The preponderance of males in tsetse-fly catches is an interesting fact that has not been understood in the past. Attention is drawn to the importance of the agefactor. Teneral flies are nearly always taken in equal numbers whereas non-teneral A.G.I flies and A.G.2 flies have the highest male/female ratio. In A.G.3, the ratio drops, indicating a decline in reproductive capacity. Females become fugitive about seven days after emergence, at the time when the first egg is almost due to descend into the uterus, i.e., at the end of the teneral stage. This is the mating phase par excellence. Mating is prolonged, vigorous, and frequent, and this accounts for the early appearance of the mating scars. As the uterus lies under and between the mating cushions, it is unsafe for females with eggs in the uterus or young larvae to mate. Third-instar larvae are safer as the highly chitinized polypneustic lobes take the brunt of the pummelling from the claspers. Safe periods also occur during the hiatus between larvipositions when the uterus is empty. There are, of course, other factors influencing the ratio, but the age factor is considered paramount, and failure to recognize this in the past has resulted in a good deal of confusion.

Twenty-five species of Simuliids are listed with indications of their relative abundance, importance as pests of man, seasonal appearance, temperature requirements, and larval habitats in Labrador. Seven of these are undescribed species. The most important species are Simulium venustum Say and Prosimulium hirtipes (Fries).

A circular area of 200 square miles around Goose Bay airport was surveyed for important breeding sites. Of 163 streams and rivers investigated, 77 were suitable as larval habitats, and larvae were virtually eliminated from them in June, 1950, by applications of a 10 per cent, solution of DDT in fuel oil at the rate of 1–5 p.p.m.- minutes from a helicopter, conventional aircraft, or boats, or by hand application from the ground. Methods of application are discussed.

The repopulation of the area by black flies was studied, and deductions are made concerning the flight habits of the most important species. On the basis of averages throughout the season, a great reduction in numbers of black flies at the centre of the area was obtained, and a worth-while reduction to a distance of between 4 and 6 miles from the centre. Even near the centre of the area, however, black flies were sometimes troublesome late in the season.

It is suggested that, where P. hirtipes is the important species, relief for at least one season could be secured by eliminating larvae within a radius of 2 miles; for S. venustum, 6 miles is suggested as a suitable radius. No adverse effects on useful animals were recorded.

The control methods used to protect new-crop groundnuts stored in Kano against insect attack are described.

The main method used was the spraying of aqueous suspensions of DDT directly on to the sacking of piles stored in the open and on the walls of warehouses before the nuts were stacked. The solutions were applied with a slow-moving orchard power sprayer, and 50 per cent, wettable powder applied at the rate of 360 mg./sq. ft. was found satisfactory. The BHC wettable powder applied at about 12 mg./sq. ft. was cheaper and equally as good and has now been found safe. Treatment markedly reduced the Tribolium population but had little effect on Trogoderma. Sprays of oil solutions were little used and were not very satisfactory.

Factors affecting the persistence of deposits from aqueous suspensions of insecticides have been studied.

There is an inverse relationship between particle size of insecticides and the initial contact toxicity to mosquitos. The influence of particle size on effectiveness decreases as the intrinsic toxicity of the insecticide increases. The compounds investigated can be arranged in order of immediate contact toxicity to mosquitos (Aëdes aegypti): dieldrin ≥ gamma-BHC > aldrin > DDT.

The surfaces of bags containing fumigated cocoa were sprayed with the macrodosage of 956 mg./sq. ft. DDT applied as a 5 per cent, suspension of wettable powder in water.

After exposure to an infestation of Ephestia cautella and Tribolium castaneum, no appreciable effect was obtained in preventing an attack by E. cautella, though the larvae appeared to choose unusual pupation sites on the surface of the bags. T. castaneum were rapidly affected and prevented from entering into the sacks.

Bruchus baudoni (Caillol) infests the seed of Acacia arabica in the Sudan and renders it largely infertile. Attack is not only in stored seed but also in the green pods before these have fallen from the trees. The life-history was studied and the newly hatched larva found to move freely about amongst the seed before boring. As this vulnerable stage occurred only once every six weeks with each new generation, a contact insecticide rather than a fumigant would be more likely to give satisfactory control. Parasites were found of the Bruchids of other Acacia species but not on B. baudoni. The search for a parasite is being extended to east, central and west Africa as the Acacia arabica of these countries is widely separated from that of the Sudan.

