The ovarian cycle in Culicoides barbosai Wirth & Blanton and C. furens (Poey), two biting midges of considerable importance in Jamaica, was studied in the laboratory. In C. furens, a single blood-meal was sufficient for development of a substantial number of eggs; in C. barbosai, which took a relatively smaller blood-meal, very few eggs were matured (usually between 10 and 20 but sometimes fewer than 10), and some females failed to produce any eggs at all.

A high degree of gonotrophic harmony was observed in C. furens, but in C. barbosai the degree of harmony was low and a large proportion of the ovarian follicles degenerated; these differences may be associated with the relative size of the blood-meals of the two species.

The duration of the gonotrophic cycle (from feeding to the appearance of mature eggs in the ovaries) at 68, 77, 85 and 91°F. was 156, 104, 82 and 72 hr., respectively, in C. barbosai and 102, 59, 42 and 36 hr. in C. furens.

In experiments on the effect of temperature and carbohydrate feeding on egg production, temperature did not influence egg production in C. barbosai, and greater numbers of eggs were not matured by females given access to honey during the period of egg development. However, access to honey did increse the proportion of individuals surviving the period of egg maturation and also the numbers that mastured any eggs at all. Females of C. furens kept at 77°F. matured more eggs than those kept at 91 or 85°F.; access to honey improved survival, but its effects on egg production were inconclusive in these experiments.

Observations indicated that adults of both species are probably in the habit of taking carbohydrate food in nature.

Females of both species may be autogenous, though the proportion of such individuals varied considerably between populations from different breeding sites. Autogenous females of both species emerged from the pupa with ovaries already relatively well developed; in C. barbosai the ovarian follicles were in Stage IIB or III, in C. furens they were in late Stage IIA or IIB. Large numbers of eggs were matured by autogenous females of the former, and the same is probably true of the latter.

The egg stage is apparently of longer duration C. barbosai than in C. furens. At 68, 77, 85 and 91°F., most eggs of C. barbosai hatched on days 12, 6–7, 5–6 and 5, respectively, whereas at the three higher temperatures most eggs of C. furens hatched on days 4, 3 and 2. Percentage fertility varied between individual egg batches of both species.

To permit detailed study of individual tsetse, either as insects or as the vectors of trypanosomiasis, a method has been devised which resulted in excellent survival and reproduction when tested on females or Glossina austeni Newst.

Each mated female was maintained in asmall cage comprising a stainless steel frame covered with non-absorbent black Terylene netting through which the larvae and faeces fell into a tray. Each cage was applied daily to the ear of a rabbit, and records were kept of the number of feeds, time taken to feed, numbers of larvae produced, lengths of interlarvel periods and weights of pupae.

The following conclusions are tentative as they are based on detailed studies of only eight females. Five of these produced larvae regularly at 8½- to 9-day intervals. Ninety-six interlarval periods were investigated. Although the mean interval between meals was two days, the flies tended to fast before larviposition and to engorge repeatedly afterwards.

Among nearly regular breeders, failure to larviposit did not seem to interrupt the normal feeding rhythum: the reproductive rhythum later re-integrated with the feeding ehythum. A tendency to deviate from the normal feeding pattern either by too frequent feeding after larviposition or by prologation of the fasting period before larviposition, may possible be related to pemature death, but flies which tend to feed on the day before larviposition centainly risk death from pupation in utero—a condition found in 5 per cent. of dead rabbit-fed flies; the complex of pressures which lead to this condition is described.

Limited data suggest that females which live to a great age enter a post-productive period when about 6½ month old; the feeding pattern breaks down completely, the fly fasting for periods of up to 11 days, or even longer in the immediate pre-death period. The maximum output of reasonably sized pupae is probably about 20 for G. austeni.

Pupal weight increased until the parent flies were about 90 days old, but there was much individual variation; thereafter the weight remained high, but among very old dlies it fell towards the end of reproductive life. Certain individuals tended to produce heavy pupae, a characteristic probable associated with the size of the fly and the total weight of blood taken up in each interlarval period—not with the frequency of feeding; a very infrequent feeder may, however, produce underweight pupae at irregular intervals.

