A comparison of population-samples from various localities with the respective type specimens has shown that Sogatodes brazilensis (Muir) and S. orizicola (Muir) are conspecific. Under the provision of Becommendation 24A of the International Code of Zoological Nomenclature the name S. brazilensis is suppressed and becomes a synonym of S. orizicola.

Measurements of oxygen consumption by a series of single pupae of Glossina morsitans orientalis Vanderplank maintained at 30°C. showed that the time course of respiration during this stage follows a U-shaped curve and thus resembles that of other holometabolous insects. The rate of pupal respiration was found to be directly proportional to wet weight at all temperatures investigated, and did not appear to be affected by the temperature to which females were subjected during pregnancy. The relation between temperature and the logarithm of metabolic rate was found to be curvilinear, tending to a relatively stable level between 35 and 40°C., the highest part of the range investigated.

A simple apparatus incorporating a photographic light meter is described, which is used for rapid measurement of the amount consumed by insect larvae of black filter-paper impregnated with plant extracts.

In tests of insecticides applied in a spray tower to the ventral surface of nymphs of Distantiella theobroma (Dist.) collected from lindane-resistant and lindanesusceptible populations in cocoa plantations in Ghana, the levels of resistance of the former (ratios of the LC50's of the two populations) were 20·1, 74·4 and 73·3 for lindane, dieldrin and aldrin, respectively. There was no cross-resistance to DDT. Out of 18 other compounds tested, carbaryl (the most toxic), two other carbamates and two organophosphates were more toxic to the resistant population than was lindane to the susceptible one.

Polovodova's technique for determining the physiological age of mosquitos was used in a study in 1962–64 of the age-composition of populations of Anopheles gambiae Giles and A. funestus Giles resting in houses in two areas of Tanzania. One area was around Muheza, 25 miles from the coast, where the climate is humid and equable, and the other was around Gonja, 80 miles inland, where hardly any rain falls for five months of the year.

It was found that the age-composition was almost identical in populations of A. gambiae and A. funestus at Muheza, about 20 and 23 per cent., respectively, being 3-parous and older and 1 per cent. 7-parous and older in both species. At Gonja, the population of A. gambiae was much younger, 14 per cent, being 3-parous and older and only 0·3 per cent. 7-parous and older. The oldest mosquitos found at Muheza included one 12-parous female of A. gambiae and one female of A. funestus believed to have laid eggs 14 times. No examples of A. gambiae older than 8-parous were found at Gonja.

Dissections to determine the condition of the ovariolar sacs in A. gambiae at Gonja showed that in 87 per cent, of freshly fed parous females an interval of at least 24 hours had occurred since oviposition. At Muheza, 72 per cent, of individuals of this species in the cool season and 52 per cent, in the hot season were in a similar condition.

Marking and recapturing experiments were carried out with females of A. gambiae in order to be able to correlate calendar age with physiological age. The oldest recaptured was 34 days old and was found to have laid eggs 10 times. From data on 60 recaptures, it was concluded that, although there was some irregularity, the first gonotrophic cycle lasted 3–4 days and later cycles 3 days.

Age-specific sporozoite rates in A. gambiae rose from 4·1 per cent, for 3-parous to 32 per cent, for 7-parous and older females, and in A. funestus from 3·2 per cent, for 3-parous to 30 per cent, for 7-parous and older females. Most of the infected 3-parous females were gravid, indicating that few were infective at the beginning of the fourth cycle. On this account it was concluded that some 80 per cent, of malaria infections were transmitted in the fifth, sixth and seventh cycles.

Analysis of the distribution of age-groups indicated that both A. gambiae and A. funestus showed a deficiency of nulliparous females, presumably because greater numbers of this group rested outside houses. From the second to seventh cycles the proportions of successive age-groups in both species at Muheza declined regularly at a rate corresponding to a mortality of 37·8 per cent, per cycle for A. gambiae and 38·6 per cent, for A. funestus, or 14·6 and 15·0 per cent, per day, respectively. Beyond this age the mortality was considerably higher. At Gonja, the population of A. gambiae declined at a rate corresponding to a mortality of 51·5 per cent, per cycle for the second to sixth cycles, or 20·9 per cent, per day. Above this age, the mortality was estimated to be higher still.

