The Spinach Stem Fly Hylemyia echinata (Séguy), is an important pest of spinach (Spinacia oleracea) grown in the east and south-east of England for canning and freezing. Attack by the larvae results in the blackening and distortion of terminal shoots and the splitting and discoloration of petioles and mid-ribs, and some larvae may be present in the crops when they are harvested.

The eggs are laid in May on the upper surfaces of the leaves and among the leaflets of the terminal and axillary buds. The larvae penetrate the epidermis and tunnel through the mesophyll until they reach mid-ribs, petioles or stems where they feed on the hollow inner surfaces. The puparia are usually found in the soil but may occur in the feeding sites. The second generation emerges in June and July, and further emergences occur in August and September. Larvae are present in the crops from May to October.

Eggs and larvae are described and illustrated so that they can be distinguished from those of the Mangold Fly, Pegomyia betae (Curt.), which are often present on spinach at the same time. The flies are described and the characters which distinguish them from the Bean Seed Flies, Delia cilicrura (Rond.), are noted.

Laboratory and field experiments were carried out to study the toxicity of 3:5 dinitro-ortho-cresol and its sodium salt to the honey bee.

The acid DNOC was shown to be a rapidly acting poison under a wide variety of conditions and its toxicity was not greatly affected by differences in temperature or humidity during or after treatment.

Although both the acid and salt were equally toxic as stomach poisons, considerable differences were observed between the two substances as aqueous sprays and dry films. The toxicity of the sodium salt as an aqueous spray was considerably influenced by the humidity of the environment after spraying; the higher the humidity the greater the kill.

The sodium salt was apparently non-toxic as a dry film and increasing the humidity of the environment had no effect until the saturation point was reached and the salt went into solution. At this point the salt was almost as rapid in action as the acid. The type of surface on which the film was deposited was also shown to affect the toxicity.

Experiments were carried out on the penetration of the two substances through beeswax and these confirmed that whilst the acid could penetrate the beeswax in all forms tested the salt would only penetrate in aqueous solution.

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.

All the leaf-feeding sawflies on Larix in Britain belong to the Nematine Tenthredinidae. Up till a few years ago, the most notorious recorded in this country was Pristiphora erichsonii (Hartig), though local attack of P. wesmaeli (Tischbein) and P. laricis (Hartig) have also occured. These are also the chief Tenthredinid enemies of larch on the European continent, where the genus Anoplonyx has apparently never occured in sufficiently large numbers to cause economic damage. In Britain, where larch is not a native tree, the sawflies attacking its leaves are all restricted to it and so must have been introduced into the country.

A development of grasshoppers to minor plague proportions over a limited area of the Rift Valley near Lake Elmenteita occurred in 1950. The two chief species concerned were Gastrimargus brevipes Sj. and Caloptenopsis glaucopsis meruensis Sj. but many other genera and species were present and are listed. The distribution of rain with appreciable falls followed several times by dry spells may have been a factor contributing to the increase. An unusual increase of the Coccinellid, Epilachna hirta (Thnb.) also occurred in the area a month or two before.

Observations were made chiefly in the southern Sudan, particularly at Mvolo where human onchocerciasis is common. The country and climate are briefly described.

Methods are described at some length.

The distribution of S. damnosum and places where it is known to be abundant are shown on a map. It does not appear to exist at the Fola Rapids.

Changes in certain organs were studied, chiefly in relation to the approximate estimation of age and (particularly in the case of the mid-gut and peritrophic membrane) to the movements of microfilariae. Recently emerged flies can frequently be readily detected by the clarity of the halteres (in which glycogen has not yet been stored) and the presence of abundant fat body, and by less conspicuous features such as the absence of an old peritrophic membrane. The oesophageal diverticulum often contains plant sugars and particles of grit but never blood.

The peritrophic membrane is formed at the time of a blood meal by the epithelium of the expanding part of the mid-gut. It is a laminated chitinous envelope completely surrounding the blood and remains unbroken for 24 hours or more. When very large numbers of microfilariae are ingested they appear to prevent the completion of the membrane so that blood quickly passes to the hind-gut.

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.

A study of the immature stages of the Anthomyiid flies, Delia cilicrura, D. trichodactyla, Erioischia brassicae, E. floralis and Pegohylemyia fugax, associated with injury to cruciferous crops, has shown that the several species can be distinguished. The egg stage can be identified by the sculpturing of the chorion, except in the case of the closely related species E. brassicae and E. floralis where the sculpturing is similar but there is a considerable difference in size.

The larvae can be distinguished by differences in the shape and character of the head and in its relation to the prothorax, and in the form of the mouth-parts in the three instars. The number of finger-like processes of the anterior spiracles and the number and arrangement of the tubercles of the eighth abdominal segment also contribute to the identification of the larvae.

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.

The primary object of the work which is the subject of this paper was to clarify the confusion that has existed for many years in the nomenclature and taxonomy of certain important Agrotid borers of graminaceous crops in Africa.

