1. During the past eight years field investigations on the epidemiology of yellow fever have been carried out in Bwamba County, a small heavily-forested area in the extreme west of Uganda.

During the course of this work yellow fever virus has been isolated from a human case, from Aëdes (Stegomyia) simpsoni, Theo., and from a mixed lot of Aëdes spp. taken in uninhabited rain-forest.

As it is known that yellow fever is endemic among the monkeys of the Bwamba forests and that a high rate of immunity is shown by certain species that rarely descend to the ground, it was concluded that an arboreal mosquito was the most likely transmitter of yellow fever among monkeys, and an investigation of the arboreal mosquito fauna was begun.

The best way of preventing locust outbreaks is to control them at their source. After a description of those habits of the Red Locust that have a direct bearing on control, an account is given of some of the results of three years' experience of control of this species in an outbreak area. The methods used in Rukwa are described in detail, and attention is drawn to their relative efficacy, advantages and difficulties. A number of other methods are also referred to and their values discussed. Control methods are considered with special reference to conditions in Rukwa and other outbreak areas, and in relation to large scale campaigns against large outbreaks. Conclusions on the relative values of the various methods are summarised below. These values depend both on the habits of the locusts and on the ecological, economic and social conditions of a country in which a campaign is to be waged. It must not be assumed that conclusions about control methods reached with one locust or in one country necessarily apply to another locust or another country.

Since December, 1942, a supply of adult house-flies, averaging approximately 2,500 a day, has been required in this Laboratory for experimental work on fly sprays. The production in quantity of insects suitable for such use is by no means a straightforward matter and a considerable amount of work was undertaken before a satisfactory technique was established.

There has been much confusion in the taxonomy of the species of Dysdercus in the Caribbean area, and this contribution is an attempt to straighten out the nomenclature and synonymy for future workers on these important pests, until such time as a complete revision of the Neotropical Dysdercus can be attempted.

The yellow fever mosquito, Aëdes aegypti, has been employed in experiments on the mode of action of adjuvants. With this insect under the test conditions employed, a decrease in the rate of knockdown was observed as a result of adding sesamin, sesame oil or IN 930 to a pyrethrum spray. It was shown that the increment of kill produced by activators was not attributable to any effect on either the particle size of the mist or the behaviour of the insect which led to an increase in the dose accumulated during the test exposure. No activating effect was apparent with DDT. The final mode of action remains unexplained.

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.

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 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. 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 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.

It is shown that the insecticidal value to Macrosiphum solanifolii of DDT depends upon the medium in which it is incorporated. It is more toxic (4–6 times) when dispersed as an emulsion dissolved in a water-insoluble solvent (benzene) than when dissolved in a water-soluble solvent (acetone-carbitol) and dispersed as a suspensoid.