Laboratory tests are described for determining the protective value of a number of physically and chemically active insecticidal dusts against Bruchid infestation of peas and beans. Acanthoscelides obtectus (Say) and Callosobruchus chinensis (L.) were used as the test insects and were found to be very susceptible to most of the treatments tried. Adults of A. obtectus were in general more resistant to the treatments than those of C. chinensis, but the multiplication of the former species was more easily stopped, apparently because of the vulnerability of its first-stage larvae. It is concluded that protection of peas and beans can be achieved by thoroughly mixing into 200 lb. of the commodity 6–8 oz. of one of the following dusts: colloidal silica, colloidal aluminium pentasilicate, finely ground diatomite, 0.05 per cent. y BHC (as lindane) on diatomite or kaolin, 0.5 per cent. technical DDT on diatomite or kaolin. Rock phosphate, kaolin, or talc are not recommended. Where lindane or DDT are used in the dosages given, it is unlikely that the commodity will be tainted or rendered toxic to man or animals, even if no cleaning is undertaken.

Studies have been made of the effect of feeding adults of the Mustard Beetle, Phaedon cochleariae (F.), on diets of watercress leaves (Nasturtium officinale) taken from plants grown in water cultures of known nutrient composition.

Significant reductions in egg-production were recorded when individual beetles were supplied with leaves deficient in nitrogen, phosphorus, potassium or iron, as compared with the egg-production of the same beetles supplied with leaves from plants grown in complete-nutrient solution.

A marked alteration in the rate of egg-production occurred within two or three days of changing the diet from “complete-nutrient” leaves to mineral-deficient leaves or vice versa.

Some types of joint action of insecticides described by previous authors are discussed, and experiments described on the joint action on Periplaneta americana (L.) of the γ and δ isomers, and of the γ and α isomers, of benzene hexachloride. The values of the mortalities obtained are given in tables and compared with calculations of those that would be expected according to several models of joint action in which no interaction occurs. From statistical evidence it is concluded that only one of these models, namely, independent action with a strong positive correlation of the susceptibilities to the two poisons, can give an appropriate explanation of the results. These results, however, can also be explained by suggesting that antagonistic effects play a part in the joint action of the BHC isomers investigated.

The theoretical objections to the explanation of the persistence of yellow fever virus in areas subject to a prolonged dry season by cycles involving only mosquitos and wild primates are discussed in relation to the results of field surveys in areas of this type in Kenya. The localities studied were Gede, on the coast about 65 miles north of Mombasa, and Taveta, near Mount Kilimanjaro.

The topography, climate, vegetation and human population of the areas are briefly described.

Gede was visited towards the end of the dry season, Taveta during the main wet season. Thus most of the data relating to conditions during the dry season are derived from Gede, the results from Taveta being used mainly for comparative purposes. The work included 24-hour baited catches at two levels, moving catches, and larval collections in all the main typical environments.

All the species of biting arthropod encountered at each locality are recorded; in each case most were mosquitos.

At Gede the only mosquitos which were abundant as biting adults were species which breed in sea water, Aëdes fryeri (Theo.) and A. pembacnsis (Theo.), and they were practically confined to the close vicinity of their breeding places. The vertical distributions and biting-cycles of these species are defined.

At Gede, mosquito larvae could readily be obtained by filling tree holes artificially with water but no naturally water-filled tree holes were discovered by intensive searches in all the natural environments present in the area. Nor were any water-containing leaf axils discovered.

Recent taxonomic studies have recognised that Lygus pratensis (L.) consists of several species and other workers have shown that the Tarnished Plant Bug of N. America is L. lineolaris (P. de B.), a species confined to that continent. Although it is impossible to be certain what species is referred to in all of the earlier works on biology and pest incidence of L. pratensis in the Palaearctic region, evidence is given which shows that L. rugulipennis Popp. is the more important pest in this region and it is to this species that the name European Tarnished Plant Bug should be applied. Observations on the life-cycle of L. rugulipennis in England have been carried out and they show that there are normally two generations per year; the second generation becomes adult in the autumn and overwinters in this stage, egg-laying occurring the following spring. This agrees in general with that previously described for L. pratensis, sens. lat.

A survey of an empty granary was undertaken to assess the size and composition of itsinsect fauna, and the possible importance of such insects as a source of infestation of stored goods. The most important feature of the building in this connection was the presence of boarded-up cavities in the walls.

Samples were taken at random from behind all walls, from parts of the grain-distributor system, and from certain other areas.

Many grain pests were found associated with the residues. In the wall cavities large populations had been built up, reaching in one case over 2,000 insects in the food material behind a foot length of wall (the average concentration over all cavities examined was 266 insects per foot of wall).

The largest populations were behind the north and south walls and, in general, the numbers of insects increased on descending the warehouse. The difference in size of population of the different walls and stories depended largely upon the volume and quality of the débris present in the cavities. The increase in numbers was due to increase in number of species and to increase in individuals of some species.

