Field trials were conducted to compare toxicity and residual activity on cattle of 18 acaricides against Rhipicephalus appendiculatus Neum., Amblyomma variegatum (F.), and Boophilus decoloratus (Koch). Ticks were counted one, four and seven days after the cattle were sprayed. Each of the seven experiments involved three sprayings at seven- to eight-day intervals.

Toxaphene at 0.25 per cent., included as a standard, was relatively slow acting compared to organophosphorous and carbamate acaricides, but was equal to or better than most of the new acaricides in residual activity and over-all effectiveness. Carbaryl, Mopham and toxaphene were tested at the highest concertration, 0.5 per cent., and found to have the maximum over-all effectiveness, including maximum residual activity. Nevertheless, even these treatments did not protexct cattle against tick attachment and engorgement for as long as seven days.

All acaricides tested were very effective against B. decoloratus and A. variegatum, but none completely prevented attachment of R. appendiculatus foe as long as four days, even though all were very toxic to this tick. The smallest number (1.8 per beast) of R. appendiculatus attaching in four days occurred on the cattle sprayed with 0.5 per cent. carbaryl, but by seven days after spraying there were many ticks attached and some were already partially engorged. The inference is that none of the compounds tested gave promise of prevention of tick-borne disease transmission when used on a seven-day schedule. No inference is made concerning tick-borne disease control by reduction of tick numbers on the pasture land.

Mortality among ticks on the cattle one day after treatment was greatest for 0.1 per cent. coumaphos, 0.25 per cent. Prolate, 0.05 per cent. Bayer 9053, 0.2 per cent. Geigy GS 13006, 0.2 per cent. and 0.5 percent. carbaryl, 0.1 per cent dioxathion, 0.05 per cent. Bayer 9037, 0.1 per cent. prothidathion, 0.1 per cent. Dursban, 0.2 per cent. and 0.5 per cent. Mobam, 0.025 per cent. and 0.05 percent. chlorfenvinphos, 0.2 per cent. fenitrithion and 0.1 per cent. ethion. Mortalities of 83.1 per cent. to 88.5 per cent. were given by 0.05 per cent. diazinon, 0.1 per cent. bromophos-ethyl, 0.025 per cent. Dursban, and 0.5 per cent. toxaphene. Mortality below 74 per cent. was caused by 0.25 per cent. toxaphene, 0.2 per cent. bromocyelen, and 0.1 per cent. carbophenothion.

Previous attempts to control Woolly Apple Aphid (Eriosoma lanigerum (Hsm.)) in Rhodesia are briefly reviewed. By the application of dimethoate at a rate of more than 5.0 grams a.i. or of vamidothion at more than 6.0 grams a.i. to the soil in the drip area of the tree, it was found that good control of both the foliar and root populations of the insect could be obtained on three-year-old apple trees 10 feet high. and the treatment appeared to remain effective for three seasons. It is considered that the timing of the application, the soil temperature, and the amount of wead cover are all important factors in affecting the amount of insecticide taken up by the apple trees.

Results are presented of a study of the host specificity of Plagiohammus spinipennis (Thorns.) under conditions that emphasised the behaviour of the insect in the field in the presence of an abundance of its host-plant, Lantana cantata. The results of this and previous studies are compared.

The adult beetles fed on various test plants but had little or no deleterious effect. Oviposition was restricted to the insect’s normal host, L. camara, and to Cordia ambigua, G. grandiflora, G. curassavica, Lippia umbellata, Lippia sp. (? miocephala), Tectona grandis and Vernonia deppeana. Of these, only T. grandis is of commercial importance. Larvae were unable to complete their development on this plant and died after feeding briefly. Development by larvae of P. spinipennis was restricted to a small group of mostly related, unimportant plant species as well as the serious weed L. camara.

P. spinipennis thus shows a high degree of host specificity, and was therefore liberated for control of Lantana camara in Australia in 1967.