In field experiments carried out at Kutsaga, Rhodesia, tobacco plants that had received high or low amounts of nitrogen, in addition to a basic dressing, were examined over five-week periods for the presence of alates and newly; deposited nymphs of Myzus persicae (Sulz.). It was found that settling and larviposition were reduced as a result of nitrogen deficiency in the plants, I apparently due more to some effect associated with slower plant growth than to reduced nutritional suitability. Washing with water enhanced the attractiveness of leaves in laboratory flight-chamber tests with alatae, suggesting the presence of a repellent substance on unwashed leaves. In flight-chamber tests with alatae, and choice-chamber tests with apterae, using artificial leaves made by forming Parafilm sachets on yellow Perspex discs, it was found that larviposition and nutritional suitability were related, and that both were affected by altering the balance of nutrients in the sachets, in the absence of any stimuli on the surfaces of the membranes.

Field trials in 1958–62 at Gatooma Research Station, Rhodesia, in which carbaryl, DDT, endrin and endosulfan were compared for controlb of insect pests of cotton, confirmed earlier laboratory results which showed that larvae of Diparopsis castanea Hmps. were more susceptible to carbaryl than those Heliothis armigera (Hb.) but that the latter were more susceptible to DDT. Counts of larvel populations showed that neither insecticide used alone could control the bollworm complex statisfactorily. The results indicated that optimum control could best be achieved by applying one or other insecticide as appropriate after inspection of the crop to determine the level of insects attack at diffetent stages during the seasons, rather than by use of mixtures of both insecticides. It is recommended that dimethoate should be added to either of the insecticides for aphid and red spider mite control when required.

A species of Xyloryctid moth bred from larvae feeding on the leaves of tea (Camellia sinensis) in Hong Kong is described as new and is named Neospastis sinensis sp.n. The species is differentiated from the three other known representatives of the genus, and also from Synchalara rhombota (Meyr.), which is a pest of tea in India, and S. rhizograpta Meyr., which was originally described from China. Illustrations of both sexes of the adult and genitalia and of N. sinensis are given.

A study of the egg shells of 11 species of Anopheles was made with the stereoscan electron microscope. A number of structures have been found that are useful in distinguishing between eggs of different species; all of them can also be seen with the light microscope. A list is given of these structures, together with others already known to be of taxonomic importance.

The functional significance of the network of the outer layer of the chorion of Anopheles eggs is discussed. It is suggested that the film of gas held by the network is of selective advantage in that it contributes to the buoyancy of the egg, provides it with a part of its protective coloration, and functions as a plastron when the egg is submerged. The plastron of A. labranchiae atroparvus Van Thiel resisted wetting at an excess pressure of more than half an atmosphere.

The relation of Anopheles eggs to the surface film is discussed. A highly stable line of contact with the water is formed, such that the water surface is depressed along the sides of the egg and raised at each end. Because like menisci are attracted and unlike ones repelled, eggs make contact with each other end to end or side to side, never end to side. Water spreads on most natural objects, forming menisci like those at the ends of the egg, which is thus provided with anautomatic trapping device that tends to attach the egg endwise to an object projecting from the water. The selective advantage of endwise over sideways attachment is not known, but it may facilitate hatching.

The structure of the egg of A. pseudopunctipennis Theobald has been disputed, and it is therefore described in some detail.

Nanophyes sp. nr. nigritulus Boh. infests the aquatic weed, Jussieua repens (Onagraceae) in India, its larvae feeing and developing inside the fruits. Adults feed on the leaves and also on the pollen and nectar of flowers. Eggs are laid singly in the interior ovaries of flower buds or blossoms. The ovaries hypertrophy and develop into deformed fruits which, when severely infested, are also completely seedles. The number of eggs laid by six females was found to vary from 89 to 410. The female that laid 410eggs distributed them in as many as 167 flowers, 7 being the maximum number of flwers in which eggs were laid and 13 the maximum number of eggs laid per day. In the laboratory, one of the females lived for 207 days and one of the males for 93 days. The period hatched in 4–8 days, the larval period occupied 7–16 days and teh pupal period, 3–6 days. The larvae moulter three times and pupated in separate chambers that they formed before pupating. Adults emerged by biting holes in the wall of the fruit. The egg and immature stages of the weevil are briefly described. Three species of Pteromalid wasps belonging to Habrocytus, Trichomalopsis and an unidentifies genus, and a species of Eupelmus (Eupelmidae) attacked the larvae.

