Methods that have been used to confine insects to the test surface during exposure to insecticidal deposits are briefly reviewed, and their limitations are discussed. Some unsuccessful preliminary experiments on alternative methods are mentioned.

A temperature-preference method of inducing house-flies, Musca domestica L., to remain on a treated surface is described, and the apparatus is illustrated. The treated surface forms the floor of a chamber; it is maintained at a higher temperature than the walls and lid. The flies are introduced by means of a plunger device.

The damage caused to cotton by the yellow tea-mite,Hemitarsonemus latus(Banks),was first seen in Uganda in 1945 and is now known throughout the important cotton-growing areas of the country. Experiments on cotton in the Belgian Congo showed that sprays and dusts of several insecticides would control or prevent infestations of H.latus;earlier published work in Ugandasuggested that BHC reduced tea-mite damage and DDT increased it,when both were appliedas sprays from wettable powders.However,tea-mite damage was not noticeable on trials in which single rows of cotton were sprayed with DDT emulsion,or on large-scale trials using DDT formulated as a water-miscible liquid. These trials were all directed against the pest insects Earias spp. and Lygus vosseleri Popp.,the standard rate of application being 1 lb. active ingredientper acre applied four times at ten-day intervals.

Dysdercus superstitiosus (F.) is capable of utilising a much wider range of food-plants than was previously supposed, and is able to complete a full breeding cycle on the several diets other than cotton. This has been demonstrated by rearing and breeding adults and nymphs in the laboratory, in Uganda, on selected food material, e.g., Sorghum vulgare, Pennisetum typhoides, Zea mays and Vigna unguiculata, immature seeds of each being used. Diets other than mature cotton seeds are less suitable for breeding, as judged by fecundity of females and development of nymphs, but the influence of nymphal diet on adult fecundity is not consistent. Females reared on sorghum are smaller than those reared on cotton seed and they may lay fewer eggs.

There is an indication that varieties of sorghum may differ in their suitability for producing maximum fecundity and fertility. Those varieties to which the stainer exhibits a predisposition in the field may not be the most suitable.

When adults are fed on cotton bolls of ages 1–10 weeks, the fecundity of females, and the rate of egg-production increase with increasing age of boll, and the preoviposition period decreases.

Stored cotton seed may be less suitable for egg-production than freshly harvested seed cotton.

Extraction of oil from cotton seed with petroleum ether does not wholly impair the fecundity rate of females fed on the seed, but may reduce the fertility and nymphal survival in the first instar.

A diet of cotton seed, heat treated at 150–190°C. for one hour, reduces the fecundity in the females, possibly by destroying the accessary food factors. Nymphal survival is possible on such treated seed, but not when thus heated for two hours at or above 150°C.

Early in 1959, observations on the farm Tayside, in the East London district of South Africa, suggested that populations of the ‘two-host’ red tick, Rhipicephalns evertsi Neum., were more difficult to control with toxaphene preparations than they had been in the past. Resistance to toxaphene was suspected, and both field and laboratory experiments were carried out to investigate this possibility. Field trials indicated an increase in tolerance by Tayside populations of the tick to toxaphene, γ BHC and dieldrin, but showed no increased tolerance to sodium arsenite or DDT. Similar results were obtained in laboratory experiments where Tayside adults were compared with those of other populations of the tick known to be sensitive to insecticides. Laboratory experiments with larvae indicated a high degree of resistance to toxaphene and γ BHC in the Tayside population, but no increased tolerance to sodium arsenite, Delnav, Sevin or DDT could be detected. This pattern of cross-resistance is similar to that occurring in resistant populations of Boophilus dccoloratus(Koch).

The true identity of the specimens from Africa recorded as Coccus africanus (Newst.) and C. viridis (Green) is reviewed in detail. Four other species of green scales attacking coffee in Africa south of the Sahara are described as new. These are: C. alpinus—for more than 40 years confused with africanus—C. celatus, C. consimilis and C. viridulus.

Some 246 species of mosquitos are known to occur in Uganda. Of these, 92 (37·4%) have been recorded as breeding in swamps, and the present paper brings together published data and the results of work on the collection and identification of larvae from habitats in a wide variety of types of swamp between 1955 and 1958. Notes on the occurrence and habitats of the larvae are given under each species.

In the present work, only 58 species were found breeding, but these included six new swamp records. Only 26 species appear to breed exclusively in swamps. In addition to the species identified, larvae representing some 14 unrecognised and probably undescribed species were collected. The majority of the swampbreeding species are Culicines, the Anophelines comprising only 21·7 per cent.