The examination of samples of Antestiopsis orbitalis (Westw.) from different parts of South Africa has shown complete intergradation between the colour patterns of the typical subspecies and that of the form facetus (Germ.), hitherto of indeterminate infraspecific status, and the latter name is suppressed. Additional localities of ocurrence are given for A. orbitalis, and Antestia rufovittata Dist. is redescribed and transferred to Antestiopsis.

The timing of sprays in relation to the stage of development of wheat plants and larvae of the wheat-bulb fly, Leptohylemyia coarctata (Pall.), was studied in the laboratory and field. The main growth of young wheat plants was of the centre shoot and such plants died when the centre shoot meristems were destroyed. Older plants survived by growth of lateral shoots. Sprays of dimethoate, trichloronate and thionazin applied before the larvae had emerged did not kill many larvae in the soil, and only insecticide that entered the plants was effective. Severely attacked two-leaf plants yielded little, whether sprayed or not, whereas three-leaf plants sprayed in early March gave a worth-while increase in yield: older plants had enough shoots to give moderate yields even when not sprayed.

In a large field trial, plants from two sowing dates, 22nd October and 1st November, were both at the late two-leaf stage of growth in late February. Wheat-bulb fly larvae had entered nearly all the shoots but plants from both sowings had buds or small lateral growths hidden beneath the outer leaves. The yields of October-sown plots sprayed on 22nd February, 2nd March, 9th March or 16th March were 28·2, 28·8, 25·5 and 23·2 cwt. grain per acre, respectively, (yield of unsprayed plots = 18.9 cwt./acre) and of November-sown plots were 31·0, 27·5, 17·9 and 14·9 cwt. per acre, respectively, (yield of unsprayed plots = 116 cwt. per acre). Sprays had most effect when applied soon after larvae had entered the plants. Spraying severely-attacked late two-leaf to three-leaf plants gave the greatest benefits because these plants recovered by growth of lateral buds or small lateral shoots.

Experiments were conducted to ascertain whether the rearing density of Dysdercus fasciatus Sign. affected its rate of development, colour, size, reproduction and general activity. The length of the nymphal and adult life decreased when more than 12 insects were reared per 200-cc. cage. Isolated virgin females and females that eopulated once lived longer than females each kept constantly with one male. Nymphal crowding in adults that were smaller than those reared in isolation and in an excess of males. Nympha derived from crowded parents became red at an earlier age than the progeny of one male and one female per cage. Crowding reduced feeundity when the density of nymphs or adults, either male or female, was increased.

The pre-oviposition period and the time interval between successive egg-batches were greater for virgin than for mated females. Infertile eggs were the longest; females allowed to copulate once laid eggs intermediate in size between infertile ones and those laid by females each kept with a male. The number of eggs laid by females isolated throughout life with one male was found to be higher than the number laid by those that were crowded either in the nymphal stages or were crowded with males in the adult stage. When Dysdercu8 was crowded with one or two locusts the number of eggs laid and the number of egg-batches were considerably reduced; amputation or painting the antennae, which caused the Dysdercus to be less active, also reduced egg production but disturbance by mechanical shaking of the container had little effect. These findings are discussed in relation to the ' phases ' of locusts and other insects, and it is concluded that the effects of crowding on D. fasciatus do not completely parallel phase differences in locusts.

In a study of the incidence of damage to coconut palms in Madagascar and the Comores Archipelage caused by species of Oryctes (Scarabaeidae) it was found that attack is heaviest in localities where there are abundant breeding sites for the beetle, and that tall palms are more often attacked than short ones. The most important larval breeding sites are dead standing coconut palms and decaving coconut trunks and stumps. Larvae also breed in decaying satra trunks (Medemia sp.), wood of Albizia in coffee plantations, decaying Raphia trunks, and occasionally in rubbish heaps and manure, but are only rarely encountered in decaying wood in forests. Coconut palms are important feeding sites for O. gigas, O. blucheaui and O. simiar. O. pyrrhus attacks coconut seedlings and young oil palms. Forest palms are occasionally attacked. O. ranavaloattacks bamboo on the east coast. Banana plants are occasionally attacked by O. simiar.

