Emigration of moths of the Noctuid Spodoptera exempta (Wlk.) from their developmental sites occurred within a few hours of emergence, and captive moths have lived in semi-outdoor conditions for several weeks. Flight has been recorded at all times of night in the Kenya highlands, and has shown a very marked association, seasonally, nightly and even hourly, with rain; it has been observed at temperatures down to 13°C, and inferred at temperatures several degrees lower, so that over the greater part of eastern Africa flight activity is very unlikely to be restricted by low temperatures.

The breeding season of S. exempta differs markedly and consistently in different parts of eastern Africa; outbreaks of larvae recorded over the past forty years in Kenya, Tanzania and Uganda have been confined to November-July (very largely to December-May), alternating with those recorded over the past twenty years in Ethiopia, which have been confined to March-December (very largely April to August). The progressive establishment of a network of fifty light-traps in these countries since late 1962 has repeatedly recorded the arrival of invading moths before the first infestations of larvae, and has also provided evidence of a strikingly complete seasonal evacuation of much of the region; all traps in Kenya and most of those in Tanzania have revealed a period of several months in every year without a single moth of S. exempta.

Seasonal successions of moth catches and outbreaks of larvae have provided repeated evidence of a progressive northward movement of populations of S. exempta, developing in March in Tanzania and Kenya, and extending across Ethiopia, in some years as far as northern Eritrea by June. The extent of these inferred displacements is consistent with the evidence so far available on behaviour and other factors affecting range of flight, which has been examined in as much detail as the limited data permit.

Evidence of a return migration southwards to Kenya and Tanzania is relatively scanty. There are some indications of a north to south sequence of moth catches and outbreaks; the heaviest infestations in Kenya and Tanzania during the four-year period of detailed study were preceded by the largest catches so far recorded at the relevant time of year in Ethiopia; and in several years the first moths arriving in Kenya and Tanzania, in November-December, have appeared with the onset of the north-east monsoon, representing the southward movement of the intertropical convergence zone. Conversely, appearances of moths towards the northern limits of their inferred seasonal migration, in Ethiopia and around the Gulf of Aden in June, have shown an analogous association with the establishment of the south-west monsoon, i.e., with the northward movement of the intertropical convergence zone. Brief reference is made to evidence of seasonal migration in other parts of Africa; possibly in some years the eastern African populations may be supplemented by migrants from the south.

Two recorded moth ‘ swarms ’ have been associated with weather systems characterised by particularly vigorous wind-convergence. It is suggested that wind-convergence may have contributed to the density of the ‘ swarms ’ and of the subsequent infestations of larvae.

The overall effect of the seasonal changes in distribution which have been demonstrated is to bring the population into areas experiencing seasonal rains. Such a pattern of seasonal migration is likely to be of particular survival value for grass-eating insects, and such concentration of the insects as may be attributable to the associated wind-convergence may be significant in relation to the status of such insects as pests of cereal crops.

Records in the literature of long-range geographical displacements of some other Lepidoptera have been found to be associated in a similar manner with analogous systems of wind and weather in other parts of the world.

Field studies on the biting habits of Culicoides barbosai Wirth & Blanton were made near Montego Bay, Jamaica, during 1959 and 1960. Females of C. barbosai were collected in sufficient numbers for analysis in. seven experiments, six from Florida beach and one from Beading. Four positions were marked out on each site. Begular meteorological observations were made in the middle of the catching positions. An experiment consisted of four trials held on different days, each trial being composed of four collecting periods of 15 min. separated by 5-min. intervals. In each period four individuals collected, two exposing an arm each and two a leg. Individuals collected in a different position in each period of a trial.

Catches were logarithmically transformed for analysis and tests of significance. The experiments were designed to provide correction factors for limbs, positions on Florida beach, and collectors, for use in other experiments. Correction factors are given as logarithms for application to transformed catches.

More C. barbosai were collected from arms than legs, and catches in position IV were significantly higher than those in positions I, II and III. Five collectors (C, D, K, L and S) were compared. The ratio between leg/arm catches from D, who collected in only two experiments, was significantly different from those of C, L and S. The differences between the catches of C, K and L were insignificant, but all three caught significantly more than S. The catches from L were smaller after sea bathing and, compared to C and S, L’s catches increased significantly immediately after sunset. For this reason and to avoid inhibiting winds, quantitative studies on females of C. barbosai are best conducted in the early morning (dawn + 40 min.).

