The possibilities of migrations in the West African species of Dysdercus are discussed and a hypothesis of long-range migrations associated with the Inter-Tropioal Convergence Zone and its wind systems is proposed. Catches of adult Dysdercus in four light-traps distributed from south to north of the Ivory Coast showed that the phenology of assumed migratory activity in D. voelkeri Schmidt differs with latitude and may be correlated with particular types of weather; stainer migrations taking place during the warm, wet and sunny part of the year. The whole life cycle of the insects as well as their flight activity occur under these climatic conditions, prevailing in a belt of 600–900 km width, situated immediately to the south of the Inter-Tropical Front. Colonisation of newly available habitats is thus only possible when climatic factors allow: (i), migratory flight activity and (ii), survival in the colonised area. A close examination of the timing of both migrations in the two main species, D. voelkeri and D. melanoderes Karsch, and of annual movements of the I.T.F. leads to the only logical hypothesis that the transportation of migrating insects is effected by atmospheric convergence, prevailing wind currents and air mass displacements.

Light-traps were used to sample populations of C. comutus De Meillon, C. pallidipennis G, I. & M. and C. schultzei (End.) gp. at sites at Embakasi, Kiboko and Makindu between 1971 and 1975. The samples were graded into age-groups by the degree of abdominal pigmentation, estimates of calendar ageing were made, and the seasonal variation in age-structure of the populations was recorded. Survival rates were calculated on the basis of a graphical model of the continually overlapping generations, and the survival rate of 0·8 was found typical. This rate is considered sufficiently high for C. cornutus, C. pallidipennis and C. schultzei gp. to act as vectors of bluetongue virus disease of sheep and/or ephemeral fever virus disease of cattle.

Light-traps were used to collect adult Culicoides from 61 sites throughout Kenya and to sample long-term population fluctuations at six sites. Activity patterns were recorded with a suction trap and larval habitats were sampled with laboratory emergence traps. Culicoides cornutus De Medllon, C. milnei Aust., C. pallidipennis C, I. & M., C. schultzei (End.) gp. and C. zuluensis De Meillon were found widespread and also concentrated at livestock pens. Their seasonal population fluctuations did not correlate clearly with rainfall but all these species persist throughout the year. The activity of C. pallidipennis and C. schultzei gp. extends over the whole night and is inhibited by winds in excess of 3 m/s and stimulated by high temperatures and relative humidity. Larval habitats were mainly in mud mixed with detritus or dung; larvae of C. pallidipennis and C. schultzei gp. were both found in swamp mud but not in dung pats. The significance of these findings is discussed in relation to the epidemiology of bluetongue virus disease of sheep and ephemeral fever virus disease of cattle.

Movements of individual fourth instar Coccinella septempunctata L. larvae on pot-grown broad bean plants in England were recorded continually to assess plant recognition and the effects of prey capture. Prey capture was also studied in a 25X25 cm artificial arena. Approximately 80% of the total distance moved by larvae on plants was along leaf edges and mid-veins. Typical search speeds were 0−38−0−51 cm s−1. An average of only 3−2% of larval search time on plants was spent on leaf laminae on which movement was considerably slower, about 0−15 cm s−1. Discovery of Acyrthosiphon pisum (Harris) nymphs on plants induced intensive re-searching of the general area of discovery for periods of up to 12 min whereas in the arena the intensive search following prey capture lasted only up to 72 s and was much more localised. Examination of larval search times on plants revealed that 64% and 36% of maximum search times were recorded for the first and for the second or third searches, respectively, in a sequence of searches of the same plant. Only after prey capture was a fourth or subsequent search the longest. Plants previously searched unsuccessfully were recognised by detection of a chemical marker, specific for each individual, secreted via the anal disc during searching. Since C. septempunctata larvae are unable to detect aphids by sight or smell, recognition of areas previously searched unsuccessfully minimises wasteful energy expenditure.