Scoliid parasites of the larvae of Oryctes are widely distributed but not commonly found. Gregarines in larvae are also widespread but of rare occurrence. Oxyurid nematodes were often found in the fermantation chamber at the gut of Oryctes and Cetonid larvae. The fungus Cordyceps sp. was found at only one locality where it was attacking 56 per cent. of the larvae of Oryctes. Examples of infection by the fungus Metarrhizium were rarely encountered. Namatodes often occurred in the aedeagus of adult males of O. gigas and in the bursa copulatrix and colleterial glands of adult females, as well as under the elytra. They were less common in the other species of Oryctes examined. Mermithid nematodes were found in adults of Oryctes on rare occasions. No insect parasites of the adult stage of Oryctes were found. Elaterid larvae, possibly predacious on those of Oryctes were occasionally found but did not appear to be of much importance.

It is concluded that the major factor limiting Oryctes populations in Madagascar and the Comores is the number of suitable breeding sites.

The natural moth emergence-pattern of Diparopsis castanea Hmps. from non-diapause and diapause pupae is described for Malawi and Rhodesia and related to the growth of the cotton plant. Pupal populations and mortality in the field are assessed and the location of pupae in the soil for both ridged and flat land is determined. The effect of temperature on the development of diapause pupae is investigated. Temperatures both above and below 75°F. are shown to cause inhibition of pupal development. The investigations show that it is possible to effect a major alteration in the period of moth emergence from diapause pupae by burying the pupae to a depth of eight inches and thus avoiding heat inhibition. In this way, the majorrity of moths emerge before the cotton crop is able to support an infestation. Attempts to achieve this effect with a natural field population of pupae failed and further investigation is required. Heavy grass mulches are shown to inhibit pupal development possibly throgh reduction in soil temperature and retention of soil moisture.

An account is given of Diconocoris hewetti (Dist.), a sporadic pest of pepper in Sarawak. Most of the observations were made during a single outbreak in 1964. The egg and the five nymphal stages are described. The life cycle is completed in about 30 days at 27 ± 1°C., 80 ± 2 per cent. R.H. and the duration of individual stages is as follows: egg, at least ten days; first instar, four days; second instar, three days; third instar, three days; fourth instar, four days; fifth instar, five days; adults in laboratory cultures lived, on average, for 27 days.

Eggs are laid singly in the flowering inflorescences, and nymphs do not generally move far from their hatching sites during nymphal life. Both nymphs and adults feed on the inflorescences and infestation is particularly heavy on those spikes in which fertilisation of the flowers has ocurred but where the developing fruits do not yet exceed 1 or 2 mm. in diameter.

A survey of 60 holdings in the Kuching area showed that numbers of Tingids are very low during non-outbreak periods, only 0.4 individuals per vine (adults and late nymphal instars) being obtained during the flowering season. Numbers deceased to 0.03 insects per vine during the fruiting period. In the outbreak studied, numbers per vine varied from 3 to 10, a ten- to one hundred-fold increase over the normal levels; these figures are relative estimates only as there was no satisfactory method of estimating absolute densities in the time available.

It is suggested that serious outbreaks of Diconocoris may be due to exceptional prolongation of the flowering period of pepper vines in a district, due to cultural practices or climatic factors.

Yield losses due to Tingids in the area studied were estimated at about 30 per cent. Diconocoris can be satisfactorily controlled with sprays of various insecticides including BHC, DDT, malathion, carbaryl (Sevin) and nicotine.