The experimental errors (residual variances) were homogeneous with probabilities of 0.1 (C. barbosai—7 experiments) and 0.4 (C. furens (Poey)—8 experiments).

Sufficient pupae of G. pallidipes Aust. for testing were available from the Zambezi valley only between September and early November and were of all ages. These pupae or the adult fly were exposed to gamma-radiation from a 60Co source at rates between 54 and 122 rads per min., and reproduction and mortality were studied by described procedures.

Effective pupal mortality due to radiation increased, and the proportion of males among the viable emerging flies decreased, with dosage between 4,000 and 16,000 rads. Eeproduction and survival of adult males emerging from treated pupae decreased with an increase in dosage and a decrease in pupal age at the time of treatment. Irradiation of adult males within three days of emergence produced slightly lower levels of sterility and similar survivals. Complete male sterility was rarely obtained with any of the treatments, though all the females, with one exception, were sterilised from 4,000 rads upwards, but the flies were fully competitive with untreated males and reduced reproduction below expected values. Treated males were fully capable of inseminating female flies and the sperm was motile and apparently behaved normally. Dominant lethality in the males appeared to be expressed by the failure to produce pupae and in the females by the complete failure of oogenesis.

Investigations, using tantalum-182, into the behaviour of Glossina morsitans Westw. in large field cages are described. Individual straight-line displacements occurred on average about every three hours and were generally small and erratic in direction. The perimeters of the cages tended to ‘ trap ’ an enclosed population, but flies appeared to move to the walls more quickly when they were shaded by an outer covering of hessian. Horizontal distribution and movements of flies did not appear to be associated directly with the enclosed vegetation, artificial roosting sites or host animals. Observations on vertical displacements indicated diurnal movements to and from boles of trees and changes in roosting heights. The majority of flies rested between six and ten feet above the ground, though individuals were seen from ground level to 30 ft. Few observations were done at night, but two flies were seen on the underside of leaves.

Investigations into the survival and breeding of the tsetse fly Glossina morsitans Westw. in large and small cage volumes under insectary and ambient climatic conditions in the Zambezi valley, and using oxen as host animals, are described. Under ambient conditions, flies emerging from puparia collected at Kariba, and held in the insectary, survived longer than flies emerging from puparia collected at Chirundu. Flies caught from the bush did not live as long as flies emerging from puparia held in the insectary, and generally lived longer under variable than under constant climatic conditions. The survival of ‘ wild ’ flies decreased during the hot, dry months under ambient conditions. Flies lived longer and were more reproductive in small cages than in large cages. Reproduction in small cages was higher when the flies were exposed to a variable climate instead of controlled conditions, but two colonies of ‘ wild ’ flies declined under both climatic conditions. Eeproduction was better in the small, standard cages (8 × 8 × 11 in.) than in Petana boxes, while Geigy 25’s were intermediate in this respect, but survival and mean puparial weights tended to be similar. The results show a complete failure to breed G. morsitans in large cages.

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 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.

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.

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.

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.

Locusts and other Orthoptera have been reared free from Gregarine parasites in culture jars made from jam jars. Food can be added easily without the escape of insects. A special feature of the jars is the removable base in which faeces accumulate and from which they can be taken at intervals without exposing the insects to the infective stages of Gregarine parasites.

The host range and aspects of the biology of Hispine beetles recorded from plants in the genus Lantana is reviewed. The host specificity of Octotoma scabripennis Guér. and Uroplata girardi Pic was studied in Hawaii where these insects had been imported and established for biological control of the important weed L. camara. New techniques were employed in which feeding and oviposition behaviour was studied in field and simulated-field experiments embracing a wide range of plants interplanted amongst an abundance of the Hispines' normal host. Eesults indicated that both species are restricted almost entirely to L. camara, and subsequently these insects have been imported into and established in Australia. Both insects are particularly well suited to use as biological control agents and should be extremely useful in many countries where L. camara is a weed.