Males of Diparopsis castanea Hmps. were caught in a water trap baited with sex pheromone sited 2·0 m above ground level in a cotton field in the Lower Shire Valley, Malawi. Analysis of catches for 21 nights between 8.iii.75 and 3.vi.75 showed that optimal catches of males occurred at wind speeds of 1·0−2·5 m s−1. Wind speeds in excess of 3–4 m s−1 depressed activity. Regression analysis revealed an optimal relative humidity for flight of 60−70%. Inclusion of humidity in a multiple regression analysis with wind speed and temperature failed to improve significantly the relationship with catch provided by a model that considered wind speed and temperature only. No simple relationship existed between temperature and moth abundance, and wind speed clearly exerted the greatest independent effect on catch. Male Diparopsis nevertheless exhibited a temperature-related pheromone responsiveness, with peak catches occurring earlier in scotophase during periods of cool weather. Analysis of data gathered during the 1973 and 1974 seasons indicated a slight, but significant, positive correlation between night rainfall and moth catch. However, none of the various independent and joint relationships established between moth catch and climatic factors could be reliably used for forcasting moth abundance.

Studies on the biology of Acanthomia tomentosicollis (Stål) at Ibadan, Nigeria, showed that the periods of development in the field and the insectary averaged 17 and 18 days, respectively. The hemispherical, hexagonally sculptured eggs were laid in batches of 2.99 (mean=7 eggs per batch in the insectary and 20 in the field). Preoviposition periods were 11–22 days in unmated and 6–9 days in mated females. The mean number of eggs deposited by mated females (202) was significantly higher than that deposited by unmated females (135), although the average oviposition period of 16 weeks in unmated females was three weeks longer than in mated females. Unmated males and females were longer-lived than their mated counterparts, and females generally lived longer than males. These results and other observations on 'the biology of A. tomentosicollis are discussed in the context of its seasonal biology and the pattern of infestation of pigeon pea (Cajanus cajari), its main host plant.

Field studies of predators on Aulacaspis tegalensis (Zhnt.) and laboratory breeding experiments, supplemented by taxonomic studies, showed that Chilocorus discoideus Crotch and C. bilineata Korsch. are junior synonyms of C. schioedtei Muls. and that two other forms, originally described as ‘aberrations’, may also belong to this species. Similarly, C. erythrocephalus Muls. and C. solitus Weise are junior synonyms of C. distigma (Klug). C. rufoplagiatus sp. n., allied to C. distigma, is described from the shores of Lake Victoria, and the Oriental species C. nigritus (F.) is recorded from the African mainland for the first time. C. distigma is found in the savanna and steppe areas of Africa and C. schioedtei in the forest and adjoining zones. Comparative studies suggest that, although C. schioedtei has a higher fecundity, it is not displaced by C. distigma as, unlike the latter, it is unable to breed under hot dry conditions. Comparison of host records for these two species show that C. distigma is not restricted to feeding on Diaspididae, as is C. schioedtei, but that otherwise the range of hosts and associated plants is similar for both species. The potential of these species and C. nigritus for use in biological control is discussed and it is suggested that C. schioedtei is only suitable for trial in tropical areas without a dry season, but that C. distigma and C. nigritus may be useful under a wider range of conditions.

The height and direction of mosquito flight related to wind speed and direction, in the absence of a host, was investigated in open savanna in The Gambia, West Africa. Non-directional suction traps (at heigts of 0·68, 2·13 and 3·15 m); directional flight traps facing four directions ar three levels (0·00–1·37 m, 1·45–2·82 m and 2·90–4·27 m) and directional suction traps facing two directions at three heights (0–1·2 m, 2·4–3·7 m nd 4·9–6·1 m) were used. Catches form the non-directional suction traps and pooled data from all flight traps at each level showed an inverse relationship between wind speed and the height of flight of Anopheles melas (Theo.), of gravid females and of male mosquitoes. There was no indication of a similar relationship for the Culex decens Theo. group or for C. thalassius Theo. The results from flight traps and directional suction traps showed that all mosquitoes were apparently flying upwind at all the levels investigaed. It is concluded that, although upwind flight probably does not occur naturally in the open at eights of more than 1 or 2 m, these experiments indicate that upwind flight could occur at higher levels, in the lee of tree and other obstacles.

