than this species of Simulium, had returned to the treated streams, three months after the last application.

4. A microfilaria index of 37 per cent. in children aged four to eight was established as a base-line for future surveys.

This work was found necessary when the Pong-Tamale Veterinary Laboratory and Livestock Farms were built in 1930–31 in the Naboggo Valley. The site was chosen because of ample water and abundant available ground.

In the course of a study of the biology of the Buprestid, Prospheres aurantiopictus, Cast., in Australia, Mr. A. R. Brimblecombe has obtained from the eggs an interesting small Chalcid belonging to the family Encyrtidae.

Several Encyrtid parasites of insect eggs are already known. In Australia Ovidencyrtus pallidipes, Girault, parasitises Reduviid eggs, Tetracnemella megymeni, Dodd, and T. hyalinipennis, Dodd, Pentatomid eggs, and Cheiloneurus viridiscutum, Girault, has been bred from those of cockroaches. In Hawaii the genera Ectopiognatha, Perkins, and Fulgoridicida, Perkins, are found parasitising the eggs of Homoptera. In addition Leefmansia bicolor, Waterston, has been bred from the eggs of the Orthopteron, Sexava sp., in Amboina and Leurocerus ovivorus, Crawford, from the moth, Amathusia phidippus, L., in Java. But most of the Encyrtid egg parasites belong to the genus Ooencyrtus, Ashmead, and it is among them that is placed the only other species known to breed in the eggs of a Coleopteron, Ooencyrtus batocerae, Ferrière, from Malaya. Another species, Tyndarichus rudnevi, Nowicky, is said to have been obtained from the eggs of Cerambyx cerdo, L., in Russia, but as the species of Tyndarichus are generally considered to be hyperparasites, the real parasite of this European Longicorn is still uncertain.

Laboratory and field observations have been made on the biology of Wheat Bulb Fly in the years 1943–45. The eggs hatch in late January and early February. Severe frosts delay hatching but do not kill the eggs. In a laboratory experiment a high proportion of eggs buried 18 inches below the soil surface, hatched, and the larvae infested plants. Field observations showed that proportions of the eggs also survive prolonged flooding.

The development and habits of the larvae are recorded. It was confirmed that oats are not a suitable host and though a very small number of these plants were infested the larvae did not survive. Occasionally two larvae infest the same shoot and when this happens one larva dies. The larvae leave the plants in April or early May and pupate in the soil. The pupal stage lasts six to seven weeks.

The adults emerge, males first, in June. Copulation occurs about three weeks after emergence and at this time dense aggregations of flies occur. Usually males predominate in these and in certain circumstances all the flies are males. The flies disperse gradually from the field in which they emerged and the females start laying eggs in suitable areas about a month after emergence. In Yorkshire egg laying occurred in July and early August and lasted about a month. Even within the limited area and time of these observations variations up to three weeks were noted in different places and seasons. Lateness was associated with heavy soils.

1. The Garden Chafer (Phyllopertha horticola) causes extensive deterioration of the fell grassland in the Lake District.

2. The flight period of the adult beetles occurs between the end of May and the latter end of June.

3. Eggs are laid in the soil at a depth of about 2½ inches, but the depth varies according to the nature of the soil. The eggs take from 27 to 30 days to hatch in the field.

The present study is based primarily on beetles collected in the field. Although several individuals of Capnodis carbonaria, Klug, and C. tenebrionis, were reared successfully from egg to maturity, these beetles were as a rule weak and short-lived, and consequently unsatisfactory for the purposes of this investigation.

These experiments are part of the series made by No. 2 Entomological Field Unit, R.A.M.C., on the potentialities of DDT (dichlor-diphenyl-trichlorethane) for military purposes. A report on the use of DDT as a mosquito larvicide on still water has already been published (Ribbands, 1945).

The toxicity of DDT as a contact spray under laboratory conditions has been tested on a number of insect species. The particulars of the species used are set out below.

The toxicity of the DDT spray was compared in every instance with nicotine. A rotenone or derris suspension was included in the tests on Myzus cerasi, Phaedon cochleariae, Pieris brassicae, Pteronus ribesii and Phymatocera aterrima, and a pyrethrin spray in the tests on Pieris brassicae, Pteronus ribesii and Phymatocera aterrima.