Laboratory experiments carried out in Jamaica in 1963 showed that the number of eggs matured by blood-fed females of Leptoconops becquaerti (Kieff.) was only slightly increased when they were allowed access to a source of dilute honey during the subsequent period of egg maturation. A majority of the females imbibed some honey, and over half took large amounts; survival was better in groups given honey than in those not. The amount of fluid in the crop of field-collected females indicated that more than half had fed on nectar. In the laboratory, field-collected females took on average more than their own weight of blood.

The use of chromosome translocations for the control of pests, with particular reference to Glossina, is proposed. A translocation arises if two non-homologous chromosomes in the same cell undergo breakage and the fragments re-join with the wrong partners. At meiosis in an individual heterozygous for a translocation, gamete nuclei with several different combinations of chromosomes are produced. Some of these are diploid for one part and lack completely another part of the normal chromosome set; when such unbalanced gametes fertilise normal gametes inviable embryos are produced. It has been found in a number of organisms that about half the gametes of translocation heterozygotes are of the unbalanced type and such heterozygotes are described as semi-sterile. If an individual inherits the same translocation from both parents it is described as a translocation homozygote; this is often inviable but, if not, its fertility is usually normal.

Adult males of G. austeni Newst. have been irradiated and each of their progeny are being screened for the occurrence of semi-sterility. Any individuals found to be semi-sterile would probably be translocation heterozygotes and their progeny will be inbred to try to produce a viable stock, homozygous for a translocation. If this can be done, large numbers of such translocation homozygotes could be reared and released into a wild population, where matings with wild types would produce heterozygotes, and hence a reduction in the fertility of the population.

Using simple assumptions, the effects of releasing translocation homozygotes were computed. Provided the numbers released were such that the translocation frequency approached the optimum value of 50 per cent., the reduction in population fertility would be prolonged for many generations after the releases had finished. It is shown that it would be more efficient to release the translocation homozygotes at successive generations rather than all at once and that the homozygotes released could with advantage be of both sexes. For this reason, and because of the prolonged effect of releases of translocations, it is concluded that the number of individuals that would have to be reared to achieve a given result by the translocation method might be considerably less than if the sterile-male method was used. However, the reduction in population fertility at each generation that can be achieved with the translocation method is limited, and the method would therefore be ineffective against populations whose size was strongly buffered by density-dependent factors.

The larvae and pupae of Tryporyza innotata (Wlk.), T. incertulas (Wlk.), Chilo suppressalis (Wlk.), C. polychrysa (Meyr.) (Pyralidae) are described and notes are given on Sesamia ingerens (Wlk.) (Noctuidae) with particular reference to setal characters of the larvae. No obvious difference in chaetotaxy was found between T. incertulas and T. innotata, but the two species of Chilo could be distinguished on this basis. The pupae of the species of Tryporyza could be separated by differences in the shape of the labrum and those of the species of Chilo by differences in that of the thoracic tubercles.

During 1964–65, 1,646 newly emerged females of Glossina pallidipes Aust., 1,898 of G. palpalis fuscipes Newst. and 2,528 of G. brevipalpis Newst. were marked and released in an area on the north-eastern shore of Lake Victoria in Uganda so that, by examination of those subsequently recaptured, the relation between physiological and calendar age could be determined. In the light of the results, records of physiological age and trypanosome infections in large numbers of wild-caught females of the same three species caught in the same area in 1962–63 were examined, together with published observation on the animals on which they fed, and the effects of age and food-animals on the incidence of infections were investigated.

Physiological age was determined by examination of the reproductive system and was expresses as the exact or approximate number of ovulations that had taken place. Infections with Trypanosoma were classified as brucei-type, vivax-type or congolense-type, and the last two as mature (infective) or immature, according to the sites in which trypanosomes were found in the flies. All brucei-type infections were regarded as mature.

The relation between physiological and calender age indicated that the length of the ovulation cycle was 11 days in G. pallidipes, 11 1/2 in G. brevipalpis and about 15 in G. palpalis fuscipes, but from other evidence that the last figure should have been about 11 days it is considered that ovulation was retarded in the released females of G. palpalis fuscipes.

The incidence of mature vivax- and congolense- type infections rose with age in all three species, beginning for the most part when flies were about a fortnight old. Brucei-type infections were rare and were found only in flies more than about 35 days old; nearly all flies with such infections also had one or both of the other types. The incidence of immature vivax-type infections rose with age up to about 25 days and then levelled off, which suggests that all eventually became mature. Immature congolense-type infections were rare.