Aphids of the genus Amphorophora collected from European raspberry, Rubus idaeus, have a chromosome complement of 2n(♀)=18, whereas Amphorophora from R. fruticosus agg. (blackberry, brambles) have a basic chromosome complement of 2n(♀)=20. Canonical variates analysis based on eight characters measured on numerous samples of apterous virginoparae showed that Amphorophora on European Rubus can be separated morphologically into two groups consistent with the differences in host plant and karyotype, and these two groups are concluded to be separate species. The correct name for the aphid on raspberry that is a vector of European raspberry viruses is Amphorophora idaei (Börn.), and the species on blackberry is A. rubi (Kalt.). Simple biometric methods of discriminating between A. idaei and A. rubi based on pairs of variables are suggested, and their reliability is discussed. Taxonomic problems in the European and North American Rubus-feeding species of Amphorophora are considered with particular reference to their importance in applied entomology.

Glossina morsitans morsitans Westw. and G. pallidipes Aust. flying to and from a stationary ox were captured by a wall of electrocuting netting at distances ranging from 45 m upwind of the ox to 120 m downwind. The pattern of catches at each distance suggested that most flies not recently fed were attracted to the ox from downwind, from distances up to about 90 m. Most flies leaving the ox flew downwind. This was most marked for flies that had fed on the ox, some of which travelled 120 m within about 30 min of engorging.

A latex agglutination test to identify the sources of blood-meals of Culicoides is described. The method requires the minimum amounts of reagents and apparatus and would be suitable for rapid tests under field conditions. Blood-meals of Culicoides nubeculosus (Mg.) and C. variipennis (Coq.) from laboratory cultures, which had engorged on blood from several species of domestic animals, were differentiated without difficulty. In a series of ‘blind’ tests, the blood-meals of 49 C. variipennis from seven species of domestic animal were identified with 100% accuracy. The differentiation of blood-meals from closely related hosts, such as mouse and guineapig or ox and sheep, is entirely dependent upon the specificity of the antisera conjugated to the latex. Blood-meals could be identified reliably for about 48 h after ingestion at 20–25°C, but at higher temperatures the reaction became less reliable after 24 h. Detergents commonly used in collecting midges had no effect on the latex agglutination test, but 0–01% mertbiolate, often used as a preservative, caused auto-agglutination and cannot be used when this test is to be applied.

For nine weeks from 14 April to 13 June 1975 an average of over 500 double translocation heterozygote male Aedes aegypti (L.) were released daily into a village where the estimated adult mosquito population was 1200. The two purposes of this release were to suppress the A. aegypti population by sterility induced by chromosomal translocations and to assess the effect of rainy season conditions on the population dynamics of the indigenous and released mosquitoes. As a result of the releases, hatchabirity of eggs from females collected during landing-biting catches dropped from over 93% to 30–40%. For eight weeks following the termination of the releases, hatchability remained below 70% while that of the reference village averaged between 80 and 99% hatch. A relative population decline observed in the release village is not attributed solely to the effect of the releases, partly because it occurred before sufficient time had elapsed to allow induced sterility to build up in the field population.

The larvae and pupae of Elachiptereicus abessynicus Becker and of Pachylophus lugens Lw. are described and illustrated and those of the latter species are compared with those of Pachylophus beckeri Curr. A previous misidentification of P. beckeri is recorded and additional records of host plants and distribution are given for all three species.

A highly significant negative linear correlation (r=– 0·911, P=0·001) was observed between Xyleborus fornicatus Eichh. population levels in tea plants and the crop size in the preceding month. A highly significant negative linear correlation (r=– 0·858, P=0·001) was also observed between Xyleborus population levels and the percentage of healed galleries of the respective samples. Cambial activity, which has a direct relationship with crop size, determines the rate of healing of brood galleries, and this seems to be the critical factor that regulates population size within a pruning cycle. Since the population has an inverse relationship to crop size and as the latter could be predicted in advance using weather parameters, it should be possible to predict population levels of Xyleborus in advance.

A species of Hydrellia, discovered on rice at Ibadan, Nigeria, is described and named Hydrellia prosternalis sp. n. The third-instar larva and puparium are described. Eggs are laid singly per seedling on leaves, and larvae consume the growing points of the shoots, resulting in severe stunting. Pupation takes place in the centre of the shoot, just below the ligule. Hymenopterous parasites of a species of Opius (Braconidae), a genus near Peckelachertus (Eulophidae) and a genus near Cirrospilus (Eulophidae) were reared from pupae.