Argyrostagma niobe (Weym.) suddently appeared as a defoliator of wattle in 1955 in the Turbo area of Eldoret District, Kenya, and spread in this area and outbreaks also developed in two other isolated areas, at Sotik and on the Mimosa-Nandi Border. Study of the life-cycle, of which the various stages are described, revealed a number of causes of mortality of which the initially most promising for control were parasites and a predatory Pentatomid, Glypsus conspicuus (Westw.). None of these, however, increased greatly above their first recorded level of incidence and the population of A. niobe was eventually controlled by a naturally-occurring nuclear polyhedrosis. This disease was found to be transmissible in the laboratory by allowing larvae to feed on foliage sprayed with suspensions of polyhedŕa whilst an indication that this could also be done in the field was obtained in one experiment.

Chamical control presented a number of difficulties, the chief arising from insufficient dispersion of the spray through the canopy of tall trees and the failure of small droplets finally adopted consisted of an application of endrin applied at a rate of 2–4 oz. active ingredient per acre in 2 gall. diesolene. This was satisfactory when applied to yonug trees through a Micron sprayer, and to trees of all heights by aerial boom sprayers. This mathod of control is only suitable where complete elimination of a population is necessary, such as in a new outbreak area, as the costs are too high to permit frequent applications.

Dasychira georgiana Fawc. was recorded in small numbers at about the same time that A. niobe was first recorded, but the population did not build up to serious proportions. Its life cycle, of which the various stages are described, was broadly similar to that of A. niobe but natural agents of control, chiefly the pupal parasite Compsophorus fumosus (Morl.) (Ichneumonidae), were usually effective in keeping the population in check. The reason for the success of this parasite, as compared with those of A. niobe, is not known. The larvae were successfully controlled with the same endrin spray as was used for A. niobe.

This paper describes the derivation of a compound shape measure for discriminating between populations of the desert locust, Schistocerca gregaria (Forsk.). The discriminant is the first canonical variate and is based on measurements of three parameters for samples from twelve locust populations. It is argued that the first canonical variate is a measure of phase.

Puparia of Glossina morsitans Westw. were collected in the Zambesi valley and contained developmental stages from final phases of third-instar larvae to pupae near to eclosion. These puparia or the emerging adults were exposed to gamma-radiation from a Co60 source at rates between 54 and 122 rad/min. Effective mortality in the pupal stage increased from 23 per cent, at 2,000 rads to 64 per cent, at 15,000 rads, while those deposited in spring (August-October) were more sensitive to gamma-rays than those collected in winter (May-July).

Under described test conditions, 25 pairs of untreated flies produced a mean of 21 pupae in a 28-day test period, insemination averaged 95 per cent., and 56 and 62 per cent, of the males and females survived, respectively. Continuous irradiation reduced reproduction by over 95 per cent, between 8,000 and 15,000 rads wiih males emerging within the first two weeks after treatment; while males emerging during the third post-treatment week were completely sterilised with dosages above 4,000 rads. Treatments given as fractions one and four days apart gave a slightly higher level of residual fertility than that obtained with similar but continuous total dosages. Irradiation of adult males reduced reproduction to an extent comparable with that observed in males emerging from pupae within two weeks of treatment (> 90 per cent, from 8,000 rads). Females treated either as adults or as pupae were completely sterilised with doses of 1,000 to 8,000 rads. Males exposed to 8,000 and 12,000 rads retained their sterility throughout 39- and 45-day test periods, and were fully competitive with untreated males.

Survival of virgin flies emerging from treated pupae was reduced both by increasing dosage from 4,000 to 15,000 rads, and decreasing pupal age at the time of treatment. Mortality during the 28-day mating period decreased with 1,000 and 2,000 rads, increased up to 8,000 rads, and apparently decreased with 12,000 and 15,000 rads. When the doses were fractionated, survival was longer than when treatment was continuous, and mortality was reduced to the level expected from the size of the first fraction. Virgin adult males given doses between 4,000 and 18,000 rads, and females given 2,000 and 4,000 rads, lived longer than the corresponding controls.