From the regression of infectivity on age it was estimated that 6·8 and 6·1 per cent, of A. gambiae and A. funestus, respectively, became infected at each blood-meal.

These findings are discussed in the light of current epidemiological theory.

Details are given of a cabinet, with a working space of 9 cu. ft., affording temperatures constant to within ± 0·5°C. over the range 5–25°C. and relative humidities constant to within ±2·5 per cent, over the range 40·85 per cent. The apparatus has electrically operated automatic controls. The only maintenance required is two-weekly renewal of the wet-bulb wicks and filling of the distilled-water reservoirs. Most of the construction was carried out in the laboratory. The cost of the cabinet and control equipment was approximately £170.

In insecticide trials in 1962–63 in Rhodesia against woolly apple aphid, Eriosoma lanigerum (Hsm.), no appreciable control was achieved by applying ½ fluid oz. of a 40 per cent, emulsifiable concentrate of dimethoate per tree at 2- to 3-week intervals for 16 weeks in any of the following ways: painted directly on the lower trunk; absorbed in a cotton-wool band applied to the trunk, after being diluted 1:3 in water; applied to a furrow around the stem after being diluted in four gallons of water; injected into the soil with a nematicide injector after being diluted 1:4 in water.

A foliage spray of DDT (0·195% active ingredient) had a gradual controlling effect on the aphid and caused no upsurge such as might have occurred had the parasitic activities of Aphelinus mali (Hald.) been suppressed.

Activity of the ant Pheidole megacephala (F.) was immediately halted on trees sprayed with DDT and was suppressed on trees the trunks of which were painted with dimethoate and on those banded with a dimethoate-soaked barrier.

Over a fourteen-month period, the numbers of living aphid colonies fluctuated before decreasing at the same time as the activity of A. mali intensified.

Assessment of the effects of dichlorvos (DDVP), released from a Ciba XI dispenser, on females of Anopheles gambiae Giles and Mansonia uniformis (Theo.) entering a verandah-trap hut in the Umbugwe area of Tanzania was made over a period of two months in 1964. Of the numbers of A. gambiae that entered one treated and one untreated hut, 27 per cent, of those entering the hut treated with dichlorvos and 48 per cent, of those entering the untreated hut left again. Of the numbers leaving each hut, 38 per cent, left through the eaves of the treated hut as compared with 9 per cent, in the untreated one. In the case of M. uniformis, 88 per cent, of those entering the treated hut and 94 per cent, of those entering the untreated hut left again. Of the numbers leaving each hut, 59 per cent, left through the eaves of the treated hut as compared with 61 per cent, in the untreated one.

Over-all mortalities were 56 per cent, for A. gambiae and 34 per cent, for M. uniformis when the eave-egress fraction from the treated hut was taken into account, compared with 62 per cent, for A. gambiae and 43 per cent, for M. uniformis when the eave-egress fraction was ignored.

The results of bioassays and of chemical analyses showed that the problem of mortality from fumigation in situ was considerably less in verandah traps than indoors or in window traps fitted with funnels of cotton netting.

The inheritance of black pupa in Lucilia cuprina (Wied.) was investigated by means of a series of back-crosses through five generations. Since an approximate 1:1 ratio of reddish brown to black pupae was observed throughout, it is concluded that the character black pupa is due to a single recessive gene (bp).

A test for the existence of a linkage group containing genes for black pupa and dieldrin-susceptibility was then made. The exposure of females from reddish brown and black pupae derived from back-crosses to discriminating levels of dieldrin, and the pattern of mortality observed with scalar concentrations of dieldrin, indicated that genes for black pupa (bp) and dieldrin-susceptibility (rdi) are on different chromosomes.

Factors affecting the susceptibility of seeds of sorghum (Sorghum vulgare) to attack by Sitophilus oryzae (L.) were investigated in the laboratory. It was known that varieties in which a majority of the seeds have a predominantly vitreous endosperm (vitreous varieties) are less attacked than those in which the majority have a predominantly mealy endosperm (mealy varieties). A method of measuring the relative amounts of vitreous and mealy endosperm in a seed was devised, and was used to classify samples from ten varieties of sorghum that had been grown in East Africa. The varieties ranged from vitreous to mealy, and the seeds from them formed the test material.