The swamp environment in Uganda, with respect to the breeding of mosquitos, is extremely varied. Some possible classifications of the many and various swamps found in the country are given. The distribution of certain species of mosquitos is more or less limited to certain types of swamp This is briefly discussed and examples are given. There is also a definite zonal distribution of some species within a swamp, e.g., Culex (Culex) grahami Theo., C. (C.) guiarti Blanch, and Ficalbia (Ficalbia) malfeyti Newst. occur only in peripheral zones. In general, the interior of the large swamps is unfavourable to the breeding of Anophelines, but Culicines are very abundant there.

Breeding of mosquitos is profoundly affected when swamps are altered by human interference. In certain cases this has resulted in increased production of Anophelines, with the consequent aggravation of the malaria situation.

It is concluded that, from the point of view of human disease, the swamps of Uganda (especially in their natural untouched state) are not as dangerous as previously thought.

Nupserha bicolor postbrunnea Dutt has become established on olitorius jute (Corchorus olitorius), possibly from its wild food-plant, Sesbania aegyptiaca, and from jute it has spread to other agricultural crops. Incidence on the green-manure crop, Sesbania bispinosa, has increased so much in recent years that it has surpassed that on olitorius jute. The stem diameter most favourable for girdling and oviposition in S. bispinosa ranges from 3·1 to 5 mm., whilst in C. olitorius it is from 2·6 to 3 mm. In spite of this wide difference in preferred stem diameter, the ratio of mandibular length to depth of extra-medullary tissue of such stems in the two plants agrees well.

All the varieties of capsularis jute (C.capsularis) are unacceptable to the adults though they are acceptable to the larvae. Adults obtained from larvae reared on varieties of capsularis jute also show aversion to capsularis types. The pest selects the susceptible olitorius from amongst capsularis jute when these are grown as a mixed crop. Amongst the olitorius varieties, C.G. is the most susceptible. Plants coming within the height range of 100 to 200 cm. are attacked more than others. Girdling causes suspension of unidirectional vertical growth, and this is followed by the appearance of a number of side branches, which are of little value from the point of view of fibre.

The size-specific fat content of tsetse flies recently emerged from their puparia was determined and by comparison with the size-specific fat content of newly deposited larvae an estimate was obtained of the consumption of fat during pupal development. Experiments with Glossina morsitans Westw. were carried out at a number of different temperatures and it was found that the amount of fat consumed was least at temperatures between 22 and 24°C.

Knowing the duration of the pupal period at different temperatures, the rate of fat consumption could be calculated and the logarithm of this rate was found to be linearly related to temperature. The occurrence of an optimum temperature in respect of fat consumption thus reflects the fact that at high temperatures the rate of fat consumption is greatly increased without a corresponding reduction in the duration of the pupal period, whereas at low temperatures the pupal period is very greatly lengthened without a corresponding decrease in the rate of fat consumption.

In pot experiments, the ability of newly hatched larvae of the wheat bulb fly, Leptohylemyia coarctata (Fall.), to move through nine in. of soil and infest wheat plants was tested for three different types of soil: sandy loam, clay loam and peaty loam and also clay loams at different levels of acidity. Each soil was inoculated with 200 freshly hatched larvae and the effects associated with soil were measured by the number of larvae subsequently recovered from infested plants.

The larval recoveries for different soil types were: sandy loam 28 per cent., clay loam 19 per cent, and peaty loam 2 per cent. The larvae could infest plants grown in clay loam within a pH range of 4·9 to 7·8 and the results suggested a possible optimum at pH 6·2. The relative failure to infest in peaty loam appeared to be due to this soil impeding larval movement rather than interfering with the mechanism of host-plant location.

In an attempt at some assessment of the errors to which fly-round data obtained for the study of populations of Glossina are subject, three fly-rounds at Shinyanga, Tanganyika, were worked every weekday for four weeks. The species studied was G. swynnertoni Aust. One of the rounds was a ‘transect fly-round ’, the others, the older type, divided into a few long sections according to the vegetation. The catches showed no obvious trend during the experiment, suggesting that the true population had not altered in the period, but in all three rounds there were considerable day-to-day variations in catch and, in this respect, the transect fly-round did not differ from the older method. An analysis of variance of the transect fly-round data showed that the variance between days was greater than could be accounted for by random errors

By considering separately the data collected on certain days of the week, it is concluded that a 7,500-yd. fly-round done once a week could not detect less than a five-fold change in the mean catch. To detect a two-fold change, a 15,000-yd. fly-round done twice a week would be necessary.

The relation between fly-round catch and true density is discussed. This relation is usually termed ‘ availability ’. Earlier workers have shown that its mean value, over periods of about one month, is not necessarily constant; the present work shows that it varies in one place from day to day.

