Eggs of Aëdes do not necessarily hatch on becoming mature, even though conditions are known to be compatible with hatching. Even the eggs laid by a single female in a single batch and kept submerged in a single container may hatch in instalments over a very long period and, although on one occasion a high proportion of the eggs may hatch within a given period, on another, for no apparent reason, very few may hatch.

The problem of erratic hatching has been studied here mainly in Aëdes africanus (Theo.) and A. aegypti (L.). It is considered that mature eggs enter a state of diapause, the depth of which varies with the passage of time, and that the manner of this variation with time itself varies from egg to egg. Different batches of eggs laid by females of the same species vary in the proportion of the different kinds of egg present.

Variation in response of the eggs has been studied by the application of a suitable hatching-stimulus in equal daily doses. The stimulus used was sufficiently weak to allow variation in response to be manifested, but sufficiently strong to outweigh uncontrolled variables in the environment.

A stimulus is necessary for the hatching of eggs of Aëdes mosquitos, but, while many different kinds of change in the external environment may be adequate as hatching-stimuli, there is variation in the response of the eggs to any given one of them.

Not only is there variation between species as regards behaviour of the eggs, but batches of eggs laid by different females in a single species may vary one from another and there is even variation of behaviour between the eggs laid in a single batch.

The response of the eggs of A. aegypti (L.) has been studied here and evidence produced that both parents contribute to their hatching-behaviour. Egg behaviour has also been studied in two populations of this species, one originating from West Africa and the other from East Africa. In the former, only a very low proportion of the mature eggs (0–9%) responded to the daily application of a suitable stimulus over a short period, whereas in the latter the proportion of responders in the same period with the same stimulus was very much higher (46–100%). The next generation reared from each of these gave very similar results (0–11 and 65–100%, respectively), while reciprocal crosses between them gave a wide range of scatter (16–100 and 4–99%, respectively).

Australian workers have been interested for some time in the common Ceroplastes on coffee in Kenya as a source from which parasites of Ceroplastes destructor Newst. might be obtained.

The doubt that more than one white waxy scale occurs on coffee in East Africa led to an examination of material of C. destructor and certain other allied species. It was found that C. destructor was present in Uganda and Kenya but did not occur on coffee in Kenya, so far as is known at present. C. brevicauda Hall, here raised to specific rank, was found to occur on coffee in Uganda and a new species, C. luteolus, on the same crop in Kenya.

Descriptions of C. luteolus, Lecaniodiaspis erratica and Pseudococcus latipes, spp. n., all from coffee, are given.

Anopheles (Myzomyia) farauti Lav. is recorded from the upper reaches of the Nevaka river, south-western Espiritu Santo, New Hebrides, to an altitude of 1,100 ft. and a distance of 12 miles from the coast. The presence of Plasmodium vivax and P. malariae in the blood of children from hill villages with no nearby Anopheline larval habitats is noted. These children, most of whom have never visited the coast, become exposed to infection during prawning trips to the valleys below their homes. The transmission of P. vivax and P. malariae is shown to take place in the interior of Guadalcanal, British Solomon Islands Protectorate, where a proven vector, A. (Myzomyia) punctulatus Dön., breeds at altitudes of up to at least 1,900 ft. above sea level. A. (Myzomyia) solomonis Belkin, Knight & Rozeboom, the status of which as a vector of Plasmodium is unknown, was found breeding at an altitude of 3,000 ft. Neither P. falciparum nor Wuchereria bancrofti were recorded from the hill districts visited. During the investigations several species of Culicines were collected. Features of the larval morphology of some of these are illustrated and briefly discussed in a systematic appendix.

It is confirmed that the scutellaris-growp mosquito of the Tokelau and Ellice Islands is Aëdes (Stegomyia) polynesiensis Marks. No other mosquitos are known from the former Group, but Culex (Culex). annulirostris Skuse, A. (Aëdimorphus) vexans nocturnus (Theo.) and A. (Stegomyia) aegypti (L.) are also recorded from Funafuti, Ellice Islands. C. annulirostris and A. vexans nocturnus are listed—apparently for the first time—from Tarawa, Gilbert Islands. Reference is made to the microfilaria rate at Nukunono in the Tokelau Group, and to some potential mosquito larval habitats, as yet unutilised, in all three Groups.