Adult weevils confined singly in tubes with seeds of either a vitreous or a mealy variety consumed more per day of the latter than of the former (about 0·2 and 0·15 mg., respectively, per mg. body-weight of weevil). When females were allowed to oviposit in seeds and the next-generation adults were counted, greater numbers were obtained from mealy than from vitreous varieties, the extreme results from a range of five being in the ratio of about 20:1. Seeds of vitreous varieties have a lower moisture-content than those of mealy ones at the same humidity, but this was not the cause of the differing numbers of adults, for the results were similar when the experiment was repeated with seeds of a vitreous and a mealy variety treated so that the moisture contents were identical. Attempts to compare the numbers of eggs laid in seeds of these two varieties gave inconclusive results; it was shown that none of the methods used was entirely reliable; in two experiments, no difference could be detected, but in a third, in which the seeds were examined by means of X-rays as well as by other means, significantly more eggs were laid in seeds of the mealy than of the vitreous variety. There was no evidence of a preference for any particular size of seed of either.

The hardness of the seeds of all ten varieties was estimated by grinding equal quantities in a mill and weighing the amounts that then passed through a 60-mesh sieve. This was done twice, with seeds at 10 and 14 per cent, moisture content. The order of hardness was not appreciably affected by moisture content, and was clearly correlated with the proportion of seeds with predominantly vitreous endosperm; the more vitreous varieties had harder seeds than the more mealy ones. It is inferred that hardness of the seed is the principal factor responsible for resistance to weevil attack.

A Phycitine species bred from larvae boring in stems of black pepper (Piper nigrum) in the Cameroons and Central African Republic is described as new and is named Anonaepestis tamsi sp.n. The species is differentiated from A. bengalella Rag., the only other known representative of the genus, and illustrations are given of the adults and female genitalia of both species and the male genitalia of A. tamsi.

A description is given of the damage caused by the larvae of two weevils, Systates exaptus Mshl. and Mesoleurus dentipes (Mshl.), which are soil pests of germinating maize and other crops in Rhodesia. Information is given on their life-cycles and some features of their biology. The larvae are nearly full grown at the beginning of the dry season, which is passed in an inactive state in the soil. Activity is resumed with the onset of the main rains, and it is at this time that the larvae may cause serious damage by attacking seedlings of maize or other crops growing in infested soil. Factors that encourage local increase of field populations are examined. It is shown that sunn hemp, soya bean and groundnut, all crops with high plant populations, favour the presence of large numbers of weevil larvae in the soil at the beginning of the following season. Growing closely planted maize year after year on the same land has been found to be one of the main causes of serious infestations in farm fields.

Results of soil-insecticide trials are given, and these show that larvae are very difficult to control. In the discussion, attention is drawn to similar weevil larvae indigenous to other parts of Africa, which are tolerant of soil insecticides and are also pests under conditions of intensive crop production.

Ways are suggested for reducing infestation in the following season. It is shown that properly timed applications of DDT to the maize crop will kill adults and prevent oviposition. Otherwise, infested fields may be left fallow, planted to grass or planted very late in the season.

No method of protecting germinating seedlings has been found, but reference is made to a soil-sampling technique that is useful for detecting infested fields before crops are planted.

The results are described of 202 24-hr, catches of Stomoxys and Tabanids on cattle at Lugala on the north-eastern shore of Lake Victoria, and also of six 24-hr, catches at Sukulu, 33 miles from Lugala, all of which were made in 1961–63.

Species of Tabanus and Ancala were more abundant in open grassland than inside the edge of the lake-shore forest. Stomoxys nigra, Macq. and S. Calcitrans (L.) were equally numerous in both situations, whereas S. omega Newst. was most abundant inside the forest edge.

Many species were caught during all months of the year. In both catching areas, there were seasonal rises in numbers of nearly all species between May and August and again in November or December, that is, towards the end of the rains and early in the dry seasons. At one of the two areas there was also a large increase in catch of a few species in April, in the middle of the main wet season.

Diurnal activity of Tabanus and Ancala was greatest near the middle of the day, the exact timing of the peak varying with season. Four species of Haematopota exhibited morning and evening peaks with lower activity at midday, and a rather rare fifth species was apparently more active in the middle of the day. Three species of Stomoxys were also most active in the morning and late evening, but peak activity of a fourth species, S. calcitrans, occurred shortly after midday. Activity during the night was rare.