The ability of the males to inseminate females was not affected by any of the treatments, and sperm from irradiated males were mobile and apparently behaved normally. Dominant lethality in the males was expressed by the failure to produce pupae in matings with untreated females, and in the treated female fly by the complete failure of oogenesis.

Pupulations of the West African cocoa capsids Distantiella theobroma (Dist.) and Sahlbergella singularis Hagl. were sampled in 1966–67 by several methods: fast knockdown over sheets with pyrethrum, mercury-vapour light-trap, direct counts in a small artificially established area of high population, and observations of presence or absence in randomly selected inspection squares.

A population build-up in mature cocoa accompanies and probably directly depends on development of the main crop from July or August to October. When pods become scarce after harvesting there is in S. singilaris a period of dispersal in which the species becomes more widespread as feeding is transferred to vegetative tissues, and in D. theobroma a more local change of feeding sites.

Subsequent events vary greatly between areas and between years. It is suggested that the extent to which capsids are able to utilise vegetative tissues varies and depends on nutritional changes in the external parenchymatous tissues from which their food is obtained.

Low humidities during spells of harmattan in January and February almost certainly kill larvae in exposed situations, but feeding conditions following such periods may be particularly favourable to capsids as large rapid population increases can occur locally. The factors involved are obscure but may be related to processes of regeneration stimulated by leaf loss and other damage in dry conditions.

The densities and seasonal patterns found are discussed in relation to results of previous workers and some implications for control briefly considered.

A procedure is described whereby, by the use of appropriate statistical methods, the approximate vertical distribution of the eggs of Aedes vexans (Mg.) in a pool can be ascertained from a relatively few samples taken without any previous knowlwdge of their position.

Adults of Aedes taeniorhynchus (Wied.) were reared from larvae under five environmental variables—quantity of food, density of larvae, salinity of medium, light regime and temperature—singly and in combination. On emergence these adults were analysed for morphological characteristics, dry body weights, energy reserves and autogeny.

The minimal expression of adult characteristics and autogeny was effected by lack of food, crowding of larvae, and higher salinity, singly and in combination, at a constant temperature of 27°C. These three factors in turn showed a distinct relationship with delay in onset and prolongation of pupal ecdysis.

The maximal expression of adult characteristics and autogeny was found when 75 to 100 larvae per pan were reared on 2 × - or 4 × -basic ration in 10 to 25 per cent, sea water at 27°C. under alternating 12-hr. light-dark cycles. Above the optimal quantity of food, i.e., 2 × -basic ration, there was almost no enhanced effect on the adult characteristics; in fact, with 4 × - and 8 × -basic ration the morphological characteristics were suppressed. Of the three light regimes, continuous light produced adults that were largest, heaviest, had the most energy reserves and the highest level of autogeny. Adults reared on 4 × -basic ration in ten per cent, sea water under alternating 12-hr. light-dark cycles and at temperatures from 24 to 34°C. showed that even though largest mosquitos were obtained at 24°C, the heaviest mosquitos with maximal lipid and glycogen contents and maximal expression of autogeny were found at 28 and 30°C. Temperature changes during the pupal stage did not affect the adult characteristics.

Temperature and light regimes show distinct complex effects on adults at emergence, but the quantity of food, density of larvae and salinity of the rearing medium are more important.

Earias biplaga Wlk. has been recorded to attack Theobroma cacao from the Ivory Coast to the Congo (Léopoldville) and also in San Thomé and is the only species of the genus to do so in Africa. Attack is most serious on seedlings in the field as the apical buds are destroyed.

Eggs are laid on the stem mainly, especially on leaf bracts. The first half of the larval period is passed within the apical bud and the last half in feeding on unhardened flush leaves, or, in their absence, in burrowing down the stem below the apex or in devouring the epidermis of the upper stem.

The length of the larval and pupal periods is inversely related to the mean maximum temperature; they are shortest in the dry season and longest in the wet season.