The paper deals with two members of the Simulium neavi Eoub. complex found at Amani in the forest of the Usambara Mountains, Tanganyika Territory. They have already been described but are at present termed the Amani unhanded and banded forms, scientific names being witheld until the taxonomy of the whole complex is better understood.

Some methods of study are described.

Pupae of the unhanded form constituted a large proportion of the total number found on the common local crab, Potamon (Potamonautes) lirrangensis Eathbun, which amounted to roughly one pupa to seven crabs. This form predominated in the lower and more open parts of the drainage system examined. The adults were not seen to bite man. This and the banded form were found at a much lower altitude than any hitherto reported for the complex, probably owing to the particular nature of the local climate. Neither form was abundant.

The larvae and pupae of the banded form, like the unhanded one, live externally on the crabs. The variability of wing size of the banded form is described. Observations were made on the internal anatomy of the adult with special reference to the ovaries in which the follicular relics are usually very large, indicating that the female probably bites soon after laying eggs. As in S. damnosum Theo. there is an easily recognisable class of old flies with clear Malpighian tubes. Nulliparous and parous flies have rather different biting cycles. The banded form bit man readily but only about five were taken per hour in good catching places and far fewer elsewhere.

Human onchorcerciasis has been reported from Amani but is not known to do any harm there. The existence of the disease in the presence of rather small numbers of Simuliids is of interest in relation to a belief that S. neavei is a more efficient vector of onchocerciasis than is S. damnosum. Out of 359 banded females dissected 41·2 per cent, were parous and 12·8 per cent, of these were infected with nematodes, at least some of which were not Onchocerca volvulus.

Taxonomy, the ovarioles and the Simuliid-crab association are discussed. The formation of the large follicular relics of the banded form is considered in relation to the history of the follicular epithelium before and after ovulation. The crab association is regarded as commensalism-, and it is suggested that the crabs benefit the Simuliids by carrying them a short distance to a suitable current and that they thus enable them to live in fast rivers and so extend their range.

Indications of the type of paddy grain most commonly infested by Sitophilus sasakii (Tak.) and Rhyzopertha dominica (F.) have been obtained from the examination of infested samples of paddy grown in Trinidad, W.I., and in British Guiana.

Small-scale experiments with sound mature paddy have shown that S.sasakii is unable to feed and breed in a grain with an intact husk, even when the moisture content is high. It is also probable that R. dominica finds it extremely difficult to attack and infest such grains.

The rapid multiplication of S. sasakii in paddy is dependent on there being a high proportion of grains with badly damaged husks. Infestation can occur in grains with a slight separation of the lemma and palea, or with slightly split husks, but the adult that develops is often unable to emerge from such grains.

In 1956 and 1957, tests were made in the Sudan Eepublic of four methods of applying insecticides for the control of heavy infestations of midges, particularly Tanytarsus lewisi Freeman, which breed in the Blue Nile. During the winter season the adults occur in myriads in areas adjacent to the river in Khartoum and similar localities, resting in trees and shrubs by day and being attracted to artificial lights after dusk

An emulsion containing 0·4 per cent. DDT applied from the ground to shadetrees in Khartoum at the rate of 0·5·1·0 lb. DDT per tree achieved local control of the midges for three days and detectable reduction for 10 days. An emulsion containing 12·5 per cent. DDT applied from an aircraft to the wooded riverfrontage at Khartoum at 2·1 lb. per acre reduced the numbers of adult midges for the next 15 days, but subsequent applications under conditions of greater air turbulence were ineffective.

The application of DDT as a larvicide in oil solution from aircraft to the river 10 miles above Khartoum, at a concentration approximately equivalent to 0·1 p.p.m. in 2 hours' riverflow, did not appear to reduce the numbers of adults or immature stages at Khartoum, and was followed by some mortality of fish.

Using a deterministic model of a tsetse population, theoretical calculations have been made of the effect of repeated applications of a non-persistent insecticide upon a natural population. It has been assumed that the insecticidal applications instantaneously reduce the adult population, and that there is no residual effect.

For the numerical work it has been assumed a female fly has a pupal period of four weeks and an average expectation of life of six weeks and produces her first larva three weeks after emergence, and subsequent ones at intervals of one-and-a-half weeks.

Results have been calculated for kills of females varying from 50 per cent, to 95 per cent, per application, for series of up to eight successive applications, and for intervals between successive applications of from one to six weeks and also for the case when the population is allowed to become stable between applications.

Baris granulipennis (Tourn.), originally described from Egypt, has become a serious pest of water-melons (Colocynthis citrullus) in Israel, where hitherto its presence has not been recorded, and has been found on melons and cucumbers, but not on vegetable marrow or squash. Economically serious damage results from girdling of the stem end of the fruit by the female, prior to oviposition.