In the present study, which represents an extension of earlier work, a method is described for comparing the metabolic status of cacao leaves by measuring the time of survival of excised discs of leaf tissue, and, when used with appropriate sampling technique, is considered reliable for indicating differences in the physiological age of such tissue. Leaf-tissue samples from trees with a history of impeded growth and low yield, and wet-seasonal liability to attack by cacao thrips, Selenothrips rubrocinctus (Giard), were compared with samples from trees of the same clone growing in the same field, with a history of relatively rapid growth, superior yield and freedom from such attack. Their relative survival periods were found to be concordant with their relative physiological ages (as expressed by percentage of dry matter and of total nitrogen and response to foliar injections) and with the subsequent incidence of cacao thrips. A similar comparison, using leaf material from two clones, susceptible and relatively resistant to attack by cacao thrips, respectively, included samples from the susceptible clone collected at a locality where cacao thrips was common in the wet season, and at another where the insect was never common at any time, and samples from the resistant clone taken in the former locality from fully exposed and shaded portions of individual leaves. Leaf samples of the susceptible clone collected at the inferior site and those from the fully exposed parts of the leaf of the resistant clone were found to be similar in length of life, and were both relatively physiologically senescent and demonstrably of subnormal nutrient status, whereas the corresponding samples from leaves of the susceptible clone at the superior site, and from the shaded portions of the leaves of the resistant clone were also similar in length of life, significantly longer lived than the former samples, physiologically younger, and apparently of normal nutrient status. The distribution of cacao thrips that subsequently developed in the field on leaves of the resistant clone was confined to the fully exposed part of the leaf. Leaves of the resistant clone were found to contain more moisture and more solid matter than those from the susceptible clone. A comparison was made of leaf tissue from leaves debilitated by lime-induced chlorosis and of leaf tissue from areas of similar leaves that had recovered as a result of foliar injection with an acidified solution of ferrous sulphate, and the subsequent incidence of cacao thrips in the field on the two types of tissue was recorded. The debilitated tissue was found to be shorter-lived than the restored, and was heavily attacked, whereas the restored tissue remained uninfested. The incidence of cacao thrips on ripening pods was found to be restricted to pods with a history of relatively slow growth prior to infestation. The findings are discussed in the light of information obtained in an earlier investigation, and it is concluded that the results can be explained by assuming that establishment of a cacao-thrips colony on cacao is obligately dependent on the prior occurrence of metabolic derangement in the host leaf leading to a retardation of protein synthesis, and that in Trinidad, W.I., where the investigation was made, such derangement results from the effect on the tree of seasonally adverse factors in its physical environment.

With the aid of reflective patches fixed to flies, nocturnal resting sites of Glossina morsitans Westw. released in teak woodland near the Mashi River in Zambia were detected by torchlight. Within this habitat, sites on the margins of woody vegetation were chosen for the tests, so as to slow up fly dispersal and raise the chances of seeing the marked flies. Over 500 flies were marked and released, and of these 82 (16%) were subsequently seen resting, the maximum height recorded being 20 ft. above ground-level. The distribution of resting heights is shown in tables. Leaves and small twigs comprised 77 per cent, of the nocturnal resting sites. In one series of tests, the proportion of marked flies detected was considerably lower than in other tests, and an environmenal factor is thought to be the cause.

Plots on arable land in southern England that had received an annual application of MCPA herbicide for 10 out of 13 years between 1951 and 1963, and similar untreated plots, were sampled to see whether there were any long-term or short-term effects on the arthropod fauna. Samples were taken before and after spring sowing, before and after spray application of the herbicide, and about a month later when weed counts were made. The fauna was divided into orders or suborders initially, and no differences between treated and untreated plots were detected either at the beginning of the season, as a residual effect from previous years, or in the period immediately following spraying. The Acari population was then analysed in more detail for possible qualitative differences between treatments, and the recorded numbers of 12 common species and two genera in treated and control plots were examined. No effect that could be attributed to the use of MCPA was found. The density of the fauna is discussed in relation to other soil arthropod surveys, and the wealth of Acari species is commented on. A list of the species of Acari and Collembola collected is appended.