G. pallidipes had the highest total infection rate and G. brevipalpis the lowest. The percentage of order flies in the samples was, however, greater in the later than in G. palpalis fuscipes, which suggests that age is not the sole factor determining infection rate. Food-animals appeared to influence it, since the infection rates of the three species were proportional to the percentages of meals obtained from Bovids.

The age at which females were inseminated was lowest in G. palpalis fuscipes, greatest in G. pallidipes and intermediate in G. brevipalpis. Abnormal ovulation cycles were rare in wild-caught flies, and few females that from their age should have been pregnant were found with an empty uterus.

A method is described by which Homorocoryphus nitidulus vicinus (Wlk.) was reared in numbers continuously in the laboratory. This is believed to be the first account of the continuous labouratory culture of a Tettigoniid. Details are given of a substitute oviposition site that enables the eggs to be easily collected. The basic food used was grass, which was supplemented with cereals. The problem of cannibalism and methods of reducing it are discussed. Brief information on the bionomics of the crickets under these conditions is included.

The names of 156 Culicine mosquitos that are known to occur in Tanganyika are listed, together with a further three species of undetersting status. Systematic notes are included for species that show interesting taxonomic features, and locality records and the source of the information are given for each species. The distribution of the species in relation to zoogeographic and climatic regions if summarised in a table.

A new species of Tachinidae, Mycteromyiella phasmatophaga sp.n., from Guadalcanal in the Solomon Islands is described and figured; descriptive notes and figures are also given for the related species M. laetifica (Mesnil), to supplement the original description. Both species are recorded as parasites of the Phasmatid Ophicrania levari Günther in the Solomon Islands.

A new genus and a new Malsxoodes farinosus Fennah, are erected to accommodate examples of a population of Tropidocephaline Delphacidae (Homoptera: Fulgoroidea) found infesting Molasses Grass (Melinis minyutiflora) at Kitale, Kenya.

The rate of digestion, as reflected in the rate of excretion, on a blood-meal was measured in males of Glossina morsitans Westw. (subsp. orientalis Vanderplank) under identical conditions of temperature and relative humidity but varuing conditions of other factors. The rates of excretion in non-teneral males captured after feeding on bait-oxen in two different habitants were identical and were significantly higher than those of non-teneral field-collected males fed on guineapig in the laboratory. The latter excreated the meal more rapidly than non-teneral males that emerged and were fed on guinea-pig in the labortory. That the variations were not due differences in blood type was shown by feeding teneral laboratory-emerged males on different hosts; the rates of excretion of meals from different mammals did not significantly one from another. Teneral laboratory-emerged flies excreted more rapidly when fed on reptilian or avian blood than when fed on mammalian. The lower rate of excertion in laboratory explanations in terms of a metabolic uncoupliing and pre-feeding behaviour are described.

In tests of the reactions of freshly hatched larvae of Plodia interpunctella (Hb.) to droplets of liquids containing an insecticnde, 16 droplets of the test material were disposed in a ting 23 mm. in diameter on a glass surface. The mean diameter of dtoplets of the different oils used as solvents varied from about 330 to 615 μ. Minute glass beads about 680 μ in diameter were used as controls. The larvae were tested individually by placing them at the ecntre of the ring and noting whether ot not they succeeded in escaping from it without making contact with a droplet, and their time to do so, termed the avoiding-time.

Six petroleum hydrocarbon oils, and pyerthrin at different concentrations in one of them (Shell Risella Oil 17) and pyrethrin synergists, piperonyl butoxide and Bucarpolate (2-(2-n-butoxyethoxy)ethyl 3,4-methylenedioxybenzoate), were tested. Droplets containing 20 per cent. pyrethrins proved the most repellent, over 98 per cent. of the larvae avoiding contact with them, whereas only 47.5 per cent. avoided the glass beads. The degree of avoidance elicited by the oils was inversely related to the values of their physical characteristics, such as initial boiling point and mean molecular weight. Increasing concentrations of pyrethrins increased both the degree of avoidance and the avoidingtime, and the addition of piperonyl butoxide or Bucarpolate enhanced both these reactions.