The genera involved are Spcia, Sciomesa, Poeonoma, Conicofrontia, Bussecla and Sesamia, and of these the first three are new and are described and the others are redescribed. A key to the genera and keys to the species of Sciomesa, Poeonoma and Sesamia are given. The genus Speia is erected for Phalaena vuteria Stoll; the name vuteria Stoll has been wrongly applied to the important pest of sugar-cane in Mauritius, which is, in fact, the well known Sesamia calamistis Hampson. Sciomesa is erected to contain three species previously included in Conicofrontia. Poeonoma also contains three species, of which one is Phragmatiphila serrata Hampson and the other two are new. Hampson's species Conicofrontia sesamoides is redescribed in Conicofrontia and is the only species of that genus dealt with in detail; Phragmatiphila bipartita Hampson is synonymised with it. In the genus Busseola, only the well known pest, B. fusca (Fuller) is described.

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.

This work was undertaken to unravel past confusion concerning the identity of certain economically important species of Cryptophlebia. It involved the study of several other species of the same genus and has resulted in the recognition of three new species and the transfer to Cryptophlebia of several species hitherto placed in other genera, mainly Argyroploce.

The three new species are described and 14 species are redescribed. The distribution of each is given and the food-plants are listed where known. The adult female and the male and female genitalia of each of the new species and certain others are illustrated.

The physical state of deposits from various formulations of insecticides applied to different materials is considered in relation to the availability of the insecticide to insects making contact with the surface of the treated material.

Applications of oil solutions of insecticides to absorptive material result in absorption of the solution, and the insecticide is thereby rendered ineffective. On a nonabsorptive surface, oil solutions are the most efficient formulations, but only so long as the deposit remains wholly or partly liquid; if evaporation of the solvent gives a dry crystalline residue, this is much less efficient than the original solution.

On some fibrous absorptive surfaces, a solution of DDT in oil remains in a supersaturated condition in and around the fibres. If crystallisation is stimulated by mechanical means, the resulting crystals project from the treated surface and it is suggested that, in these circumstances, crystals are more readily available to insects than the oil solution from which they were derived.

DDT on compressed wall board shows the induced crystallisation to a greater degree than other insecticides. It is concluded, therefore, that wall board and similar surfaces should not be used in comparing the potencies of chlorinatedhydrocarbon insecticides applied as oil solutions, as DDT would be more available than others. Some factors that affect the degree of induced crystallisation are mentioned.

The process of build-up of reserve substances in Locusta migratoria migratorioides (R. & F.) is very closely correlated with the feeding activity of the insect. Locusts attain their maximum body weight in the initial period before maturation. In the females there is one minor build-up period after each laying.

As measured by the weight of faeces produced, the gregaria female consumes more food than the solitaria during development. It also has a lower rate of increase in body weight, maturation and oviposition.

Locusts start to build up fat soon after the final ecdysis. The fat content reaches its maximum in the early part of adult life, and then begins to decline in both sexes of both phases.

By far the greater part of the fat reserve thus built up in the gregaria female is used up before oviposition, and only a small amount goes to the making of the first egg-pod. The fat of the subsequent egg-pods (of both phases) is derived from the fat built up each time after a new egg-pod is laid.

The solitaria females may mature their eggs at various stages in the development of the fat body. Those which have a longer pre-maturation period have a higher fat content.

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 larvae and pupae of the following Lepidoptera, all of which are of economic importance in Mauritius and most of them elsewhere also, are described:—

The Agrotids, Sesamia calamistis Hamps. and S. inferens (Wlk.); the Crambids, Proceras sacchariphagus Boj. and P. indicus Kapur (larva only); and the Olethreutids, Argyroploce schistaceana (Snell.), A. leucotreta Meyr., Cryptophlebia peltastica (Meyr.) and C. williamsi Bradley.

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.

In Nigeria, shelled groundnuts are stored in sacks in covered warehouses and as pyramids in the open air. At the beginning of storage the nuts comprise approximately equal quantities of whole, split and broken nuts of a moisture content of 3·4 per cent. The sacks are exposed to direct hot sun whilst stacking.

The mean monthly maximum shade temperature in Kano ranges from 101°F. in April to 85°F. in January and August and the mean monthly minimum from 75°F. in May to 56°F. in January. Monthly maximum relative humidities range from 100 per cent, in August and September to 45 per cent, in February, and the monthly minimum from 71 per cent, in August to 12 per cent, in February. The range of mean relative humidity is 81 per cent, in August and 18 per cent, in February. Rains fall between April and September, 70 per cent, falling in July and August. Heavy falls are recorded on about 25 days.

Inside warehouses, the maximum monthly temperatures are 102°F. in May and 79°F. in January and February, and minimum temperatures are 81°F. in June, and 58°F. in February. In August the mean relative humidity range is 93 per cent, to 70 per cent. In December it is 34 per cent. to 20 per cent.

Just under the roof of a warehouse and on the surface of pyramids the diurnal range is very large.

The mean size of the males of the three tsetse species Glossina pallidipes, G. morsitans and G. swynnertoni is negatively correlated with the mean 2 p.m. saturation deficit of 2 months before.

The correlation is highest (—0·90) for G. pallidipes, the largest species, and lowest for G. swynnertoni, the smallest. The variation coefficient of mean vein length also is highest for G. pallidipes and lowest for G. swynnertoni.

The reason for the apparent 2 months' lag in the effect of saturation deficit on size of flies is that the mean male pupal period is 35 days in Shinyanga (23°C.) and the mean age of males measured is 3–4 weeks. If 1 month's lag is tried, the correlation for G. pallidipes drops from —0·90 to —0·32, and with no lag at all it is —0·24. The correlation with maximum temperature of 2 months earlier is insignificantly lowerthan that with saturation deficit; it is —0·79 for G. pallidipes.