The deposits found on apples at various times after application of 11 insecticides were determined by chemical analysis of samples from an orchard in south-eastern England sprayed in 1959 and 1960. The results, from samples taken simultaneously, of studies of the effectiveness of these and other chemicals for control of the codling moth, Cydia pomonella (L.), have already been reported.

The period in which 50 per cent, of an initial deposit disappeared in the field (half-life) was calculated from the chemical data and used as a measure of persistence. For comparisons of intrinsic toxicity, the levels of fresh deposits causing 50 per cent, mortality of newly emerged codling-moth larvae (LD50) were determined in the laboratory by chemical and biological tests on apples dipped in a range of concentrations of commercial formulations. The LD50's, in μg./cm.2, were less than 0·025 for carbophenothion, parathion and diazinon, between 0·025 and 0·05 for azinphos-methyl and -ethyl, between 0·05 and 0·10 for malathion, DDT and carbaryl, between 0·1 and 0·5 for DDD and dimethoate, between 0·5 and 1·5 for lead arsenate and above 1·5 for phenkapton.

Chemicals with an LD50 exceeding about 0·1 μg./cm.2 were considered not worth further investigation as codling-moth larvicides. The LD90's of the remainder were found and were taken as the minimum deposits that would have an adequate effect from the standpoint of control (minimum effective levels). From the half-life values, the periods for which the deposits found in the orchard in 1960 should have remained above the minimum effective levels were calculated; these were 24 days for DDT emulsion, 22 for DDT wettable powder, 15 for carbophenothion, 14 for carbaryl, 12 for azinphos-ethyl, 11 for parathion, 7 for malathion and 6 for diazinon. They were in good agreement with the results of the biological tests except in the case of DDT emulsion, the effectiveness of which was unexpectedly short-lived.

The persistence, as assessed by biological and chemical methods, of field deposits on apples from two spray programmes, each of DDT, carbaryl or azinphos-methyl, was compared throughout eight weeks following the first application in an orchard in south-eastern England. Newly emerged larvae of the codling moth, Cydia pomonella (L.), were used to assess, in the laboratory, the biological activity of the deposits. The spray programmes studied were (1) two applications of conventional concentrations (i.e., 0·1 per cent, for DDT and for carbaryl, 0·04 per cent, for azinphos-methyl) three weeks apart and (2) three applications of half these concentrations at two-weekly intervals. DDT wettable powder, carbaryl and azinphos-methyl were compared in 1961, DDT emulsion, DDT wettable powder and carbaryl in 1963. Results of biological and chemical assessment of the deposits are presented graphically. Over-all, the performance of the three-application programmes was as satisfactory as that of the two-application programmes, although a smaller amount of chemical was used. The serious reduction in deposit caused by heavy rain shortly after the first application of DDT wettable powder and of carbaryl in 1961 is noted. In the absence of heavy rain, carbaryl was biologically the most persistent, but the best performances of the other chemicals were almost as good as that of carbaryl.

LD50 values of fresh deposits obtained by field spraying were shown to be similar to those obtained by laboratory dipping.

Comparison of the toxicity of fresh and weathered field deposits of similar magnitude indicated that the biologically available proportion of a DDT deposit from either formulation decreases as a result of weathering. This phenomenon was not found to occur with carbaryl and either not at all or to a much lesser extent with azinphos-methyl.

The deposits obtained in the comparison of the spray programmes were separated into their fresh and aged components, so that differences in the contribution to the final deposit provided by each application could be seen. With the very persistent DDT emulsion, only about half of the six-week deposits was composed of chemical from the final application, but, with the much less persistent carbaryl and azinphos methyl, the six-week deposits were almost entirely derived from the final application. By substitution in an equation to obtain the rates of decay of the deposits from the three-application programmes of all chemicals, it is shown that deposits from the second and third applications were, in all cases, more persistent than those from the first. Possible reasons for this difference are discussed.

The significance, in terms of field control, of the results for the larvicidal activity of the deposits from the different spray programmes is indicated. It is concluded that data on the LD90 of insecticidal deposits on apples, together with measurement of their persistence in the field, can be used to assess the probable field performance of codling-moth insecticides and to determine the most efficient means of employing them, although the deposit level that ensures 90 per cent, larval mortality in the field is higher than the LD90 determined in the laboratory.