An effort was made to determine the best conditions to achieve maximum saturation and persistence of small droplet insecticide (5-200 microns droplet diameter) within a type of African woodland. The problem is entirely one of atmospheric turbulence within the woodland. No attempt was made, or is likely to be fruitful, to introduce a detailed or mathematical argument. The relevant factors pertaining to atmospheric turbulence were observed and in some cases were directly compared with simultaneous observations made in the open.

The absence of zero wind speeds, considerations of changing lapse rates, bi-directional wind vane records, and visual observations of smoke, all combine to suggest that when conditions of calm or light winds exist in the free air, there is, under moderately dense woodland canopies, an almost continuous and slow transfer of air between the canopy and the ground, these movements tending towards laminar or sheet flows. With stronger winds, eddying about the trees swamps these gentle movements and air motion becomes erratic and turbulent, although such turbulence is less the denser the canopy. During the daytime there is notable horizontal movement of air towards clearings where convection is at a maximum.

Attempts have been made to eradicate the tsetse flies G. morsitans and G. swynnertoni from two blocks of savannah woodland situated in the Central Province of Tanganyika.

The insecticides were applied from aircraft. Coarse aerosols were used, with mass median diameters of approximately 90 microns; droplet diameters varied from 4 microns to 250 microns approximately.

Eight applications of insecticides were made at intervals of two weeks. Each application was carried out at a nominal dosage of 0·25 gallons per acre, which was equivalent to 0·20 1b. per acre of the p, p'isomer of DDT or 0·03 lb. per acre of the γ isomer of BHC.

In the area treated with DDT it is possible that both species of flies were eradicated for a short period, but small populations were re-established there by immigrant flies. In the other block the reduction was not so great, but it is not considered that this was due to a lesser effectiveness of the BHC, but to a combination of circumstances that led to less effective applications.

Some general observations are made upon the use of aircraft for this sort of work, particularly in connection with the effect of meteorological conditions.

Wheat of three moisture contents was fumigated with ethylene oxide, methyl bromide and hydrogen cyanide. Both chemical and biological assays were used to follow the changing distribution of the fumigant when applied with sustained vacuum, in a vacuum fumigation with simultaneous admission of air and fumigant, or at atmospheric pressure.

As these various factors were altered, in a multifactorial experiment, the changes in the fumigant distribution were also recorded chemically, and then analysed statistically. Changes in the mortality of both species of Calandra, either buried in a one-cwt sack of wheat or in the free-space, were estimated so that that part of the changes which was associated with the altered fumigant distribution was segregated by a covariance analysis and the remainder formed an estimate of the direct influence of the experimental Conditions on the susceptibility of the weevils to the fumigants.

When either ethylene oxide or methyl bromide is used as a fumigant for wheat, vacuum fumigation with simultaneous admission of air and fumigant gives results, in terms of the control of Calandra spp., which are almost indistinguishable from those obtained at atmospheric pressure under comparable conditions. When hydrogen cyanide is the fumigant, atmospheric fumigation is superior, quite apart from the capital expense and other practical disadvantages of fumigations at reduced pressures.

The direct action of reduced pressures, in the absence of any fumigant, on C. oryzae and C. granaria have been investigated in glass chambers of about 1 litre capacity. C. oryzae is sufficiently sensitive to make the direct effect of reducing the pressure within the range 2 to 10 cm. mercury of some practical importance, but C. granaria is more resistant. Mortality of both species increases for exposure periods of up to 8 hr. and for increased temperatures from 20°C. to 28°C. A large part of the observed mortality must be associated with enhanced water-loss from the insects at reduced pressures, as little response occurs when the atmosphere is kept saturated with water-vapour.

Theraptus sp. is widespread in the coastal region of British East Africa where it severely damages developing coconut fruits.

The female may lay over 100 eggs. There are five nymphal instars and, in the field, it is probable that about nine generations are produced each year.

Damage to coconuts is similar to that caused by Amblypelta cocophaga China in the Solomon Islands. Female coconut flowers and young nuts may be destroyed by a single feeding puncture. Damaged 10–16-week-old nuts may reach maturity but are undersized and often distorted by lesions from which gummy material exudes.