The duplication of a clypeal spine and the bending of some of the hairs of an antennal tuft in a fourth-instar larva of Culex (Culex) annulirostris Skuse, and the gross malformation of the antennae and siphon of an apparently younger larva from the same pool, are described and discussed.

An analysis is made of the records of inspections for infestation by insects of cargoes imported into Britain from West Africa. The exporting territories extend from Angola to Senegal but the bulk of cargoes were produce of the four British colonies.

The ready spread of insects from one cargo to another causes infestation to be similar for all cargoes but a few species are especially associated with a particular crop. Groundnuts in shell are normally shipped alone and therefore relatively protected from cross-infestation.

The three major cargoes are cocoa, palm kernels and groundnuts which form four-fifths of the inspected shipments. Fifteen other kinds of produce are also considered.

Twelve species were found on more than ten per cent. of cargoes of cocoa beans. Of these five were probably acquired from groundnuts and one from palm kernels by cross-infestation. Ephestia cautella (Wlk.), Tribolium castaneum (Hbst.) (from groundnuts), Lasioderma serricorne (F.), Necrobia rufipes (Deg.) (from palm kernels) and Araecerus fasciculatus (Deg.) all infested over 40 per cent. of cargoes.

The fluctuations of infestation year by year are examined, and it is shown that these are similar for all the species acquired from groundnuts except T. castaneum. Variations in frequency of other species appear to be unrelated.

The swollen-shoot virus of cacao is transmitted in the Gold Coast by mealybugs, of which Pseudococcus njalensis Laing is the most important, and these are tended by ants of the genus Crematogaster, which build carton tents over the colonies, thus affording them protection against contact insecticides. An account is given of an investigation which was carried out at Tafo, Gold Coast, between 1950 and 1953, of the possibility of controlling mealybugs and thus the spread of the virus, by the use of systemic insecticides. Dimefox, schradan, paraoxon and parathion were tested, although the two last are not strictly systemic in action.

A method is described of applying even deposits of insecticide to leaves without detaching the leaves from the plants. The insecticide is sprayed by hand from an air-operated paint-spray gun under controlled conditions. Using this method for applying the insecticide, the persistence of DDT on living leaves and on glass plates was investigated.

Percentage mortality by itself is not a good measure of the practical value of an insecticidal treatment. In a relatively simple case, such as the fumigation of stored products, the control value can be expressed in terms of the time required for the reduced population to return to its former level of density, provided the mode of increase of the population is known.

Assuming that increase is at a regular exponential rate, the control values of different mortality percentages can be compared in terms of the calculated recovery times; thus, each of the values in the series 99·6, 93·75, 75, 50 and 29 per cent. mortality is twice as good as the one that follows it. Such relationships can be deduced from the graph provided, which is essentially a curve of constant exponential growth, made linear by the use of the logarithmic scale.

The above comparisons do not depend on the value of the constant rate of increase. If the rate of increase varies, control values can still be compared so long as it is possible to calculate the relative times needed for recovery from different levels of density.

A description is given of Ukara Island, which lies in the Tanganyika part of Lake Victoria, with an annotated list of mosquitos and other arthropods of medical importance found there. There are also notes on local plants and vertebrates.

The inhabitants, called Bakara, live in cone-shaped grass huts over 20 ft. in height and diameter. People and cattle are housed together.

The area of the island is about 45 sq. miles. The 17,000 inhabitants, almost entirely African, support themselves by advanced agricultural practices involving the use of manure and nitrogenous plants. There is a coastal belt of intense cultivation and a large central area of uninhabited grassland with extensive deep erosion. The beds of rivers which radiate from the centre are occupied by large irrigated areas. Seasonal fluctuations in lake level have little effect in general on cropping practices which are affected more by seasonal variations in rainfall.

The average rainfall for 1950–52 was 62 inches per annum. Temperatures are equable throughout the year. Mean maxima for 1953 were 81°F. for April, 83°F. for May, 82°F. for June and 81°F. for July—mean minima were 70°F. for April, 68°F. for May, 69°F. for June and 67°F. for July. Wind velocities, recorded at noon, vary between 4·8 metres per second in June and 2·4 in January.

The paper describes the layout and analysis of a test of two types of insect light-trap, the Rothamsted and the Robinson, and two types of illumination. The layout consisted of four variations of the sequence of six nights X A B O D D (X being a night of no trapping and A-D the four traps) in each of four sites in a small woodland. At the end of a complete cycle of 24 nights there had been four nights without trapping; each trap had been an equal number of times in each site; and each trap had followed all four trap-types, and also no-trapping, an equal number of times. The complete cycle was repeated four times at intervals between May and September. All insects captured were sorted into orders and counted and each order was analysed separately. By analysis of variance (after transforming the numbers caught to a logarithmic scale) it was possible to show separately the effect of differences, (1) between nights, (2) between sites, (3) between types of trap, (4) between types of light, and, (5) between cycles, and also the effect (if any) of the previous night's trapping. It was found that ultra-violet light was more efficient for all orders than ordinary electric light, that the Robinson type of trap was more efficient for the larger Lepidoptera but much less efficient for the small Diptera, but that there was no regular effect of the previous night's trapping. The largest source of variation was the difference between nights: difference between locations was small.