Differences between the sexes exist in the wing coloration, and in the shape of the labial palps, the last segment of which is much longer in the female than in the male. The dry-season form, which has the forewings suffused with golden brown in the female and with yellow-green in the male, instead of the wet-season green, occurs from January to March in the region of Ibadan, Western Nigeria.

The adults are largely nocturnal and they are attracted to ultra-violet light.

Adults lived longer in the laboratory on a diet of sucrose in water (males, on average, 17 days and females, 28 days) than on water alone or without either. A mean of 95 eggs per female was recorded from sucrose-fed adults in the laboratory and the greatest number of eggs laid by a single female was 461. The peak period of oviposition was the fourth to fifth day after mating (fifth to sixth after emergence). A method of rearing E. biplaga in the laboratory is described.

Six alternative host-plants in Nigeria, all in the Malvales, are listed, and one, Hibiscus esculentus, is a locally important food crop. Nine Hymenopterous parasites were found to attack E. biplaga in Western Nigeria, the most important being Trichogramma luteum (Gir.) which attacks the eggs, destroying over 90 per cent, of them at certain times of the year. All the other parasites, with one possible exception, appeared to attack only the larval stage of the host.

In a laboratory investigation in Rhodesia of the ability of Glossina morsitans Westw. to digest blood from the impala (Aepyceros melampus), the efficiency of digestion, as measured by the regression of the amount of haematin excreted in 48 hr. on the size of the blood meal, was found not to differ significantly between flies fed on impala blood and flies fed on blood from a variety of vertebrate hosts. This result, together with the report that captive flies can be induced to engorge from a live impala, refuts the suggestion that the low incidence of impala blood meals recorded in the firld is because impala blood contains a facor lethal to tsetse. One possible reason for the non-utilisation of this antelope, despite its abundance in tsetse areas, is its vigorous reaction to biting insects.

Five species of aphid differed in susceptibility to a systemic organophosphorous insecticide injected into the stems of broad beans. The differences in susceptibility were not related to previously reported differences in feeding behaviour on this plant.

The distribution and trypanosome infection rates of Glossina morsitans submorsitans Newst. were studied during the wet season of 1967 along 75 miles of the main trade cattle route which passes through the savannah country between Ilorin and Oyo in south-western Nigeria.

G.m. submorsitans was found inhabiting open woodland, grassland, farmland and the environs of towns associated with the cattle route. In comparison with the types of habitat this species occupies in its zone of wide distribution in northern Nigeria, those habitats studied were considered atypical. It is suggested that the presence of G.m. submorsitans in the area investigated had resulted from a southward population advance over the last 50 years and this hypothesis is discussed in relation to existing knowledge of G.m. submorsitans advances.

The trypanosome infection rates of 61.6 and 76.6 per cent, found in 364 examples of G.m. submorsitans dissected are much higher than previously recorded for any of the subspecies of G. morsitans Westw. A steady southward increase in the trypanosome infection rates of G.m. submorsitans was demonstrated for populations inhabiting 200 miles of cattle route. Trypanosome infections in G.m. submorsitans are attributed to Trypanosoma vivax and T. congolense, and the absence of brucei-group infections is discussed in relation to the incidence of T. brucei infections in trade cattle and limitations of the technique used for demonstrating infections in tsetse flies.

It is stressed that epizootiological aspects of the present findings cannot be clarified until reliable data on trypanosome infections of trade cattle in the area studied are available.

Myzus persicae (Sulz.) has a wide range of possible host plants in Rhodesia though most may be physiologically unattractive to alate aphids that alight on them during the dry months of the year. Infested plants are difficult to find, yet as many winged aphids are trapped in the dry season (June) as in the wet (December). A wide dispersal of small colonies on a large variety of partially acceptable host plants during the dry season in therefore suggested. Potatoes and other garden plants may contribute to the population but tobacco regrowth is discounted as a source of aphids, though not of viruses.