In the coastal region of British East Africa three ant species, Anoplolepis custodiens, A. longipes and Pheidole punctulata may destroy the ant Oecophylla longinoda which is a valuable predator on the coconut pest Theraptus sp. (Coreidae). The three first-named species do not prey on Theraptus, which may severely damage palms occupied by them.

Nesting habits of the three ant species and their behaviour towards O. longinoda and certain other insects are described.

O. longinoda has been exterminated in the limited areas occupied by the two Anoplolepis species. P. punctulata is widespread and is usually common in areas occupied by O. longinoda and is also present, though relatively less common, in A. longipes areas.

The distribution of the Anoplolepis species, particularly A. custodiens, is correlated with sandy soils bearing a sparse ground vegetation. Where there are heavy soils or a thick ground vegetation of grasses and creepers the Anoplolepis species are absent and O. longinoda is usually present. It is suggested that the Anoplolepis species are limited by the relatively low temperature of soils shaded from sunlight by thick vegetation.

A simple, but reliable, technique is described for the study of the acceptability to locust hoppers of poison baits under field conditions.

This was applied to the study of a number of vegetable materials which might be used for the manufacture of wet baits to destroy hoppers of the Desert Locust.

The materials tested could be divided into five classes of acceptability, and consideration of these indicated that heavy lignification detracted from acceptability while the presence of starch added to it.

It was shown that molasses adds to the acceptability of only the least acceptable materials unless very large amounts are used.

Simple tests showed that acceptability was not correlated with water-absorbing properties, that the rate of drying of bait was dependent on the amount of water initially absorbed, and that molasses influences the rate of drying only when large amounts are added.

Kumasi is a rapidly expanding township of about 80,000 inhabitants. This has led to an extensive building programme which has followed the ridges in the vicinity of the town, leaving the valleys in between potentially dangerous isolated habitats of Glossina. The danger from these isolated habitats is enhanced by the large numbers of itinerant labourers.

The topography of the town and its surroundings is hilly; the vegetation is of semi-deciduous rain forest type, but with very thick secondary bush along most of the valleys in which the farms had been abandoned.

The climate is remarkably equable with the rainfall showing periodicity but the percentage relative humidity is high and even throughout the year.

The experimental clearing of an isolated habitat of Glossina in the Dechem valley was commenced in July 1950 and finished in March 1951. The clearing was of a discriminative nature, with cutting, stumping and burning of a strip of bush up to 20 ft. high and 250–300 yards wide along the stream, and a high reduction of fly population was achieved. This reduction was such that further clearings were planned.

The reduction in fly population was assessed from fly-boy catches and from trap catches. These records showed that rainfall affected the catches.

At the time of writing, about a sixth of the protective clearings planned around Kumasi have been completed, the fly population being reduced between about 80 per cent. and complete eradication.

Of the various methods for the eradication of G. palpalis that have been tried in Kenya, hand-catching has the most limited application.

Total and discriminative bush-clearings of the river banks have been used on a considerable scale and progress on the Yala, Magori, and Nyando rivers is reviewed. The decrease in fly-populations caused by these clearings is gradual, but complete eradication may be achieved. Maintenance of the clearings is however difficult, the initial cost varied from £200 to £300 per mile and labour was often difficult to obtain in sufficient numbers.

The use of 5 per cent. DDT sprays on the fringing vegetation along 20 miles of the Mbogo river gave dramatic results and G. palpalis was eradicated at a cost of £42 per mile. The rate of application was 15 to 20 lbs. of DDT per acre and the residual effect lasted for at least 14 days during dry weather, but was rapidly lost during the rains.

Spraying along the Ainamotua gave equally promising results.

Areas under treatment, either by hand-catching, bush-clearing or spraying with DDT, must be properly isolated from other tsetse-infested areas if quick results are to be achieved.

Between December 1947 and May 1949, six colonies of body lice from various sources were cultured in the laboratory. Three of the strains originated from natural infestations in England and the others came from laboratory cultures in Hamburg, Basle and Tunis. After being bred for at least one generation in the laboratory, these lice were subjected to a standard test for resistance to DDT. Only one strain showed any evidence of abnormal resistance; this was the strain from Tunis where it had been laboratory-cultured for over 12 years.