The incubation period of the egg, on average, is 3·7 days at 30° and 6 days at 22°C. The larvae feed on developing seeds inside the fruit and pupate there. The total development period occupied from 25 to 42 days in the summer, when the temperature fluctuated between 24 and 29°C. The cocoon is made by glueing minute pellets together. These consist of dried pulp from the fruit mixed with a secretion which is ‘milked’ from the anus, and is believed to be produced in the Malpighian tubules. The preoviposition period is about four days, and the length of adult life is several weeks. There are three generations a year, and four if weather permits. Adults overwinter in hibernation. It is suggested that the increase of cucurbit cultivation, and the lengthening, by irrigation, of the cropping period, may have permitted an increase in the weevil population to pest proportions.

An account is given of the biology of the phytophagous Chalcidoid, Eurytoma sp. near howardi D.T., and of its bionomics in Mauritius. The insect was introduced into Mauritius from Trinidad to supplement the activity of the Galerucid beetle, Schematiza cordiae Barber, in the control of Cordia macrostachya, an introduced shrub, indigenous to Central America and the Caribbean Islands. The egg and larval stages are described and figured.

The entire development of Eurytoma takes place within the fruit of Cordia, which contains usually only one seed when mature and has a very hard and stony endocarp and a soft and fleshy mesocarp. Oviposition by Eurytoma takes place before the endocarp hardens; the egg is laid inside the seed and the larva feeds on the nucellus and endosperm and later on the developing cotyledons, until the entire seed, except for the seed coat, has been consumed. The attacked fruit continues to grow and its endocarp hardens, but final swelling of the mesocarp does not take place. Although more than one egg may be laid in a seed, only a small percentage of the many seeds dissected contained two mature larvae or two pupae. Pupation takes place within the seed, from which the adult escapes by boring a round hole through the endocarp.

Development from egg to adult occupies about 23 days in the hot season (November–April), but in the cooler months (June–September) the fully-grown larva enters a resting period, which may last several months.

Adults kept in jars, and provided with honey in water, at a mean temperature of 25°C, lived for an average of 11 days (males) or 20 days (females). A newly emerged female contains about 12 fully developed eggs. Virgin females oviposit readily, all the progeny being male.

Releases of adults from material received from Trinidad were made between October 1949 and May 1950; by the latter date it was evident that the insect had become established at the first liberation site and further colonies were established in various parts of the island from material collected there. Estimates of infestation of samples of fruit collected in October 1951 at or near 22 liberation points ranged from 16 to 81 per cent, (mean, 53·7). The latest island-wide estimates, in February, June and October 1953, showed averages of 64·7, 40·8 and 48·7 per cent, infestation, respectively.

Infestation of fruits is highest (70–80%) in the hot season, when fruit production is at its maximum, and lowest in the cooler months, when, although the rate of fruiting declines, the life-cycle of Eurytoma is prolonged.

Schematiza cordiae had achieved a high degree of control of Cordia before Eurytoma became widely established, and it is difficult to assess the contribution made by the latter, which has no known specific natural enemies in Mauritius; but the two unrelated insects acting jointly are likely to stabilise control more effectively than would one insect alone.

In an appendix, P. 0. Wiehe gives notes on the present ecological status of Cordia in Mauritius and contrasts it with that prevailing before the introduction of Schematiza and Eurytoma. He concludes that the secondary succession of vegetation has now reverted to its former course.

Emergence and life-span of wheat bulb fly, Leptohylemyia coarctata (Fall.), have been studied by the use of a field-cage-marking technique. Emergence was investigated by observing the numbers of flies emerging daily from an area of infested wheat enclosed by a cage of fine mosquito-netting, and life-span by making a daily census of marked and individually recognisable flies which had been liberated in the cage. Flies were handled only when being marked and in the later part of the work all observations were made without touching either them or the wheat.

Flies were chilled to render them comatose for marking and under certain circumstances this and the marking was-harmful. Attempts were made to reduce these harmful effects.

Emergence dates varied from year to year depending on the temperatures of spring and early summer, and there were also considerable differences between the emergence dates of populations of adjacent fields in the same year. Consistently, males appeared before females.

The ratio of the number of flies seen to the number known to be alive on each day varied according to weather, flies being more difficult to find on windy days than on calm ones and on bright days than on dull ones.

The observed life-spans of both sexes varied greatly, up to a maximum of 75 days for females and 55 days for males. An exact statement of mean life-span was not possible because there was a tendency for flies emerging later in the season to be less long-lived than those emerging earlier. Most flies of both sexes lived for over 30 days.

The observed life-spans fall short of the true life-spans by amounts that depend on the proportions of living flies seen each day. Two methods are shown by which the mean unrecorded life-span can be calculated.