There are three moth-borers of sugar-cane in Mauritius, Proceras sacchariphagus Boj. (Crambid.), Sesamia vuteria (Stoll) (Agrotid.) and Olethreutes schistaceana (Snell.) (Olethreutid.).

The eggs of all three are parasitised by Trichogramma sp. ? australicum Gir., while a second undetermined species of Trichogramma parasitises the eggs of Sesamia and Olethreutes. Sesamia eggs are also parasitised by a Scelionid, Platytelenomus sp. ? hylas Nixon.

There has been considerable confusion in the determination of I. suspiciosus Wesmael. In fact, in Wesmael's series of this species in the Brussels Museum, the two species here differentiated were both represented. However, only one of these species agreed completely with his original description, and unfortunately this is not the species determined as suspiciosus by Thomson and by Roman. This latter form I regard as being a subspecies of I. septentrionalis Holmgren.

Game animals were shot in an isolated area of some 600 sq. miles over a period of about five years. The density of animals was originally in the neighbourhood of 10 to the sq. mile.

This density is very low compared with densities recorded from national parks, and examination of the evidence available shows that the Tanganyikan bushland is understocked with game.

As the result of the shooting in the present experiment, two species of tsetse fly, G. morsitans and G. swynnertoni, were exterminated, and a third, G. pallidipes, was either exterminated or very heavily reduced. Experimental cattle then remained healthy in the area for 11 months, after which they were removed.

This result was achieved in spite of considerable invasion of the area by cattle, particularly intense at a late period when such an alternative source of food might have been expected to be particularly valuable to the tsetse.

There was evidence that the fat, residual dry weight and size of the flies decreased, but there was no apparent effect on mean age or the proportion of females in the catches, nor apparently did the flies turn to avian blood.

The cost was £50 per sq. mile; but this figure would be very much greater in normal practice, with areas not isolated from the rest of the fly belt.

Game destruction is not recommended except in isolated areas of manageable size; discriminative clearing of the habitats, even at initially greater cost, is preferable as offering a more lasting solution.

The most obvious effect of sleeping sickness is depopulation, which can be occasioned directly, through mortality from the disease, and indirectly, through a lowering of the reproductive rate of a community because of induced sterility and increased infant mortality.

The problem was studied in the north of the Gold Coast and the neighbouring French Upper Volta Territory, where severe epidemics have occurred, in localised form since at least the middle of last century, and in widespread form during the past 30 years. The vectors have been the riverine tsetse Glossina palpalis and G.tachinoides.

A close correlation was found to exist between the incidence of sleeping sickness and the population trend with a marked depopulating effect coming in at infection rates above 3 per cent. It was also found that both the rates of trypanosomiasis infection and the extent of depopulation showed closely similar relationships to the proximity of affected villages to the nearest flybelt.

The biology and systematics of the predatory mites of the family Laelaptidae have received increased attention since they have been shown to be of importance in the control of phytophagous mites, especially Tetranychidae, resistant to modern insecticides. The predatory mites of economic importance are almost entirely confined to the sub–family Phytoseiinae Berl., 1910.

Insecticidal treatments against Heteronychus consimilis Kolbe, a serious pest of wheat in Kenya, killed large numbers of adults and markedly reduced the damagedone by them. Subsequent damage by larvae was prevented.

The most effective of the treatments tested were aldrin at 7.2 oz. per acre applied with the fertiliser, BHC in the form of Mergamma A applied as a seed dressing at 3¼ oz. per acre, and BHC in the form of Agrocide 7 applied as a seed dressing at 3¼ lb. per acre. The best treatments resulted in considerable increases in yield and gave promise of effective practical control on a large scale.

The tick, Ornithodoros moubata, was named by Murray in 1877 as Argas moubata; his specimens came from Angola (Portuguese West Africa), where twenty years earlier, Livingstone had noticed that such ticks were common in native huts; but Murray's description was “quite useless” (Nuttall & others, 1908) and it was Pocock (1900) who first published a recognizable description of the species and distinguished between 0. moubata and 0. savignyi (Audouin).

An investigation was made into means of increasing the effectiveness of the usual DDT-containing residual sprays with a kerosene base.

The common house-fly, Musca domestica, was used as biological material.

It was found that there exists a distinct relationship between crystal size and residual toxicity. Finely crystalline residues from DDT solutions in volatile solvents, such as xylene, proved to be considerably more toxic than coarsely crystalline residues from DDT solutions in less volatile solvents, such as kerosene. Addition of small quantities of coumarone resin to a DDT solution in kerosene was found to reduce the size of the DDT crystals and to increase the toxicity considerably.