Colonies of Aëdes aegypti from Karachi, Poona and Delhi were being cultured at the Virus Research Institute, Lagos, together with a local Nigerian strain. Extensive tests showed no difference in average susceptibility of the four strains to DDT, though there was some evidence of differences in the spread of resistance through the various populations.

A colony of A. aegypti was started with larvae taken from Ilaro, a Nigerian town which had been regularly sprayed with BHC for 2½ years. Comparative tests showed no difference in resistance to γ BHC between this colony and a laboratory culture at the Malaria Service Laboratory, Lagos.

Colonies of house-flies were initiated and maintained at Lagos. Tests with insecticides gave the following results:

(a) M.d. vicina from Ilaro were much more resistant to γ BHC than similar flies from Yaba, near Lagos, or M.d. domestica from England.

(b) The M.d. vicina from both Lagos and Ilaro were considerably more resistant to DDT than M.d. domestica from England. This is surprising, as no DDT-spraying has been done at Ilaro and, so far as can be ascertained, virtually none in Lagos.

(c) The M.d. vicina flies from Lagos were considerably more susceptible to γ BHC and dieldrin than M.d. domestica from England. M. sorbens was much more susceptible to γ BHC and to DDT. These differences could be explained by the smaller average sizes of the two susceptible species.

The chief aims of the survey and an important conclusion reached during some preliminary work are briefly stated. This latter was the recognition of two distinct nest types—the wet nest, exposed to rain, and the dry nest, sheltered from rain.

The methods used to examine materials and record results are described. They were closely similar to those described in a previous publication.

The insect fauna is listed under three headings: (a) ectoparasites of birds, which includes 12 species; (b) scavengers, including 66 species; and (c) predators, comprising 14 species. Figures are given for the frequency of occurrence and the abundance of the more important nidicole species, abundance being given as an arbitrary estimate. The importance of each as a pest is also briefly stated, and detailed records are given for uncommon or particularly interesting species.

The mite fauna is dealt with in a similar manner. It includes one ectoparasite, 10 scavengers and 11 predators.

The basic composition of nests and the temperature and humidity conditions within them are described briefly and the possible influence of these factors upon the nest fauna is discussed.

The species of the dry nest community are classified, according to their feeding habits, as ectoparasites of birds, scavengers and predators, and according to their status in the nest, as regular, occasional and incidental inhabitants. The distribution of the group of species which truly characterises this community is discussed.

A description is given of a technique for breeding the parasite Spalangia drosophilae Ashm. (Spalangiidae). Various biological “constants” such as fecundity and longevity were studied at 70°, 75° and 83°F., and the variation in the figures for these is given. The oviposition rate, efficacy of single matings, sex ratio, percentage in diapause, developmental period of both male and female at the different temperatures are also give.

The small, hooked epidermal hairs on french beans (Phaseolus vulgaris) may have a profoundly detrimental effect on colonies of Aphis craccivora. The hairs are present on the petioles, stems and undersurfaces of the leaves but are absent on the uppersurfaces of the leaves. They are most dense and therefore most injurious to the Aphids on the growing shoots. The Aphids' legs become impaled on the hooks and the results of the subsequent bleeding, starvation and exhaustion are decreased longevity and reproductive rate, high larval mortality, increased time of larval development and decreased size; this last factor is associated with a reduced fecundity. On some varieties of beans the hairs are less dense than on others and on these varieties the action of the hairs in inhibiting predators may be more important than their effect on the Aphids.

The taxonomy of a complex of parasites associated with mealy-bugs on cacao in Trinidad is dealt with. The descriptions of nine species new to science are given and species not new have been treated in comparable detail. Fresh taxonomic or other data have been given for some related species.

The inclusion of an aberrant Thysanid species of biological importance necessitated a comparative study of characters that have been used within this group. In this connection, Thysanid parasites of Tachinidae attacking moth larvae in sugar-cane were considered and found separable into three closely related species, two of which are described as new.