Studies have been made of the bionomics and ecology of Aëdes aegypti (L.) entirely under natural conditions and in its natural habitats on the Kenya coast.

Development from egg to adult under conditions approximating as nearly as possible to those in nature took a minimum of eight days and a maximum of twenty-five.

Males were in excess of females, in the proportion seventeen to ten, from eggs hatched in natural breeding places.

Although the mosquito may be able to propagate in houses, adults from outside habitually enter premises. If this entry is for egg-laying, then eradication by domestic larval control alone, although reputedly achieved elsewhere, is not possible under conditions obtaining in the coastal belt of Kenya. Windowtrap captures, however, indicate that the entry may not be for the purpose of egg-laying.

The seasonal reduction of both larvae and adults in houses during the hot, dry months of February and March is attributed to a combination of the absence of breeding places outside and the shorter life span of the mosquito at this time.

It is shown that both sexes enter and leave native huts throughout the 24-hour period, but the movement is confined almost wholly to the hours of daylight. The flight from houses is much reduced in the cool months (July and August). This corresponds with the season when most enter.

Ukara Island was selected for studies on the transmission of bancroftial filariasis because it provided a naturally circumscribed area with a substantial human population of which adequate numbers showed miorofilariae. It is a closely-knit and stable community.

Filarial infections also occur in bird, lizard, dog and hyrax (rock-rabbit) on the island. The determination of the vectors of human filariasis thus depends on evidence of different kinds, the present paper considering only the general correlation of microfilarial incidence with the distribution of common domestic mosquitos in villages of the island.

A study of the development and fecundity of the Oriental Fruit Moth, Grapholitha molesta (Busck), under controlled temperatures of 60°, 65°, 75°, 85° and 95°F. and relative humidities of 35, 70 and 100 per cent, was carried out at East Lansing, Michigan, in 1950–51. The technique adopted is described. The incubation period of the eggs decreased from 7–8 days at 60°F. to 2–76 days at 94°F., increasing to 3–56 days at 95°F. A large number of eggs withstood an exposure of 40 hours at 98°F., but an exposure of 48 hours proved fatal. An exposure of 21 hours to 105°F. reduced the viability of eggs to 25–43 per cent, and increased the incubation period by 36–40 hours.

A description is given of the bionomics of Leucoptera caffeina Wshbn. in the Kilimanjaro District, Tanganyika, and of the characters that distinguish it in its various stages from L. coffeella (Guér.), together with the results of population studies of the former insect and its parasites in both shaded and unshaded coffee in 1938–40.

During the 1939 outbreak, the numbers of eggs per tree, and the number of live pupae present in samples of about 100 cocoons (estimated from te number of moths and parasites emerging) showed large fluctuations. The times between peak numbers approximated to the total life-cycle, indicating that at any moment one developmental stage was dominant.

The action of certain drugs and insecticides on the frequency of the beat of the isolated cockroach heart, immersed in an aerated physiological solution at 29°C., have been studied. The frequency of the heart-beat is counted by eye and the drugs applied in the physiological solution. Acetylcholine at a concentration of 5 × 10-8 to 10-5 causes a sustained acceleration of the heart-beat which is blocked by atropine (5 × 10-5) and is unaltered by hexamethonium (5 × 10-5), prolonged exposure to nicotine (5 × 1O-5) or ergotamine (3 × 10-6). In this range of concentration ACH has a “muscarine-like” action.

Adrenaline (3 × 10-6 to 5 × 10-8) also causes an acceleration of the heart-beat, which soon passes off. Nor-adrenaline has the same action. Nicotine, hexamethonium or atropine do not modify the action of adrenaline, but ergotamine antagonises it.

Nicotine (5 × 10-5 produces an acceleration of the heart-beat which declines with prolonged exposure until ultimately no effect is produced on reapplieation, but recovery occurs with sufficient washing. Hexamethonium antagonises the effects of low concentration of nicotine. It is concluded that nicotine acts on the cardiac ganglia. Since atropine substantially reduces the action of nicotine, it is suggested that the ganglia excited may be chiefly cholinergic.

ACH in high concentration (10-3) in the presence of atropine (5 × 10-5) has a stimulant effect which is abolished by nicotine. It is inferred that under these conditions, ACH is stimulating ganglia which may be adrenergic.

Anopheles (Myzomyia) sergentii (Theo.) has been shown to be the most important vector of malaria, especially of Plasmodium falciparum, in Israel at the present time.

The morphology of the adults, larvae and eggs is discussed, details being given of variations in the pigmentation of the fronto-clypeus in the larvae, a factor the possible genetical significance of which is felt to warrant further research.

Resistance of the aquatic stages to extreme variations in environmental conditions and their ability to survive and even metamorphose in minimal amounts of water have been observed. Breeding in nature has been found between 12°C. and 36°C. At 30°C. the time elapsing from egg-laying to hatching is one and a half days. Pupal development takes a further one and a half days and the total time from oviposition to the emergence of the adult is nine days, whereas in winter it may be as much as three months.