The susceptibility of various mosquitos to DDT, dieldrin and BHC has been studied. Adult females were exposed in small tubes lined with filter papers impregnated with insecticide-oil solutions. Larvae were exposed to insecticideacetone suspensions in water.

Adult mosquitos tested in London showed no striking differences in susceptibility to DDT, though the median lethal concentration (MLC) of Culex pipiens molestus Forsk. (1·6 per cent.) was greater than the MLC of Aëdes aegypti (L.) (0·9), Anopheles maculipennis var. atroparvusvan Thiel (1·0), or A. quadrimaculatus Say (·7). C. p. molestus and Aë. aegypti showed the same order of susceptibility to dieldrin and BHC, with Anopheles m. atroparvus more susceptible to both insecticides.

In order to test their ability to survive the winter in unheated buildings, 68 species of storage and domestic insect pests were exposed throughout one or more winters in wooden screens and various outbuildings at the Pest Infestation Laboratory, Slough, Bucks.

Generally, cultures containing all developmental stages were exposed. The chief aim was to demonstrate some survival or else the complete failure of the culture; conclusionsabout single stages were added where possible.

The ability or failure of a species to overwinter may be affected by the following factors, which are discussed: cold-hardiness, effects of previous conditions, differences between strains or races within a species, severity of the winter, length of period of exposure, moisture conditions, type of building, protection by materials in storage, biological heating of the immediate environment.

The shortest experiment lasted 16 days, the majority for about six months.

In breeding Glossina palpalis (R.-D.) in captivityin Northern Nigeria, it was found that even though the sexes are segregated within 24 hours of emergence, a few females succeed in producing larvae. Examination of the spermathecae of females thus segregated shows that nearly 4 per cent. are fertilised. This low fertilisation rate is due to the impotence of most males under 24 hours old. When young males of different ages were forced to compete with older males for the females' favours, it was found that young males must be 7 to 8 days old before their virility approaches that of older males.

When virile males are added to mating cages containing virgin females, pairing startsimmediately, but the number of pairs decreases steadily until after 23 hours, pairing has virtually ceased. The cessation of copulation is due to the female becoming unwilling to pair and to her ability to repulse the male; but if she is re-fed her willingness will be restored to a considerable extent. There is no need to leave the sexes together formore than 24 hours, as excellent fertilisation can be achieved in that time.

Data on the populations of the Pea Aphid, Acyrthosiphon pisum (Harris), have been accumulated over four years on several leguminous crops in East Anglia. The populations on lucerne have provided the most extensive studies.

Considerable annual variation was shown by the populations, but in spring the development of a peak in the numbers of Aphids occurred on lucerne, hop trefoil and sainfoin. On lucerne, which was periodically cut, the Aphids persisted throughout the growing season and a tendency towards the development of a peak in numbers in the autumn was also recorded.

All the factors which affected the number of Aphids varied considerably in the influence they exerted. The probable reason for the more obvious trends in the populations have been given in fairly broad outline, but how the effect of these factors had been altered or predisposed by less apparent factors has been speculated upon only in certain instances.

Egg populations of the Pea Aphid, Acyrthosiphon pisum (Harris), overwintering on lucerne and hop trefoil have been followed. On hop trefoil the overwintering mortality of these eggs was 83 per cent. Although the mortality was apparently less on lucerne, a wide discrepancy existed between the two crops in the ratio between the total numbers of eggs at the beginning of eclosion and the number of Aphids which successfully established themselves the following spring. The peak number of fundatrices on lucerne was three times the egg total at the beginning of eclosion whereas on hop trefoil it was only half. Many more eggs than were recorded were undoubtedly laid on the lucerne plants and the high number of fundatrices subsequently found must have emerged from eggs that had fallen or been knocked off the host-plant.

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.

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.

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.

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.

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.