A new species of Scirtothrips found damaging tea in Kenya is described and named S. kenyensis, and a note is given on damage caused by members of this genus. The name Heliothrips minutissimus Bagn. is suppressed as a synonym of Scirtothrips dorsalis Hood, and S. sweetmani Bianchi and S. tilschacki Ananthakrishnan are suppressed as synonyms of S. bispinosus (Bagn.), a combination that is here restored.

The susceptibilities to DDT and to dieldrin of one-day-old teneral examples of Glossina palpalis (R. -D.), obtained from pupae collected from the field, were measured in the laboratory in Nigeria by two methods, one recommended by the W.H.O. Expert Committee on Insecticides (1963) and the other described by Kernaghan & Johnston (1962).

Pupae were kept in dry sand at a controlled temperature of 78–79°F. and 70–80 per cent. relative humidity until the adult flies emerged, and the latter were then kept individually in 3 × 1 in. glass tubes. All exposures to insecticides were carries out at room temperatures. Five flies were exposed together for one hour in the W.H.O. method, and flies were exposed individually for 1 1/2 minutes in the other method. After exposure, they were kept in a cabinet at 78–79°F. and 60–70 per cent. relative humidity. Mortalities were assessed 8, 24 and 48 hr. after the end of exposure, but only the 24-hr. results are presented. Regression lines and values for LC50’s were calculated by the method of probits

The mortalities amongst untreated flies averaged 5.6 per cent. for males and 5.1 for females, the latter value being insignifiantly affected by the method used. Dieldrin was far more toxic than DDT to both sexes, and females were apparently more susceptible than males to both insecticides; it is suggested that females pick up relatively more of a given deposit because of their greater weight.

The slope of the regression line relating mortality to insecticide concentration was steeper for long exposures than for short ones; it is suggested that this comes about because some insecticide picked up by the flies is lost after they are removed from the treated surface, the loss being relatively greater when greater discussed, and it is concluded that exposure for 1 1/2 minutes is long for satisfactory assessment of susceptibility when continuous contact with the insecticide is ensured (as in the method used for this period), but that exposure for 1 hour, ensuring 100 per cent. mortality at some concentrations, is preferable for detection of resistance. Although mortality from an insecticide may not be completed until 72 hr. after exposure, observations 24 hr. after are considered adequate.

The relative merits of the two methods of testing susceptibility are discussed. It is concluded than the method of Kernaghan & Johnston, which involves less handling and therefore less stimulation of the flies, is the more precise. The impregnated papers available from W.H.O. are a convenient means of exposing flies to known deposits of insecticide.

Cartographical analysis of the distribution of recorded swarming populations of Locusta migratoria migratorioides (R. & F.) in western Africa for the first four years of the 1928–41 plague of this species has shown seasonal latitudinal displacements in each year with a nroth-to-northweastward movement of swarms during the monthe February-March to August-September, and a south-to-south-westward return during the priod October until the end of the year or January or Ferbruary of the following year.

Changes in the position of the northern limit of distribution of swatms in western Africa from month during 1931 have indicated a probable relationship between its position and that of the Intertropical Front, in its seasonal displacement, the position of the surface front being inferred from that of the 10-mm. isohyet. From February to September 1931, following the northward displacement of the Intertropical Front and the northward penetration of south-westerly winds, a general northward displacement of swarms occurred. Similarly, following the southward advance of northerly winds, there was a southward displacement of swarms.

There was an eastward movement in the main latitudinal displacement. This was particularly marked in 1929 and 1930. By September 1929, the infestation that in April had been restricted to parts of south-western Guinea and norther Sierra Leone had spread north-eastwards to cover the greater part of the Voltaic Republic and southern Mali; from December 1929 to January-February 1930, following the south-westward movement from late September to November 1929 which confined swarms to the countries bordering the Atlantic and the Gulf of Guinea. there was a spread eastwards along the coastal areas from south-eastern Ghana to southern and eastern Nigeria; and following the main northward movement of swarms which began in western AFrica in April 1930, there was, from May-June onwards, a pronounced eastward migration to the central and eastern parts of the continent. Each of these eastward movements occurred in areas where, at that particular time of year, the prevailing winds would be from the south-west.

The deduced movements suggest that swarms of Locusta in western Africa move downwind, and that the principal seasonal changes in the distribution of swarms in that area occur in response to the latitudinal displacement of the Intertropical Front and its associated wind field.